Synthesis, Crystal and Band Structures, and Properties of a New Mixed Three-Dimensional Framework Metal Pnictidehalide Semiconductor, (Hg₆Sb₄)(CdI₆)

Abstract

A new, quaternary mercury and cadmium pnictidehalide semiconductor (Hg6Sb4)(CdI6) (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 R-3c of the rhombohedral system with four formula units in a cell: a=13.3818(9) A, alpha=90.93 degrees, and V=2395.3(3) A3. The crystal structural novelty of 1 derives from the fact that a 3-D mercury antimonide cationic network interpenetrates with an unusual 3-D cadmium iodide octahedral anionic network through the weak covalent interactions between mercury and iodine atoms to form a mixed 3-D framework. Among them, the cationic moiety features a perovskite-like 3-D network while the anionic moiety is characterized by a 3-D I6 octahedral anionic network with two-thirds I6 octahedra being occupied by Cd atoms. 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 calculated by the density functional theory method indicates that compound 1 is a semiconductor with a direct band gap and that the optical absorption of 1 is mainly ascribed to the charge transitions from I-5p and Sb-5p states to Cd-5s and Hg-6s states.

Large Mid-IR Second-Order Nonlinear-Optical Effects Designed by the Supramolecular Assembly of Different Bond Types without IR Absorption

“…The shortest interatomic distances between the halogen atoms of the guest anions and the Hg atoms in the host frameworks of 1 and 2 are 2.894(4) and 2.941(3) Å, respectively, which are much longer than the Hg–Cl covalent bond length but shorter than the sum of the van der Waals radii of the Hg and Cl atoms. This indicates that there are weak supramolecular interactions between the cationic and anionic moieties in the crystal structures of 1 and 2 , as was the case found in the literature . It can be seen from Table S2 in the SI that Zn1 and Zn2 atoms in 2 are equivalently split into two symmetric positions, which can be ascribed to the weak supramolecular interactions between the host and guest.…”

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

“…11 Recently, we have begun a systematic investigation of mixedframework compounds composed of pnictide-based mixed-anions to explore new semiconducting materials. 12 In the present work, in order to obtain a new class of mixed-framework compounds, we have chosen to incorporate the Hg 2+ cation with chalcogenide and oxochalcogenide anions because mercury chalcogenides and mercury oxochalcogenides show good chemical and physical properties. During the course of our research the series of chalcogen elements from S to Te as anions was used, we succeeded only in obtaining a new mercury selenide diselenite semiconductor, (Hg 3 Se 2 )(Se 2 O 5 ) (1), with a new mixed-framework structural type.…”