Investigating metal size effects in the Ln/As/Se/amine (Ln = lanthanide excluding Pm, amine = en, dien, en+trien) systems: solvothermal syntheses and characterizations of lanthanide selenidoarsenates

Abstract

Three solvothermal systems Ln/As/Se/en, Ln/As/Se/dien and Ln/As/Se/(en+trien) (Ln = lanthanide excluding Pm, en = ethylenediamine, dien = diethylenetriamine, trien = triethylenetetramine) were investigated in detail across the lanthanide series, and ternary lanthanide selenidoarsenates [Ln(en)₃(H₂O)(μ-η¹,η¹-AsSe₄)] (Ln = La(1a), Ce(1b), Nd(1c)), [Ln(en)₄]AsSe₄·0.5en (Ln = Sm(1d), Gd(1e), Dy(1f)), [Ln(dien)₂(μ-η¹,η²-AsSe₄)] (Ln = La(2a), Ce(2b), Pr(2c)), [Ln(en)(trien)(μ-η¹,η²-AsSe₄)] (Ln = La(3a), Nd(3b)) and [Sm(en)(trien)(η²-AsSe₄)] (3c) were prepared. Systematic investigations of the three systems clarify the relationship between the molecular structures of the synthetic lanthanide selenidoarsenates and the metal size evolution of the lanthanide series. Meanwhile, the coordination modes of the [AsSe₄]³⁻ tetrahedral anion to the same lanthanide ion are dependent on the denticity of ethylene polyamine as the second ligand. The lanthanide selenidoarsenates exhibit semiconducting properties with E_g between 2.15 and 2.31 eV.