Department of Chemistry
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Item Open Access Metal-free and Transition Metal Complex Mediated Synthetic Approaches towards the Development of Bioactive Compounds(University of North Bengal, 2023) Mahato Rajani Kanta; Biswas BhaskarBioactive compounds are found in mainly plants kingdom, fruits, vegetables, whole grains and various oil seeds. These compounds are secondary metabolites and provide the good health benefits from ancient times. Therefore, both laboratory and industrial synthetic chemists around the globe became extremely interested in the synthesis of these valuable compounds. Biomimics is a very popular protocol for the synthesis of pharmaceutically important compounds where transition metal complexes have been employed to produce the value-added products day by day. Due to the economic and environmental sustainability the metal-free, additive-free synthetic method has become a promising alternative which gained great interest in the recent decades. Chapter I: This is an introductory chapter of my thesis. Here, the importance of the transition metal complex and bioactive compounds are discussed along with the objectives of the present study. Chapter II: This chapter deals with the the synthesis, structural description, bio-mimics of phenazine oxidase activity and in-vitro antibacterial as well as antiproliferative activity of mononuclear aurum(III) complex, [Au(bpy)Cl2]NO3 (Complex 1) [bpy = 2,2'-bipyridine]. The crystal structure analysis of Complex 1 reveals that Au(III) centre adopts a nearly perfect square planar geometry and theoretical calculations agree well with the structural features. Examination of the catalytic fate for Au(III) complex towards oxidative coupling of o-phenylenediamine (OPD) in acetonitrile displays a good catalytic activity with a high turnover number, kcat = 6.75×102 h-1. The cytotoxic effect of complex 1 against the human lung cancer cell line (A549) is assessed through changes in morphologies observed in different fluorescent staining methods as well as MTT assay. The experimental outcomes ensure that most of the cell destruction of A549 occurs by apoptosis mode. The antibacterial activity of complex 1 against pathogenic bacteria is examined through the nature of variation in mitochondrial trans-membrane potential and depolarization pattern which suggests that destruction of mitochondrial membrane drives the development of antibacterial properties. Chapter III: In this chapter, we demonstrate the synthesis, structural characterization, computational studies and bio-mimics of the phenazine oxidase activity of a newly designed cobalt(III) complex, [Co(dpa)(dpa-H+)(N3)2]Cl2 (complex 2) [dpa = 2,2'- dipyridylamine] under an aerobic condition. The crystal structure analysis reveals that the cobalt(III) centre adopts an octahedral geometry and the complex forms a beautiful supramolecular frameworks through non-covalent interactions. The cobalt(III) catalyst turns out to be a promising catalyst for the oxidative coupling of o-phenylenediamine (OPD) in oxygen-saturated methanol with an excellent turnover number, kcat = 7.85×103 h-1. Spectrophotometric, electrochemical, mass spectrometry and computational analysis ensure that the course of catalysis undergoes through a catalyst-substrate complexation, facilitating the development of cobalt-iminobenzoquinone species in the solution. The computational calculations employing the density functional theory (DFT) throw a light on the mechanistic insights of the phenazine oxidase mimics. ETS-NOCV plots of the reactive intermediates portray the coordination-driven depletion of electron density from the nitrogens of OPD to the cobalt centre leading to the enhancement of electrophilic character on para-positioned C-atoms with respect to N-atoms of OPD, thereby catalysing the nucleophilic attack by second OPD to produce the oxidation product, 2,3-diaminophenazine (DAP). Interestingly, we are able to isolate the oxidation product of the OPD oxidation reaction as a hydrated chloride salt, DAPH+Cl- .3H2O (2). The crystal engineering perspectives of 2 attribute the intriguing fate of the secondary chlorides to the stabilization of the oxidation product in the crystalline phase. Chapter IV: This chapter highlights the phenazine scaffolds which are the versatile secondary metabolites of bacterial origin. It functions in the biological control of plant pathogens and contributes to the producing strains‟ ecological fitness and pathogenicity. In light of the excellent therapeutic properties of phenazine, we have synthesized a hydrated 2,3-diaminophenazinium chloride (DAPH+Cl- .3H2O) through direct catalytic oxidation of o-phenylenediamine with a cobalt(III) complex, [Co(dpa)(dpa-H+)(N3)2]Cl2 (complex 2) [dpa = 2,2'-dipyridylamine] in ethanol under aerobic condition. The crystal structure, molecular complexity and supramolecular aspects of DAPH+Cl- were confirmed and elucidated with different spectroscopic methods and single crystal X-ray structural analysis. Crystal engineering study on DAPH+Cl- exhibits a fascinating formation of (H2O)2…Cl-…(H2O) cluster and energy framework analysis defines the role of chloride ions in the stabilization of DAPH+Cl-. The bactericidal efficiency of the compound has been testified against a few clinical bacteria like Streptococcus pneumoniae, Escherichia coli, and K. pneumoniae using the disc diffusion method and the results of the high inhibition zone suggest its excellent antibacterial properties. The phenazinium chloride exhibits a significant percentage of cell viability and a considerable inhibition property against SARS-CoV-2 at non-cytotoxic concentration compared to remdesivir. Molecular docking studies estimate a good binding propensity of DAPH+Cl- with non-structural proteins (nsp2 and nsp7-nsp-8) and the main protease (Mpro) of SARS-CoV-2. The molecular dynamics (MD) simulation studies attribute the conformationally stable structures of the DAPH+Cl- bound Mpro and nsp2, nsp7-nsp8 complexes as evident from the considerable binding energy values, –19.2±0.3, –25.7±0.1, and –24.5±0.7 kcal/mol, respectively. Chapter V: This chapter addresses a metal-free methodology for the synthesis of 1,2-disubstituted and 2-substituted benzimidazoleswith high to excellent yields has been developed. The course of synthesis involves easy work-up, straightforward purification, inexpensive reaction setup, and wide substrate scope under extremely mild and operationally simple conditions which makes the synthetic strategy more lucrative, practical and reliable. The serious challenge to carry out these reactions in a pure aqueous medium has been achieved at 75 °C in the presence of air bubbles. The applicability of this operationally simple and metal-free synthetic approach for the gram-scale synthesis of benzimidazole derivatives with good yield (~74%) further strengthens its potentiality for synthesis at an industrial scale. Chapter VI: Here, we report the solvent-free green synthesis of two Schiff bases, (E)-2-((2-hydroxy-3-methoxybenzylidene)amino)-4-methylphenol (H2L1) and (E)-2-((2-hydroxybenzylidene) amino)-4-methylphenol (H2L2), and their inclusion complexes with β-cyclodextrin (β-CD). The encapsulation phenomenon, structural characteristics and hydrolytic stabilities of the H2L1, H2L2 and their inclusion complexes are determined with a suite of spectroscopic, analytical and crystallographic analyses. Dose and time-dependent cytotoxicity study of H2L1-β-CD and H2L2-β-CD against two breast cancer cell lines, Michigan Cancer Foundation-7 (MCF-7) and Metastatic mammary adenocarcinoma1 (MDA-MB-231), exhibit excellent inhibitory activity with significant non-cytotoxic concentrations and ensure a multifold elevation of bio-potency than the parent Schiff base compounds. The annexin-V assay determines the efficacy of these inclusion complexes to trigger apoptosis, suggesting that H2L2-β-CD possesses better efficacy as an anti-cancer drug. To the best of our knowledge, we, for the first time, report the inclusion of nanocrystalline Schiff bases into β-CD for multifold enrichment of bio-potency. Page | iv Chapter VII: Finally, this chapter has defined the conclusion outlook and the future range of the research endeavour.Item Open Access Explorative studies towards the synthesis of biocogically active carbocyclic and heterocyclic systems(University of North Bengal, 2023) Kundu Tandra; Ghosh PranabBeginning from the summer days of 2018, it took nearly five long years for me to finish the research work incorporated in this thesis entitled “EXPLORATIVE STUDIES TOWARDS THE SYNTHESIS OF BIOLOGICALLY ACTIVE CARBOCYCLIC AND HETEROCYCLIC SYSTEMS”. The work is mainly focused on development of efficient and environment benign methodologies for the synthesis of carbocyclic and heterocyclic compounds. The entire work depicted in this thesis has been divided into five chapters. In the beginning, Chapter I deals with a brief review on the development of novel reaction protocols for the transformation reaction on carbocyclic and heterocyclic compounds. These compounds have extensively been used in the designing of various pharmaceutically significant compounds. Apart from this, they are considered to be powerful building blocks for the construction of biologically active compounds. In Chapter II bio-based, environmental benign media ethyl lactate was used in synthesis of verities of unsymmetrical azobenzenes. The methodology proceeds without the use of toxic transition metal catalyst and avoids harsh reaction conditions. A green methodology is thus reported with synthesis of good yield of the product. In Chapter III a very simple, efficient and environment benign protocol for the synthesis of diverse array of 2,3-dihydroquinazolin-4(1H)-ones using wide range of aldehydes, isatoic anhydride with ammonium acetate was described. Eucalyptol, a bio-degradable solvent was used in this methodology which itself acted as a catalyst thus avoiding the use of toxic metals or hazardous materials. The activity of this bio-based reaction medium, eucalyptol was further extended towards the synthesis of isoxazolone derivatives using wide range of aldehydes, ethyl acetoacetate and hydroxyl amine hydrochloride. In Chapter IV synthesis of 1-amidoalkyl-2-naphthol and 1-thioamidoalkyl-2-naphthol is discussed. These derivatives carry great importance now a day as because they can easily be transformed to biologically potent heterocyclic entities via hydrolysis of amidic groups. In this chapter humic acid has been explored as catalyst with the association of operational simplicity of the method, mild reaction conditions, shorter reaction time. By this process, good yield of desired product 1-amidoalkyl-2-napthol is obtained by using aldehyde, β- napthol and acetamide. And 1-thioamidoalkyl-2-napthol is also prepared by using aldehyde, β-napthol and thioacetamide. In Chapter V inexpensive, environmental benign catalyst boric acid was used in synthesis of verities of bis-lawsones. The methodology proceeds without the use of toxic metal catalyst and avoids harsh reaction conditions. A green methodology is thus reported with synthesis of good yield of the product by reacting lawsone with wide range of aldehydes.Item Open Access Polydentate ligands and transition metal complexes : photophysics and catalysis(University of North Bengal, 2013) Pariyar, Anand; Bandyopadhyay, P; Biswas, A. N.A brief overview of polydentate ligands and their metal complexes, with special emphasis on their photophysical and catalytic behaviour, has been made. In this background, the objective, scope, and application of the present investigation have been described in Chapter I. A series of novel polydentate macrocyclic corrole ligands has been synthesized and described in chapter II. The photophysical properties of the newly synthesized family of substituted nitrophenyl free base A2B-corroles have been studied. The metal ion sensing abilities of the free base ligands are explored. The A2B corroles emerge as efficient polydentate fluorophore system for selective Hg(II) ion detection in solution. Among all the corroles, the free base 10-(tridecyloxyphenyl)- 5,15-bis(nitrophenyl)corrole substituted with a long chain has been found to exhibit the highest Hg(II) sensing ability. High guest count (up to three mercuric ions per corrole) with a high association constant is observed. The experimental evidences show that the emission intensity quenches with the addition of Hg(II) ion, initially via metal coordination and subsequently through exciplex formation. This is the first report of exciplex formation of corroles with mercury ions. The results obtained will help to improve the design of sensors for the direct determination of Hg(II) ions present in ultra low concentration. The synthesis and characterization of new iron complex of 5,10,15 tris- (difluorophenyl)corrole have been described in chapter III. The catalytic properties of newly synthesized 5,10,15-tris(difluorophenyl)iron(IV)chloride complex [(tdfc)FeIVCl] with benign tert-butylhydroperoxide as the terminal oxidant has been evaluated. The [(tdfc)FeIVCl] /t-BuOOH system has been found to efficiently catalyze the oxidation of alkanes, alkenes, alkylbenzene and alcohols at room temperature. The homolytic cleavage of the O-O bond of tert-butylhydroperoxide by the catalyst is observed and the oxygenates have been shown to be derived from organoperoxides. The results clearly indicates that the main role of the iron(IV) corrole complex is the activation of alkyl hydroperoxide rather than oxygen atom transfer (OAT). Selective hydroxylation of unactivated C-H bonds of alkanes has also been realized using catalyst [(tdfc)FeIVCl] with m-chloroperbenzoic acid as the terminal oxidant. Chapter IV describes iron-corrole complex 5,10,15-tris(pentafluorophenyl) iron(IV) chloride [(tpfc)FeIVCl] catalyzed epoxidation of olefins in ionic liquid [BMIM]PF6 medium at room temperature with different terminal oxidants. For the first time, metallocorrole catalyzed epoxidation of a series of conjugated and nonconjugated olefins has been undertaken in ionic liquid ([BMIM]PF6) medium at room temperature using different terminal oxidants such as t-BuOOH, PhIO and aqueous NaOCl. The product selectivity achieved in ionic liquid medium shows remarkable improvement over those obtained in molecular solvents. The highest product yield is achieved by a biphasic system involving ionic liquid with aqueous NaOCl as the terminal oxidant. The biphasic system provides easy recovery and recycling of the catalysts without any modification of structure. The studies of homoleptic copper dipyrromethene complex has been discussed in Chapter V. The bidentate dipyrromethene complex of Cu(II) has been synthesized. The X-ray crystal structure of [Cu(II)(dpm)2] has been determined. The neutral bis(5- (4-nitrophenyl)dipyrromethene)Cu(II) complex [Cu(II)(dpm)2] is found to undergo ligand centred oxidation process to give [Cu(II)(dpm)2 •+], which has been substantiated by combined experimental and theoretical investigation. The metal bound ligand centred oxidation at high potential is of irreversible nature. The DFT calculation reveals increase in spin density over ligand moiety in the one electron oxidized [Cu(II)(dpm)2] complex, suggesting radical character of the ligand. Complex [Cu(II)(dpm)2] is found to catalyze C-H activation of alkanes and alkenes with tertbutylhydroperoxide at room temperature. The oxidation under ambient condition with benign terminal oxidant clearly indicates the involvement of the ligand based oxidation of [Cu(II)(dpm)2] in catalyzing C-H activation at room temperature. Chapter VI presents the ligand co-opertative effect in metal complex catalyzed oxidation elaborating the role of redox-neutral or redox-innocent cyclam ligand (1,4,8,11-tetraazacyclotetradecane) in C-H bond activation. The chapter describes efficient and selective hydroxylation of cycloalkanes (R-H→R-OH) catalyzed by high spin non-heme iron(III) cyclam complex [FeIII(cyclam)(OTf)2]OTf with hydrogen peroxide under mild condition. Remarkable increase in conversion and selectivity has been achieved by the addition of acid suggesting acid promoted O-O bond heterolysis. The efficient functional model of monoxygenase group of enzyme based on a highspin iron(III) complex of cyclam [FeIII(cyclam)(OTf)2]OTf provides the first example wherein a non-heme iron complex catalyzes alkane hydroxylation with 100% selectivity. The intercalation of cis-[Fe(III)(cyclam)Cl2]Cl (cyclam = 1,4,8,11- tetraazacyclo- tetradecane) complex on smectite montmorillonite K-10 is described in chapter VII. The intercalated solid is fully characterized using powder EDXRF, XRD, TGA, IR and UV-Visible analysis. Complex cis-[Fe(III)(cyclam)Cl2]Cl intercalated into Montmorillonite K-10 emerges as an efficient catalyst for selective hydroxylation (R-H→R-OH) of alkanes using environmentally benign H2O2 at room temperature. Cyclohexane and adamantane are selectively oxidized to their corresponding alcohols with remarkably high turnover number (198 and 265 respectively). Relative reaction without the clay matrix proves that a cooperative effect between the constituents of the intercalated catalyst is responsible for the enhanced selectivity.Item Open Access Synthesis, characterization and applications of some nanoparticles supplemented with living and chemical substances(University of North Bengal, 2022) Das, Debasmita; Roy, Mahendra NathItem Open Access Synthesis and characterisation of host-guest inclusion complexes for better applications by physicochemical techniques(University of North Bengal, 2022-06) Bomzan, Pranish; Roy, Mahendra NathItem Open Access Theoretical study of spin polarized electrical and thermal transport properties of mesoscopic systems(University of North Bengal, 2022-01) Sarkar, Sudip; Misra, AnirbanItem Open Access Synthesis of bioactive organic heterocyclic compounds using novel catalysts(University of North Bengal, 2022-09) Dey, Sourav; Ghosh, PranabItem Open Access Exploration of Catalytic Activities of Some Transition Metal Borates for Green Synthesis of Nitrogen Containing Heterocyclic Compounds(University of North Bengal, 2022-07) Chettri, Sailesh; Sinha, Biswajit; Brahman, DhirajItem Open Access Methodological approach on carbon-hetero bond formation reaction(University of North Bengal, 2022) Mukherjee, Suvodip; Ghosh, PranabItem Open Access Organic transformations using novel catalytic system(University of North Bengal, 2022) Basak, Puja; Ghosh, Pranab