Mononuclear and dinuclear indium(III) complexes containing methoxy and hydroxy-bridge groups, nitrate anion and 4,4′-dimethyl-2,2′-bipyridine ligand: synthesis, characterization, crystal structure determination, luminescent properties, and thermal analyses

[In(4,4′-dmbipy)(η2-NO3)2(η-NO3)(H2O)] complex (1) and [{In(4,4′-dmbipy)(η2-NO3)2}2(µ-OCH3)2] complex (2) (4,4′-dmbipy is 4,4′-dimethyl-2,2′-bipyridine) were prepared from the reaction of In(NO3)3·4H2O with 4,4′-dmbipy in CH3CN and CH3OH, respectively. [{In(4,4′-dmbipy)(η2-NO3)(η-NO3)}2(µ-OH)2] complex (3) was also prepared from the reaction of InCl3·4H2O with 4,4′-dmbipy in mixture of CH3CN/H2O in 3:1 ratio. These complexes were characterized by elemental analysis, IR, 1H NMR, 13C{1H}NMR, UV–Vis, and luminescence spectroscopy and their structures were studied by single-crystal X-ray diffraction method. Compound 1 is an eight-coordinated mononuclear complex, compound 2 is an eight-coordinated centrosymmetric dinuclear complex with two methoxy-bridges, and compound 3 is a seven-coordinated C2-symmetric dinuclear complex with two hydroxy-bridges. Also, the thermal stabilities of 1–3 were studied by thermogravimetric (TG) and differential thermal analyses (DTA).