Molecular structure and intramolecular hydrogen bonding in 2-hydroxybenzophenones: A theoretical study

Abstract

The intramolecular hydrogen bonding (IHB) in a series of 3-, 4- and 5-substituted 2-hydroxybenzophenone (HBP) is studied using density functional theory calculations. All calculations are performed at the B3LYP level, using 6-311 ++G** basis set. To understand the substitution effects on the nature of IHB and the electronic structure of the chelated ring system, the vibrational frequencies, 1H chemical shift, topological parameters, natural bond orders and natural charges over atoms involved in the chelated ring of HBP and its derivatives were calculated. The Wiberg bond indices and the natural charges over atoms involved in the chelated ring have been computed using the natural bond orbital (NBO) analysis. The computations were further complemented with an atoms-in-molecules (AIM) topological analysis to characterize the nature of the IHB in the considered molecules. Several correlations between geometrical parameters, 1H NMR chemical shift and topological parameters with the IHB strength are obtained. The intramolecular hydrogen bonding in a series of 3-, 4-, and 5-substituted 2-hydroxybenzophenone is studied using density functional theory calculations and AIM and NBO analysis. It is shown that position of substitution and the nature of substituents have are very important in determining the nature of hydrogen bond.