A novel azocompound, 2-(4-phenylazoaniline)-4-phenylphenol: Spectroscopic and quantum-chemical approach

摘要

A novel azocompound with two nonequivalents azo groups, 2-(4-phenylazoaniline)-4-phenylphenol, was synthesized and characterized by spectroscopic and computational analysis. An intramolecular hydrogen bonding (HB), -O_1-H_1···N_1-, involving the -N_1=N_2- group and the proton in a neighbor hydroxyl moiety, was identified. It was found responsible for a characteristic π-conjugated H_1-O_1-C_(18)=C_(13)-N _2=N_1- six-membered cyclic fragment. It is worth noting that this azo group is involved in an azo-hydrazo equilibrium, being the azo form the most stable one. This resonance-assisted HB was characterized using the OH-related infrared bands and the corresponding signals in ~1H NMR. In addition, conformational studies and geometrical and electronic parameter calculations were performed using the density functional theory, at B3LYP/6-311++G~* level. Bond and ring critical points were identified using the atoms in molecules theory, which allowed confirming the intramolecular HB. The second azo-group cannot be involved in HB, but it also presents two stereoisomerics forms corresponding to cis (Z) and trans (E) configurations, with the later being the one with the lowest energy.