A theoretical study of biphenylene in its ground and excited states

Molecular orbital studies of biphenylene in its geometrically optimized ground and triplet states have been performed at the INDO level. These calculations, together with CNDO/S, specially parameterized CNDO and calculations involving empirical force constants, are used to estimate the relative energies and geometries of the T₁ and S₁ excited states of biphenylene. The relation of these geometry changes on excitation to the unusual photophysical properties of biphenylene are discussed.