The utility of hypervalent (HV) iodine(III) compounds in organic transformations, traditionally as oxidants, and recently as electrophilic group-transfer reagents have been well established and documented. However, the potential of these compounds, and their reactivity to yield useful materials and polymers remains largely untapped. In the first part, a series of heterocyclic HV iodine(III) compounds containing fused tetrazole and benziodazole rings, i.e., derivatives of benziodazolotetrazole (BIAT) with various ligands attached to the iodine atom were prepared and characterized by 1H and 13C Nuclear magnetic resonance (NMR) spectroscopy, Electrospray ionization high-resolution mass spectroscopy (ESI-HRMS), and single-crystal X-ray crystallography. Their reactivity and thermal stabilities were examined. The enthalpies of exothermic degradation were measured by thermal gravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC). The next project is focused on studying the structure-thermal stability relationships of a well-known class of heterocyclic HV iodine(III) reagents, benziodoxolones (BIOs) with alkoxy and acyloyloxy ligands. The inspiration to perform these studies was drawn from the conclusions of a collaborative project with theoretical chemists, who assessed and predicted the stability using local vibrational mode (LVM) analysis, also taking experimental infrared (IR) spectra into account. The insights obtained from these thermal stability experiments were applied in designing BIOs with methacrylic and acrylic moieties as ligands, which were synthesized, isolated, and characterized by 1H, 13C NMR spectroscopy, and the crystal structures were determined by single-crystal X-ray diffraction. Owing to the presence of a polymerizable moiety and an initiating site (I–O bond), they were able to generate radicals upon ultraviolet (UV) light-induced homolysis, thereby serving as inimers. These inimers were employed in the synthesis of polymers through the popular self-condensing vinyl polymerization approach. The thermal stability of inimers was investigated by TGA and their hydrolytic stability was studied and compared. (Co)polymerization was performed under different wavelength UV sources with various monomers and by varying ratio of monomer with respect to inimer. The corresponding polymers were characterized using size exclusion chromatography (SEC). Additionally, the half-life and rate constant of decomposition of the initiator, 1-chloro-1,2-benziodoxol-3(1H)-one (ClBIO), a well-known heterocyclic HV iodine(III) compound with an exocyclic I–Cl and an endocyclic I–O HV bond, that was employed for the polymerization of methyl methacrylate (MMA), was determined at 80 oC and the end-groups of isolated polymer were analyzed by 1H NMR spectroscopy. In the final chapter, synthesis of a novel HV iodine(III) compound from BIAT family is reported and the crystal structure, resolved from powder X-ray diffraction analysis is presented and the future directions are briefly discussed.
Nicolay V. Tsarevsky
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Sayala, Kapil Dev, "Benziodazolotetrazoles and Benziodoxolones: Synthesis, Stability, Structural, and Reactivity aspects" (2022). Chemistry Theses and Dissertations. 30.
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