Br?Br and Van der Waals interactions along a homologous series: crystal packing of 1,2-dibromo-4,5-dialkoxybenzenes
SEBASTIAN SUAREZ; FEDERICO MULLER; MATÍAS E. GUTIÉRREZ-SUBURU; ANA FONROUGE; RICARDO F. BAGGIO; FABIO D. CUKIERNIK
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials
John Wiley and Sons Inc.
Lugar: New Jersey; Año: 2016 vol. 72
The crystalline structures of four homologues of the 1,2-dibromo-4,5-di(alkoxy)benzene 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 an 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 have 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 to 18) seem to arise from van der Waals interchain interactions and, to a lesser extent, type II Br...Br interactions. The dominant role of interchain interactions provides direct structural support for the usual interpretation of melting point trends like the one found along this series. AIM analysis allows a comparison of the relative magnitude of the interchain and Br...Br interactions, an analysis validated by the measured melting enthalpies.