Five benzoic acid derivatives: Crystallographic study using X-ray powder diffraction, electronic structure and molecular electrostatic potential calculation

Abstract

Crystal structures of five ortho-, meta-, and para-substituted benzoic acid derivatives, 2-fluoro-4-hydroxymethyl benzoic acid (1), 4-chloro-3 nitrobenzoic acid (2), 5-bromo-2-methyl benzoic acid (3), 4-bromo-2 nitrobenzoic acid (4) and 4-chloro-2-iodobenzoic acid (5) have been determined using X-ray powder diffraction. DFT optimized molecular geometries of 1–5 agree closely with those obtained from the crystallographic study. The nature of intermolecular interactions in 1–5 has been analyzed through Hirshfeld surfaces and 2D fingerprint plots, and compared with that of unsubstituted benzoic acid compound. The crystal packing of 1–5 exhibits an interplay of intermolecular OH⋯O, CH⋯O and CH … X (X = F, Cl, Br) hydrogen bonds, and C-X (X = Cl, Br, I)⋯O halogen bonds, which assemble molecules into a supramolecular framework. Hydrogen- and halogen-bond based interactions in 1–5 have been complemented by the molecular electrostatic potential (MEP) surface calculation. The electronic structure of compounds (1–5) reveals that the estimated band gap in 4, with the nitro and bromo groups at the ortho and para positions with respect to the COOH group, is the lowest (2.72 eV) among the molecules; the corresponding value in the unsubstituted benzoic is 3.95 eV.