Photophysical processes in electronic states of zinc tetraphenyl porphyrin accessed on one- and two-photon excitation in the soret region

摘要: Abstract Photophysical processes in the model metalloporphyrin, 5,10,15,20-tetraphenyl-21 H ,23 -porphine zinc (ZnTPP), have been investigated by means of conventional electronic spectroscopy, and picosecond transient emission femtosecond absorption methods. The radiative radiationless decay parameters ZnTPP determined under conditions low solute concentration where dimer formation is unimportant, effects at higher concentrations assessed. Careful measurements relative S 1 –S 0 fluorescence quantum yields produced on excitation to states compared with direct itself reveal that a second process bypasses operates when excited Soret region. A dark state, assigned most probably triplet ( T n ,  > 2) or an upper singlet gerade parity, involved. importance this function nature solvent, wavelength (vibrational energy content state) parity accessed two-photon employed. Sequential occurs exciting fs pulses region becomes significant even modest pulse energies increasing sample absorbance. implications these reinterpreting dynamics electronically are discussed.