Effect of lanthanide contraction on the mixed polyamine systems Ln/Sb/Se/(en+dien) and Ln/Sb/Se/(en+trien): Syntheses and characterizations of lanthanide complexes with a tetraelenidoantimonate ligand

Mixed polyamine systems Ln/Sb/Se/(en+dien) and Ln/Sb/Se/(en+trien) (Ln=lanthanide, en=ethylenediamine, dien=diethylenetriamine, trien=triethylenetetramine) were investigated under solvothermal conditions, and novel mixed-coordinated lanthanide(III) complexes [Ln(en)₂(dien)(η²-SbSe₄)] (Ln=Ce(1a), Nd(1b)), [Ln(en)₂(dien)(SbSe₄)] (Ln=Sm(2a), Gd(2b), Dy(2c)), [Ln(en)(trien)(μ-η¹,η²-SbSe₄)]_∞ (Ln=Ce(3a), Nd(3b)) and [Sm(en)(trien)(η²-SbSe₄)] (4a) were prepared. Two structural types of lanthanide selenidoantimonates were obtained across the lanthanide series in both en+dien and en+trien systems. The tetrahedral anion [SbSe₄]³⁻ acts as a monodentate ligand mono-SbSe₄, a bidentate chelating ligand η²-SbSe₄ or a tridentate bridging ligand μ-η¹,η²-SbSe₄ to the lanthanide(III) center depending on the Ln³⁺ ions and the mixed ethylene polyamines, indicating the effect of lanthanide contraction on the structures of the lanthanide(III) selenidoantimonates. The lanthanide selenidoantimonates exhibit semiconducting properties with E_g between 2.08 and 2.51 eV.