EFFECT OF SUBSTITUENTS ON NH BOND DISSOCIATION ENTHALPIES AND PROTON AFFINITIES OF ANIONS OF DIPHENYLAMINE DERIVATIVES: A DFT STUDY USING B3P86 FUNCTIONAL

Abstract

In this article, the N−H bond dissociation enthalpies (BDE) of a series of di-substituted diarylamines (YAr)2NH (Y = H, NH2, NO2, CF3, N(CH3)2, Cl, F, OCH3, CH3, CN) were determined using the DFT-based method of B3P86/6-311G with the deviation from the experimental data (about 0.2 kcal/mol). It was found that the effects of the substitu-ents on the BDE(N−H) change slightly for the meta substituted position, and a clear effect trend was found when the substituent was at the para position. The BDE(N−H)s decrease remarkably at the para site with strong electron donating groups (EDGs) like OCH3, NH2, N(CH3)2 with the amount of 4.3, 7.9 và 7.9 kcal/mol, respectively, and a good correlation was observed between the Hammett constants and the BDE(N−H) values. Electron withdrawing groups (EWGs) increase the BDE(N−H)s up to 4.5 kcal/mol. In addition, the insight into the effects of the substituents and the theoretical mechanism of antioxidant activity of these compounds were clarified via the potential energy surfaces (PES), proton affinity (PA), and bond length (C1−N).