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Polyoxometalates (POMs) represent a large and structurally versatile class of anionic metal-oxo clusters derived from high-valent early transition metals such as tungsten(VI), molybdenum(VI), and vanadium(V). A particularly important subclass is peroxo-functionalized POMs (peroxo-POMs), in which peroxo groups are coordinated to the metal centers. The peroxo groups enhance the oxidative reactivity of these species and promote the efficient activation of oxidants such as H2O2. Accordingly, the synthesis of new peroxo-POMs and the study of their properties are of interest for both academic and industrial applications. In this thesis, the focus is placed on the synthesis of novel peroxo-POMs and their characterization in both the solid state and solution. Chapter 1 introduces POMs and peroxo-POMs, highlighting key concepts and providing a literature overview relevant to the research presented in this thesis. Chapter 2 describes the motivation and objectives of PhD work. Chapter 3 provides a detailed overview of the instruments and analytical techniques used for the structural characterization of the synthesized compounds. Chapter 4 focuses on the synthesis of peroxo-thorium(IV)-containing silico- and germanotungstates, [Th3(μ3-O2)(OH)2(H2O)3(A-α-XW9O34)2]12− (X = Si, Ge), prepared in aqueous solution. In the absence of H2O2, the corresponding oxo-analogues, [Th3(μ3-O)(OH)3(H2O)(A-α-SiW9O34)2]13− and [Th3(μ3-O)(OH)3(A-α-GeW9O34)2]13−, were obtained. Single-crystal X-ray diffraction revealed that all polyanions consist of two {XW9} units sandwiching a central triangular thorium core. In the peroxo derivatives, the central peroxo group adopts a rare side-on μ₃-coordination mode linking the three thorium centers, representing the first examples of peroxo-thorium(IV) polytungstates. All four synthesized POMs were further characterized by 183W NMR, solid-state and solution Raman spectroscopy, and electrochemistry, confirming their structural integrity and redox behavior. Chapter 5 reports the synthesis of peroxo-containing heteropolyanions [{XW3O7(O2)2}2O]6− (X = HPO42−, HAsO42−, CH3AsO32−). All polyanions adopt dimeric structures, consisting of two {XW3} subunits connected by three oxo bridges. The solution stability of these polyanions was systematically studied using 1H, 13C{1H}, 31P{1H}, and 183W NMR spectroscopy. Additionally, antibacterial activity of the peroxo-tungstoarsenate(V) and its organoarsonate(V) derivative was evaluated against representative Gram-negative and Gram-positive bacterial strains. Chapter 6 presents the synthesis of the peroxo-hafnium(IV)-containing decatungstophosphate(V), [Hf8(O2)8(PW10O38)4]28−, obtained via the reaction of [P2W19O69(H2O)]14− with Hf(IV) ions in aqueous solution. X-ray diffraction analysis showed that the structure is composed of four [Hf2(O2)2(PW10O38)]7− subunits, which assemble into a cyclic tetrameric framework. The cyclic tetramer features an inner cavity approximately 10 Å in diameter that accommodates two Na+ ions. FT-IR, solid-state Raman, and 31P{1H} NMR were used to characterize the compound. Chapter 7 reports the synthesis of the polyanions [Hf4(O2)2(O)2(H2O)4(X2W16O59)2]16− (X = P, As), consisting of two dilacunary Wells-Dawson [X2W16O59]12− polyanions sandwiching a tetranuclear cationic [Hf4(O2)2(O)2(H2O)4]8+ unit. This central unit exhibits a compact arrangement in which four Hf(IV) centers are interconnected through μ3-oxo and μ2-peroxo bridges. The structural and solution behavior of the polyanions were elucidated using FT-IR, solid-state Raman, and 31P{1H} NMR spectroscopy.

The thesis comprises three main sections, in which the central theme revolves around the supramolecular reporter pairs. The first and second sections aim to design intricate coupled reactions, namely supramolecular tandem enzyme membrane assays and supramolecular membrane enzyme assays, achieving the simulation of continuous physiological processes. In the supramolecular tandem enzyme membrane assays section, we describe the usage of two supramolecular reporter pairs, with one set located inside the vesicles and the other set positioned outside the vesicles, to mimic the simple process of digestion and absorption. The second section, the supramolecular tandem membrane enzyme assays, focuses on simulating the processes of cellular uptake and metabolism using a single set of reporter pair located within the vesicles. In the uptake process, the transport of substrates across the vesicle membrane is monitored by the internal reporter pair calix[4]arene•luciginin (CX4•LCG) or cucurbit[7]uril•berberine (CB7•BE). Similarly, the metabolic process is monitored by the same reporter pair within the vesicles, monitoring the enzymatic conversion of the substrates. The third section represents an intriguing exploration of the effects of variations in the vesicle surface microenvironment on the interactions between supramolecular hosts and guests. The aim is to gain a deeper understanding of the mechanisms underlying the regulation of cell signaling transduction, transmembrane transport, and sensing processes, which are governed by the dynamic and complex presence of proteins, saccharides, and other molecules on the cell surface.

The popularity of plant-based proteins, especially legumes has experienced a remarkable surge in recent years, due to the heightened awareness health benefits, concerns on animal welfare, environmental sustainability, and advancements in food technology. Apart from their nutritional value, many of the encrypted peptide sequences have shown remarkable bioactivities. However, most of the legume crops consumed worldwide are not evaluated for protein profile and bioactive potential, except for soya beans, peas, and lentils. The lack of scientific evidence has become a major barrier in successful utilization of these legumes. Also, there are many chemical and physiological barriers which limit the protein digestion such as protease inhibitors and complex structural diversity. So, this study was planned to evaluate the amino acid profile, presence of bioactive peptide sequences and improving the digestibility of proteins from common legumes cultivated in Sri Lanka, including pigeon pea-Cajanus cajan, green gram- Vigna radiata, cowpea - Vigna unguiculata, black gram - Vigna mungo and horse gram- Macrotyloma uniflorum. Extraction with acid, alkaline, salt, alcohol and TRIS buffers were compared for the yield and the diversity of protein profile. Digested protein extracts with trypsin, chymotrypsin and pepsin were analysed by LC-ESI-MS. Peptide sequencing was performed with PEAKS software to identify proteins, post-translational modifications, and amino acid profile. The peptide fragments identified from trypsin, pepsin and chymotrypsin hydrolysates were screened with different in-silico approaches and in vitro bioassays. Also, the effect of domestic processing methods including soaking, gemination, boiling and roasting on the digestibility of green gram proteins was evaluated. Results showed that the alkaline extraction is effective in extracting an optimum protein yield with most diverse and balanced protein profile, comprising storage, enzyme, and other functional proteins. Most of the cultivars tested show similar storage protein profiles, but there were significant differences in functional proteins important in abiotic stress management. Also, seed storage proteins show extensive post-translational modifications, which serves as another level of protection and functionalities such as dormancy release and metabolic resumption. They also have balanced essential amino acid profile, except for Methionine (M) and tryptophane (W). All legumes exhibited significant potential in antioxidant and antibacterial properties, and trypsin mediated digestion is more successful in generating bioactive peptides. Boiling and roasting enhanced the digestibility of legume proteins, which can be attributed to the removal of protease inhibitors, unfolding of globular storage proteins and alterations in secondary structures into less ordered conformations.

This thesis is divided into six chapters. Chapter I generally introduces the historical background, structural aspects, properties, and applications of POMs, the state of the art of polyoxo-noble-metalates, noble-metal-containing POMs and arsenic compound, as well as the motivation to perform this work. Chapter II includes the information of applied analytical techniques and synthetic procedures for the used POM and organorhodium(III) precursors. Chapter III is devoted to polyoxoplatinate, polyoxopalladate and mixed polyoxo-noble-metalates, and 7 novel polyoxo-noble-metalates have been obtained with the following highlights: (i) The first PtIV-containing discrete polyoxoplatinate(II) Pt7 and polyoxopalladate(II) PtPd6 have been prepared and characterized in the solid-state, in solution, and in the gas phase; (ii) The first discrete mixed platinum(IV)-gold(III) oxoanion Pt2Au3 was structurally characterized in the solid state by single-crystal XRD and TGA, and in solution by multinuclear NMR and ESI-MS studies. Chapter IV presents 3 novel Platinum(II/III)-containing isopolytungstates. The polyoxoanion Pt3W11 consists of three {W3O13} and one {W2O10} fragments connected by three Pt(II) atoms forming linear {Pt3O12} triad. The polyoxoanion PtII2W5 and PtIII2W5 both consists of one lacunary Lindqvist fragments {W5O18}6− coordinated by two Pt(II) in square planar coordination and two Pt(III) with direct Pt–Pt bonding, respectively. Chapter V describes the synthesis of three all-inorganic platinum arenate(III) compound. The first two full inorganic discrete platinum arsenate(III) clusters: PtAs6 and Pt4As8, have been synthesized in aqua media. In Pt4As8, Each Pt atom is coordinated by two O atoms and two As atoms involved in direct As-Pt bonding. And a platinum arsenate(III) heteropolytungstate Pt2As6W4 has been synthesized in aqua media and characterized by 195Pt NMR.Chapter VI deals with the synthesis and characterization of two RhCp*-containing heteropolytungstates.

For almost 40 years, difluoromethylene phosphonates – compounds of general formula RCF2P(O)(OR)2 – have attracted much interest as molecular tools to study enzymes and their behavior in biochemical processes. First, we discuss the chemistry of difluoromethylene phosphonates through the prism of its historical development and with an emphasis on general synthetic methods, highlighting the existing challenges and unsolved problems. We then explore the formal [3,3]-sigmatropic rearrangements of 2,3,3-trifluoroallyl phosphates leading to isomeric 1,1,2-trifluoroallyl phosphates under thermal and Lewis acid-promoted reaction conditions. Although the products of these rearrangements were unstable, the insights we gained while studying these reactions prompted us to explore similar formal [2,3]-sigmatropic rearrangements of 2,3,3-trifluoroallyl phosphorus (III) compounds. Finally, we describe the newly developed method for the preparation of CF2–P (V) phos- phonate analogs – difluoromethylene phosphonic and phosphinic amides, and phosphine oxides. The method is based on a formal [2,3]-sigmatropic phospha-Wittig rearrangement of readily available fluoroallyl bis(amido)phosphites, amido(aryl)phosphonites and diarylphosphinites. It allows for the preparation of title compounds in a straightforward fashion on a multigram scale, complementing the existing phosphoryldifluoromethylation methods. A powerful one-pot multistep protocol has been developed based on this method. It utilizes ubiquitous starting materials, such as THP-O-protected 2,2,2-trifluoroethanol, directly furnishing phosphonic, phosphinic and phosphine oxide analogs of α,α-difluoro-β-ketophospho- nates without the need for isolation and purification of the intermediate products. Besides providing access to unique compounds hardly accessible through other routes, the developed method benefits from the fact that, unlike most other existing general methods, it does not rely on ozone-depleting HCF2Cl and CF2Br2.