THE PRODUCTION OF SINGLET MOLECULAR OXYGEN BY ZINC(II) PHTHALOCYANINE IN ETHANOL AND IN UNILAMELLAR VESICLES. CHEMICAL QUENCHING AND PHOSPHORESCENCE STUDIES |
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| Authors: | Giuliana Valduga Santiago Nonell Elena Reddi Giulio Jori Silvia E Braslavsky |
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| Institution: | Max-Planck-Institut für Strahlenchemie, Stiftstrasse34–36,D–4330 Mülheim a.d. Ruhr, W. Germany;Department of Biology, University of Padova, Via Loredan 10,1–35131 Padova, Italy |
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| Abstract: | Abstract— Zn(II)phthalocyanine (ZnPc) generates O2(1Δg) with a quantum yield of ca. 0.4 upon photocxcitation at 354 or 600 nm in ethanolic solution as determined by time-resolved phosphorescence studies at 1270 nm and photooxidation experiments using 1,3-diphenylisobenzofuran (DPBF) as substrate. The quantum yield of photooxidation slightly increases upon incorporation of ZnPc into unilamellar liposomes of dipalmitoylphosphatidylcholine. Under our irradiation conditions (600 nm, 18°C, and short light exposure times), DPBF(5–50 μM) undergoes photooxidation by a pure Type II mechanism; the rate constant for the O2(1Δg) + DPBF reaction is (1.1 ±0.1) x 109 M-1 s_1 in ethanol solution and determined to be about two orders of magnitude smaller when both ZnPc and DPBF are embedded into liposomes. |
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