Br...Br and van der Waals interactions along a homologous series: crystal packing of 1,2-dibromo-4,5-dialkoxybenzenes

SEBASTIAN SUAREZ; MULLER, FEDERICO; GUTIERREZ SUBURU, MATIAS E.; FONROUGE, ANA; BAGGIO, RICARDO F.; CUKIERNIK, FABIO D.

ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 72 p. 693 - 701

0108-7681

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] havebeen solved by means of single-crystal crystallography. Comparison along theseries, including the previously reported n = 10 and n = 16 derivatives, shows aclear metric trend (b and c essentially fixed along the series and a growinglinearly with n), in spite of some subtle differences in space groups and/orpacking modes. A uniform packing pattern for the aliphatic chains has beenfound 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 interactionsprovides direct structural support for the usual interpretation of melting pointtrends like that found along this series. Atoms in Molecules (AIM) analysisallows a comparison of the relative magnitude of the interchain and BrBrinteractions, an analysis validated by the measured melting enthalpies.