Three-Dimensional Mercury Pnictide [Hg_4Z_2]~(2+) Cationic Frameworks Stabilized by Tetravalent Metal Halide Anions in Supramolecular Complexes: [Hg_4Z_2][MCl_6](Z = P, As; M = Zr, Hf)

摘要

Four new inorganic supramolecular complexes,[Hg_4P_2][ZrCl_6] (1), [Hg_4As_2][ZrCl_6] (2), [Hg_4P_2][HfCl_6] (3), and [Hg_4As_2][HfCl_6] (4), have been prepared by moderatetemperature solid-state reactions. All compounds crystallize in the space group Pbca of the orthorhombic system with Z= 8. Their structures are built up of mercury pnictide cationic hosts and distorted octahedral [MCl_6]~(2-) (M = Zr, Hf) guests. The isolated octahedral guests consist of tetravalent Zr~(4+) and Hf~(4+) cations coordinated by chlorine atoms and are embedded in the infinite channels formed by the host framework. Their optical properties were investigated in terms of their diffuse reflectance and FTIR spectra. The electronic band structures along with densities of states (DOS) calculated by DFT indicate that all of the title compounds are semiconductors with direct band gaps, and their optical absorptions mainly originate from charge transitions from Cl 3p and P 3p/As 4p states to Hg 6s, Hg 5p, and Zr 4d/Hf 5d states. Optical dielectric constant calculations show that 1-4 possess dielectric anisotropy, which is consistent with their structural studies.