Theoretical Characterization of Hydrogen Bonding Interactions between RCHO (R = H, CN, CF3, OCH3, NH2) and HOR′(R′ = H, Cl, CH3, NH2, C(O)H, C6H5)

In this work, density functional theory and ab initio molecular orbital calculations were used to investigate the hydrogen bonded complexes of type RCHO ⋯HOR′ (R = H, CN, CF 3 , OCH 3 , NH 2 , R′ H, Cl, CH 3 , NH 2 , C(O)H, C 6 H 5 ) employing 6-31 ++g** and cc-pVTZ basis sets. Thus, the present work considers how the substituents at both the hydrogen bond donor and acceptor affect the hydrogen bond strength. From the analysis, it is reflected that presence of –OCH 3 and –NH 2 substituents at RCHO greatly strengthen the stabilization energies, while –CN and –CF 3 decrease the same with respect to HCHO as hydrogen bond acceptor. The highest stabilization results in case of (H 2 N)CHO as hydrogen bond acceptor. The variation of the substituents at –OH functional group also influences the strength of hydrogen bond; nearly all the substituents increase the stabilization energy relative to HOH. The analysis of geometrical parameters; proton affinities, charge transfer, electron delocalization studies have been carried out. Graphical Abstract Theoretical calculations were carried out on the RCHO•••HOR’ (R = H, CN, CF 3 , OCH 3 , NH 2 ; R’ = H, Cl, CH 3 , NH 2 , C(O)H, C 6 H 5 ) hydrogen bonded complexes. The role of substituents on hydrogen donor and acceptor ability has been explored on the basis of analysis of geometrical data, proton affinities, NBO, AIM, SAPT, MESP and stabilization energies.