A comparative analysis of UV-vis transitions in hetaryl and ferrocenyl thioketones

Electronic transitions in a series of symmetrical and nonsymmetrical hetaryl- and/or ferrocenyl-functionalized thioketones have been studied using quantum chemistry methods. An in-depth theoretical characterization was carried out for low-energy electronic transitions. The effects of hetaryl and ferrocenyl groups on the energy of these transitions were recognized and elucidated in terms of atomic and molecular orbital contributions involved in the transitions. A comparison was drawn between the low-energy transitions in the thioketones and in their carbonyl counterparts. The effect of solvents on the position of UV-vis absorption bands, in particular, on those originating in the low-energy transitions, is discussed. The theoretical calculations indicate that the introduction of ferrocenyl group into the hetaryl-functionalized thioketones changes the character of their first two electronic transitions from n -+ pi* and pi -+ pi* into dominant d -+ pi*. The most intense band of all studied thioketones appears in the near-UV region and undergoes a redshift upon solvation.