The utility of 4-aminobenzoic acid in promotion of hydrogen bonding in crystallization processes: the structures of the cocrystals with halo and nitro subsituted aromatic compounds, and the crystal structures of the adducts with 4-nitroaniline (1:1), 4-(4-nitrobenzyl)pyridine (1:2), and (4-nitrophenyl)acetic acid (1:1)
A number of molecular adducts of 4-aminobenzoic acid (4-ABA) have been prepared and characterized using infrared spectroscopy and in three cases by X-ray diffration methods. These three compounds are with 4-nitroaniline [(4-ABA) (C6H6N2O2)], 4-(4-nitrobenzyl) pyridine, [(4-ABA)2(C12H10N2O2)4], and (4-nitrophenyl)acetic acid, [(4-ABA) (C8H7NO4)]. Other compounds described are with 4-chlorobenzoic acid, [(4-ABA) (C7H5ClO2)], 4-bromobenzoic acid, [(4-ABA) (C7H5BrO2)], 4-cyanobenzoic acid, [(4-ABA) (C7H6N2)], 2-nitrobenzoic acid, [(4-ABA) (C7H5NO4)], and 3-nitrobenzoic acid, [(4-ABA) (C7H5NO4)]. All compounds have 1:1 stoichiometry except that with 4-(4-nitrobenzyl)pyridine (1:2) which is unique in being retro-stoichiometric. A review of the systematics of the 4-aminobenzoic acid adducts is also made, particularly with respect to the infrared characterization of the cocrystalline materials and prediction of their NLO potential.