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artículo con referato
"Influence of methoxy-substituents on the strength of BrBr type II halogen bonds in bromobenzoic acid"
Pablo A. Raffo, Juan P. Marcolongo, Alejandro V. Funes, Leonardo D. Slep, Ricardo F. Baggio and Fabio D. Cukiernik
J. Mol. Struct. 1108 (2016) 235-244
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)°. The crystal structure shows head-to-head dimeric units linked via type II BrBr interactions as well as Brπ and weak H-bonding interactions. The whole structure exhibits features similar to those of the parent 4-bromobenzoic acid (II), most notably the overall geometrical features involved in the BrBr type II interactions. Both structures display comparable C–BrBr angles (θ1 = 98.3 and 91.6° and θ2 = 163.0 and 163.5° for (I) and (II) respectively), but the BrBr distance is significantly shorter in (I) (3.58 Å) than in (II) (3.81 Å). QM computations provide the magnitude of the intermolecular interactions present in both (I) and (II), and allow disclosing the individual covalent and electrostatic contributions to the BrBr halogen bond in terms of interaction energies, electrostatic potentials, and a molecular orbital (MO) analysis.
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