Solvothermal syntheses and characterization of new thioantimonates [Pr(en)3(H2O)(μ2-SbS4)] and [Gd(en)4]SbS4·0.5en (en = ethylenediamine): The anion acting as a bridging ligand to lanthanide complex

Two new lanthanide thioantimonates, [Pr(en)3(H2O)(μ2-SbS4)] and [Gd(en)4]SbS4·0.5en (en = ethylenediamine), were synthesized using the solvothermal method by reacting LnCl3, Sb and S in en at 160 °C. The crystal structure of 1 consists of a one-dimensional [Pr(en)3(H2O)(μ2-SbS4)]∞ neutral chain, in which the SbS 4 3 - anion act as a bridging ligand to connect [Pr(en)3(H2O)]3+ ions. The Pr3+ ion is in a nine coordination geometry involving six nitrogen atoms of three bidenate en ligands, two sulfur atoms of two different SbS 4 3 - anions, and an oxygen atom of one water molecule to form a distorted monocapped square antiprism. The crystal structure of 2 contains an isolated bicapped trigonal prism complex cation [Gd(en)4]3+, a tetrahedral anion SbS 4 3 - and half a free en molecule in the asymmetric unit. The structural difference between the two thioantimonates is related with the stability of Pr3+ and Gd3+ complexes with en ligands. The band gaps of 2.35 eV for 1, and 3.21 eV for 2 have been derived from optical absorption spectra. Thermogravimetric measurements show that both compounds decompose in two steps in the nitrogen stream.