Synthesis and characterization of benzo-2,1,3-thiadiazole derivatives and their metal complexes

xxi, 147 leaves ; 29 cmThis thesis describes the synthesis and characterization of some 2,1,3-benzothiadiazole derivatives, specifically 2,1,3-benzothiadiazole-4,7-dicarbonitrile (DCBTD) and diethyl 2,1,3-benzothiadiazole-4,7-dicarboxylate (DEBTD). The crystal structures have been determined; also both compounds exhibit two sequential one-electron reductions in square-wave and cyclic voltammetry. Stable radical anions are detected by EPR spectroscopy. In the solid-state, DEBTD displays endo/endo, exo/exo and endo/exo conformational isomerism. Silver(I) complexes of DCBTD and DEBTD have been prepared with a number of anions (BF4, ClO4−, PF6−, and SbF6−) and their crystal structures are determined. All these complexes exist as coordination polymers, some of which are dry and others are solvates (benzene, water). DCBTD is found to coordinate through one or more nitrile and one or more ring N atoms. DEBTD exclusively forms bis chelate complexes using ring N and ester carbonyl O donors. Evidence from electrochemistry and ESI mass spectrometry indicates that these polymers break down on dissolving in CH3CN. Conversion of DEBTD into 2,1,3-benzothiadiazole-4,7-dicarboxylic acid, 2,3-diaminobenzene-1,4-dicarboxylic acid and salts thereof has been substantiated by crystal structure determinations