Department of Chemistry

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Open Access
Probing assorted host-guest interactions prevailing in various environments to explore different target analytes by diverse spectroscopic contrivances
(University of North Bengal, 2024) Maiti, Arpita; Roy, Mahendra Nath; Ray, Tanushree
Probing the host-guest interaction to identify various environmentally harmful and biologically important substances which are known as target analytes of paramount importance to the scientific communities to sustain peaceful and livelihood life in modern civilization. These are known substances with known chemical, physical, and other properties. They are either known or thought to be in samples, and they must be determined to meet the objectives of the environmental analysis program. The target analytes which are known as guests and chromo-fluorogenic compounds which show signaling in the presence of analytes are known to be hosts. These interactions strategy is broadly accepted, understood, and used in analytical and environmental research, environmental security programs, and many other surveys of investigation. It is employed in most environmental quality surveys and government regulatory compliance monitoring programs. Target analytes include cations, anions, chemical warfare agents (CWAs), pesticides; herbicides used by farmers in cultivation, and food adulteration that negatively affects public health. In very small amounts, many of these are necessary to support life such as cations and anions. However, in larger amounts, they become toxic. They may build up in biological systems and become a significant health hazard. The abuse of CWAs and explosive materials has become a severe issue globally and is used by anti-national terrorist groups for the sake of power. The suppression of abuse of these lethal substances and unwanted crimes for the sake of the livelihood environment and humankind's safety are urgently needed. The researchers are actively engaged in developing and updating the field of detecting these toxic and explosive chemicals. Among the various CWAs, sarin gas and explosive nitroaromatic compounds are highly dangerous, poisonous, and harmful. However, the direct use of some lethal substances such as CWAs is strictly prohibited in laboratories; instead, the use of some surrogate substances has been taken into focus, usually serving as its mimics owing to their similar properties and lower toxicity. Keeping the above facts in mind, in the present thesis, we have introduced various chromo-fluorogenic host molecules that are characterized by diverse conventional analytical techniques which are employed for the detection of some metals, anions, explosive nitroaromatic compounds such as picric acids, sarin gas mimics diethylchlorophosphate exploring the host-guest interaction strategy by versatile spectroscopic contrivances in various environment. A summary of each chapter of the present thesis is given below, one by one. Chapter 1: This chapter commences with a concise examination of assorted host-guest systems employed in chemosensors, transitioning to an exploration of the fundamental principles and working mechanisms behind the design of chemosensors based on various photophysical processes, illustrated with relevant examples. A brief survey of the literature on national and international status is also discussed to establish the novelty of the present thesis in the current scenarios. At the end of the chapter main objectives and applications of the current research work within the broader context of scientific advancements are described. Chapter 2: This chapter discusses the general methods and instruments used throughout the research work. Chapter 3: This chapter explores the affordable and incredibly sensitive sustainable sensors for recognizing Al3+ ions with enormous practical applications. A simple and reliable sensor DPAB was developed. by reacting benzene-1,4-diamine with N, N-dimethyl cinnamaldehyde. The sensor is extra highly reputable concerning Al3+ ions and exhibits an incredible color change in DMSO and DMSO-H2O (9:1 v/v) solution, allowing us to visually distinguish Al3+ ions from other metals and anions essentially including Al3+ and PO43- in the DPAB solution, the sensor's spectral responses and apparent color shift can be switched backward and forward. This can be conceptualized as a complementary "INHIBIT" logic gate at the molecular phase. We have developed a molecular-scale subsequent memory device based on a reversible and repeatable detection system that exhibits "Writing-Reading-Erasing-Reading" and "Multi-Write" functionalities as binary logic. The lowest detection limits (LOD) for Al3+ and PO43- ions are determined to be 3.29 nM and 3.89 nM, respectively, considerably lower than other chemosensors described in the literature. Additionally, for on-the-spot detection, the probe may also be utilized in the test strips with a superior selectivity for the detection of Al3+ and PO43- ions. Moreover, we also performed the smartphone-based technique for the practical utility of DPAB in the DMSO-H2O (9:1 v/v) solution for on-spot detection and quantification. The effectiveness of DPAB and DPAB-Al3+ complex suggests that DPAB may be used as a sensitive probe and be applied to the analysis of real samples. Figure 1: Pictorial demonstration of detecting performances of our introduced imine linkage DPAB chromogenic probe for cascade detection of Al3+ and PO43- ions. Inorganica Chimica Acta 121966 (564) 2024. Chapter 4: In this chapter, a new symmetrical aza-substituted chromo-fluorogenic sensor, BPH, for specific detection of sarin gas, one of the fatal G-series nerve agents surrogate, diethylchlorophosphate (DCP) has been introduced. BPH shows a noticeable naked eye colorimetric change from pale yellow to light pink in the presence of DCP, displaying highly intense bright greenish cyan color photoluminosity under a 365 nm UV lamp, which is also manifested from the color chromaticity diagram. A BPH-staining paper stirps-based test kit experiment has been demonstrated for the onsite detection of nerve agent mimics. A more attractive and efficient application of BPH as a sarin gas vapor phase sensor mimics DCP in solid and solution phases. The BPH-based chromo-fluorogenic sensor shows excellent selectivity toward DCP with a detection and quantification limit in the μM range. The work invokes a new way for the researchers to detect DCP employing a simple chromo-fluorogenic sensor, which could be prepared by a time-saving, straightforward, handy protocol from the cost-effective starting materials. Figure 2: Pictorial representation of detecting performances of our introduced azine-based BPH chromo-fluorogenic probe for detection of DCP. Journal of Fluorescence, DOI: 10.1007/s10895-024-03681-1. Chapter 5: This chapter highlights the investigation of the detection of essential trace elements for living organisms such as copper (Cu2+) ions. The Cu2+ ions are the most important from kitchen to industrial life. However, Cu2+ ions are vital for the human body and are associated with necessary physiological processes; insufficient or excessiveness has many hazardous effects on our bodies. In the present contribution, strategically, we have introduced a julolidine-coupled azine-based (HDBQ) reversible chromo-fluorogenic probe for specific detection of Cu2+ ions. Probe HDBQ exhibits observable orange colorimetric change from yellow, which is visible to the naked eye in daylight. The highly green fluorescence HDBQ becomes a non-fluorescent one with the incorporation of Cu2+ ions. Interestingly, the colorimetric change and non-fluorescent HDBQ-Cu2+complex reverse to the original HDBQ in the presence of ethylenediamine tetraacetic acid (EDTA). The detection and quantification limit of HDBQ towards the detection of Cu2+ ions is found to be in the μM range, which is much lower than the limit (31.5μM) recommended by WHO. We have also performed a colorimetric and fluorometric paper-based test strips-based experiment employing HDBQ for real-time on-site detection of Cu2+ ions. Using the reversibility characteristics of HDBQ for the consecutive addition of Cu2+ and EDTA, we have established the INHIBIT molecular logic gate. The present report brings a precise and sensitive probe for the detection of Cu2+ ions in real environmental and biological samples. Figure 3: Pictorial demonstration of detecting performances of our introduced julolidine coupled azine-based reversible chromo-fluorogenic probe for specific detection of Cu2+ ions having sensitivity in the μM range. Journal of Fluorescence, https://doi.org/10.1007/s10895-023-03577-64. Chapter 6: The severe toxicity and easy availability of nerve agents have caused an increase in the need to develop effective methods for identifying these lethal substances. Among the traditional platforms employed for this kind of purpose, chromophore-based chemosensors have garnered a significant amount of attention. In this chapter, we have designed, prepared, and characterized (N1E, N4E)-N1, N4-bis((Z)-3-(4-(dimethylamino)phenyl) allylidene)benzene-1,4-diamine, BDPA, a simple chromogenic probe of symmetrical diimine, having the extreme capability to sensing DCP, the mimic of chemical warfare agent sarin not only in solution but also in solid and vapor phases with highly selective and sensitive manner. In the presence of DCP, a remarkable color change from light yellow to blue is observed in pure acetonitrile solvent and also shows pink color in 10% acetonitrile-water by the naked eye, comes back to its former state after the introduction of triethylamine (TEA) which is found to be five times recyclability by alternately adding DCP and TEA. The detection limit of BDPA with DCP has been estimated in the nanomolar range, and also, response time towards sarin surrogate DCP is within a few minutes (~ 5-6 minutes.). To determine its practical usability, we have developed a portable test kit that uses paper strips to assess the capability of BDPA for in-situ recognition and measurement of DCP. A dipstick method has also been executed to recognize gaseous DCP within the stores of analogous hazardous analytes to prove the effectiveness of the sensor, BDPA. A smartphone-based readout novel technique, i.e., RGB analysis, has provided an innovative platform for the instant, on-site, visible identification and measurement of DCP in remote areas. The current work presented an incredible probe and method for conveniently and instantly detecting and quantifying sarin gas mimics in actual dangerous circumstances. Figure 4: Demonstrate the detecting performances of our introduced imine-linkage simple chromogenic probe, BPDA for the detection of sarin gas mimic, DCP with a nanomolar range detection limit. Microchemical J. 10997 (199) 2024. Chapter 7: This chapter attempts to introduce a chromone-coupled adenine-based fluorogenic chemosensor (BD1) that has been introduced and characterized by different conventional analytical methods. Our developed sensor can selectively and sequentially detect Zn2+ and HSO4- or Zn2+ and picric acid (PA) based on the fluorescence ‘OFF-ON-OFF’ mechanism. A momentous fluorescence improvement has been observed after the accumulation of Zn2+ ions in the BD1 solution at 475 nm due to the creation of the Zn2+ chaleted BD1 complex. A cyan color fluorescence enhancement is visible under the exposure of a 365 nm UV lamp, which is also manifested in the CIE diagram. The detection limit of our developed sensor BD1 and Zn2+- BD1 complex towards the identification of Zn2+ and HSO4- ions are in the nM and μM range, respectively, in the solution phase. Among the several explosive nitroaromatic compounds (NACs), only PA quenches the fluorescence Zn2+ chelated BD1 complex, and the nature of quenching is both static and dynamic. Zn2+ chelated BD1 complex could detect PA selectively in the μM range among all the tested NACs. We have fabricated a paper strips-based test kit and successfully utilized it for practical on-spot identification of Zn2+ ions and PA. Based on the chemically encoded input as Zn2+ ions, PA, and the fluorescence intensity as output, we constructed an INHIBIT molecular logic circuit. The present report evokes a new approach for the development of new chemosensors from bioinspired materials such as adenine, a purine nucleobase. Figure 5: Represent the detection performance of BD1 for cascade detection of Zn2+ and HSO4- ions or Zn2+ ions and picric acid. ChemistrySelect, https://doi.org/10.1002/slct.202304947. Chapter 8: Finally, a summary of the present thesis and the future perspective from the present research work has been delineated in this chapter.
Open Access
Assorted interactions of some noteworthy compounds prevailing in host guest and solution chemistry investigated by physicochemical contrivance
(University of North Bengal, 2024) Debnath, Subhajit; Nath Roy, Mahendra; Sinha, Anuradha
By the thesis title, I aim to demonstrate my profound understanding of the fields of amino acid-ionic liquid as well as vitamin-ionic liquid interaction in aqueous medium and supramolecular host-guest inclusion complexation. The supramolecular assembly has become increasingly important in drug release these days because of its exceptional bioavailability and unique capacity to change the solubility, stability, pharmacokinetics, and pharmacodynamics of the medication. They also show improved encapsulation, controlled release, and benign qualities. The inclusion complexation of diverse bioactive compounds and their distinct photophysical properties in aqueous media are confirmed by the spectroscopic contribution. The development of supramolecular assembly can be qualitatively understood by the use of SEM analysis, powder XRD, 1H-NMR, FTIR, and UV-visible analysis, all of which can satisfactorily express the inclusion phenomenon. Studying TGA and DSC can help to explain why such an arrangement is thermally stable. Confirming the data from the experimental research are studies of the supramolecular system using theoretical molecular modeling. Significant information on a variety of thermodynamic properties of electrolytes and non-electrolytes, the impacts of variations in ionic structures, and the mobility of ions in addition to their common ions can be gained from the study of the physicochemical properties of solutions. Measurements of apparent molar volume ( v  ), limiting apparent molar volume ( 0 v  ), molar refraction ( M R ), limiting molar refraction ( 0 M R ), molar conductance (Ʌ), Surface tension (γ) and viscosity B coefficients obtained from various physicochemical methodologies are typically used to reveal the genesis of diverse interactions between amino acids, vitamins and ionic liquid in the aqueous phase. This study has looked at the encapsulation of several biologically active compounds. There may be uses for these bioactive compounds in biological systems. Pharmacological activity is frequently used to characterize the advantageous properties of bioactive compounds. In host–guest chemistry, the application of macrocyclic hosts in molecular recognition, controlled release of a drug and sensing field has received considerable interest. The incorporation of guest molecules in the aqueous environment within the cavity of the host molecule such as α-cyclodextrin, provides new insight into molecular recognition (e.g. inclusion or complexation) through non-covalent interactions. A general understanding of the development of an inclusion complex between the host and guest molecules can be obtained from supramolecular host-guest chemistry. The host's hydrophobic cavities can bind various guest compounds. The supramolecular assembly as a whole has been extensively researched recently in a variety of disciplines, including analytical chemistry and medication delivery. When combined with different guest molecules of the right size, cyclodextrin and its derivative appear to be the most promising host molecules for the formation of inclusion complexes. Thus, the main goal of this thesis is to investigate the impact of supramolecular recognition and solution chemistry, which are unavoidably important due to their numerous applications in a variety of sectors, including the biological and pharmaceutical sciences. SUMMARY OF THE WORKS CHAPTER I This chapter includes a full description of the research project, its scope, and its applications to modern science. It also explains the rationale for the selection of solvent systems, cyclodextrins, ionic liquids, and bioactive compounds. A summary of all the investigation techniques used in the research project is provided in this chapter. CHAPTER II The earlier study on this topic, conducted by different scientists and researchers worldwide, is reviewed in this chapter. Additionally, a detailed explanation of the findings is provided in this chapter, which describes the forces that interact between the molecules. The theory underlying each of the investigation techniques—1H-NMR, FTIR, UV-visible, Differential Scanning Calorimetry, Thermogravimetric analysis, Powder XRD, Scanning Electron Microscopy, Molecular Docking study, Antimicrobial study, Cytotoxicity study, Surface Tension, Conductivity, Density, Viscosity, and Refractive Index has been covered in detail here, along with the importance of their application to the research described in this thesis. CHAPTER III The experimental section is covered in this chapter. It discusses the names, compositions, characteristics, and uses of cyclodextrin, ionic liquids, solvents, and biologically active compounds that are employed in research projects. It also contains information about the instruments used in this research, their descriptions, and the specifics of the experimental procedures. CHAPTER IV This chapter consists of the formation of the new inclusion complex between the 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [Bdmim]BF4 ionic liquid (IL) and the host α-Cyclodextrin (α-CD) by a 1:1 ratio and newly formed inclusion complex was further explored by the 1H-NMR, FT-IR, UV-vis spectroscopy, PXRD, DSC, and SEM analysis. Molecular docking was also performed to investigate the encapsulation of the inclusion complex in which orientation and it have been seen that the IL [Bdmim]BF4 enters into the α-CD cavity with a 1:1 ratio. It was further established with the help of Job’s plot. The antibacterial activity of [Bdmim]BF4 IL and its inclusion complex was also verified against some Gram-positive and Gram-negative bacterial strains. *Published in Zeitschrift für Physikalische Chemie, 2023 CHAPTER V This chapter includes investigating the encapsulation of polyether compounds such as mephenesin (MEP) into the nano hydrophobic cage of α-cyclodextrin as a host molecule. The consequential inclusion system was characterized by UV−visible spectroscopy, 1H NMR, PXRD, TGA, DTA, SEM, and FTIR studies. Molecular docking was performed for the inclusion complex to discover the most proper orientation, and it was seen that the drug mephenesin fits into the cavity of α-cyclodextrin in a 1:1 ratio, which was also confirmed from the Job plot. Furthermore, a comparison was done based on cell viability between the drug and its inclusion complex *Communicated. CHAPTER VI This chapter includes the solute–solvent interaction between ionic liquids (ILs) and amino acids (AA) in aqueous media plays a significant role in the optimization of several important biotechnological processes. L-Phenylalanine and LTryptophan (two solute molecules) interact with an ionic liquid (Benzyltributylammonium chloride) in an aqueous medium. Based on the different parameters such as apparent molar volume, viscosity B-coefficient, molar refraction, molar conductance, surface tension at different temperatures and different concentrations from density, viscosity, refractive index, conductance, surface tension measurements have been used to explain the molecular level interactions. Using Masson equation, the experimental slopes and the limiting apparent molar volumes are obtained which explain the solute-solute and solute-solvent interactions. Hepler’s technique and dB/dT values have been used to examine the structure-making and structure-breaking nature of the solutes in the solvents. Viscosity parameters, A and B obtained from Jones- Doles equation explained the solute-solute and solute-solvent interactions in the solution. Lorentz-Lorenz equation has used to calculate the molar refraction. The specific conductance and surface tension also explained the interaction properties. In our findings, we emphasized on the nature of solute–solvent interactions and the presence of structural effect on the solvent in solution to analyze the molecular-level interactions prevalent in the systems. *Published in World Journal of Engineering Research and Technology, 2021 CHAPTER VII In this chapter the densities, viscosities, conductances and surface tension of Vitamin C (Ascorbic acid) in Ionic Liquids viz: Benzyltributylammonium chloride (BTBAC) and Benzyltriethylammonium chloride (BTEAC) aqueous mixtures have been measured at 298.15K, 308.15K and 318.15 K. Apparent molar volumes (Фᴠ), viscosity Bcoefficients, molar conductances are obtained from these data supplemented with densities, viscosities and specific conductances, respectively. The limiting apparent molar volumes (Фᴠ0) and experimental slopes (SV*) derived from the Masson equation have been interpreted in terms of solute-solvent and solute-solute interactions, respectively. The viscosity data have been analyzed using the Jones-Dole equation, and the derived parameters B and A have also been interpreted in terms of solute-solvent and solutesolute interactions, respectively. The surface tension parameter has also been utilized to support the investigation. The structure-making/breaking capacities of ascorbic acid in the studied ionic liquid systems have also been discussed. *Published in Journal of Chemical, Biological and Physical Sciences, 2024 CHAPTER VIII This chapter includes the concluding remarks about the research works done in this thesis. CHAPTER IX Bibliography and references of all the previous chapters has been included in this chapter.
Open Access
Experimental and computational studies of various interactions of some significant compounds prevailing in solutions and inclusion complexes by different methedology
(University of North Bengal, 2024) Karmakar, Paramita; Roy, Mahendra Nath; Ekka, Deepak
The focus of this thesis is to delve deeply into the realm of Supramolecular Host-Guest Inclusion Complexation and the interaction between Food Chemicals and Ionic Liquid along with vitamins with caffeine solution in the solution phase, culminating in molecular synergism that enhances microbial activity. In the field of supramolecular chemistry, biologically potent molecules such as drugs, and bio-active molecules, which are often water-soluble with underdeveloped delivery systems, were selected to form inclusion complexes with cyclodextrins. The objective is to improve solubility and bioavailability. The research employs various physicochemical and spectroscopic methodologies to investigate the mechanisms behind the formation, stability, thermodynamic feasibility, binding ability to albumin protein, and sustained release of drug molecules from inclusion complexes into the surrounding medium. In the context of solution chemistry, first, the interaction between Food chemicals and Ionic Liquid demonstrates molecular synergism. This aspect holds great importance in food chemistry, considering the substantial global food production and the associated challenges of spoilage. The investigation of diverse interactions involves measuring apparent molar volume (φv), limiting apparent molar volume (φv 0), molar refraction (RM), and limiting molar refraction (RM 0). These parameters are obtained through various physicochemical methodologies. My research in supramolecular chemistry is substantiated by the successful advancement of the following novel aspect: (a) Improvement of drug solubility in water to enhance bioavailability (b)Controlled drug delivery facility (c) Enhancement of antioxidant activity (d) Facilitation of cyto-toxicity (e) Augmentation of antimicrobial activity For a drug to exhibit heightened therapeutic effectiveness, achieving substantial bioavailability and solubility is crucial. The pharmacological response necessitates the drug to attain a minimum concentration, underscoring the significance of reaching a desired level of aqueous solubility. A molecule's solubility is qualitatively defined as the spontaneous interaction of two or more substances, resulting in a homogeneous molecular dispersion. Through experimentation, it was discovered that the formation of drug-cyclodextrins (CDs) inclusion complexes significantly enhances the aqueous solubility of the drug, thereby increasing its bioavailability. This enhancement is attributed to the encapsulation of the hydrophobic segment of the guest molecule within the hydrophobic cavity of appropriately sized CDs. The cavity dimensions of the CDs play a crucial role, as they should be moderate enough to minimize contact between water and the nonpolar regions of both the host and guest molecules. Notably, α and β- cyclodextrins were selected due to the dimensional suitability of their cavity sizes in this context. Summary of work done CHAPTER I This chapter provides a comprehensive exploration of the research work's subject matter, elucidating its scope and applications in modern science. It delves into the rationale behind selecting bio-active molecules, drugs, vitamins, nerve stimulating chemicals, food food chemicals, ionic liquids, cyclodextrins, and solvent systems for study. CHAPTER II This chapter presents a comprehensive review of prior research conducted by scientists and researchers globally in the relevant field. It also provides a detailed theoretical framework for the investigation, elucidating the forces that interact between molecules. The chapter extensively discusses the theories and applications of various analytical techniques such as 1H NMR, 2D ROESY, FTIR spectroscopy, UV-Visible spectroscopy, Scanning Electron Microscopy, Powder X-Ray Diffraction, High- Resolution Mass Spectroscopy, computational study, Conductivity, Density, Viscosity, and Refractive Index. It underscores the significance of employing these methods in the research conducted within this thesis. CHAPTER III This chapter encompasses the experimental aspects, detailing the nomenclature, structure, physical attributes, purification methods, and applications of biologically active molecules, drugs, vitamins, cyclodextrins, food chemicals, ionic liquids, and solvents employed in the research. Additionally, it provides comprehensive information on the experimental methods, including descriptions and applications of the instruments utilized in the research. CHAPTER IV This chapter includes an investigation on the diverse molecular interactions between implausible food chemicals (potassium oxalate, sodium oxalate and lithium Oxalate) and 1-butyl-1-methyl-pyrrolidinium chloride in aqueous solutions has been presented. The experiments have been discovered thoroughly by different types of physicochemical methodologies like density, refractive index, viscosity, and conductivity at three different temperatures 298.15K, 308.15K and 318.15K. The genesis of diverse interactions of the ternary mixtures were exposed by measurement of the apparent molar volume (φv), limiting apparent molar volume (φv 0), viscosity B coefficients, molar refraction (RM), limiting molar refraction (RM 0). The results have revealed the predominant solute-solvent interaction over the solutesolute as well as solvent-solvent interactions. The ionic liquid is more strongly interacting with potassium oxalate than sodium oxalate, which in turn is greater than lithium oxalate at a higher range of temperature. Moreover, Density functional theory calculations were performed to evaluate parameters like adsorption energies, molecular electrostatic potential maps and mode of binding which corroborate the experimental observations. CHAPTER V This chapter consists of encapsulation of Nicotinuric acid in the cavity of cyclodextrins. Nicotinuric acid is an agent in the pathogenic mechanism for metabolic syndrome to diabetes and atherosclerotic cardiovascular disease. To protect these external effects (e.g., oxidation, structural modification etc), a systematic study of hostguest complexation of nicotinuric acid with α and β-cyclodextrins has been incorporated. The analysis has been empowered by Spectroscopic study like UV-Vis, FTIR, 2D ROESY NMR, and SEM. Job’s plot by UV-vis spectral data shows 1:1 stoichiometric combination of nicotinuric acid and cyclodextrin. The noticeable shifts in FTIR stretching frequency also assisted the inclusion phenomenon. The reliable magnitude of the association constants (8.27×103 & 8.84×103 in α-CD and β-CD respectively), obtained from Benesi-hildebrand method, is in good agreement with the stabilities of the inclusion phenomena. In 2D ROESY analysis three offdiagonal peaks are observed due to the intermolecular dipolar cross correlation between the proton of the pyridinium ring of nicotinic acid with the H3 and H5 of α and/or β- CD. Surface morphologies from SEM of the complexes have also been added. Molecular docking has been carried out to explore the fitting mechanism of NUA insight into the cavity of CDs. The guest scores -6.1 kJ/mol and -6.4 kJ/mol with α-CD and β-CD respectively. CHAPTER VI In this paper, Volumetric and viscometric analysis of ascorbic acid and thiamine hydrochloride in caffeine aqueous solution at different mass fractions over the temperature range (298.15K -318.15K) and at 1 atm pressure, have been implemented. All analyses have been interpreted in terms of solute–solute, solvent–solvent and solute-solvent interactions of the considered system. The parameters like apparent molar volume(φv) and limiting apparent molar volume (φv 0), have been estimated from the density data. Falkenhagen A-coefficients and Viscosity B-coefficients have been predicted from viscosity by implementing the Jones-Dole equation. The Hepler’s constant and RM have been evaluated. DFT calculation predicts the mode of binding which correlates the practical observations. By the help of physicochemical and computational techniques, we found that vitamins behave as structure breaker in caffeine solution. CHAPTER VII In this paper, Esculetin and α-cyclodextrin, as well as beta-cyclodextrin host molecules, have been intermixed with the help of the coprecipitation method to form a supramolecular complex to offer physical insights into the formation and stability of the inclusion complex (IC). The characterization of the synthesized product was done by Powder X-ray diffraction (XRD), electrospray ionization mass spectrometry (ESIMS), 1H nuclear magnetic resonance (1H NMR), Fourier transform infrared (FTIR) spectroscopy, electrospray ionization (ESI) mass spectrometry, Scanning Electron Microscopy (SEM). The stoichiometric ratio of 1:1 is obtained from Job Plot and the Benesi−Hildebrand double reciprocal plot provides the association constant values supported by the ESI mass data. The inclusion complexation is validated by the systematically analyzed results of molecular modeling, additionally, the outcomes achieved from 1H NMR and FTIR spectroscopy studies which reinforce the complexation phenomenon. The encapsulation of Esculetin into α-cyclodextrin along with beta-cyclodextrin is determined by the results acquired from computations in addition to experimental data. CHAPTER VIII This chapter includes the concluding remarks about the research works done in this thesis.
Open Access
Understanding the Target Analyte Interaction for the Design and Development of Efficient Optical Sensor: A Combined Photophysical and Theoretical Analysis
(University of North Bengal, 2024) Rajbanshi, Madan; Das, Sudhir Kumar
The photophysical properties of optical sensors can be altered by binding a specific target analyte to the receptor, resulting in enhancement or quenching in fluorescence signal that helps us to detect and analyze specific target analytes with high sensitivity and selectivity. So, Optical sensors are found in many different fields of application, including metal sensors, pH sensors, biomedical imaging and diagnostics, photovoltaic devices, solar energy conversion, display technologies, etc. Optical sensors have recently received a lot of attention due to their photophysical properties that are sensitive to the understanding of the target analyte interaction. Chapter I: In this chapter, different types of target analytes with their important role and adverse effects in biological and environmental systems have been discussed. Also, a brief discussion on optical sensors, their photophysical properties, and several signaling mechanisms, based on different photophysical processes such as ICT, PET, ESIPT, FRET, paramagnetic fluorescence quenching mechanism, and DFT analysis have been done here to understand the interaction between sensor and target analyte. Chapter II: A simple ratiometric, turn-on chromo-fluorogenic sensor, (E)-2-((2- hydroxybenzylidiene) amino)-5-nitrophenol (HBAN), has been developed, synthesized, and characterized by several conventional analytical methods. HBAN is found to be selective for the sequential detection of Al3+ ions and picric acid (PA), respectively, based on the fluorescence „off-on-off‟ method. A remarkable fluorescence enhancement of HBAN is detected at 540 nm upon binding with Al3+ ions with visual yellow color fluorescence under a portable 365 nm UV light irradiation. Among the various tested nitroaromatic compounds, PA selectively quenches the fluorescence of the Al3+ ions chelated HBAN complex. The formation of the complex between HBAN and Al3+ ions is found to be in a 1:1 stoichiometric ratio and the LOD is found to be nanomolar range. The mechanistic aspects of detecting Al3+ ions have been elucidated by different spectroscopic and density functional theoretical analyses. Additionally, a test kit based on paper strips coated with HBAN is demonstrated to selectively detect Al3+ ions. Chapter III: A phthalimide-decorated novel acid-responsive probe Z1 is designed and synthesized based on a conjugated donor-acceptor (D-A) subunit. The synthesized probe shows a colorimetric visual change through protonation and deprotonation processes with the addition of acid and base in the non-aqueous medium. A ratiometric UV-visible absorption spectral change is observed with the addition of acid, and the density functional theory investigation supports the experimental findings. A colorimetric paper strip-based experiment has been demonstrated to detect trace amounts of acid and bases in non-aqueous solvents. Furthermore, the overlapping indicator method is explored to estimate acid dissociation constants in the nonaqueous medium. The acid-responsive colorimetric behavior of this probe is fully reversible with the addition of bases, and using this reversible colorimetric response, we have constructed the INHIBIT (INH) and IMPLICATION (IMP) molecular logic gates. The present report invokes a new avenue for synthesizing several acid-base sensors and estimating the acid dissociation constants of diverse acid-base compounds in the non-aqueous medium. Chapter IV: Detection of fluoride (F-), acetate (AcO-), and cyanide (CN-) anions are vital from the biological and environmental aspects. In the present contributions, we have introduced a simple Salen-type chromogenic sensor, BEN, to detect these biologically important anions. Changes in UV-Visible absorption spectra and color of BEN solution from very pale yellow to pink color are similar for each of these anions and found to be reversible only in the case of Fions in attendance of HSO4 - ions. Estimated limit of detection of BEN solution for detecting F-, AcO-, and CN- anions are found to be below the micro molar (μM) concentration level. Our fabricated handy paper test kit is suitable for qualitatively naked-eye detection of the anions. An immediate quantitative estimation of these important anions is possible using our BEN employing a smart phone, avoiding any costly experimental setup. Chapter V: Extremely toxic G-series nerve agents are used as weapons for mass destruction in wars and terrorist attacks. So, rapid and accurate detection of these dangerous nerve agents is immediately required to save our environment and nation. In this article, we have designed and developed a chromone-coumarin coupled fluorogenic probe MATC that can selectively detect sarin gas mimicking diethylchlorophosphate (DCP) with the detection and quantification limit in the nM (nanomolar) range. MATC solution with DCP exhibits remarkable fluorescence intensity at wavelength 465 nm displaying bright cyan color photoluminosity under the exposure of 365 nm UV lamp, which is also manifested from the color chromaticity diagram as a result of disruption of excited state intramolecular proton (ESIPT) process due to the phosphorylation process. Straining our probe, MATC, on Whatman-41 filter paper, we have also fabricated a paper strips-based test kit for on-the-spot recognition of sarin gas as a movable and displayable photonic device. A dip-stick and dipped-vial-conical-flask experiment has also been demonstrated to recognize and quantify DCP in the vapor phase. The present report demonstrates a complete description of a fluorogenic and specific chemosensor to identify and quantify deadly nerve agents within the stores of analogous organophosphates and inorganic phosphates. Chapter VI: The summary and future scope of present research work have been mentioned in this chapter.
Open Access
Studies on coordination compounds of cobaltand tungsten, having biochemical relevance to pterin-containing metalloenzymes
(University of North Bengal, 2015) Sen, Samir,; Roy, Parag Sinchan
Open Access
An approach of computer aided drug design tools for in silico pharmaceutical drug design and development
(University of North Bengal, 2024) Sarkar, Kaushik; Das, Rajesh Kumar
The work in this thesis utilizing various in silico techniques to explore potential leads against aurora kinase, hepatitis C virus, COVID-19, monkeypox virus, adenovirus, HKMT, and GOAT. CADD accelerates lead discovery and optimization, leveraging both high speed and low cost, thus enhancing drug development success rates. In this study, both structure-based (molecular docking) and ligand-based (QSAR) techniques were employed, providing a robust tool for ligand investigation. Drug repurposing emerges as a transformative strategy, offering innovative therapeutic avenues for approved drugs. Additionally, QSAR aids in lead optimization, minimizing time, cost, and animal use. Key steps in QSAR model development include dataset collection, descriptor calculation, model construction, and validation. This thesis proficiently employs QSAR to understand structural activity relationships, improve selectivity, and design molecules with enhanced efficacy, predicting the activity of newly designed compounds. CHAPTER I This chapter contains the in details about CADD which has been extensively explored for facilitating lead discovery and optimization with advantages in terms of both high speed and low cost, increases the probability of success in the drug development process. A variety of in silico methods have evolved in CADD that have two major application areas, i.e., LBDD and SBDD. The first part of the chapter deals with the object of CADD with aurora kinase and hepatitis C. The second part of the chapter deals about drug repurposing with COVID-19, monkeypox, and adenovirus. The last part deals about QSAR study with HKMT, and GOAT. CHAPTER II The major in silico techniques that are usually popular among researchers are molecular docking, molecular dynamics (MD) simulation, density functional theory (DFT), molecular mechanics Poisson Boltzmann surface area (MM-PBSA), quantitative structure activity relationship (QSAR), artificial neural network (ANN) and absorption, distribution, metabolism, excretion, toxicity (ADMET) prediction. Collective use of all of the mentioned computer aided techniques is necessary to predict potential inhibitors. It includes methodologies of all of the above mentioned techniques in detail. CHAPTER IIIA Aurora kinase (AURK) belongs to the serine/threonine kinase family and play a crucial role in regulating the cell cycle. Therefore, AURKs are the hopeful target for anticancer therapies and these findings have encouraged researchers to rigorously hunt small molecule aurora kinase inhibitors, not only for research articles but also for use as therapeutic agents. This study helped us to identify and screen the best phytochemicals as potent inhibitors against AURK. These potent inhibitors came from the various substitution of rosmarinic acid (RA). Here, we selected different tested derivatives for designing anticancer drugs by substituting various functional groups of standard drug RA. In silico studies were carried out to Abstract appreciate better drug candidature of some of these derivatives. This study was performed on 56 derived compounds of the standard RA. Out of the 56 derivatives, 11 have passed all the rules of drug candidature, to serve as best AURK inhibitor, in a theoretical manner. This study should be supported by a new proposal to explore future studies with these 11 compounds against cancer. CHAPTER IIIB The NS3/4A protease is a common target for HCV infection. Telaprevir and danoprevir have promising activity in combating these virus-associated infections and are used as HCV protease inhibitors. In this study, we have found different tested derivative compounds for developing various HCV NS3/4A protease inhibitors by designing the chemical structures of telaprevir and danoprevir. In silico studies were carried out to find better drug candidature from these derivative compounds. The docking studies were performed on HCV NS3/4A protease receptors (PDB: 3SV6 & 5EQR). DFT, global reactivity, ADME (Absorption, distribution, metabolism & excretion), and toxicity analysis were also performed for these designed compounds. The stability of the protein-ligand complexes was quantified by MD simulation and MM-PBSA studies. 16 derivatives (four as telaprevir and twelve as danoprevir) have satisfied higher binding affinity of interaction with NS3/4A protease, compared to telaprevir and danoprevir. These compounds have also passed all rules of drug candidature to serve as the best HCV inhibitors. These 16 ligands can be used as effective inhibitors against HCV NS3/4A protease. These ligands could be considered to follow the drug candidate behaviour by in vitro and in vivo analysis to inhibit HCV infection. CHAPTER IVA Novel coronavirus disease, COVID-19 caused the outbreak situation of global public health. In that pandemic situation, all the people lives of 212 Countries and Territories were affected due to partial or complete lockdown and also as a result of mandatory isolations or quarantines. This was due to the non-availability of any secure vaccine. This study helped us to identify and screen the best phytochemicals as potent inhibitors against COVID-19. In this study, we have selected two standard drugs namely hamamelitannin and rosmarinic acid as a probable inhibitor of pandemic COVID-19 receptor, compared to antimalarial drugs hydroxychloroquine, anti-viral drug remdesivir, and also baricitinib. This study was done by taking into consideration of molecular docking study. This work has provided an insightful understanding of protein-ligand interaction of hamamelitannin and rosmarinic acid showing comparable binding energies than that of clinically applying probable COVID-19 inhibitors hydroxychloroquine (an anti-malarial drug) and remdesivir (an anti-viral drug). We would expect that if its anti-SARS-CoV-2 activity is validated in human clinical trials, these two drugs may be developed as effective antiviral therapeutics for infected patients with COVID-19. CHAPTER IVB In view of the non-availability of any secure vaccine for COVID-19 caused by SARS-CoV-2, scientists around the world have been running to develop potential inhibitors against SARS-CoV-2. This study helped us to identify and screen best phytochemicals (chemical drugs or plant based compounds) as potent inhibitors against COVID-19. Here, we have measured the virtual interactions of COVID-19 main protease (PDB: 6LU7) with lung cancer, bronchitis and blood thinner drugs as well as some natural plant based compounds. Best docking results have been considered on the basis of disulfiram, tideglusib and shikonin. ADME and toxicity were also predicted for these compounds. From this study, we would expect these drugs to undergo validation in human clinical trials to be used as promising candidates for antiviral treatment with high potential to fight against COVID-19. CHAPTER IVC Monkeypox virus (MPXV) is considered as zoonotic disease with characteristics comparable to smallpox virus. The disease was also a global epidemic concern. Tecovirimat was approved by US Food and Drug Administration (FDA) for MPXV treatment. The aim of this in silico study was to repurpose approved pharmaceutical drugs as potential inhibitors of MPXV target. In this study, molecular docking was performed on 406 pharmaceutical drugs, and results were compared with reference tecovirimat. Results showed that 7 compounds, bictegravir, glimepiride, glyburide, lasmiditan, olaparib, rimegepant, and ubrogepant, have shown higher binding energies compared to the reference. After that, these best hits were further assessed by 100 ns molecular dynamics simulation and the best results were observed for bictegravir, glimepiride, glyburide, olaparib, and ubrogepant. The docking analysis was further validated by MM-PBSA binding free energy calculations. In addition, pharmacokinetics and density functional theory (DFT) studies were also discussed for these best hits. In conclusion, three compounds, bictegravir, glimepiride, and glyburide, have satisfied all the criteria for better leads against MPXV. CHAPTER IVD Human adenovirus (HADV) infection can pose a serious threat to children, leading to a variety of respiratory illnesses and other complications. Particularly, children with weak immune systems are vulnerable to severe adenovirus infections with high mortality. The main focus of this study was to propose new antiviral agents as lead HADV inhibitors for children. So, several antiviral agents used in children were subjected to finding new HADV inhibitors using important computational methods of molecular docking, molecular dynamics (MD) simulation, MM-PBSA binding free energy calculations, DFT, and pharmacokinetic analysis. Molecular docking of standard cidofovir along with other ligands, suggested that sofosbuvir has the highest binding energy (-10.8 kcal/mol), followed by baloxavir marboxil (-10.36 kcal/mol). Further, the analysis of molecular interactions using MD simulation (100 ns) and MM-PBSA indicated that baloxavir marboxil has formed the most stable protein-ligand complex with HADV, followed by sofosbuvir. The binding free energies of baloxavir marboxil and sofosbuvir were found to be -61.724 kJ/mol and -48.123 kJ/mol, respectively. The DFT and drug-likeness properties of these compounds were also investigated. Overall, two antiviral agents, such as baloxavir marboxil, and sofosbuvir, were suggested as lead repurposed candidates against HADV. CHAPTER VA Initiation and progression of several diseases by post-translational histone modifications are considered a worldwide problem. Enhancer of Zeste Homologue 2 (EZH2), which belongs to HKMT family, has been emphasised as a promising target for cancer therapy. It is a major challenge for the scientific community to find novel approaches to treating this disease. In this study, a series of 51 derivatives of the benzofuran and indole families, previously experimentally evaluated against HKMT, was used to develop the best QSAR model with promising anticancer activity. The multiple linear regression (MLR) method was used with a genetic algorithm (GA) for variable selection. The model with two descriptors (minHBint4 and Wlambdal.unity) was found to be the best and its parameters fit well, and its validation was well established. The applicability domain was also validated for this model. Furthermore, its robustness (R2 = 0.9328), stability (Q2LOO = 0.9212, Q2LMO = 0.9187), and good predictive power (R2ext = 0.929) were also verified. Hence, this model was assumed to have predictive HKMT anticancer activity for designing active compounds. Molecular docking was also performed to identify binding interactions, and new molecules with better predicted biological activity (pIC50) were designed. The binding energy of the three designed compounds demonstrated higher binding activity at the target receptor, followed by complex stability, determined by a 100 ns molecular dynamics simulation and binding free energy calculation. DFT and pharmacokinetic analyses also confirmed their drug-like properties. Finally, it could be declared that the proposed tools allow rapid and economical identification of potential anti-HKMT drugs (anticancer drugs) for further development. CHAPTER VB Diabesity is a major global health concern, and GOAT acts as an important target for the development of new inhibitors of this disease. This work highlighted a detailed QSAR study, which provides an excellent model equation using descriptors. Here, the best model equation developed has two variables, namely MLFER_E and XlogP, with statistical parameters R2 = 0.8433, LOF = 0.0793, CCCtr = 0.915, Q2LOO = 0.8303, Q2LMO = 0.8275, CCCcv = 0.9081, R2ext = 0.7712, and CCCext = 0.8668. A higher correlation of the key structural fragments with activity was validated by the developed QSAR model. Furthermore, molecular docking helped us to identify the binding interactions. Thirty four new molecules with better predicted biological activity (pIC50) were designed. The binding energy of four compounds have shown higher binding activity into the membrane protein. Molecular dynamics simulation has established the stability of the protein-ligand complex over 100 ns. DFT and ADME-toxicity analyses also confirmed their drug-like properties. Based on our findings, we would expect these new oxadiazolo pyridine derivatives to undergo further development.
Open Access
Photophysical and sensorial behaviour of different chromophoric systems comprising electron donor-acceptor units
(University of North Bengal, 2023) Rahman, Ziaur; Das, Sudhir Kumar
Research on developing new electron donor–acceptor (EDA) based molecular systems, which benefit from extended π-conjugation, is a rapidly growing research area. That has resulted in several technological applications, including fluorescent dyes, laser dyes, brightening agents, metal sensors, pH sensors, bio-imaging, organic photovoltaics (OPVs), organic light-emitting diodes (OLEDs), and many more. The photophysical properties of donor (D)-acceptor (A) based molecular systems depend on the substitution pattern and the D-A unit's nature, making them prime derivatives for application in organic photonics. The most frequent method for tuning the photophysical properties of organic compounds is to connect an electron-rich “D” and an electron-deficient “A” group directly or indirectly. The π-linkage between the “D” and “A” units results in a D-π-A type of conjugated molecular system, where the photophysical/electronic properties of D-π-A systems can be tuned by either (i) changing the “D” or “A” unit strength or (ii) varying the π-linker between the “D” and “A” units. A wide range of D-A conjugated systems with varying “D” and “A” units have been developed for various applications in chemistry, physics, materials science, and biology. Because of their superior photophysical characteristics, these are used to develop and create various sensory materials for monitoring biological events and detecting various target analytes. Chemosensors based on photoluminescence are essential among the many approaches and methodologies because they have multiple benefits, such as on-site detection, real-time monitoring with rapid response, innately high sensitivity, and simplicity of handling compared to other techniques. Considering the real benefit of the chromo-fluorogenic EDA system, present thesis explores its practical benefit for detection of various target analytes. A brief summary of each chapter of the present thesis are given below one by one. Chapter 1: This chapter begins with a brief discussion of the EDA system-based chemosensors and then moves to the general principle and working mechanism for designing chemosensors based on different photophysical processes with examples. This chapter deals with the objectives and applications of the present work in the present context of scientific development. Chapter 2: This chapter explores the reversible acidochromic behavior of a benzoxazole-based scaffold (BPP), which is highly sensitive to the acid-base in the liquid and gas phases. With the addition of acid, the solution of BPP changes its color from yellow to pink fuchsia due to the transformation of its imine into quinonoid form. The color change is completely reversible in the presence of the base, confirming the reversible acidochromic behavior of the present BPP system. Further, a paper strips-based test kit has been demonstrated for the practical utility of the present acidochromic BPP to identify a trace amount of acid-base in solution and gas-phase, respectively. The mechanistic aspects of detecting acid-base and colorimetric change in the presence of acid-base have been explored by density functional theoretical investigations and 1H NMR experiments. Moreover, we have constructed a reconfigurable dual-output combinatorial INH/IMP logic gate. Chapter 3: This chapter highlights the investigation of anion interactions and recognition abilities of naphthalene derivative, [(E)-1-(((4-nitrophenyl) imino) methyl) naphthalen-2-ol], (NIMO) by UV–visible spectroscopically and colorimetrically. NIMO shows selective recognition of F− ions colorimetrically, and the naked eye observes a visual color change from yellow to pink. The F− ions recognition is fully reversible in the presence of HSO4− ions. The limit of F− ions detection by NIMO could be possible down to 0.033 ppm-level. A paper strips-based test kit has been demonstrated to detect F− ions selectively by the naked eye, and a smartphone-based method for accurate sample analysis in the non-aqueous medium has also been demonstrated. The pKa value calculation and DFT analysis support spectroscopic behavior to find a correlation with receptor analyte interaction. The optical response of NIMO towards the accumulation of F− ions and, subsequently, HSO4− ions as chemical inputs provide an opportunity to construct INH and IMP molecular logic gates. Chapter 4: In this chapter, a fluorosensor derived from 4-aminophthalimide, ((E)-5-((2-hydroxy benzylidene) amino) isoindoline-1, 3-dione, HID working with excited state intramolecular proton transfer (ESIPT) mechanism is synthesized and employed for the selective recognition of aluminum (Al3+) ions and picric acid (PA) based on 'off-on-off' fluorescence mechanism. The sensor HID shows a turn-on fluorescence response towards Al3+ ions in H2O/DMSO (9:1, V/V) with a rapid response time (2 minutes) and exceptional sensitivity (LOD = 0.77 μM). The binding constant (K) of HID with Al3+ ions is estimated to be 1.32 × 108 M-2. The 1:2 stoichiometries of the complex between HID and Al3+ ions are confirmed through Job's plot and 1H NMR spectral analysis. Al3+ chelated HID complex is further employed to detect explosive nitroaromatic compounds, especially PA. Furthermore, using these two chemically encoded inputs, and corresponding optical output, we constructed the INH molecular logic gate with Al3+ and PA. The HID chemosensor and Al3+ chelated HID complex are also applied to map Al3+ ions and PA in the living cell. The HID chemosensor and Al3+ chelated HID complex's performance toward detecting Al3+ ions, and PA demonstrates that it might be used as a signaling tool for analyzing biological and environmental samples. Chapter 5: This chapter attempts to introduced a photoluminescence ionic liquid and its application for detecting nitro explosives. Due to the rising menace of illicit actions and pollution aroused by explosive nitroaromatic compounds (NACs), the growth of an adept sensor for detecting these NACs is essential. Herein, in this communication, a photoluminescent IL-assimilated group of uniform materials based on organic salt (GUMBOS) and Nano-GUMBOS has been fabricated by integrating pyrene butyrate with a quaternary phosphonium IL (PbIL) via a simple ion exchange process. Neat PbIL shows a bright cyan color photoluminescence under a 365 nm UV lamp irradiation and is employed as photoluminescence security ink and picric acid (PA) detection among the tested NACs. By simple reprecipitation method, we have developed water-suspended crystalline pyrene assimilated nanoparticles, nPbIL, characterized by various analytical techniques. The PbIL-derived water-suspended nanomaterials, nPbIL, display a robust cyan color excimer-like emission, which turns blue (monomeric) due to adding PA over the other related NACs. This ratiometric cyan-to-blue photoluminescence change is due to the displacement of the anionic pyrene moiety of the nPbIL by the picrate anion. The fabricated organo nanosensor is enormously discerning and responsive towards PA with a LOD of 0.77 nM and is superior to many available in the literature. Additionally, a fluorogenic paper strip-based test kit experiment has been demonstrated to detect and quantify PA selectively in aqueous solvents amongst the other tested NACs. The present contribution evokes a novel approach to developing different IL-based chemosensors for detecting and quantifying various target analytes. Chapter 6: This chapter attempts to demonstrate the role of different mimics of G-series nerve agents and their detection method. There is a pressing need for rapid and accurate recognition of hazardous G-series nerve agents in the solution and vapor phases to protect individuals from undesirable wars and terrorist attacks. However, achieving this goal in practice presents significant challenges. This contribution introduces a specific and selective acridine-based fluorogenic sensor, AMA, which exhibits turn-on behavior from cyan to blue photoluminescence under the exposure of a 365 nm UV lamp in response to diethylchlorophosphate (DCP), a mimic of sarin gas, in both liquid and vapor phases, respectively. The mechanism underlying the identification of DCP using AMA has been elucidated through 1H-NMR titration investigation and HRMS analaysis. The fluorgenic, DCP-specific AMA shows an outstanding selectivity, excellent sensitivity, and a broad linear span of 15-38 μM, with an identification limit of 7.9 nM, which is found to be superb than many chemosensors available in the literature without any interference. To facilitate its potential practical applications, we have introduced an AMA-coated test kit utilizing Whatman-41 filter paper, which can be used as a handy and visual photonic device for on-spot identification of DCP as a mimic for sarin gas under the colonial crowding condition of other analogous analytes. Furthermore, we have demonstrated a fluorogenic dip-stick method to detect and quantify the DCP vapor under the exposure of a 365 nm UV lamp. Chapter VII: Finally, a brief summary of the present thesis and the future perspective from the present research work has been delineated in this chapter.
Open Access
Metal free C- H Functionalization: a unique tool for library synthesis of functionalized 4- pyrimidiones
(University of North Bengal, 2023) Roy, Sanjay; Das, Sajal
The Present Thesis entitled as “Metal free C- H Functionalization: a unique tool for library synthesis of functionalized 4-pyrimidiones” has made some efforts to synthesize the diverse 4 pyrimidones with varied functional groups via different approaches and their applications in medicinal and pharmacological domains. Based on different direction and contents of the work; the thesis has been divided into four chapters. Chapter I: describes an introduction to present work, the “A brief review on C-H functionalization/activation and a literature study regarding the synthesis of 4Hpyrido[ 1,2-a]pyrimidin-4-one derivatives” Summarizes a brief review on pyrimidines and it was further subdivided into following points: 1) Origin, background theory, importance and current status of C-H Functionalization. 2) Use of C-H functionalization techniques in selective functionalization of heterocycles. 3) Importance of 4-pyrimidiones and current literature status 4) Different approaches of its synthesis and further derivatization Chapter II: describes “Microwave-assisted straight forward synthesis of 2-substituted alicyclic fused pyrimidone” We have divulged here a metal free- and MW assisted route to tetrahydro-4H-pyrido[1,2- a]pyrimidin-4-one and dihydropyrrolo[1,2-a]pyrimidin-4(6H)-one has been demonstrated by the reaction of aminoacrylates with lactams in presence of phosphorous pentachloride. This transformation comprises of the sequential formation of three new bonds to produce pyrimidone derivatives under mild reaction conditions and this strategy is well compatible for both electron deficient and electron rich amino-acrylates. This method is amenable for gram scale reaction.
Open Access
Assorted interactions of some antibacterial and anticancer drug molecules and ionic liquids prevaling in supramolecular and solution chemistry investigated by experimental and computational apporach
(University of North Bengal, 2023) Sharma, Antara; Roy, Mahendra Nath
Proposed work covers the Supramolecular Host-Guest Inclusion Complexation of some bioactive molecules and the solute-solvent interaction of amino acids (AA) with ionic liquids (ILs) aiming to compare the molecular interaction existing among these different chemical compounds and resulting molecular synergism in solution phase. Supramolecular assemblage has garnered a huge importance during recent years in the field of drug delivery owing to their significant biocompatibility and excellent potential to expand the spectrum of medical application in pharmaceutical industries and biomedical sciences. The spectroscopic techniques confirm the inclusion complex formation of numerous bioactive molecules and their photophysical properties in solution phase. The UV-Visible, 1H NMR and FT-IR spectroscopy along with mass spectrometry studies supports the formation of inclusion complex. Further, SEM and PXRD analysis implements the qualitative aspect for the generation of supramolecular framework. Thermal and photostability of such assembly have been examined through DSC and UV- visible studies. Computational and theoretical molecular modelling studies of this system reaffirms the results observed in the experimental studies. In this study, inclusion of variety of biologically potent molecules such as, Rodanine, Gemcitabine and Nitrofurantoin have been examined. These compounds find significant medicinal applications. Pharmacological aspect is specifically considered to illustrate the biocompatibility of such biologically active molecules. Molecular recognition, controlled release of a drug and sensing field have received the great consideration under host–guest chemistry. Encapsulation of guest molecules in aqueous phase inside the nanocage of host molecules, such as cyclodextrins and several other water-soluble hosts lights up an advanced technique into the field of molecular recognition (inclusion or complexation) owing to extensive non-covalent interactions. The potent pharmacological activity of bioactive compounds often gets influenced through molecular recognition. Supramolecular host-guest chemistry covers a broad aspect related to the inclusion complex formation between the host and the guest molecules. Hydrophobic nanocage of host molecules are very efficient in binding variety of guest molecules. Over the past few decades, the supramolecular assembly has been extensively investigated in several fields including analytical chemistry and drug-delivery. Cyclodextrins (CDs), are the most suitable host compounds owing to their ability for controlled passage of guest molecules after inclusion complex formation thereby increasing bioavailability of the compound. Ionic liquids (IL) or famously known as molten salts at room temperature currently received great consideration in many areas of chemistry by the researchers across the globe. The most significant characteristic of ILs is the “tunability” of various physical and chemical properties by modifying structure. Many reviews have highlighted the different characteristics of ILs and their potential application. ILs are blessed with some exceptional properties as most of them have a negligible vapor pressure, unparalleled thermal and electrochemical stability, low flammability and commending dissolution properties with large variety of organic/inorganic compounds. ILs mainly consist of different category of cations and anions. They found significant applications as biphasic systems for separation, solvents for many synthetic and catalytic applications, lubricants, extensively in lithium batteries, supercapacitors, actuators, substitute for conventional solvents, alternative for reaction media and active pharmaceutical ingredients. However, the most important characteristic associated with ILs is the “tunability” of their structure. They can easily modify their structure to achieve the specific chemical or electrochemical applications. In order to investigate the stability of proteins, (ILs) are generally employed as a novel medium . Amino acids are considered ideal system for investigating the characteristics of proteins. Further denaturation, solvation and dissociation of enzyme are highly affected by the neighbouring environment. The emergence of assorted interactions is conventionally examined by estimation of the apparent molar volume ( v  ), limiting apparent molar volume ( 0 v  ), molar refraction ( M R ), limiting molar refraction ( 0 M R ) viscosity B coefficients obtained from different physicochemical methodologies. This study features the variety of physicochemical characteristics of amino acid in solution of Ionic liquid in water. This work helps in interpretating the behaviour of these compounds in complex structures of proteins. Here we have selected an Ionic liquid as an additive (electrolyte) as they are blessed with various advantages as a function of concentration, temperature, and ambient pressure. Thermodynamic, viscometry, volumetric, refractometric, surface tension measurements have been carried out as these properties are susceptible towards the solute-solute and solute-solvent interaction. Investigation of these properties greatly support to understand the structure and characteristics of solutes in aqueous medium and gives a reliable explanation for the complicated nature of molecular interactions in various biochemical processes occurring in the human body. Therefore, the objective of this thesis is to (1) investigate and understand the significance of supramolecular recognition owing to their diverse range of applications in varied fields such as pharmaceutical, biomedical sciences etc. (2) understand and evaluate the molecular interactions between ionic liquid and various biomolecules in order to manifest the behaviour of these compounds in complex structures of proteins for further application. Summary of work done Chapter I This chapter contains the details of the research work, their objective, scope and applications in the modern science. A detailed discussion about the scope of selecting the biologically active molecules, cyclodextrins, amino acids and ionic liquids have been included. This chapter consist a brief list of all the techniques of investigations i in the research work. Chapter II This chapter consist the review of the previous works reported by scientists and researchers in the field of supramolecular and solution chemistry around the world. This chapter also includes the detail of theories of investigation. The interactive forces existing among the various molecules have been discussed in detail. The underlying theories of investigating techniques, i.e., theory of 1H NMR , FT-IR, Fluorescence, UV-Visible spectroscopy, Mass spectrometry and Thermogravimetric analysis, Powder X-ray Diffraction, Scanning Electron Microscopy, Surface tension study, Molecular docking study, Antibacterial activity study, Cytotoxicity study, CT-DNA interaction study, Photostability study, Surface tension, Conductivity, Density, Viscosity, Refractive index studies have been discussed thoroughly and the importance of this research work also included in this thesis. Chapter III This chapter presents the experimental section. It includes the details of name, structure, physical properties and applications of the biologically active molecules, cyclodextrins, amino acids, ionic liquids and solvents used in the research work. It consists the briefing about the experimental methodologies. Chapter IV This chapter contains of the encapsulation of rhodanine within the cavity of α-cyclodextrin and β- cyclodextrin. This work has been investigated by spectroscopic, physicochemical methods. Job plots using UV-Visible spectroscopy confirms the 1:1 stoichiometry of the host-guest molecular assembly. This observation was again supported by mass spectrometric analysis. UV-Visible spectroscopy has been employed to calculate association constants for the inclusion complexes using Benesi– Hildebrand method. Thermodynamic parameters have been calculated and it ascertains the thermodynamically spontaneity of the overall inclusion processes. 1H NMR and FT-IR investigations illustrates the quantitative insight on the possible mode of encapsulation in inclusion complexes. Thermal stability of rhodanine on inclusion with cyclodextrins has been evaluated by DSC analysis. Computational study further provides the useful understanding on the inclusion mode of rhodanine molecule into the nanocage of cyclodextrins. The surface morphology of the inclusion complexes was investigated by SEM. Photostability and CT-DNA interaction studies are investigated by UV Visible spectroscopy. Finally, the biological activity namely; cytotoxicity and antimicrobial activity of the inclusion complexes were evaluated and a comparative study was carried out with respect to pure rhodanine. Chapter V This chapter presents the study of the host-guest inclusion complex of gemcitabine with β-cyclodextrin, photostability, CT-DNA study and its biological activity. The prepared complex was characterized by numerous physicochemical and spectroscopic methods. Job plot, and mass spectrometric analysis confirms the 1:1 ratio host-guest inclusion complex. Association constant has been determined by Benesi–Hildebrand method. The Gibb’s free energy of binding has been calculated by evaluating the binding constant which confirms the inclusion process is spontaneous. The mode of inclusion was investigated by 1H NMR and FT-IR spectroscopic analysis. PXRD and SEM analysis have been carried to reaffirm the inclusion complex formation. The enhancement in the photo stability of gemcitabine through complexation was investigated by UV-visible spectroscopic analysis. Molecular docking study presented the most preferred site for binding of gemcitabine molecule within the cavity of β-cyclodextrin. The apoptosis and antibacterial activity of the inclusion complex was investigated in detail and subsequently compared with free gemcitabine. Chapter VI This chapter presents the thorough analysis on the diverse molecular interactions of implausible amino acid, L-leucine (AA) in the aqueous solution of Benzyltriethylammoniun chloride (BTEACl), Benzyltributylammoniun chloride (BTBACl) have been carried out by numerous physicochemical techniques such as Density, Refractive index, Viscosity, Electrical conductivity, at four different temperatures ranging from 298.15 K to 318.15 K. 1HNMR and UV-visible analysis were carried out to investigate the solute- solvent interaction. Association constant for L-Leucine-BTBACl system as well as for L-Leucine-BTEACl system were evaluated to understand the diverse intermolecular interactions in the solution phase using UV-vis spectroscopy. Formation of thermodynamic background owing to different interactions occurring in the ternary mixtures were studied by evaluating the free energies of numerous molecular interactions. The source of various interactions is evaluated by calculating the apparent molar volume (ϕV), limiting apparent molar volume (ϕV0), viscosity Bcoefficients, molar refraction (RM), limiting molar refraction (RM0), molar conductivity (Λ) and surface tension (σ)volume, molar refraction, limiting molar refraction, viscosity B coefficients. Furthermore, adsorption energy, molecular electrostatic potential (MESP) maps and reduced density gradient (RDG) obtained by the application of density functional theory (DFT), have been used to determine the type of interactions which are consistent with the experimental observations. Chapter VII This chapter provides the detail analysis and application of supramolecular complexations of a very important antibiotic and a potential acetylcholine esterase inhibitor nitrofurantoin with α and β-cyclodextrins in aqueous medium. The molecular interactions have been investigated using 1HNMR spectroscopic studies, Job plot confirms the 1:1 stoichiometry of host with guest in the inclusion complexes. Binding constants for the formation of inclusion complexes have been determined using Benesi–Hildebrand method with the help of UV-visible spectroscopy. Free energy of binding of nitrofurantoin with cyclodextrins have been calculated from the binding constant value. This information subsequently determines the thermodynamic feasibility of the encapsulation process. PXRD and SEM studies further supports the inclusion complexes formation. Photo stability, CTDNA interaction studies of the inclusion complexes was carried out using UV-visible spectroscopy. Molecular docking study indicates the most preferable binding orientation of nitrofurantoin within the cavity of cyclodextrins. Chapter VIII This chapter contains the concluding remarks related the research works carried out in this thesis.
Open Access
Polydentate ligand based metal complexes for oxidase activity
(University of North Bengal, 2023) Sahin Reja; Das, Rajesh Kumar
Polydentate ligands have been widely studied due to their ability to form stable and efficient metal complexes. In recent years, there has been growing interest in the use of these metal complexes as catalysts for various chemical reactions, including oxidase activity. Oxidases are enzymes that play a crucial role in biological processes such as cellular respiration and metabolism. The development of synthetic metal complexes with oxidase-like activity has the potential to provide alternative catalysts for these important processes. In this abstract, we discuss the design and synthesis of polydentate ligand based metal complexes for oxidase activity. We focus on the use of N, O-chelating ligands that have been shown to form stable and efficient metal complexes. The metal complexes are characterized using various spectroscopic techniques, and their oxidase activity is evaluated using a variety of assays. We also explore the mechanistic aspects of the oxidase activity of these metal complexes and compare their activity to that of natural oxidase enzymes. Overall, the results demonstrate the potential of polydentate ligand based metal complexes as efficient catalysts for oxidase activity. These complexes may provide a viable alternative to natural oxidase enzymes, and their development could lead to the development of new therapeutic agents and industrial catalysts. Polydentate ligands are molecules that possess multiple donor atoms capable of bonding with a central metal ion. Metal complexes of polydentate ligands have gained significant interest in recent years for their potential applications in various fields, including catalysis, drug design, and biotechnology. In particular, metal complexes of polydentate ligands have been shown to exhibit exceptional oxidase activity, making them an attractive candidate for various oxidation-based reactions. Oxidation is an essential process in biological systems, and the use of metal complexes of polydentate ligands in catalyzing oxidation reactions is a promising area of research. The oxidase activity of these metal complexes can be attributed to the presence of redox-active metal centers, which can donate or accept electrons during the oxidation process. The polydentate ligands stabilize the metal ion and enhance its reactivity, resulting in increased catalytic activity. The catalytic activity of polydentate ligand-based metal complexes for oxidase activity is dependent on several factors, including the types of metal ion, the coordination environment, and the ligand structure. The choice of metal ion plays a significant role in determining the catalytic activity of the complex. Transition metals such as copper, iron, and manganese have been extensively studied for their oxidase activity. These metals possess a variable oxidation state, allowing them to undergo redox reactions during the oxidation process. The coordination environment of the metal ion is another critical factor in determining the oxidase activity of the metal complex. The coordination environment influences the electron transfer properties of the metal ion, which in turn affects the catalytic activity of the complex. Ligands that provide a favorable coordination environment, such as chelating ligands, can enhance the catalytic activity of the complex. The structure of the polydentate ligand also plays a crucial role in determining the catalytic activity of the metal complex. The ligand structure can influence the binding affinity of the ligand for the metal ion, as well as the redox properties of the metal ion. Ligands with multiple donor atoms, such as bidentate and tridentate ligands, have been shown to exhibit excellent catalytic activity due to their ability to stabilize the metal ion. Polydentate ligand-based metal complexes have been shown to exhibit oxidase activity in various reactions, including the oxidation of alcohols, amines, and sulfides. These complexes can also catalyze the oxidation of organic compounds under mild conditions, making them attractive for industrial applications. The use of polydentate ligand-based metal complexes in the oxidation of biomolecules, such as DNA and proteins, is an exciting area of research that holds promise for various biotechnological applications. In conclusion, polydentate ligand-based metal complexes have shown exceptional oxidase activity, making them a promising candidate for various oxidation-based reactions. The catalytic activity of these complexes is dependent on several factors, including the choice of metal ion, the coordination environment, and the ligand structure. The use of these complexes in industrial applications and biotechnology holds significant promise and is an exciting area of research for the future. CHAPTER I Chapter I is an introductory one that describes polydentate ligand based metal complexes as efficient catalysts for oxidase activity and their applications in various fields as well as single crystals, their classification and methods of growth. Object and application of the present research work has also been outlined in this chapter. A brief description of the advantages of different type of technique of crystal growth was described. CHAPTER II Chapter II involves the experimental section briefly describing the chemicals and materials used in completing this research. This chapter also describes the novelty behind choice of organic linkers/ligands used in the works embodied in this thesis. This chapter also contains details of the physico-chemical and spectroscopic techniques, viz., single crystal, FTIR spectroscopy, NMR, and EPR, etc., used for the physicochemical characterization of the synthesized complexes. This chapter also describes the theoretical characterization (DFT, etc) of the hybrid complexes. CHAPTER III 2-(3-(Dimethylamino)propyl)isoindoline-1,3-dione (DAPID) has been synthesized and utilized to produce 3-(1,3-dioxoisoindolin-2-yl)-N,N-dimethyl propan-1-aminium perchlorate (DIDAP). Both DAPID and DIDAP were characterized using different spectroscopic techniques. Structure of the DIDAP has been determined using single crystal X-ray diffraction technique. DIDAP found to self assemble in a helical motif in its supramolecular structure with the aid of different hydrogen bonding, Cg···Cg and short interatomic contacts in the solid state. The compound DIDAP exhibited anticancer activity against the human hepatomas cell line (Hep G2) and the activity was further complemented by performing docking study. In addition, the computational studies have also been performed to examine the chemical reactivity of the compound. Shape index and Curvedness surfaces indicated -stacking with different features in opposed sides of the molecule. Fingerprint plot showed C···C contacts with similar contributions to the crystal packing in comparison with those associated to hydrogen bonds. Enrichment ratios for H···H, O···H and C···C contacts revealed a high propensity to form in the crystal. CHAPTER IV N1, N4- Bis(3-(dimethylamino)propyl)succinamide (DAPS) has been synthesized and utilized to produce 3,3'-[succinylbis(diazaneyl)]bis(N,N,N-trimethylpropan-1-ammonium) perchlorate (SAPAP). Both DAPS and SAPAP were characterized using different spectroscopic techniques. Structure of the SAPAP has been determined using single crystal X-ray diffraction technique. The compound SAPAP had excellent anticancer activity against the human colon carcinoma cell line (HT-29), proposing them as a suitable candidate for future anticancer therapies. Docking, Molecular dynamics simulation, pharmacokinetic predictions and ELISA were also employed to evaluate the inhibitory action of the synthesized compound against the said cancer cell line HT-29. CHAPTER V Keeping in mind the importance of oxidase activity it includes a versatile bioinspired metallocatalyst [Cu2L2(OAc)4] (L = 2-(3-(dimethylamino)propyl)isoindoline-1,3-dione), which has been synthesized and characterized as reported. To the best of our knowledge, a very few articles of paddlewheel type complexes have reported behave as catechol oxidase activity and phenoxazinone synthase activity. The EPR, CV, and ESI Mass analyses collectively support that the complex exhibits such activity via oxygen dependant enzymatic radical pathway. Furthermore, these activities are observed under fully aerobic conditions in which 3,5-di-tert-butylcatechol (3,5-DTBC) and 2-amino phenol (2-AP) are used as model substrates. Michaelis-Menten analysis derived from the pseudo first-order reaction kinetics established that this complex shows prominent catalytic activity towards 3,5- DTBC and 2-AP (Kcat 12.0726×103 h-1 and 6.6654×103 h-1). Molecular electrostatic potential (MEP) diagrams and density functional theory (DFT) reveals the charge density region within the complex while growth inhibition (GI50) and molecular docking study exposes substantial dose dependent anti-leukemic activity against Hep-G2 cell line. Moreover, promising anti-bacterial property was also detected on multi-drug resistant E. coli and B. cereus bacteria. CHAPTER VI In this chapter a promising bioinspired metallocatalyst [Cu(L1)2(L2)] (L1 = P-hydroxybenzoic acid, L2= N1,N1-dimethylpropane-1,3-diamine) has been produced and characterized in accordance with reports.. In the octahedron arrangement around the copper ion, the elongation along one axial direction and one equatorial direction results in a distorted geometry. Molecular assembly shows both inter and intra molecular H-bonding along with C-H---π interactions evident from the Hirshfeld surface analysis. The fingerprint plot discloses the relative contribution of percentage of intermolecular contacts (H⋯H, C⋯H and O⋯H) in the complex. To the best of our knowledge, no one has reported catechol oxidase activity and phenoxazinone synthase activity of Cu(II) complexes with P-hydroxy benzoic acid and propyl amine ligands so far. The EPR, CV, and UV analyses collectively support that the complex exhibits such activity via oxygen dependant enzymatic radical pathway. Furthermore, these activities are observed under fully aerobic conditions in which 3,5-di-tert-butylcatechol (3,5-DTBC) and 2-amino phenol (2-AP) are used as model substrates. Michaelis-Menten analysis derived from the pseudo first-order reaction kinetics established that this complex shows extremely high catalytic activity towards 3,5- DTBC and 2-AP (Kcat 1.729×105 h-1 and 0.260×105 h-1). The suggested mechanism has been supported by UV spectra data in which formation of hydrogen peroxide by observing the appearance of spectral band at λmax 353 nm indicates the active participation of molecular oxygen in the catalytic process. CHAPTER VII Future research in the field of polydentate ligand-based metal complexes with a focus on enhancing oxidase activity holds significant promise. These studies may lead to the development of novel ligands, versatile multifunctional complexes, and applications spanning biotechnology, medicine, energy conversion, and industrial processes, offering innovative solutions with broad-reaching implications for various fields.

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