Singlet and Triplet (π, π*) Excited States of Zinc(II) Octaalkylporphyrins: A Time-Resolved Resonance-Raman Study
The excited states of porphyrins and hydroporphyrins act as primary intermediates in processes ranging from biological energy transfer and electron transfer to photocatalysis and photodynamic therapy. We report resonance Raman (RR) spectra of the singlet S1 and triplet T1 excited states of zinc(II) octaethylporphyrin (ZnOEP) and zinc(II) etioporphyrin-I (ZnEtio), using picosecond and nanosecond RR techniques. Picosecond time-resolved resonance Raman experiments were performed using 532 nm photoexcitation pulses and 436 nm probe pulses (both 100 ps, 50 Hz); the experimental apparatus consisted of a mode-locked Nd:YAG laser (Coherent) in combination with a Nd:YAG regenerative amplifier (Continuum) and an H2 cell for stimulated Raman shifting. The apparatus used for nanosecond time-resolved RR experiments has been described previously . Porphyrin samples were prepared in a nitrogen atmosphere at a concentration of 0.5 mM (tetrahydrofuran solvent).
KeywordsZinc Ethyl Porphyrin Tetrahydrofuran Spiro
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