Theoretical study of the triplet state aryl cations recombination: A possible route to unusually stable doubly charged biphenyl cations

Abstract

The self-recombination reactions of 4-aminophenyl cations and parent phenyl cations, each in ground triplet states, are studied within the framework of density functional theory. Only the total zero spin (singlet state) is chosen, as the quintet and triplet counterparts are nonreactive in these systems. The recombination products are the benzidine and biphenyl doubly charged cations. These species are unexpectedly stable. The transition state of the 4-aminophenyl cations reaction is located at the distance of about 4.0 Å between the ipso-carbon atoms. The activation barrier is predominantly formed by electrostatic repulsion between two cations and is estimated to be 27.6 kcal mol 21 [B3LYP/6-3111G(d,p)]. Similar results are obtained for the phenyl cations recombination. The general importance of the participation of other aryl cations in analogous organic reactions is discussed. V C 2013 Wiley Periodicals, Inc.

Electronic descriptors for analytical use of the benzidine‐based compounds and the mechanism of oxidative coupling of anilines

“…Herein, we refer to our recent results relating to QTAIM and charge distribution analysis of the Bzd 2+ dication. [59] According to these results, all the carbon atoms, except the Nbound, have atomic charges that are less than +0.04. The hydrogen atoms, except those that are N-bound, have atomic charges being equal to~+0.10.…”

“…These are oriented near the most electrophilic centers of the Bzd 2+ dication, which are the N-bound carbon atoms. [59] Despite the C 2h point group, the Bzd 2+ moiety is not absolutely planar. Electrostatic interaction leads to slight distortion of the dication, so that the N-bound carbon atoms lie partly out of the plane approximately defined by the carbon rings (Fig.…”

“…[59] Therefore, the structural properties of this species are not the issue of the present paper. To the best of our knowledge, we have not found in the literature the data concerning calculations of electronic spectrum of the Bzd 2+ dication.…”

“…This is typical for recombination of radicals, not for the charged species of the same sign. [59] Such unusual barrierless reaction of two radical cations will be explained in the succeeding text in terms of the positive charge displacements.…”

“…Such approach was effectively used earlier for similar mechanistic studies. [59,67,68] As a result of these relaxed scans, we obtain profiles of the PESs for the recombination reactions. These PESs for the A + B and A + C types of reactions are illustrated in Fig.…”