Asymmetric Diradical Made By π-Core Modification: Comparisons with Its Symmetric Parents.

Abstract

Asymmetric conjugated diradicals are much less common than their symmetric counterparts because they expand the feasibility of symmetry, but they also present some detrimental aspects. Hence, stud-ies comparing analogue symmetric and asymmetric diradicals are of interest. Previous studies regard-ing the structure of asymmetric conjugated diradicals only focused on analyzing different radical moie-ties attached to the same π-core bridge, while none of them explored the diradicals with asymmetric π-core (same radical moieties). Herein, we report a series of azine derivatives PNP-n (n=1-3). The symmetric diradicals PNP-1 and PNP-3 have a π-core comprising two benzenes or two thiophene units linked to a central azine, respectively. Replacing a benzene unit with thiophene in symmetric PNP-1 diradical yields the asymmetric PNP-2 diradical altering the energy gap and the spin-spin coupling strengths thus modulating the diradical characteristic. This work highlights the advantages and incon-veniences of moving from symmetric to asymmetric diradicals, as well as providing a molecular de-scription of the intrinsic properties of ones and others made of similar chemical compositions.