Solvothermal syntheses, and characterization of [Ln(en)4(SbSe4)] (Ln=Ce, Pr) and [Ln(en)4]SbSe4·0.5en (Ln=Eu, Gd, Er, Tm, Yb): The effect of lanthanide contraction on the crystal structures of lanthanide selenidoantimonates(V)

Two types of lanthanide selenidoantimonates [Ln(en)4(SbSe4)] (Ln=Ce(1a), Pr(1b)) and [Ln(en)4]SbSe4·0.5en (Ln=Eu(2a), Gd(2b), Er(2c), Tm(2d), Yb(2e); en=ethylenediamine) were solvothermally synthesized by reactions of LnCl3, Sb and Se with the stoichiometric ratio in en solvent at 140 °C. The four-en coordinated lanthanide complex cation [Ln(en)4]3+ formed in situ balances the charge of SbSe43− anion. In compounds 1a and 1b, the SbSe43− anion act as a monodentate ligand to coordinate complex [Ln(en)4]3+ and the neutral compound [Ln(en)4(SbSe4)] is formed. The Ln3+ ion has a nine-coordinated environment involving eight N atoms and one Se atom forming a distorted monocapped square antiprism. In 2a–2e the lanthanide(III) ion exists as isolated complex [Ln(en)4]3+, in which the Ln3+ ion is in a bicapped trigonal prism geometry. A systematic investigation of the crystal structures reveals that two types of structural features of these lanthanide selenidoantimonates are related with lanthanides contraction across the lanthanide series. TG curves show that compounds 1a–1b and 2a–2e remove their organic components in one and two steps, respectively.