Solvothermal syntheses, crystal structures, and properties of lanthanide(III) thioarsenates [Ln(dien)_2(μ-1κ, 2κ~2-AsS_4)]_n (Ln==Sm, Eu, Gd) and [Ln(dien)_2(1κ~2-AsS_4)] (Ln==Tb, Dy, Ho)

摘要

Solvothermal reactions of Ln_2O_3, As and S in diethylenetriamine (dien) at 170 C for 6 days afforded two structural types of lanthanide thioarsenates with the general formulae [Ln(dien)_2(μ- 1κ,2κ~2-AsS_4)]_n [Ln=Sm(1), Eu(2), Gd(3)] and [Ln(dien)_2(1κ~2-AsS_4)] [Ln=Tb(4), Dy(5), Ho(6)]. The Ln_2O_3 oxides were converted to [Ln(dien)_2]~(3+) complex units in the solvothermal reactions. The As atom binds four S atoms, forming a tetrahedral AsS_4 unit. In 1-3, the AsS_4 units interconnect the [Ln(dien) _2]~(3+) cations via Ln-S bonds as tridentate μ-1κ,2κ~2-AsS_4 bridging ligands, resulting in the neutral coordination polymers [Ln(dien)_2(μ-1κ, 2κ~2-AsS_4)]_n (Ln1). In 4-6, the AsS _4 units coordinate with the Ln~(3+) ion of [Ln(dien) _2]~(3+) as 1κ~2-AsS_4 chelating ligands to form neutral coordination compounds [Ln(dien)_2(1κ ~2-AsS_4)] (Ln2). The Ln~(3+) ions are in nine- and eight-coordinated environments in Ln1 and Ln2, respectively. The formation of Ln1 and Ln2 is related with ionic size of the Ln~(3+) ions. Optical absorption spectra showed that 1-6 have potential use as semiconductors with the band gaps in the range 2.18-3.21 eV.