PHOTOINDUCED ELECTRON-TRANSFER IN ZINC PORPHYRIN-CROWN ETHER SUPRAMOLECULE WITH EU3-ACCEPTOR IN CROWN VOID( ELECTRON)

Photoinduced electron transfer (ET) reactions in the zinc porphyrin-cr own ether (ZnPCE) supramolecule, in which one crown ether moiety conta ining Eu3+ as electron acceptor is covalently linked to zinc porphyrin (ZnP), were studied by flash photolysis. In methanol solutions, highl y efficient charge separation occurs via intramolecular ET from (ZnP)- Zn-3 to Eu3+ encapsulated in the crown ether void (k(1) = (3 +/- 1) X 10(3) s(-1)) and intramolecular ET from 3ZnP to uncomplexed Eu2+ (k(2) = (2.5 +/- 0.5) X 10(3) s(-1)). Intermolecular ET from Eu2+ escaped f rom the crown ether void to ZnP.+ (k(tau) = (4.3 +/- 0.7) X 10(8) M(-1 ) s(-1)) seems to be the main pathway of charge recombination.