PhD Theses (Chemistry)

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Expeditious Reactivity of Sulfoximines and o-Alkynylanilines Towards the Construction of C-C and C-Heteroatom Bonds
(2024) Chakraborty, Nikita
The contents embodied in this thesis is divided into five chapters including one introductory chapter based on experimental results obtained during the research period. The introductory chapter represents an overview of the utility of sulfoximines and o-alkynylanilines towards the construction of C-C and C-heteroatom bonds. This includes a brief discussion about all the possible reactive sites present in sulfoximines and their possibility of forming different functionalized molecular complexities. Similarly, the reactivity of o-alkynylanilines for the formation of diverse heterocyclic scaffolds has been discussed.
Effects of Addictives on Bio-inspired mineralization of CaCO3 and application of its Composites
(2022) Paul, Debojit
The thesis entitled “Effect of additives on bio-inspired mineralization of CaCO3 and application of its composites” is categorized into eight chapters based on the results obtained by experimental works performed during the research period.
Photo and Electrochemical Strategies to C-N Bond Formation
(2024) Alam, Tipu
The contents of this thesis have been divided into six chapters based on the experimental works performed and results obtained during the research period. The introductory chapter of the thesis represents a summary of ‘Photo and Electrochemical Strategies to CN Bond Formation’. For simplicity and brevity, Chapter I is divided into two parts. Chapter IA includes a photochemical CN bond formation via difunctionalization of alkenes and indoles, whereas, Chapter IB deals with electrochemical approach for the CN bond construction. The subsections of Chapter IA and IB are based on the mode of reactivity of difunctionalization and cross-coupling reactions.
Self-assemblies of Sulphonamide Derived Urea, Thiourea and Conformational Isomers of a Mercury complex
(2024) Nath, Jitendra
The thesis described various solid-state assemblies of urea and thiourea derivatives of sulfa-drugs that had sulphonamide functional group as part of the structural backbone. The hydrogen bonded assemblies of these compounds, solvates, and polymorphic solvates were structurally characterized. The role of dimeric hydrogen bonded moieties within those self-assemblies to modulate the number of solvent molecules in solvates and also providing an aid to understand polymorphs were discussed. A theoretical calculation on dimeric hydrogen bonded assemblies could establish the observed trends in the melting points in a series of positional isomeric compounds. The utilities of these thiourea or urea-based compounds to encapsulate tetrabutylammonium halides, and also in the detection of fluoride ions in solution were described in the thesis. The content had descriptions on the conformational isomers of a mercury complex involving a thiourea based compound linked to an anthracenyl unit where distinctions of the isomers in solution as well as in solid states could be possible. The conformational changes observed from experimental studies were also complemented by theoretical energy optimizations to provide insights to the structure-property relationships
N-Propargylamines: A Key Precursor for the Construction of Functionalized Nitrogen and Sulfur Heterocycles
(2023) Behera, Bipin Kumar
The contents of the present thesis have been divided into five chapters based on the results achieved from the experimental works performed during the entire course of the PhD research programme. Chapter 1 highlights an overview of N-propargylamines. This includes a brief discussion about synthetic reactivity and utility of N-propargylamines. It emphasizes on its unique structure bearing both free amine and an alkyne group, thus focusing on its dual role either as nucleophile and electrophile or as N-centered radical donor and radical acceptor. Chapter 2 highlights an efficient methodology developed for the synthesis of tetra- and penta-substituted pyrroles via N-centered radical initiated oxidative self-dimerization of N-propargylamines catalyzed by silver benzoate in the presence of K2S2O8. The protocol provides a simple route for the synthesis of highly functionalized pyrroles with two carbonyl groups in the side chain. The methodology can be extended towards the synthesis of fluorescent pyrrolo[3,4-d]pyridazine derivatives. Chapter 3 represents an efficient methodology for the synthesis of both di- and trisubstituted thiazol-2-ones from N-propargylamines via [3,3]-sigmatropic rearrangement/5-exo-dig cyclization. The protocol utilizes silver(I) trifluoromethanethiolate (AgSCF3) as a C–S source and eco-friendly H2O as nucleophile under open air condition. The methodology can be extended for the synthesis of bioactive analog of thiozole-2-thione derivatives and photophysical properties have been studied for some synthesized compounds. Chapter 4 describes an efficient methodology developed for the synthesis of methylene-dihydrothiazole derivatives via Michael-addition followed by hydrothiolation of N-propargylamines. The protocol utilizes silver(I)trifluoromethanethiolate (AgSCF3) as a S source and malonate ester derivatives as nucleophiles. The reaction is compatible with many functional groups with moderated to good yield. Chapter 5 highlights a facile and efficient synthesis of structurally diversified 2-pyridones is demonstrated using the [4+2] annulation of in situ generated azadienes from N-propargylamines and active-methylene compounds. The reaction is promoted by an inorganic base giving moderate to good yields. The developed methodology is applicable for direct and formal synthesis of various bioactive molecules. The synthetic utility of the protocol was also illustrated by late stage functionalization of the products.
Studies Towards C-C and C-N Bond Formation using Strained Rings: A Probe for Heterocycle Formation
(2024) Karjee, Pallab
The thesis is organized into four chapters. The initial chapter delineates a tandem C–N bond formation for the oxidative annulation of indolines with aziridines, utilizing a combination of DDQ and NaOCl under ambient conditions. The second chapter addresses the annulative coupling of donor-acceptor cyclopropanes with cyclic secondary amines, employing Ni(OTf)2 and visible light-assisted eosin Y catalysis for tandem C–N and C–C bond formation. The third chapter focuses on the coupling of cyclic secondary amines with donor-acceptor cyclopropanes using MgI2 and Mn(OAc)3•2H2O, leading to the synthesis of fused indolizine derivatives. The fourth chapter showcases an efficient annulation of in situ formed azaoxyallyl cations with diaziridines, yielding 1,2,4-triazines at room temperature.
Site-Selective C-H Functionalization of Indoles: Studies towards C-C and C-N Bond Formation
(2024) Banerjee, Sonbidya
The thesis is structured into four chapters. The first chapter describes a Ru-catalyzed regioselective C-N bond formation of indolines and carbazole with acyl azides via C7(sp2)-H activation followed by an intramolecular C-N bond formation for the construction of 7- aminoindoline and 1-aminocarbazole scaffolds. The second chapter deals with Cu-catalyzed C7- selective C-H/N-H cross-dehydrogenative coupling of indolines and azaindoles with sulfoximines. The third chapter demonstrates a Rh-catalyzed site-selective C7 and C6 dual C-H functionalization of indolines expending 7-azabenzonorbornaiene for the formation of functionalized pyrrolocarbazoles. The fourth chapter focuses on Pd-catalyzed weak-coordination facilitated C4- selective redox-neutral nitration of indoles with tert-butyl nitrite under aerobic oxidation catalysis.
Expeditious Thermal(Photo) Induced Functionalization/Annulation: En route to N-Heterocycles
(2024) Khandelia, Tamanna
The content of the thesis has been divided into four chapters. The thesis streamlines the synthesis of aromatic and non-aromatic N-heterocycles. It contributes towards the facile formation of C−C, C−N, C−O and C−S bonds using o-alkynylanilines, maleimides, 2-aryl quinoxalines, (benz)imidazoles, boronic acids and disulfides. Chapter I introduces transition metal induced (thermal) and photochemical construction of C−C and C−Heteroatom bonds. The mechanism involved in both transition metal induced (thermal) and photochemical approach are discussed. Both the processes are explained in details with the help of suitable examples. Chapter II describes a Cu(I) mediated cascade cyclization/annulation of unprotected o-alkynylanilines with maleimides in one-pot. The protocol offers sequential formation of one C−N and two C−C bonds to deliver fused benzo[a]carbazoles having free NH skeletons. The annulated products have been exploited towards various applications. Chapter III describes a Cu(OTf)2 mediated regioselective de-aromatized aryl-hydroxylation across C(sp2)=N bond of 2-aryl quinoxalines and bis-N-arylation of (benz)imidazoles using aryl boronic acids. For dearomative aryl-hydroxylation, the C-center should be electrophilic (ca. 0.08), N-center nucleophilic (ca. −0.50), and the C(sp2)=N bond should be polarized (Δe = 0.609).
Small Molecules and Porous Silica Nanoparticle Encapsulated Gd(III) and Mn(II) Complexes as MRI Contrast Agents
(2024) Mallik, Riya
The content of this thesis has been divided into five chapters according to the results of experimental works that have been performed during the research period. Chapter I is the intorductory chapter of the thesis that represents an overview of Gd(III) and Mn (II) based complexex and nanoparticles as alternative MRI contrast agents with enhanced relaxivity and other physiochemical properties to target various endogenous conditions.
Chemically Twisted Superlattices of Two-dimensional Assemblies of Copper Nanoclusters
(2024) Das, Priya
The organization of molecules or atoms in a hierarchical manner leads to the formation of complex superstructures with enhanced properties and functionalities, resulting in superior performance when compared to mono-morphological units. Researchers have been motivated by the impact of these achievements to explore the design and fabrication of materials with hierarchical assembly at the nanoscale level. In this regard, research on the hierarchical assembly of two-dimensional (2D) nanomaterials has led to several exciting discoveries in various fields such as energy storage, optoelectronic devices, chemical sensors, catalytic performance, membranes, and solar cells.
Studies Towards Stereoselective C-C/C-Heteroatom Bond Formations of Strained Rings
(2024) Mishra, Manmath
Chapter I. General introduction to ring opening and cyclization of D-A cyclopropanes Nitrogen- and oxygen-containing heterocycles are among the most prevalent moieties found in both pharmaceutical and naturally occurring compounds. Research and development into these compounds is of high interest and of ongoing importance in organic synthesis. Recently, C-C and C-heteroatom bonds formation by ring expansion of three-membered strained ring systems, particularly in D-A cyclopropanes have provided a great synthetic space for easy access to structurally complex scaffolds. The inherent ring strain and electrophilic character made them an attractive building blocks for the selective synthesis of five, six and seven-membered heterocycles through ring-scission. In this chapter, the studies behind the background, reactivity and synthetic methodologies of ring-opening and cyclization of D-A cyclopropanes are discussed.
Facile Chemical Approaches to Derive Scalable and Tolerant Liquid Repellent Surfaces
(2024) Dhar, Manideepa
Nature-inspired liquid-repellent surfaces, such as superhydrophobic and slippery surfaces, have gained enormous attention because of their potential applications in environmental remediation, anti-corrosion, self-cleaning, bio-medical devices and so on. In the past, several approaches were adopted to develop artificial surfaces with desired wettability. However, significant challenges, such as poor durability and mechanical and chemical robustness, continue to impede its real-world application. This synopsis report outlines the strategic utilization of a facile and catalyst-free 1, 4-conjugate addition reaction between amine and acrylate functional groups for developing liquid-repellent surfaces with enhanced robustness and durability following a simple, scalable, and rapid fabrication approach. The synopsis report entitled “Facile Chemical Approaches to Derive Scalable and Tolerant Liquid Repellent Surfaces" is divided into six chapters. Chapter 1 gives a concise overview of bio-inspired wettability, general methods adopted to develop artificial anti-wetting surfaces, existing challenges, and objectives behind this thesis work. Chapter 2 demonstrates the strategic use of a catalyst-free 1,4-conjugate addition reaction between distinct and strategically selected small molecules allowed to prepare an active deposition solution with prolonged shelf-life in various and commonly used reaction media to derive optically transparent superhydrophobic coating. Chapter 3 introduces a covalent cross-linking chemistry between selected reactants to achieve tolerant and hard superhydrophobicity. Chapter 4 demonstrates the design of chemically functionalizable coatings with a combination of a physically unclonable porous topography and distinct physiochemical properties (e.g., fluorescence, water wettability, and water adhesion) obtained through orthogonal chemical modifications (i.e., 1,4-conjugate addition reaction and Schiff-base reaction at ambient conditions) for multilevel anti-counterfeiting application. Chapter 5 accounts for the utilization of a crystalline comb-like polymer to derive a non-fluorinated, substrate-independent, and self-healable amphiphobic solid slippery coating following a simple and scalable fabrication process. Chapter 6 provides a comprehensive summary of the presented work and a future perspective of this discussed research work.
Designing of hetero-bimetallic cyclic trinuclear, polymeric chains, and linear trinuclear from Cu(II), Fe(III), and Co(III) complexes using alkali, alkaline, and transition metal ions
(2024) Chanreingam, L
A simple ligand, which is chiral and flexible, was used to synthesize Cu(II) complexes such that the resulting complex can act as a chiral host and is flexible enough to obtain a secondary coordination sphere. Cu(II) bis complex, when reacted with K+ ion, forms a cyclic trinuclear, which resembles an inorganic crown ether. In this process, the trans-oriented Cu(II) bis complex was converted to a cis-oriented complex. An excess of [18] crown-6 was added, and the K+ was removed from the assembly, thereby obtaining a cis-oriented Cu(II) monomer. The cis-oriented disassembled Cu(II) monomer, when reacted with K+, forms back the assembly.
Synthesis of Furan, Pyran, Pyrrolidine, and Piperidine Scaffolds via Tandem Prins Cyclization Reactions
(2023) Shit, Sudip
The content of this thesis has been divided into five chapters on the basis of results of experimental work performed during the complete course of the PhD tenure. The chapter 1 describes the tandem Prins cyclization reactions and their mechanisms to construct Furan, Pyran, pyrrolidine and piperidine scafolds in brief. The chapter 2 deals with the stereoselective synthesis of hexahydrofuro[3,4-b] furan-4-ol and its dimer via tandem Prins and pinacol rearrangement. The dimer was conveniently converted into its corresponding monomer using aqueous zinc(II) chloride in THF in quantitative yields. Chapter 3 describes synthesis of spiro[furan-2,1′-isoindolin]-3′-ones from 2‑(4- hydroxybut-1-yn-1-yl)benzonitriles and aryl aldehydes under the action of triflic acid. The plausible mechanism of the reactipon has been drawn on the basis of control experiments and literature evidence. The synthetic utility of the reaction was performed using Sonogashira reaction and click reaction conditions. In chapter 4, nitrile stabilized synthesis of pyrrolidine and piperidine derivatives via tandem alkynyl aza-Prins-Ritter reactions is described. In chapter 5, regio- and chemoselective synthesis of 3-(dihydrofuran-3(2H)-ylidene)isobenzofuran-1(3H)-imines via tandem alkynyl Prins- and intramolecular oxycyclization reaction is disclosed. The methodology was extended towards synthesis of its pyran derivatives. The post synthetic applications of the reaction were extended towards synthesis of furanylidene-isobenzofuranones in excellent yields. The mechanistic investigation of the reaction was performed on the basis of controlled experiment.
Design, Synthesis and Investigations of Liquid Crystalline Organic Semiconductors
(2023) Vishwakarma, Vinod Kumar
This thesis entitled “Design, Synthesis and Investigations of Liquid Crystalline Organic Semiconductors” describes simple and straightforward synthetic pathways, characterizations and applications of new LC/non-LC organic materials, with their potential applications in acid sensing, optoelectronic devices mainly OLEDs and OFETs applications. A brief overview of the chapters is given. Chapter 1, gives a general introduction to liquid crystals, characterization techniques and their applications. Chapter 2a addresses the synthesis and characterization of pyrazino[2,3-g]quinoxaline (PQ) derivatives where the central pyrazino[2,3-g]quinoxaline central core is substituted with eight peripheral flexible tails of varying lengths. The compounds with very short/branched peripheral chains did not stabilize any liquid crystalline phase, while the medium to long-chain homologs exhibited columnar phases. All the compounds exhibited a high molar extinction coefficient and bright greenish-yellow emission behavior in solution and solid state. One of the columnar liquid crystalline materials was used in the fabrication of host-guest OLED exhibited higher efficiency and bright green emission. Chapter 2b describes the sensing ability of the pyrazino[2,3-g]quinoxaline derivative to volatile trifluoroacetic acid in trace amounts (in parts per billion levels). The reversible detection of acid-sensing behavior was visually perceivable in both solutions as well as in the drop-casted film on a TLC paper-based strip. Chapter 3 explains new design strategies for the synthesis of donor-acceptor-donor pyrazino[2,3-g]quinoxaline carbazole derivatives with straight chain and branched alkyl peripheral chains. The electron-donating carbazole moieties that have been placed in the periphery showed a strong electron-donating ability, high molar extinction coefficients and lower band-gap, bright emission behavior in solution and solid-state, along with positive solvatochromism. One of the branched chain compounds was used in yellow and white OLEDs device fabrications. Chapter 4 describes the detailed synthesis of naphthalene and perylene-based imidazole derivatives with a new donor-π-acceptor-π-donor architecture containing ten flexible chains for solution-processable organic field effect transistor (OFETs) applications. These compounds showed a wide range of columnar LC behavior. One of these naphthalene and perylene bisimide derivatives were evaluated for their application in OFET devices exhibited high hole mobility values.
Stimuli-responsive Turn-on Fluorogenic Donors of Hydrogen Sulfide (H2S) and the Prodrugs of Anti-cancer Compounds
(2023) Mahato, Sulendar K
The dissertation entitled “Stimuli-responsive Turn-on Fluorogenic Donors of Hydrogen Sulfide (H2S) and Prodrugs of Anti-Cancer Compounds” consists of four chapters based on the results of experimental works performed during the complete course of Ph.D. research tenure.
Stereospecific Opening and Cyclization of the Strained Ring Systems for the Synthesis of Six-Membered Heterocycles
(2022) Das, Bijay Ketan
The thesis is divided into four chapters. The first chapter describes the general introduction to the opening and cyclization of the strained ring system for the synthesis of six-membered heterocycles. The second chapter focuses on the synthesis of piperazines and tetrahydropyrazines through stereospecific ring-opening and cycloisomerization of aziridines with N-propargylamines. Third chapter covers stereospecific synthesis of substituted 1,4-oxazine via Zn/Ag Relay catalyzed ring opening/hydroalkoxylation of oxiranes with N-propargylamines. Chapter four deals with the stereospecific assembly of tetrahydroquinolines via tandem ring-opening/oxidative cyclization of donor-acceptor cyclopropanes with N-alkyl anilines.
Application of Modified Smooth Exterior Scaling Method to Study Auger and Shape Resonances in Different Atomic and Molecular Systems
(2024) Banuary, Mwdansar
This thesis focuses on the application of modified smooth exterior scaling (MSES) as an efficient method to impose outgoing boundary conditions in e-atom and e-molecule scattering resonances. This is the first time that the MSES method has been applied to calculate energies and widths of Auger and shape resonances in three-dimensional many-body electron systems. MSES converts the divergent resonance wave functions into square integrable ones thereby making the study of temporary bound states (resonance states) amenable to bound state electronic structure methods. The main objective of this thesis is to formulate the MSES method in bivariational SCF and electron propagator methods.
N- and O- Donor Ligands for Fluorometric and Colorimetric Detection of Metal Ions
(2024) Bhattacharya, Araghini
This Thesis contains five chapters. Chapter 1 is the introduction which describes the contribution of metals in our daily lives and their adverse effects on human beings when exposed to excess amounts along with a brief elaboration of different detection techniques. Some recent developments in devising fluorescent and colorimetric probes are also discussed. In Chapter 2 the 2,4,5-tris(2-pyridyl)imidazole (L1H) molecule has been evaluated as a probe for dual sensing of Hg2+ and Cu2+ ions in EtOH/HEPES buffer medium (5 mM, pH = 7.34, 1:1, v/v). Probe L1H shows a good sensitive and selective turn off response in the presence of both Hg2+ and Cu2+ ions, which is comprehensible under long UV light. Its sensitivity was evaluated in different pH medium and in presence of other metal ions. Paper strip experiments and in-vitro cell imaging was done to know the sensitivity of the probe towards the metal ions in different environment. Chapter 3 describes the probe 2,6-di(2-pyridyl)-1,5-dihydroimidazo[4,5-f]benzimidazole (L2H2) and its sensing application towards metal ions. This probe could detect Zn2+ and Cd2+ ions in three different aqueous systems viz., water, DMSO/HEPES buffer (1:1, pH = 7.34, rt), and DMSO/water (1:1, rt). In water a “turn-on” response was observed for both metal ions, whereas in the latter two solvent systems, a ratiometric change in fluorescence maximum was observed. The detection limit of this probe was as low as 0.3 μM and 0.62 μM (in water) for Zn2+ and Cd2+ ions, respectively. In Chapter 4 synthesis and evaluation of a novel probe N'-(pyren-1-ylmethylene)benzo[d]imidazo[2,1-b]thiazole-2-carbohydrazide (L3H) as metal ion sensor was explored. It was found to be able to nanomolar detection of Pd2+ and Ni2+ ions by colorimetric change. This probe was also able to detect the presence of Pd2+ ions in drug samples and APIs without any major interference. LOD values were calculated to be 46.1 to 93.9 nM (4.9 to 6.0 ppb) for PdCl2 and 10.6 to 19.6 nM (1.1 to 2.1 ppb) for Pd(PPh3)2Cl2 and 9.301 nM for NiCl2 solutions. It also showed extremely good recovery of Pd2+ in presence of all the drug molecules. In Chapter 5 another novel ligand L4H based on 2,7-dichlorofluorescein was synthesized and evaluated for sensing applications. It was found to be able to detect Co2+ and Cu2+ ions differentially by different colouration of the solution in presence of these two metal ions. In situ Cu-complex of the ligand was utilised for quantification of amino acids like BSA and HSA proteins. Its differential selectivity paved the for molecular logic gate application.
Computational investigation of excited state processes in ESIPT-based systems and vinylene-linked thiophene pyrrole
(2024) Mawa, Ibanrishisha
The thesis focuses on understanding the mechanistic pathway in systems undergoing excited state intramolecular proton transfer and cis-trans isomerization. Unveiling the mechanism of these processes at an atomistic scale is of utmost importance as it would add to our understanding and assist in designing materials with better performance. These kinds of processes are observed in our everyday life such as the vision process in retinal chromophores, vitamin D production in humans on exposure to sunlight and mutation during DNA replication, etc. The application part of systems undergoing photoinduced processes are realized in the design and development of certain materials such as optoelectronic devices. The thesis has three working chapters. The first work is based on 1-hydroxy-2-acetonaphthone (HAN) due to the unsettled issues regarding the proton transfer process. In addition, the process of full photocycle including the non-radiative relaxation pathways is proposed. The second work highlights the effect of implicit solvents on the photoinduced processes in nitrile-substituted 2-(oxazolinyl)-phenols. Additionally, the mechanisms behind these two regiomers’ weakly emissive properties in the solvent phases are investigated. My last work involves the exploration of photoisomerization pathways in vinylene-linked thiophene-pyrrole system. Considering the computational cost for the dynamics study in the excited state, we have employed single-reference method such as time-dependent density functional theory (TDDFT) and algebraic diagrammatic construction scheme of second order (ADC(2)). However, multi-reference studies are also incorporated in our study wherever the single-reference methods fail.

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