Sumario: | An approach was developed to determine triplet quantum yields, ΦT, which overcomes most of the difficulties usually encountered in flash photolysis studies of triplet states. The combined application of near-IR emission and optoacoustics yields ΦT values which are independent of the absorption properties of the triplets. Thus, the triplet energies derived from near-IR phosphorescence spectra together with the values of the heat stored by the triplets determined from optoacoustic experiments afforded ΦT = 0.3 ± 0.1 for porphycene (PO) and 0.4 ± 0.1 for its tetra-n-propyl derivative (TPrPO). Several calorimetric references for optoacoustic measurements in the red region were tested. The ΦT values, combined with flash photolysis data, yielded accurate triplet- minus ground-state absorption coefficients. The quantum yields for singlet molecular oxygen production determined by time-resolved phosphorescence were ΦΔ = 0.34 ± 0.05 for PO and 0.36 ± 0.03 for TPrPO which implies an efficiency near unity for O2(1Δ8) production upon collision of the triplet states of the porphycenes with ground-state O2. © 1990 American Chemical Society.
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