Department of Chemistry

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    Studies on carbene and ketene reactions
    (University of North Bengal, 1982) Sarkar, Ranjit Kumar; Roy, S. C.
    Studies on carbene and ketene reactions have be~n submitted in tbree different paJ;ts of this thesis. ~ART ONE Studies on oarbene reactions Chapter - I. Introduction to Oarbene Chemistry In this chapter history of carbene generation and a general introduction have been given at the outset. Next section of the_ chapter surveys different methods of ~arbene - ~ . - generation with special emphasis on keto carbene generation. Addition of .. ketocarbenes to olefins have beeR discussed and mechanisms of these addition reaction have also been cited. Subsequently a background survey of a few reactions . - . involving cleavage and rearrangement of the ,_cyclopropane ring system have been furnished. Theoretical aspects of the oases have been discussed briefly. The singlet and triplet states and structure of Q.'re carbenes ia discussed. Spectroscopic e. videnc. e and chemical evidences with reference to 0-H insertion reactions and adclition to 0 = C bonds have been described• Some factors influencing the reactivity of carbenes have been illustrated in this introductory discussion. .Q!a.pter - :g_ Cleavage of cyclopropane ring In this che.p~er preparation of two cy~loprqpane ~ deriv~t~ves ~a ketooarbene addition to cyclohex/.ne }f>/ and to dibydronaphthalene (B). have been described. . [A] [B] Qyolopropane adduct (A) on ·treatment with Grignard reagent (Metbylmagnesium iodide) a Grignard adduct is formed which on acid treatinent gave a homoallylio .halide derivative ( 9). Compound (A) on treatment with phenyl magnesium bromide gave a Grignard adduct and this on acid treatment gave the - . - compound (D). Action of vieylmagnesium bromide on compound (A) £ollowed by acid treatment was studied when a solid compound (E) was found. Compound (0) on oxymercuration-demercuration reaction yielded an alcohol (F). Methyl magnesium iodide treatment of (B) followed by acid treatment of the Grignard adduct thus obtained failed complete~. In a later section of this chapter discussions on the basis of the above experimental results and their ' I I. ·' analysis, spectroscopic data such a.s IR, NMR and mass spectra are given. On the· basis of a.na],yses and sp·ectroscopic studies . the structures .of the compounds ( 0), (D) and (F) have been established. [c] ( D] [E}_ The last section deals with the experimental details of the reactions to obtain tile above compounds. Onapter - .III Decomposition of diazotetralone . In this chapter preparation of c:t -diazotetralone has -been described. Ultra-violet spectral studies on the decomposition of ~-diazotetralone·were undertaken and concluded that the application of·copper catalyst helpa thermal decomposition of 0\ -diazotetralo.ne alone. But it has· been f'otind that thermal decomposition of -ol. -diazotetra- ~· - .. lone in presence of copper catalYst and an olefin(~bstituted cinnamio .este~s, metAyl crotonate, cyclohexene etc) failed to give any cyclopropane adduct whereas dimerisation of d.. -diazotetraione was observed. Reaction ot d, -diazotetl,'EI.lone Vii th dimethyl tWJlirate ~ in presence of catalyst {copper) and in absence of catalyst gave the cy"clopropane adduct (G). Structure of this cycloprop~e adduct (G) was fully characterised by the help of analysia, IR, NMR an4 mass spectra and may be written as cooc. H.3 0 C.OOC.H3 Experimental .details of these reactions have been described .in the concluding part of. this chapter. Studies on Reactions. of Diazometbane ChaRter - I A· short review on diazomethane addition . · to olefin. · ~n this chapter a very brief survey only on the 1,3-dipolar addition of dia.zometb.ane with olefin and some - - . cyclopropanatiop. reactions of diazomet.ha.ne with olefin. have been describ·eci. Chapter- II Reactions of diazomethane with some olefiri.s . In tnis chapter reactions of diazom~thane with some sUbs~ituted cinnamic !!Sters in presence of d~-fferent _catalysts have been described. Diazomethane on reaction with o-m¢thoxy and p~methoxy einnamic esters, both in presence of catalysts palladium acetate and uracyl acetate gave cyclopropane derivative (H) a.n,d· (I) respectiYelY- in good yield • Reactions of diazomethane in presence- of same catalysts .o-chloro, p..;chloro; o"-ni tro and ·o~_ ..ooyano cinnamic esters gave 2-pyrazoline (J), (K), (L), (lVI) respe·c~±vely. 1-pyrazoiine ~N) and (0) were isolated_ in caseQ of reaction o£ d;tazomet.b.ane with trans-phenyl methyl cinnamate trans-naphthyl, o-cbloro methyl c;Jinamate respeotive~y in presence of s&UD.e cata:cy-sts. In the, results and discu. ssions section-the charact ·erisatiori.. with the help of analysis, IR, NMR ·and mass spectral datE+ have b~en described and· their structure·s have been proposed as tollows. 0 - - CH---'CH- COOCt-\3 . R \ / - CI-t~ 0 -. R.' - . I C.H- C ;_ COOC H'3 _R I I C.H NH ~ '/ _N H; R = o-OCH3 I; R ... p~OCR.3 ~(X) J, K, L, M, R R R R -- o~c1, .;,. _-p-01, ::I o-'lii02, -H, R' = H R~ = H R' = H R' -=_ON Structures of eompounds · (N) and ( 0) are assigaed as follows . ' . ' -[:.N 1 [ol Experimental· details are prese~ted in the next seotiQn of ,·, -- t}J.is :chapter. ,., . . /' . PART THR~- · · -Studies on· Ketene. R~~te!:_- II • · Reactions of Ketenes . In this chapter description of our attempts ·of_ preparing certain ketenes and their- attempted reactions. •' 1 • '. have· been ·furnished. Cyclohexa:p.e- carboxylic acid -was ": -l • - . . • prepared from cyclohexanol with formic ·acid and concentrated ~Ulphuric acid •.. Then this acid wa.s obnverted into. its acid . . . ' - . ' ·chloride. Dicbloroacetyl cblo;ride all.d tricbloroac~tyl Qblorid.e was. prepare_d -from the respective acids. C.OdH. 0 HCOOH Co"'e· H2 S04- Cyolohexane carboxylic acid- cbloride on refl uiing wi.th _diffe~ent olefine in presence ·of t.rieteyiamine affordeddilner (P) only, other I>roduc:ts could not be cbara.oterized.- QcocL + )c . c( 0 [P] (XII) Dichloroacetyl chloride on reflu.xing wi' t .b. olefin in presence of triethyl~mine, similarly, are unsuccessful . coiilpletely. ·Here al~o dimer is the cbara.cterisable product. Trich.'L0roacetyl chloride was tre·ated with activated zihc dust in· pres.m·oe of olefine and .. Ot -tetrald.ne but these ' '· raaotions also· failed to yield. a.rf3' · conc~usive resUlt. ·. EKperimental details have been described in·last· part .. o'f this chapter.
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    Virtual screening, molecular docking studies admet properties dencity functional theory and 2D-QSar modeling to design potential inhibitors
    (University of North Bengal, 2023) Sarkar, Subhajit; Das, Rajesh Kumar
    Conventional drug design processes use trial and error methods for screening natural and synthetic compounds. It costs millions of dollars and very long time approximately 10-15 years. To meet these severe challenges nowadays pharmaceutical companies rely very much on computer-aided design techniques to discover potential drugs. Throughout the research work, various natural inhibitors that regulate a variety of physiochemical processes in bacteria and human beings have been studied. Derivatives of them have been designed and developed in such a way that they may be used as potent drugs producing no or minimal side effects and overcome the antibiotic resistance property. We hope, in silico drug design processes followed in different studies would save precious time and millions of dollars, leading to novel alternate therapeutics. CHAPTER I Microorganism including bacterium communicates among themselves through a unique mechanism called quorum sensing. The different QS pathways of Gram-negative and Gram-positive bacteria have been discussed elaborately in this chapter. Bacteria develop antibiotic resistance through various mechanisms among them biofilm formation is regulated by quorum sensing. Quorum sensing inhibitors (QSIs) interrupt the expression of virulence factors production and inhibit biofilm formation without killing bacteria or inhibiting bacterial growth. The QSIs are of two types natural and synthetic. It includes a details study of different types of QSIs and inhibition mechanisms. Hamamelitannin (HAM) a phytochemical has the capability to inhibit Staphylococcus aureus agr QS system. Our approach is to modify HAM by incorporating an active functional group for better efficacy. We have followed the same in silico process in another study where the target protein was chosen as heat shock protein 90 rather known as HSP90 and found in all species ranging from bacteria to humans. Over expression of this client protein may lead to several refractory diseases including cancer, inflammation, neurodegeneration, and viral infection. It discussed the various roles and functions of HSP90 in the human body. Besides, we have performed quantitative structure activity relationship (QSAR) analysis in two different cases. Phophodiesterase-4 (PDE4) and lysine-specific demethylase 1 (LSD1) are two key proteins that regulate various physiochemical processes in humans. Over expression of PDE4 may lead to severe diseases including chronic obstructive pulmonary disorder (COPD), and cardiovascular disease whereas unregulated LSD1 may result in tumorigenesis, neurodegenerative disorders, viral infection, diabetes, fibrosis, and various types of cancers including prostate, gastric, breast, lung, and leukemia. Separate studies of QSAR on these two proteins help us to identify best-fitted designed molecules as potent inhibitors of the target proteins. Detailed information on both PDE4 and LSD1 is described here. CHAPTER II The major in silico techniques that are widely popular among researchers are molecular docking, density functional theory (DFT) calculation, molecular docking, molecular dynamics (MD) simulations, and absorption, distribution, metabolism, excretion, toxicity (ADMET) prediction. Collective use of all of the mentioned computer aided techniques is necessary to predict potential QS inhibitors. It includes methodologies of all of the above mentioned techniques in detail. CHAPTER III A set of 26 derivative compounds have been designed by incorporation of different active functional groups at various positions of hamamelitannin (HAM) shown here. All structures were optimized using Gaussian software. Gaussian outputs were used to perform molecular docking with the help of Autodock Vina software. Docking results of HAM with three target proteins of PDB ID 4AE5, 4G4K, and 2FNP exhibited the binding energy value of -6.7, -6.5 and -6.6 kcal/mol respectively. Out of 26 derivatives of HAM, 14 compounds have shown higher binding affinity than that of HAM. The above in silico studies concluded that 14 ligands could be developed as effective inhibitors of S. aureus biofilm formation and considered for in vitro and in vivo analysis. CHAPTER IV It includes the natural product oroidin (ODN) considered a potent inhibitor of heat shock protein 90 (Hsp90) and its derivatives had been designed by substituting various functional groups in the various position of five membered rings. A library of thirty nine derivatives was designed by introducing various functional groups such that amide, amine, phosphate, hydroxyl, fluorine, methoxy, and carboxylic acid in the active pharmacophore of oroidin. All the analyses expressed that seven analogues possessed better chemical activity and docking capabilities than that of the source molecule ODN. These seven computationally designed derivatives may be used as novel beneficial agents in various cancer therapies including breast, ovarian, colon, pancreas, liver carcinoma, and leukemia treatments, and could be considered to develop as effective anticancer drug candidates in the future. CHAPTER V Keeping in mind the importance of PDE4 inhibitors it includes a study where a quantitative structure-activity relationship (QSAR) modeling method was performed to develop a standard model on a dataset of sixty-six significant PDE4A inhibitors encompassing common scaffolds in pyrazolo-oxazine, and imidazo-pyridazine compounds. According to QSARINS software, the model comprises three descriptors namely MoRSEM11, MoRSEP26and MoRSEC11 were found to be the best ones. The three descriptor model which was employed to predict pIC50 values as the studied response exhibited good R2 (0.8185), and F (73.658) values. Internal validation parameters Q2loo= 0.7845, Q2LMO= 0.7771and external validation parameters Q2F1= 0.8277, Q2F2= 0.8246, Q2F3= 0.8626, confirmed the stability and robustness of the developed model. On the basis of this model equation, pIC50 values of thirty-nine designed compounds were calculated. The potent lead molecules, predicted from the QSAR model, were further investigated by performing in silico approaches such as molecular docking, molecular dynamics simulation, bioavailability assessments, and toxicity prediction. The study revealed that the eight compounds possessed potent PDE4A inhibitory activity and might be considered as future drugs subject to the viability of in situ and in vivo proceedings. CHAPTER VI In this chapter quantitative structure activity relationship (QSAR) model was built from a dataset of 44 compounds as LSD1 inhibitors. The best 10 compounds have fully satisfied all the criteria of drug-like properties and these designed lead molecules would have more potency to treat LSD1 target after going through in vivo and in vitro analysis. CHAPTER VII 3D-QSAR analysis and application of ANN validation in CADD to design potential inhibitors of many critical diseases in future.
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    Metal-free and Transition Metal Complex Mediated Synthetic Approaches towards the Development of Bioactive Compounds
    (University of North Bengal, 2023) Mahato Rajani Kanta; Biswas Bhaskar
    Bioactive 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.
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    Explorative studies towards the synthesis of biocogically active carbocyclic and heterocyclic systems
    (University of North Bengal, 2023) Kundu Tandra; Ghosh Pranab
    Beginning 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.
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    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.
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    Synthesis, characterization and applications of some nanoparticles supplemented with living and chemical substances
    (University of North Bengal, 2022) Das, Debasmita; Roy, Mahendra Nath
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    Synthesis and characterisation of host-guest inclusion complexes for better applications by physicochemical techniques
    (University of North Bengal, 2022-06) Bomzan, Pranish; Roy, Mahendra Nath
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    Theoretical study of spin polarized electrical and thermal transport properties of mesoscopic systems
    (University of North Bengal, 2022-01) Sarkar, Sudip; Misra, Anirban
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    Synthesis of bioactive organic heterocyclic compounds using novel catalysts
    (University of North Bengal, 2022-09) Dey, Sourav; Ghosh, Pranab