Intra- and inter-molecular interactions in salicylic acid — Theoretical calculations of17O and1H chemical shielding tensors and QTAIM analysis

Abstract

A density functional theory (DFT) study was performed to examine intra- and inter-molecular hydrogen bond (HB) properties in crystalline salicylic acid (SA). BLYP, B3LYP, and M06 functionals with 6–311++G** basis set were employed to calculate NMR chemical shielding isotropy (σiso) and anisotropy (Δσ) at the sites of the17O and1H nuclei of SA. From this study, it appears that the intra- and inter-molecular O–H···O as well as C–H···O HBs around the SA molecule in the crystal lattice have a major influence on the chemical shielding tensors and more specifically on the carbonyl17O isotropy value. The quantum theory of atoms in molecules (QTAIM) analysis was also employed to elucidate the interaction characteristics in SA H-bonded network. Based on QTAIM results, a partial covalent character is attributed to the intra- and inter-molecular O–H···O HBs in SA.