Solvothermal synthesis, structure and physical properties of Cs[Cr(en)2MSe4] (M = Ge, Sn) with [MSe4]4− tetrahedra as chelating ligand

Abstract

Two chromium chalcogenide Cs[Cr(en)₂GeSe₄] (1) and Cs[Cr(en)₂SnSe₄] (2) have been synthesized by a solvothermal method. Both compounds crystallize in the monoclinic space group P2₁/n. The structures of the two compounds are characterized by isolated [Cr(en)₂MSe₄]⁻ clusters separated by Cs⁺ ions. The optical properties of the two compounds were measured which indicate a similar band gap of 1.58 eV. DFT calculations demonstrated that the valance band maximum (VBM) consist of Cr 3d orbitals and Se 4p orbitals while the conductive band minimum (CBM) are composed of Cr 3d orbitals for both compounds, which explains their similar optical band gap energies. Both compounds possess paramagnetic behaviors with the effective magnetic moment of 3.97μ_B for Cs[Cr(en)₂GeSe₄] and 3.91μ_B for Cs[Cr(en)₂SnSe₄], respectively. Field-dependent magnetization measurements demonstrated their potential as magnetocaloric materials, with the magnetic entropy change of 11.6 J (kg K)⁻¹ for Cs[Cr(en)₂GeSe₄], and 14.2 J (kg K)⁻¹ for Cs[Cr(en)₂SnSe₄].