A theoretical study on H-bonding interactions in maleic acid: calculated 17O, 1H NMR parameters and QTAIM analysis

Abstract

A theoretical study was carried out to examine intra- and intermolecular hydrogen bond (HB) properties in crystalline maleic acid (MA). We investigated geometries, 17O and 1H nuclear magnetic resonance parameters of various MA clusters by means of M06 and B3LYP functionals using recently developed Jensen's polarisation-consistent basis sets, pcJ-n (n = 0, 1, 2, 3). Our results reveal that the calculated chemical shift isotropy, δiso, at the sites of 17O and 1H nuclei depends markedly on the size of the basis set. Overall, convergence of the pcJ-n series is rather similar for both B3LYP and M06 functionals. An increase of δiso(17O) and δiso(1H) in going from the pcJ-1 to the pcJ-3 basis set is a typical feature of the (MA)1–3 clusters. The quantum theory of atoms in molecules (QTAIM) and energy decomposition analyses were also used to elucidate the interaction characteristics in the MA H-bonded network. According to QTAIM results obtained, it is concluded that strong HBs are more covalent in nature and weak HBs are mainly electrostatic interactions.