Sodium Ion Effect on Photoinduced Electron Transfer of Porphyrin-Crown Ether-Affixed Quaterthiophene-60Fullerene Triad as a Gated Molecular Switch

摘要

A porphyrin-quaterthiophene-fullerene triad, in which the center of the quaterthiophene spacer is additionally bridged with a crown ether chain in a sash manner (abbreviated as H{sub}2P-(2T(crown)2T)-C{sub}60), has been newly synthesized. Photoinduced charge-separation (CS) and charge-recombination processes in the absence and presence of Na{sup}+ have been investigated by time-resolved fluorescence and transient absorption spectroscopic methods. Upon photo-excitation of H{sub}2P-(2T(crown)2T)-C{sub}60 in benzonitrile, CS via 1{sup left}H{sub}2P{sup}* generating H{sub}2P{sup}(·+)-2T(crown)2T-(C{sub}60){sup}(·-) took place, followed by a hole shift to a more energetically stable H{sub}2P-(2T(crown)2T){sup}(·+)-(C{sub}60){sup}(·-).^sIn the presence of Na{sub}+, such CS process was completely suppressed by the formation of the Na{sup}+-inclusion complex H{sub}2P-(2T(crown-Na{sup}+)2T)-C{sub}60. Extraction of Na{sup}+ with the external 15-crown-ether-5 recovered the photoinduced CS process. This result indicates that H{sub}2P-(2T(crown)2T)-C{sub}60) is an unique photo-switchable system, because (2T(crown)2T) acts as ion-responsible molecular wire.