Hydrothermal syntheses, crystal structures, and optical properties of transition metal selenidostannates
New organic–inorganic hybrid selenidostannates [{Mn(2,2′-bipy)2}2(µ2-Sn2Se6)] (1) and [TM(2,2′-bipy)3]2[Sn3Se7]2·(2,2′-bipy)·H2O (TM = Co (2), Ni (3); 2,2′-bipy = 2,2′-bipyridine) were prepared under hydrothermal conditions. In 1, two edge-sharing [SnSe4] tetrahedra condense to form a dimeric [Sn2Se6]4– unit. The [Sn2Se6]4– unit is a tetradentate chelating ligand via four terminal Se atoms to join two unsaturated [Mn(2,2′-bipy)2]2+ complexes, forming a neutral complex [{Mn(2,2′-bipy)2}2(µ2-Sn2Se6)]. Compounds 2 and 3 consist of extended [Sn3Se7]2– selenidostannate anions, octahedral [TM(2,2′-bipy)3]2+ complex cations, and 2,2′-bipy and H2O molecules. The structural features of 2 and 3 are coexistence of both 1-D and 2-D polymeric anions. The 1-D chain is constructed by interconnection of the secondary building units (SBUs) Sn3Se9 via sharing two Se atoms, while the 2-D layer is constructed by Sn3Se10 SBUs via sharing three Se atoms. Compounds 1–3 exhibit narrow semiconducting band gaps varying in the range of 1.95–2.14 eV. Compound 2 displays higher photocatalytic activity than 1 on the degradation of crystal violet in water under visible irradiation.
