POLYMER-BOUND PYRROLE COMPOUNDS, IX - PHOTOPHYSICAL AND SINGLET MOLECULAR-OXYGEN PHOTOSENSITIZING PROPERTIES OF MESOPORPHYRIN-IX COVALENTLYBOUND TO A LOW-MOLECULAR-WEIGHT POLYETHYLENE-GLYCOL

The photophysical and singlet molecular oxygen photosensitizing proper ties of two amphiphilic systems consisting of mesoporphyrin bound to o ne polyoxyethylene chain through ester or amide bonds (MPEGE and MPEGA , respectively) have been determined in aqueous and organic solvents. Steady-state and time-resolved W-Vis-NIR absorption and emission, as w ell as chemical trapping studies indicate that both systems are essent ially monomeric in CH2Cl2, their properties resembling those of mesopo rphyrin dimethyl ester. In aqueous solutions the photoproperties show a remarkable dependence on the concentration which is attributed to ag gregation phenomena. Below 10 mu M the process can be described as a m onomer-dimer equilibrium with constant K= (1.6 +/- 0.5) x 10(6) in wat er. The absorption, fluorescence, and singlet oxygen production charac teristics of both monomer and dimer have been determined. (C) 1997 Els evier Science S.A.