Solvothermal syntheses,crystal structures,and optical and thermal properties of transition metal selenidostannates

Four organic–inorganic hybrid selenidostannates, namely H₂en]H₂dien]Fe(dien)₂]₂(Sn₂Se₆)₂ (1), Fe(dien)₂]₂Sn₂Se₆ (2), Fe(dien)₂]FeSnSe₄ (3), and Mn(dien)₂]MnSnSe₄ (4) (en = ethylenediamine; dien = diethylenetriamine), were prepared in different solvents under solvothermal conditions. Complexes 1 and 2 consist of discrete Sn₂Se₆]^4? and Fe(dien)₂]²⁺ ions, as well as organic cations H₂en]²⁺ and H₂dien]²⁺ in 1. The dimeric Sn₂Se₆]^4? anion is formed by two SnSe₄ tetrahedra via edge-sharing. Complexes 3 and 4 are composed of one-dimensional polyanions TMSnSe ₄ ^2? ] _n plus TM(dien)₂]²⁺ counter cations (TM = Fe, Mn). In the TMSnSe ₄ ^2? ] _n anionic chain, the TM and Sn atoms are located at the same metal site with a ratio of 0.5/0.5. The TM_1/2Sn_1/2Se₄ tetrahedra are interlinked via edge-sharing, forming the heterometallic TMSnSe ₄ ^2? ] _n polymeric anion. The TM(dien)₂]²⁺ cations in 1–2 and 3–4 have u-fac and mer configurations, respectively. In all four crystal structures, the anions and cations are connected into extended structures via weak N–H···Se hydrogen bonds. The band gaps of complexes 1–4 calculated from the solid-state UV–vis diffuse reflectance spectra were at 2.58, 2.60, 2.21, and 2.25 eV, respectively. Thermogravimetric analyses show that complex 1 decomposes in three steps, while complexes 2–4 each decompose in one step.