Direct solvothermal growth, crystal structures, and optical properties of one-dimensional lanthanide selenidoarsenate(v) polymers [Ln(dien)2(µ3-AsSe4)] (Ln = Nd, Sm): the first example of an AsSe43− anion acting as a ligand to a lanthanide complex

Abstract

Two novel lanthanide selenidoarsenates(V) [Ln(dien)₂(µ₃-AsSe₄)] (Ln = Nd 1, Sm 2, dien = diethylenetriamine) were synthesized by the reactions of As₂O₃ and Se with Nd₂O₃ or Sm₂O₃ in dien under solvothermal conditions. 1 and 2 are in the orthorhombic crystal system with Iba2 and Pbca space groups, respectively. The [AsSe₄]³⁻ anion acts as a tridentate µ₃-AsSe₄ ligand to bridge the lanthanide [Ln(dien)₂]³⁺ complexes leading to one-dimensional neutral [Ln(dien)₂(µ₃-AsSe₄)]_∞ chains. The chains contact through hydrogen bonding to form network structures. The lanthanide center lies within a nine-coordinated environment involving six N atoms of two dien ligands and three Se atoms of two different tetrahedral [AsSe₄]³⁻ anions forming a distorted monocapped square antiprism. The novel coordination polymers [Nd(dien)₂(µ₃-AsSe₄)]_∞ and [Sm(dien)₂(µ₃-AsSe₄)]_∞ are the first examples of solvothermally synthesized selenidoarsenates with [AsSe₄]³⁻ anion acting as a ligand in lanthanide complexes. The band gaps of 2.11 eV for 1, and 2.18 eV for 2 have been derived from optical absorption spectra. TG-DSC curves show that two compounds remove coordinated dien ligands in a single step.