Title
Chiral polyoxomolybdate-based hybrid compounds obtained by spontaneous resolution: syntheses, structures and nonlinear optical properties
Author
Yujiao Hou, Haiyan An, Tieqi Xu, Sangen Zhao, Junhua Luo
Year
2016
Journal
New Journal of Chemistry
Abstract
In this paper, we report two chiral sheet-like structures based on amino acid functionalized polyoxomolybdates, [Na(H2O)2][Na(H2O)3][MMo6O21(O2CCH2NH3)3]∙2.5H2O (M=Te 1, Se 2; O2CCH2NH3 = glycine), which were synthesized by spontaneous resolution without chiral auxiliary. And they were characterized by single crystal X-ray crystallography, elemental analysis, powder X-ray diffraction, IR spectroscopy, solid diffuse reflective spectrum, circular dichroism spectrum and TG analysis. Isostructural compounds 1 and 2 crystallize in the chiral space group P21, and exhibit a 2D chiral framework in which glycine functionalized polyoxoanions [MMo6O21(O2CCH2NH3)3]2- as structural units are linked up together by alkali metal Na+ cations. According to the chiral structure of both compounds, we speculate that the symmetry breaking of the polyoxoanions 17mainly depends on attaching glycine and Na+ cation to the polyoxometalates by covalent bonds. The absolute configuration of 1 and 2 was determined from the Flack parameter by X-ray crystallography and solid state circular dichroism spectroscopy. Remarkably, the bulk sample is enantiomeric excess, confirmed by the random measurement of 8 single crystal data of compound 1 and solid state circular dichroism spectra of bulk sample 1. Furthermore, in consideration of the asymmetry structure, we detected the second harmonic generation (SHG) efficiency of both compounds, which respectively show SHG response of approximately 3.5 and 3.7 × KH2PO4. To our best knowledge, compounds 1 and 2 represent the chiral heteropolymolybdates holding the strongest SHG efficiency.
Instrument
J-810
Keywords
Circular dichroism, Solid-state Stereochemistry