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Crystal Morphology as an Evidence of Supramolecular Organization in Adducts of 1,2-Bis(chloromercurio)tetrafluorobenzene with Organic Esters

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posted on 07.09.2011, 00:00 by Andrey A. Yakovenko, Jose H. Gallegos, Mikhail Yu. Antipin, Artem Masunov, Tatiana V. Timofeeva
Low melting organic esters, ethyl acetate (1), diethyl carbonate (2), methyl benzoate (3) and phenyl acetate (4), have been grown using the miniature zone melting in situ crystallization technique and their molecular and crystal structures have been determined. Co-crystallization of the esters 14 with Lewis acid 1,2-bis(chloromercurio)tetrafluorobenzene (II) resulted in three adducts with a ratio of organic to organometallic components of 1:1 (II·1, II·3, and II·4), and one complex with a corresponding ratio of 1:2 (2(II)·2). X-ray analysis revealed presence of supramolecular 1D chain associates in crystals of II·1 and II·3, which are similar to those found before in the crystal of individual II. The crystal structures of complexes 2(II)·2 and II·4 have demonstrated the presence of 2D layer supramolecular associates. Both 1D and 2D associates are stabilized mostly by strong Hg···Cl interactions between molecules of II, which in some cases are additionally strengthen via Hg···O, Hg···π, and π–π interactions between molecules of esters and II. Clear correlation between type of supramolecular associates and crystal morphology was found: complexes with 1D supramolecular associates grow in the form of needle-like crystals, while 2D associates promote formation of the plate-like crystals. Comparison of structural characteristics of esters 14 in crystals of individual compounds, complexes, and isolated state (quantum calculations and gas electron diffraction literature data) has demonstrated similarity of the molecular geometry but possibility of conformational variations. On the basis of correlation analysis of structural and IR spectroscopic data on all compounds under investigation and taking into account that sum of the van der Waals radii of the Hg and O is equal to 3.50 Å, it was shown that shorter Hg···O contacts should correspond to an additional interactions between these types of atoms.