Investigation of the effects of substitution position on the S0 and T1 states of chlorobiphenyl

We have performed ab initio molecular orbital calculations to find the optimized geometries and predicted vibrational spectra for the S0 and T1 states of 4-chlorobiphenyl, 3-chlorobiphenyl, and 2-chlorobiphenyl. We have obtained Raman spectra of the S0 and T1 states of 4-chlorobiphenyl, 3-chlorobiphenyl, and 2-chlorobiphenyl. We find that 2-chlorobiphenyl has a nonplanar structure in its T1 state while the T1 states of 4-chlorobiphenyl and 3-chlorobiphenyl have a nearly planar quinoidal structure. Comparison to previous EPR results for methylbiphenyls suggests that the twisting of T1 2-chlorobiphenyl is likely due to an electron withdrawing effect of the ortho substituted halogen atom.