RELATIONSHIP BETWEEN SYMMETRY IN HYDROGEN-BONDED BENZOIC-ACIDS AND THE FORMATION OF ACENTRIC CRYSTAL-STRUCTURES

Using a data set of 139 benzoic acids extracted from the Cambridge Crystallographic Data File, a relationship is shown to exist between inversion in hydrogen-bonded aggregates of benzoic acid derivatives and inversion symmetry in their crystal structures. Benzoic acids that aggregate in acentric chains tend to crystallize in acentric space groups. Ortho-substituted benzoic acids are shown to be more likely to organize in hydrogen-bonded chains than meta- or para-substituted benzoic acids. This demonstrates that ortho substitution can indirectly promote the formation of acentric benzoic acid crystals. This information is of practical importance for designing new nonlinear optical materials, because only acentric crystals can exhibit second-order nonlinear optical properties.