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PHOTOPHYSICAL AND PHOTOSENSITIZING PROPERTIES OF BENZOPORPHYRIN DERIVATIVE MONOACID RING A (BPD‐MA) *
Author(s) -
Aveline Béatrice,
Hasan Tayyaba,
Redmond Robert W.
Publication year - 1994
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1994.tb05042.x
Subject(s) - singlet oxygen , quantum yield , photochemistry , intersystem crossing , chemistry , photosensitizer , triplet state , photobleaching , photodegradation , fluorescence , singlet state , absorption (acoustics) , excited state , oxygen , molecule , materials science , photocatalysis , organic chemistry , physics , quantum mechanics , nuclear physics , composite material , catalysis
The photophysical properties of benzoporphyrin derivative monoacid ring A (BPD‐MA), a second‐generation photosensitizer currently in phase II clinical trials, were investigated in homogeneous solution. Absorption, fluorescence, triplet‐state, singlet oxygen (O 2 ( 1 Δ g )) sensitization studies and photobleaching experiments are reported. The ground state of this chlorin‐type molecule shows a strong absorbance in the red (λ≈ 688 nm, ɛ≈ 33 000 M −1 cm −1 in organic solvents). For the singlet excited state the following data were determined in methanol: energy level, E s = 42.1 kcal mol −1 , lifetime, Φ f = 5.2 ns and fluorescence quantum yield, Φ f = 0.05 in air‐saturated solution. The triplet state of BPD‐MA has a lifetime, τ f >. 25 ns, an energy level, E T = 26.9 kcal mol −1 and the molar absorption coefficient is ɛ T = 26 650 M −1 cm −1 at 720 nm. A dramatic effect of oxygen on the fluorescence (φ f ) and intersystem crossing (φ T ) quantum yields has been observed. The BPD‐MA presents rather high triplet (φ T = 0.68 under N 2 ‐saturated conditions) and singlet oxygen (φ Δ = 0.78) quantum yields. On the other hand, the presence of oxygen does not significantly modify the photobleaching of this photostable compound, the photodegradation quantum yield (φ Pb ) of which was found to be on the order of 5 × 10 −5 in organic solvents.