STATE MIXINGS IN THE EXCITED TRIPLET AND SINGLET-STATES OF FLUORINE-SUBSTITUTED MAGNESIUM TETRAPHENYLPORPHINES STUDIED BY OPTICAL AND TIME-RESOLVED EPR SPECTROSCOPY

Optical and time-resolved EPR(TREPR) studies were made on the excited states of fluorine-substituted magnesium tetraphenylporphines (MgF-TPP s) including related Mg porphyrins. From the analyses of TREPR spectra it was found that the zero-field splitting parameter, D, increased wi th an increasing number of substituents, e.g. fluorine atoms. This res ult is interpreted by the fact that (3)(a(2u)e(g)) and (3)(a(1u)e(g)) configurations are heavily mixed via vibronic couplings in the lowest excited triplet (T-1) states of MgF-TPPs. Other T-1 properties such as a T-1 energy, a triplet lifetime, and an appearance of the b(1g) band in the phosphorescence supported the mixings. The mixings due to conf iguration interactions were studied in the lowest excited singlet (S-1 ) states of MgF-TPPs by measuring absorption coefficients and intensit ies of vibronic bands both in the absorption and fluorescence. The mag nitudes of the mixings were also evaluated in the S-1 states of MgF-TP Ps.