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Photoinduced Electron Transfer in Tetrathiafulvalene−Porphyrin−Fullerene Molecular Triads
Author(s) -
Liddell Paul A.,
Kodis Gerdenis,
de la Garza Linda,
Bahr Jeffrey L.,
Moore Ana L.,
Moore Thomas A.,
Gust Devens
Publication year - 2001
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20010919)84:9<2765::aid-hlca2765>3.0.co;2-s
Subject(s) - chemistry , tetrathiafulvalene , porphyrin , photochemistry , photoinduced electron transfer , excited state , electron transfer , fullerene , singlet state , electron acceptor , electron donor , triplet state , acceptor , ultrafast laser spectroscopy , quantum yield , molecule , fluorescence , atomic physics , spectroscopy , organic chemistry , catalysis , physics , quantum mechanics , condensed matter physics
The two molecular triads 1a and 1b consisting of a porphyrin (P) covalently linked to a fullerene (C 60 ) electron acceptor and tetrathiafulvalene (TTF) electron‐donor moiety were synthesized, and their photochemical properties were determined by transient absorption and emission techniques. Excitation of the free‐base‐porphyrin moiety of the TTF−P 2 H −C 60 triad 1a in tetrahydro‐2‐methylfuran solution yields the porphyrin first excited singlet state TTF− 1 P 2 H −C 60 , which undergoes photoinduced electron transfer with a time constant of 25 ps to give TTF−P 2 H .+ −C 60 .− . This intermediate charge‐separated state has a lifetime of 230 ps, decaying mainly by a charge‐shift reaction to yield a final state, TTF .+ −P 2 H −C 60 .− . The final state has a lifetime of 660 ns, is formed with an overall yield of 92%, and preserves ca . 1.0 eV of the 1.9 eV inherent in the porphyrin excited state. Similar behavior is observed for the zinc analog 1b . The TTF‐P Zn .+ −C 60 .− state is formed by ultrafast electron transfer from the porphyrinatozinc excited singlet state with a time constant of 1.5 ps. The final TTF .+ −P Zn −C 60 .− state is generated with a yield of 16%, and also has a lifetime of 660 ns. Although charge recombination to yield a triplet has been observed in related donor‐acceptor systems, the TTF .+ −P−C 60 .− states recombine to the ground state, because the molecule lacks low‐energy triplet states. This structural feature leads to a longer lifetime for the final charge‐separated state, during which the stored energy could be harvested for solar‐energy conversion or molecular optoelectronic applications.