DFT study on singlet diradical character of zethrenes

Abstract

© Pleiades Publishing, Ltd., 2011. The diradical character of zethrenes was investigated using a symmetry-broken UB3LYP/6-311G(d, p) method. The number of hexagons in the investigated molecules ranges from 6 to 12. It was found that all zethrenes are singlet diradicals, whose diradical character increases with the increasing size of the molecules. A singlet diradical structure provides a possibility for an electron pair to occupy different parts of space, and allows for achieving aromatic stabilization. It can be predicted, on the basis of the singlet–triplet values, that even higher zethrenes will be singlet, but not triplet molecules.