Metallotetrabenzoporphyrins. New phosphorescent probes for oxygen measurements
Abstract
Tetrabenzoporphyrins (TBP) of Zn, Pd, Lu, Y, Sn and Pb have been synthesized and Pd, Sn and Lu complexes characterized by 1H NMR spectroscopy. Phosphorescence at room temperature in DMF solutions was measured for Pd and Lu complexes giving quantum yields of 7.9% and 3.5% and lifetimes of 250 µs and 870 µs, respectively. Pd meso-tetraphenyltetrabenzoporphyrin 1(PdPh4TBP) was synthesized, characterized by 1H NMR and showed a red shift of the Q-band to 628 nm. Electronic absorption spectra of synthesized complexes are briefly discussed with relation to their structures. Complex 1 reacted with ClSO3H and the obtained chlorosulfonato derivative 2 was converted into two water soluble chromophores: Pd meso-tetra(sulfophenyl)tetrabenzoporphyrin [PdPh4(SO3Na)4TBP]3 and the corresponding sulfonamide [PdPh4(PEG)4TBP]4 with aminopoly(ethyleneglycol)(Mav 5000). Electronic absorption and phosphorescence spectra of 1 and its derivatives were recorded and phosphorescence quantum yields and lifetimes were measured for deoxygenated solutions. The oxygen quenching constants were measured for water-soluble complexes and the effect of binding to a large protein, serum albumin, on the phosphorescence characteristics was examined.
Metallotetrabenzoporphyrins were found to be useful phosphors for oxygen measurements in biological systems.