Crystal chemistry of open framework sulfides and x-ray diffraction study with synchrotron radiation/imaging plate system.

摘要

The hydrothermal synthesis of metal (Ge, Sn and Sb) sulfides in the presence of organic templates produced novel open frameworks. Single crystal X-ray diffraction experiments have gradually revealed their distinctive crystal chemistry. The structures of these compounds are found to be constructed from secondary building units (SBU) and are characterized by large pore volumes with unique window geometry. They are potentially useful materials for separation, ion exchange, catalytic and optical applications.; In the open framework thiogermanates, Ge is tetrahedrally coordinated. The adamantine-like cluster, {dollar}rm lbrack Gesb4Ssb{lcub}10{rcub}rbrack sp{lcub}4-{rcub}{dollar}, condensed from {dollar}rm 4 lbrack GeSsb4rbrack sp{lcub}4-{rcub}{dollar} primary building units (PMU), is the dominant SBU. It can be polymerized to form open frameworks through either corner-sharing connection or through bridging with transition metals. In the tin sulfide system, Sn tends to have higher or mixed coordination numbers. One principal building units is the {dollar}rm lbrack Snsb3Ssb7rbrack sp{lcub}2-{rcub}{dollar} semi-cube, which is an oligomer formed from three {dollar}rm lbrack SnSsb5rbrack sp{lcub}6-{rcub}{dollar} trigonal bipyramidal PMU. The semi-cubes can make frameworks through edge-sharing connections with themselves or with other 4- or 6-coordinated thiostannate species. Along with sulfides, a number of oxy-sulfide open frameworks have also been produced. In the SbS system, the Sb usually has three Sb-S bonds with S-Sb-S angles around 90 degree. The {dollar}5ssp2{dollar} lone pair on the Sb has a profound effect on the stereochemistry and is responsible for one or two "long" Sb-S bonds. They contribute the formation of the most common SBU, fused semi-cubes and fused cubes, from which a family of unique frameworks is obtained.; The open framework chalcogenides typically crystallize either as powders or as small crystals, unsuitable for conventional X-ray diffractometry. The brilliance obtainable at synchrotron radiation sources together with the higher sensitivity and the wider dynamic range of the imaging plate has made it possible to detect X-ray diffraction from a very small single crystals. This new technology has greatly facilitated the structural analysis of these materials and improved understanding of the systematics of their crystal chemistry.