WATER-SOLUBLE 1,3-DIPHENYLISOBENZOFURAN DERIVATIVES - SYNTHESIS AND EVALUATION AS SINGLET MOLECULAR-OXYGEN ACCEPTORS FOR BIOLOGICAL-SYSTEMS

Two isomeric water-soluble 1,3-diphenylisobenzofuran derivatives, cont aining an m- or p-trimethylammonium iodide group in one of the phenyl substituents (m-4 and p-4 respectively), were prepared and characteriz ed, and their ability to quench O-2((1) Delta(g)) was evaluated in bot h homogeneous aqueous media and dioctadecyldimethylammonium chloride ( DODAC) vesicles. The solubility in water of each isomer was higher tha n 2 X 10(-4) M and the respective O-2(1 Delta(g)) total quenching rate constants (k(q)) were (2.3+/-0.2) X 10(9) and (1.1+/-0.1) X 10(9) M(- 1) s(-1). The reactive pathway fraction for isomer m-4 in D2O was 0.72 +/-0.10, a value obtained by comparison with unsubstituted 1,3-di phen ylisobenzofuran in the system cetyltrimethylammonium chloride-D2O. Bot h quenchers m-4 and p-4 can be used with O-2((1) Delta(g)) generators, e.g. thionine and methylene blue, but not with anionic dyes, such as rose bengal, because of the formation of ground stare, ion pair comple xes. When methylene blue and isomer p-4 were separated by a DODAC bila yer, the quencher was consumed with zero-order kinetics, but the consu mption rate was much smaller than in the absence of the bilayer. A rou gh estimate indicates that the quencher p-4 reacts with approximately 25% of the generated O-2((1) Delta(g)) escaping from the vesicle.