PACKING OF CHIRAL MOLECULES OF METAL TRIS-ACETYLACETONATES
P. A. Stabnikov, G. I. Zharkova, L. A. Komissarova, A. I. Smolentsev, S. V. Borisov
Keywords: chiral molecules, metal tris-acetylacetonates, low temperature thermochromism and phase transformations
Pages: 575-586
Abstract
The Cambridge Crystallographic Data Centre (CCDC) is searched to organize packings of metal tris-acetylacetonates М(aa)3 (about 70 structures over the last 50 years). In all structures, planes with a hexagonal molecular environment are found. Three types of the nearest hexagonal environment are revealed in these planes with allowance for the chirality of molecules. Different superposition of these planes produces five types of packing of metal tris-acetylacetonates: α, β, γ, δ, and η. Spectrally pure Al(aa)3, Cr(aa)3, Mn(aa)3, and Fe(aa)3 complexes are synthesized and their solid solutions are studied. The effect of impurities on crystallization is established. A temperature range of 210 K to 100 K, in which we have previously detected thermochromism of metal β-diketonates is distinguished. In the same range, a symmetry change was previously found for Al(aa)3 and Mn(aa)3, however, Cr(aa)3 symmetry did not change in this temperature range. The ratios of components in solid solutions, at which low temperature symmetry change is observed in the complexes, are found experimentally. The relation between thermochromism and the symmetry change is discussed
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