Synthesis, crystal and band structures, and properties of a new supramolecular complex (Hg2As)2(CdI4)

A new quaternary supramolecular complex (Hg2As)2 (CdI4) (1) has been prepared by the solid-state reaction and structurally characterized by single crystal X-ray diffraction analysis. Compound 1 crystallizes in the space group P21 of the monoclinic system with two formula units in a cell: a=7.945(4), b=12.934(6), c=8.094(4) Å, β=116.898°(1), V=741.7(6) Å3. The structure of 1 is characterized by a tridymite-like three-dimensional cationic framework, which is composed of mercury and arsenic atoms, with the channels being occupied by discrete CdI42− tetrahedral guest-anions. The optical properties were investigated in terms of the diffuse reflectance and Fourier transform infrared spectra. The electronic band structure along with density of states (DOS) calculated by DFT method indicates that the present compound is a semiconductor with a direct band gap, and that the optical absorption is mainly originated from the charge transitions from I-5p and As-4p to Cd-5s and Hg-6s states.