Аннотация:We report stationary and ultrafast solution-phase spectra for symmetric biphenyls: pristine biphenyl (bP0), 4,4'-difluorobiphenyl (bP2), 2,3,5,6,2',3',5',6'-octafluorobiphenyl (bP8), and perfluorobiphenyl (bP10). Initial excitation to the S3 state in bP0 and bP2, where the S1 and S2 states are not selectively accessible, is followed by relaxation to non-polar S1. In bP8 and bP10, excitation to nearly degenerate S1+S2 pair of states leads to formation of polar symmetry-broken excited state due to the pseudo-Jahn-Teller interactions. The structure of the lowest singlet excited states of biphenyls is analyzed by means of the XMCQDPT2 multi-configuration perturbation theory. We also demonstrate unsatisfactory performance of the TDDFT methodology as applied to the biphenyl molecules in question.