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

摘要

Two chromium chalcogenide Cs[Cr(en)(2)GeSe4] (1) and Cs[Cr(en)(2)SnSe4] (2) have been synthesized by a solvothermal method. Both compounds crystallize in the monoclinic space group P2(1). The structures of the two compounds are characterized by isolated [Cr(en)(2)MSe4](-)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 3.97 mu B for Cs[Cr(en)(2)GeSe4] and 3.91 mu B for Cs[Cr(en)(2)SnSe4], 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)(2)GeSe4], and 14.2 J (kg K)(-1) for Cs[Cr(en)(2)SnSe4].