Influence of methoxy-substituents on the strength of Br...Br type II halogen bonds in bromobenzoic acid

RAFFO, PABLO A.; MARCOLONGO, JUAN P.; FUNES, ALEJANDRO V.; SLEP, LEONARDO D.; BAGGIO, RICARDO F.; CUKIERNIK, FABIO D.

JOURNAL OF MOLECULAR STRUCTURE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 vol. 1108 p. 235 - 244

0022-2860

4-bromo-3,5-di(methoxy)benzoic acid (I) crystallizes in the monoclinic C2/c space group,a = 22.3405 (6) Å, b = 4.85142 (14) Å, c = 18.1583 (5) Å, β = 93.086 (2)º. The crystalstructure shows head-to-head dimeric units linked via type II Br?Br interactions as well asBr...π and weak H-bonding interactions. The whole structure exhibits features similar tothose of the parent 4-bromobenozic acid (II), most notably the overall geometricalfeatures involved in the Br?Br type II interactions. Both structures display comparable CBr?Br angles (θ1 = 98.3 and 91.6º and θ2= 163.0 and 163.5º for (I) and (II) respectively),but the Br?Br distance is significantly shorter in (I) (3.58 Å) than in (II) (3.81 Å). QMcomputations provide the magnitude of the intermolecular interactions present in both (I)and (II), and allow disclosing the individual covalent and electrostatic contributions to theBr...Br halogen bond in terms of interaction energies, electrostatic potentials; and amolecular orbital (MO) analysis.