PhD Theses (Chemistry)

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Anthracene and Aminothiazole Based Organo-Cations Guiding Ionic-Cocrystals, Hydrates of Pyridinedicarboxylic Acids and Selected Metal Complexes
(2025) Singh, Abhay Pratap
The research presented in this thesis is based on the synthesis, structural characterization, and self-assemblies of salts, ionic-cocrystals and hydrates. Series of 2,6- and 3,5-pyridinedicarboxylate ionic-cocrystals were investigated to show newness in their compositions by complete or partial deprotonations. Different multi-component cocrystals with novel photoluminescence properties are demonstrated in the thesis. Multiple numbers of hydrates from different anionic cobalt(II), copper(II), and zinc(II) pyridinedicarboxylate complexes possessing anthracene-based organo-cations and their interconversions are depicted. The contribution highlights diverse non-covalent assemblies formed through weak interactions such as hydrogen bonds, halogen bonds, π-stacking, and chelate-chelate interactions. The study was extended to zinc(II) pyridinedicarboxylate complexes containing sulfathiazolium cations to demonstrate variations in the bioavailability of a drug molecule derived from the same components in each case but with different compositions. This thesis has opened scopes for newer avenues to explore assemblies of ionic-cocrystals as well as solvated metal complexes to observe new properties and transformations among the ionic forms within an assembly by stimuli such as concentration gradient or additives.
Organocatalytic Enantioselective Synthesis of Aza-Spirooxindoles and Construction of Quaternary Stereocenters by Desymmetrization Reactions
(2025) Biswas, Subhankar
The contents of the present thesis entitled as “Organocatalytic Enantioselective Synthesis of Aza-Spirooxindoles and Construction of Quaternary Stereocenters by Desymmetrization Reactions” have been divided into five chapters based on the results achieved from the experimental works performed during the entire course of the Ph.D. research programme.
Lewis Acid Driven Synthetic Approaches for Benzannulated N-Heterocycles from 2-Aminobenzonitrile
(2025) Porashar, Bikoshita
Chapter 1 highlights an overview on cascade reactions and the reactivity of 2-aminobenzonitriles. This includes a brief discussion about synthetic reactivity and utility of 2-aminobenzonitriles as a precursor for synthesis of various simple or complex heterocyclic frameworks. Chapter 2 represents a tunable one pot synthesis of tetrahydro-4H-pyrrolo[3,2-c]quinolin-4-ones and dihydro-1H-benzo[b]azepines from 2-aminobenzonitriles and donor-acceptor cyclopropanes in presence of SnCl4. The reaction proceeds via the initial ring opening of cyclopropane ring by 2-aminobenzonitrile followed by nucleophilic attack by amine to give adduct, which after unprecedented rearrangement at two different reaction temperatures provide two sets of structurally diverse nitrogen heterocyclic compounds. This methodology can be used for the synthesis of tricyclic hexahydropyrrolo[3,2-c]quinolinones (tricyclic core of martinelline). Chapter 3 describes an efficient methodology for the synthesis of highly diverse 4-methylene substituted tetrahydroquinazoline scaffolds from 2-aminobenzonitriles and alkylidene malonates in presence of SnCl4. The reaction proceeds via initial 1,4-conjugate addition of 2-aminobenzonitrile to the activated alkene followed by an unprecedented rearrangement. The methodology can be extended towards the synthesis of quinazoline analogues as well as tetracyclic dihydroisoquinolino[1,2-b]quinazoline derivatives. Some of the synthesized compounds show excellent photophysical properties. Chapter 4 demonstrates an efficient methodology for the synthesis of highly diverse 2,3-disubstituted 4-aminoquinoline derivatives from 2-aminobenzonitriles and activated alkynes in presence of FeCl3. The reaction proceeds via sequential aza-Michael addition and intramolecular annulation to afford highly substituted 4-aminoquinolines in good yields. The salient features of this protocol include the use of a minimally toxic, eco-benign and less expensive Fe(III)-salt and has high atom-economy with broad substrate scope and operational simplicity. The post synthetic application of the reaction provides 4H-benzo[de][1,6]naphthyridines. Chapter 5 highlights an efficient methodology for the synthesis of 2,4-diaminoquinazolines and 2-amino-4-iminoquinazolines from 2-aminobenzonitriles and carbodiimides. This SnCl4 mediated reaction exhibits substrate driven switchable selectivity in product formation based on the substituents of the carbodiimides used. Aryl and primary alkyl-substituted carbodiimides predominantly give 2-amino-4-iminoquinazolines, while secondary or tertiary alkyl and benzyl-substituted carbodiimides yield 2,4-diaminoquinazolines. The methodology can be extended towards the synthesis of 2-aminoquinazolin-4(3H)-one analogues as well as pentacyclic annulated derivatives.
Catalytic Transformation of Alcohols for the Production of Hydrogen, Fuels and Specialty Chemicals Using Pincer-Ruthenium and Pincer-Nickel Complexes
(2025) Arora, Vinay
The contents of the present thesis entitled “Catalytic Transformation of Alcohols for the Production of Hydrogen, Fuels and Specialty Chemicals Using Pincer-Ruthenium and Pincer-Nickel Complexes” have been divided into four chapters based on the results achieved from the experimental work carried out during the entire course of the PhD research program.
Application of Responsive Lamellar Membranes of Layered Materials for Microdroplet Handling, Sensing, and Energy Harvesting
(2025) Neog, Arindom Bikash
This thesis explores the development and application of advanced bilayer membranes and nanomaterials for precise liquid manipulation, contaminant detection, remote handling of reactive substances, and sustainable energy harvesting. A hydrophobic r-GO/agar bilayer membrane, controlled by electrical potential and infrared light, was designed to handle microliter-scale droplets with ultrafast reaction capabilities and potential for efficient chemical analyses. The same r-GO/agar membrane demonstrated shape-morphing properties sensitive to chemical impurities in liquid media, enabling real-time detection of contaminants such as water in acetone or alcohol in toluene. To address the remote handling of toxic and reactive chemicals, CNT-VO (carbon nanotube-vanadium pentoxide) and o-CNT-VO bilayer actuators were developed with light- and voltage-responsive behaviour, enabling rapid and precise manipulation of hazardous substances, alongside sensory capabilities mimicking human touch. Lastly, a novel permselective nanofluidic membrane coated with functionalized vanadium pentoxide nanosheets was fabricated for concentration gradient-driven energy harvesting. By integrating vanadium pentoxide and polyaniline electrodes, the power output was enhanced by 300%, demonstrating a significant advancement in sustainable energy generation. These studies significantly contribute to the fields of liquid manipulation, environmental monitoring, remote chemical handling, and energy harvesting.
Synthesis of Substituted Quinolines & Furocoumarins: Some Naturally Occurring Coumestan Derivatives
(2025) Faraz, Simra
The contents of the dissertation are divided into two parts, namely Part A and Part B, on two broad research topics. In Part A, the synthesis of various substituted quinolines will be highlighted. Similarly, the synthesis of furocoumarin derivatives, with special emphasis on synthesizing some naturally occurring coumestan derivatives, will be elaborated on in Part B.
Role of Kinetic Lability on the Recognition of Achiral and Chiral Amines on the Scaffold of Co(III)/Fe(III) Complexes Through Non-Covalent Interactions
(2025) Paik, Somnath
In this thesis, we investigated guest (achiral, chiral ammonium ions, and secondary metal cations) induced structural changes of chiral octahedral metal complexes of l-tryptophan derived ligand. We synthesized a kinetically inert anionic chiral Co(III) complex having multiple H-bond capable sites and used it to bind a series of achiral and chiral ammonium cations. The anionic Co(III) complex adopts different shapes to recognize different achiral and chiral ammonium ions. The change in shape, at least in one case, involves the reorganization of coordination bonds despite the inert nature of the complex. Structural reorganization of the complexes could be monitored in solution using 1D and 2D NMR spectroscopy. Recognition of enantiomer was also observed when racemic amino alcohols were used. To understand the role of kinetic inertness in these recognitions and transformations, we synthesized a labile but structurally analogous Fe(III) complex and repeated some of the transformations. In some cases, the Fe(III) complex adopts a very different shape where ligand coordination on the Fe(III) center has changed completely. The thesis contains detailed investigations and our conclusions.
Development of Novel Recyclable Coupling Reagents and Investigation on Chirality Controlled Self-Assembly of Dipeptides
(2024) Roy, Sayanta
This thesis contributes to the development of novel coupling reagents for sustainable organic transformations. We demonstrated straightforward, efficient methods for synthesizing these coupling reagents. These reagents demonstrate excellent stability and are easily scalable. They are efficient for synthesizing racemization-free amides, hydroxamates, esters, thioesters, and peptides sustainably. Additionally, they are effective in modifying natural products and drug molecules under optimized conditions and synthesizing bioactive long-chain linear and cyclic peptides in solid-phase using green solvent mixtures. Some of our coupling reagents are also effective in synthesizing nitriles and assist in the metal-catalyzed synthesis of ketones from carboxylic acids with excellent yields. We synthesized a diverse library of amides, hydroxamates, esters, thioesters, peptides, nitriles, and ketones with excellent yields.
Development of Peptide-based Physical Gels for Various Applications
(2024) Chetia, Monikha
In this thesis, we have designed and synthesized small peptide based supramolecular gels (hydrogels/organogels) for utilizing them in varied applications in both biomedical and non-biomedical sectors. We also investigated the self-assembly mechanisms to understand the role of non-covalent interactions in their gelation behavior through several spectroscopic and microscopic techniques. The peptides used for the constitution of the gels vary from small hydrophobic and highly aromatic peptides to salt-tolerant and protease-resistant cationic antimicrobial lipopeptides. The developed hydrogels have been employed in diverse biomedical applications like drug release platform, and adjuvant for potentiating antibiotics against resistant microbes and materials to prevent the growth and propagation of biofilms. The organogels, on the other hand, have been employed for water remediation by removal of spilled oil and dyes, development of conducting material, and immobilization cum stabilization of quantum dots. In addition to demonstrate their applications, we have thoroughly characterized their properties like thermostability, reversibility, mechanical stability, phase-selective gelation ability and morphology
Thermal (Photo) Induced Selective C-H Bond Functionalization/Oxidative Cyclization in Di-Nitrogen Benzenoid Heteroarenes
(2024) Ghosh, Subhendu
This thesis demonstrates a number of thoughtful approaches for selective C-H functionalization and oxidative annulation strategies under thermal(photo) catalytic architectures. This thesis has been divided into five major chapters and extended toward a future perspective. Chapter IA gives a concise overview of Transition-metal catalyzed C-H functionalization and oxidative annulation (cyclization). Meanwhile, Chapter IB depicts the different photo-induced C-H functionalization and cyclization techniques. Chapter II demonstrates Ru(II)-catalyzed regioselective C-H/N oxidative annulation of 2-arylquinoxalines with internal alkynes. In this chapter, the synthesized quaternary annulated adducts are extensively scrutinized for detailed photo-physical applications. Such donor--acceptor type molecules exhibit Aggregation Enhanced Emission (AEE) in DMF/water solvent systems. Apart from this, such annulated adducts possess reversible mechanochromism. Such small quaternary salts are utilized for latent fingerprint detection (up to 2nd level). Furthermore, such luminogens serve as cellular imaging probes. Chapter III describes a solvent-switched regiodivergent CH malemidation on 2-arylimidazopyrdines under Mn(I)-catalysis. This protocol enables selective C-H alkylation without the involvement of silver or oxidants. Before this work, Mn(CO)5Br is known for the directed C-H functionalizations. In this chapter, a non-directed CH metalation of Mn(CO)5Br apart from the directed strategy has been revealed. Chapter IV offers the regioselective C-H maleimidation at the unattained C3-H site of 2-aryl quinoxalines. Herein, the non-directed Mn-catalysis enables the challenging C3-H activation over the usual ortho CH activations. Besides these, the synthesized C3-maleimidated quinoxalines exhibit PIFA-promoted electron-drifted Spirocyclization at room temperature. Also, in the presence of Selector, the C3-maleimide quinoxalines undergo dehydrogenation of succinimides ring. Chapter V represents a reagent-less photo-induced auto-catalyzed oxygenation at sterically hindered C(sp3)-H site. This photochemical “reagent-less” solvent-dependent hydroxylation at Csp3-H and spiro-etherification involving C(sp3)-H/C(sp2)-H are unparalleled. Herein, the N-H tautomer of C3-maleimidated quinoxalines acts as a triplet sensitizer and transfers its energy to a triplet oxygen (3O2) generating reactive singlet oxygen (1O2) which facilitates oxygenation reactions at the other C(sp3)-H sites within the molecule making it a true auto-sensitized process. This photo-oxygenation represents an illustration of a tautomer-assisted 1O2 uptake
Metal Ion Based Assemblies of Gold Nanoclusters with Tuneable Photoluminescence
(2023) Paul, Manideepa
The dissertation focuses on developing metal ion-mediated crystalline assembly of gold NCs through chemical reactions to develop functional nanomaterials with tailored properties. Through the envision of inorganic complexation reaction, the assembly of ligand-stabilized gold NCs is possible with metal ions, which supersedes the constituent clusters in terms of tailorable structural properties and hold potential in the advancement of the field. Also, facile development of higher dimension cluster assembly with intriguing optical and physio-chemical properties along with well-defined geometries is achievable. In this context, the effects of transition metal ions and lanthanide metal ions for assembling NCs were investigated for such formation of crystalline nanostructures, which could induce the possibility of amplification in multifunctional properties. The present thesis is divided into five chapters. Details of works incorporated are briefly discussed here.
Harnessing the Nitrile Functionality to Heterocycles via Thermal and Photochemical Strategies
(2024) Dhara, Hirendra Nath
The Ph.D. thesis, “Harnessing the Nitrile Functionality to Heterocycles via Thermal and Photochemical Strategies,” focuses on the synthesis of biologically relevant heterocycles and is divided into five chapters, including an introduction.
Reactivity of Co(III)-peroxo Complexes with NO and Co(II)-nitrosyl with H2O2: Putative Formation of Co-peroxynitrite
(2024) Samanta, Bapan
This thesis broadly covers our endeavor to understand both the reactivity of peroxo complexes of Co(III) with NO in non heme ligand frameworks, L1, L2, L3 and nitrosyl complex of Co(II) with reduced oxygen species, H2O2 in heme ligand framework, TTMPP2- respectively. These complexes were synthesized by varying bidentate, symmetric tetradentate, asymmetric tetradentate and square planar ligand framework. The change of reactivity pattern with ligand denticity has been studied. The reactivity of Co(III)-peroxo complexes with NO was discussed in chapters 2-4, following an attempt to mimic the mechanism of the nitric oxide dioxygenase (NOD) enzyme. In every case, formation of putative peroxynitrite intermediate was observed. Efforts were made to identify and characterized the associated intermediates that form during the course of the reaction. For instance, in chapter 2, putative formation of Co(II)-peroxynitrite intermediate was observed using a bidentate ligand framework and finally it isomerizes to the corresponding nitrate complex. In chapter 3 and 4, formation of Co(II)-peroxynitrite intermediates were observed using symmetric and asymmetric tetradentate ligand frameworks, respectively. In case of chapter 3 and chapter 4, different decomposition products were obtained i.e corresponding nitrate and nitrite complexes respectively.
Cobalt(II) and Manganese(II) Nitrosyl Complexes as Potential HNO/NOˉ Donor
(2024) Saha, Shankhadeep
This dissertation addresses our attempt to understand the potential of Co(II) and Mn(II) nitrosyl complexes as nitroxyl (HNO/NOˉ) donors. A series of nitrosyl complexes were synthesized by varying the ligand framework (from electron deficient to electron rich) with a central metal ion (e.g. Co2+ and Mn2+). The ability of these metal-nitrosyl complexes to act as HNO/NOˉ donors under different reaction conditions was discussed in chapters 2 to 5. The potential of cobalt-nitrosyl complexes as nitroxyl donors was extensively discussed in chapters 2 to 4, whereas chapter 5 addresses the manganese-nitrosyl complex, which led to some significant observations. For instance, in chapter 2, the nitroxyl releasing ability of a {Co(NO)}8 complex in presence of anionic sixth ligands like BF4ˉ and DTCˉ was observed, which is the first example of such kind of reaction. Chapter 3 describes our in detailed findings of the reaction between a {Co(NO)}8 complex and DTCˉ anion, which also leads to the NOˉ donation. In chapter 4, a neutral imidazole ligand mediated NOˉ release from a highly electron rich {Co(NO)}8 complex was studied. All of these sixth ligand mediated nitroxyl release from cobalt-nitrosyl complexes are found to be concomitant in nature. The kinetic inertness of low-spin d6 cobalt-centre of {Co(NO)}8 complexes makes the release of HNO very difficult. Our recent findings on the methodology for HNO/NOˉ release from {Co(NO)}8 complexes will contribute significantly to the existing knowledge of nitroxyl donation from cobalt-nitrosyl complexes.
Annulation and Directing Group Strategies as Tools for the Construction of Heterocycles
(2024) Das, Bubul
The contents of the thesis have been divided into four chapters with initial one as introductory and the rest of the chapters are based on experimental results obtained during the research period. The introductory chapter of the thesis is a summary of alkyl isocyanoacetate’s reactivity and its usefulness in diverse (3 + n) annulation/cycloaddition reactions. Along with this, a brief description of the directing group (DG) strategy for the functionalization of C−H bond has also been added. A brief account of the formation of important heterocyclic scaffolds following annulation/cycloaddition and DG-assisted C−H activation has been included.
Design and development of synthetic anion transporters: Towards therapeutic prospects
(2024) Das, Sribash
The thesis, titled "Design and development of synthetic anion transporters: Towards therapeutic prospects," provides a brief description of several kinds of novel anionophores that exhibit significant promise for therapeutic applications. This thesis includes insights on the recognition, transportation across cell membranes, and potential therapeutic applications. The thesis is divided into four chapters based on experimental findings obtained during the research periods
Applications of Reconstructed Nanofluidic Membrane of Layered Materials in Ionic Thermoelectricity and Moisture-Electricity-Generation
(2024) Gogoi, Raktim
This PhD thesis focuses on the development of innovative ionic thermoelectric (i-TE) materials and moisture-electric generators from the reconstruction of layered materials. The first study explores clay-based i-TE materials, where exfoliated and surface-functionalized lamellar clay nanosheets are fabricated. These materials exhibit improved thermoelectric properties, high-temperature stability (up to 300°C), and water-assisted healing capabilities. The devices can convert waste heat and sunlight into electricity, with enhancements made by integrating photothermal materials like carbon nanotubes and hydrogel coatings for improved performance in low-humidity environments. The second study investigates V₂O₅-based i-TE materials, where the Seebeck coefficient is significantly enhanced by intercalating poly(4-styrenesulfonic acid) (PSS) into the lamellar structure. These materials maintain thermal stability, even at high temperatures, and demonstrate strong thermoelectric behavior.
Catalytic Asymmetric Synthesis of Cyclic Acetals and Dearomatization Reactions of Indoles & Naphthols
(2024) Shikari, Amit
The contents of the present thesis entitled as “Catalytic Asymmetric Synthesis of Cyclic Acetals and Dearomatization Reactions of Indoles & Naphthols” have been divided into five chapters based on the results achieved from the experimental works performed during the entire course of the Ph.D. research programme.
Synthesis, Photo-Physical Properties and Applications of Novel Metal Nanoclusters
(2024) Sarkar, Priyanka
The contents embodied in this thesis is divided into seven chapters. Chapter 1 is an introductory chapter which gives a concise and lucid introduction to the field and reports the major scientific contributions relevant to metal Nanoclusters. The introductory chapter represents an overview of the synthesis procedures, photo-physical properties, factors affecting its photo-physical properties and applications of these metal nanoclusters to diverse fields. Chapter 2 provides a detailed description of the material and methods used throughout the thesis. Chapter 3 describes synthesis of a biocompatible DTT (Dithiothreitol)-reduced LYS(Lysozyme) capped silver nanoclusters(AgNCs) and its application for selective and sensitive detection of Cu2+ and VB12. Detailed detection mechanism was studied. These AgNCs were also able to detect Cu2+ and VB12 inside live cells as well. Chapter 4 describes synthesis of a DTT reduced BSA(Bovine Serum Albumin) capped dual-emissive AgNCs and its application for selective and sensitive ratiometric detection of Cu2+ and IO4-. Detailed detection mechanism was studied. Chapter 5 describes a top-down synthetic approach to synthesize time-controlled two differently emissive copper nanoclusters (green and blue CuNCs) from a non-luminescent copper nanoparticles(CuNPs). Later, blue emissive CuNCs were utilized for detection of Fe3+ and GSH(Glutathione) via fluorescence turn-off-on mechanism. Detailed detection mechanism was studied. Chapter 6 reports two different strategies to produce AIDF (Aggregation induced delayed fluorescence)-based luminescent materials at room temperature from GSH-capped CuNCs by (1) simply modifying the solvent environment and (2) introducing of gadolinium (Gd3+) ions. Detailed analysis were investigated to reveal the generation mechanism of these AIDF properties. Further, Gd3+ induced AIDF of GSH-CuNCs were utilized to selectively detect Cr+6 ions. Chapter 7 provides a concise summary with future prospects.
Crystalline Molecular and Nanoparticle Assemblies with Optoelectronic Application Potential
(2024) Bhakat, Arin
The current thesis describes the production and prospective use of molecular crystals and crystallization-induced nanomaterial assembly. The current thesis reveals that the surface of molecular crystals can serve as an appropriate SERS platform. The surface functionality of molecular crystals can participate in non-covalent interactions with the deposited analyte molecules, allowing for efficient photoinduced charge transfer. The current thesis also shows that inorganic molecular crystals can exhibit metallic characteristics and cause surface plasmon. These molecular crystals may be exploited as a possible SERS substrate due to their excellent spectrum stability, simplicity of synthesis, outstanding environmental stability, biocompatibility, target molecule selectivity, and molecular cooperativity. The thesis also depicts the tuning of NC characteristics as a dopant inside molecular crystals, which sheds light on the methods for inducing tuneable phosphorescence features on simple metal NCs via ordered packing structures inside molecular crystals by altering the surrounding environment and electronic confinements. Furthermore, we used the intermolecular interaction-based surface complexation approach that causes molecular crystal formation to self-assemble nanomaterials into the crystalline superstructure.

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