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artículo con referato
"BrBr and Van der Waals interactions along a homologous series: crystal packing of 1,2-dibromo-4,5-di­alkoxybenzenes"
Sebastián A. Suarez, Federico Muller, Matías E. Gutiérrez Suburu, Ana Fonrouge, Ricardo F. Baggio and Fabio D. Cukiernik
Acta Cryst. B 72(5) (2016) 693-701
The crystalline structures of four homologues of the 1,2-dibromo-4,5-dialkoxybenzene series [Br2C6H2(OCnH2n+1)2 for n = 2, 12, 14 and 18] have been solved by means of single-crystal crystallography. Comparison along the series, including the previously reported n = 10 and n = 16 derivatives, shows a clear metric trend (b and c essentially fixed along the series and a growing linearly with n), in spite of some subtle differences in space groups and/or packing modes. A uniform packing pattern for the aliphatic chains has been found for the n = 12 to 18 homologues, which slightly differs from that of the n = 10 derivative. The crystalline structures of all the higher homologues (n = 10-18) seem to arise from van der Waals interchain interactions and, to a lesser extent, type II BrBr interactions. The dominant role of interchain interactions provides direct structural support for the usual interpretation of melting point trends like that found along this series. Atoms in Molecules (AIM) analysis allows a comparison of the relative magnitude of the interchain and BrBr interactions, an analysis validated by the measured melting enthalpies.
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