Synthesis, crystal and band structures, and optical properties of a new mixed-framework mercury selenide diselenite, (Hg3Se2)(Se2O5)

A new mixed-framework mercury selenide diselenite, (Hg(3)Se(2))(Se(2)O(5)) (1), has been prepared by a solid-state reaction and structurally characterized by single-crystal X-ray diffraction analysis. The crystal structure of 1 consists of parallel stair-like cationic (Hg(3)Se(2))(2+) chains, which are bridged by (Se(2)O(5))(2-) anionic groups to form a novel 2-D layered mixed-framework. The optical properties were investigated in terms of the diffuse reflectance and microscopic infrared spectra. The electronic band structure along with density of states (DOS) calculated by the DFT method indicates that compound 1 is a semiconductor, and that the optical absorption of 1 is mainly ascribed to the charge transitions from the O-2p and Se(-II)-4p states to the Se(IV)-4p and Hg-6s states.