Excited States of Porphyrin Macrocycles

S1 f Sn spectra of porphyrin, diprotonated porphyrin, and tetraoxaporphyrin dication have been measured inthe energy range 2-3 eV above S1 at room temperature in solution by means of transient absorptionspectroscopy exciting with femtosecond pulses. Highly excited ??* states not active in the conventional S0f Sn spectrum have been observed. The experimental data are discussed on the basis of the time dependentdensity functional theory taking advantage of large scale calculations of configuration interaction betweensingly excited configurations (DF/SCI). The DF/SCI calculation on porphyrin has allowed to assign g statesactive in the S1 f Sn spectrum. Applying the same calculation method to tetraoxaporphyrin dication the S0f Sn spectrum is reproduced relatively to the Q and B (Soret) bands as well as to the weaker Eu bands athigher energy. According to our calculation the S1 f Sn transient spectrum is related to states of g symmetrymainly arising from excitations between doubly degenerate ? and ?* orbitals such as 2eg f 4eg. In the caseof diprotonated porphyrin it is shown that the complex of the macrocycle with two trifluoroacetate anionsplays a significant role for absorption. Charge transfer excitations from the anions to the macrocycle contributeto absorption above the Soret band, justi