Abstract
Three new lanthanide selenidoantimonates [Ln(en)~4~(SbSe~4~)] [Ln = La (1), Nd (2)] and [Sm(en)~4~]SbSe~4~·0.5en (3) (en = ethylenediamine) were first synthesized by treating LnCl~3~, Sb, and Se in a stoichiometric ratio with en under mild solvothermal conditions. Compounds 1 and 2 are isostructural. The Ln^3+^ ion has a nine‐coordinate environment involving eight N atoms from four en ligands and one Se atom from the SbSe~4~^3–^ anion forming a distorted bicapped pentagonal bipyramid. [La(en)~4~(SbSe~4~)] and [Nd(en)~4~(SbSe~4~)] are the first examples of solvothermally synthesized selenidoantimonates with an SbSe~4~^3–^ anion acting as a ligand in a lanthanide complex. The crystal structure of 3 contains an isolated bicapped trigonal‐prismatic coordinated [Sm(en)~4~]^3+^ cation, a tetrahedral SbSe~4~^3–^ anion, and half a free en molecule in its asymmetric unit. The bandgaps of 2.22 eV for 1, 2.33 eV for 2, and 2.54 eV for 3 have been derived from optical absorption spectra. Compound 1 loses the en ligands in one step, whereas compound 2 loses them in two steps. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)