Abstract
Tetracationic 5,10,15,20-tetrakis(4- N -pentylpyridyl)porphyrins, [( TPePyP ) H 2]4+ and its zinc-porphyrin analogue [( TPePyP ) Zn II]4+ have been synthesized and characterized by 1 H NMR and UV-visible spectroscopic techniques. Photobleaching studies carried out in solutions of varying pH show that, in the presence of oxygen, [( TPePyP ) H 2]4+ undergoes fast photodegradation in aqueous medium when the solution is irradiated with 560 nm light. The steady-state singlet oxygen quantum yields (ΦΔ) for [( TPePyP ) H 2]4+ is 0.80 and that for its Zn analogue is 0.85. These quantities were measured using 1,3-diphenylisobenzofuran (DPBF) as a singlet oxygen scavenger, in N,N-dimethyl-formamide solution. These ΦΔ values are compared with those for other well known sensitizers such as protoporphyrindimethylester PPDME and hematoporphyrindihydrochloride HPDHC.
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