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

Abstract

The crystalline structures of four homologues of the 1,2-dibromo-4,5-dialkoxybenzene series [BrCH(OCH) 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 Br...Br 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 Br...Br interactions, an analysis validated by the measured melting enthalpies.

Heterochiral recognition among functionalized heptahelicenes on noble metal surfaces

“…1d. It is known from crystal structure studies that Br⋅⋅⋅Br interactions are not very dominant, 32,33 and on the gold surface here the additional Br atoms do not cause a different self-assembly motif than observed for [7]H. Forcefield modelling yields as binding energy of Br [7]H enantiomers in a vdW-dimer of 4.5 kcal/mol (Fig.…”

Pt(II) Complexes with Tetradentate C^N*N^C Luminophores: From Supramolecular Interactions to Temperature-Sensing Materials with Memory and Optical Readouts

“…Consequently, the interaction between the aromatic cores within the aggregates is more pronounced. Conversely, the longer alkyl moieties disrupt the interactions between the aromatic planes [56,57]. As a result of these combined effects, PtL b -12 is able to return to a Powder X-ray diffractometry of PtL a -12 was performed before and after heating the sample above the transition temperature.…”