Magnetically induced current densities in phenylenes in the ground and lowest lying triplet excited states

Abstract

Magnetically induced current densities in the lowest lying singlet and triplet states of a series of phenylene molecules were examined at the B3LYP/lanl2DZ level of theory. Previous findings have shown that in the ground singlet state, phenylenes exhibit ring currents with opposed tropicity: diatropic currents within six-membered rings and paratropic currents within four-membered rings. However, for biphenylene in the first excited triplet state, there is a drastic change in aromaticity in comparison to the ground state. Specifically, this molecule in the triplet state sustains a strong diatropic global circulation. In the present work, we showed that higher members of the phenylene family do not exhibit such radical changes in aromaticity when excited to the lowest lying triplet states.