TY - JOUR
T1 - Tetrapyrrole singlet excited state quenching by carotenoids in an artificial phótosynthetic antenna
AU - Palacios, Rodrigo E.
AU - Kodis, Gerdenis
AU - Herrero, Christian
AU - Ochoa, Ernesto Mariño
AU - Gervaldo, Miguel
AU - Gould, Stephanie L.
AU - Kennis, John T M
AU - Gust, Devens
AU - Moore, Thomas
AU - Moore, Ana
PY - 2006/12/21
Y1 - 2006/12/21
N2 - Two artificial photosynthetic antenna models consisting of a Si phthalocyanine (Pc) bearing two axially attached carotenoid moieties having either 9 or 10 conjugated double bonds are used to illustrate some of the function of carotenoids in photosynthetic membranes. Both models studied in toluene, methyltetrahydrofuran, and benzonitrile exhibited charge separated states of the type C.+-Pc.- confirming that the quenching of the Pc S1 state is due to photoinduced electron transfer. In hexane, the Pc S1 state of the 10 double bond carotenoid-Pc model was slightly quenched but the C.+-Pc.- transient was not spectroscopically detected. A semiclassical analysis of the data in hexane at temperatures ranging from 180 to 320 K was used to demonstrate that photoinduced electron transfer could occur. The model bearing the 10 double bond carotenoids exhibits biexponential fluorescence decay in toluene and in hexane, which is interpreted in terms of an equilibrium mixture of two isomers comprising s-cis and s-trans conformers of the carotenoid. The shorter fluorescence lifetime is associated with an s-cis carotenoid conformer where the close approach between the donor and acceptor moieties provides through-space electronic coupling in addition to the through-bond component.
AB - Two artificial photosynthetic antenna models consisting of a Si phthalocyanine (Pc) bearing two axially attached carotenoid moieties having either 9 or 10 conjugated double bonds are used to illustrate some of the function of carotenoids in photosynthetic membranes. Both models studied in toluene, methyltetrahydrofuran, and benzonitrile exhibited charge separated states of the type C.+-Pc.- confirming that the quenching of the Pc S1 state is due to photoinduced electron transfer. In hexane, the Pc S1 state of the 10 double bond carotenoid-Pc model was slightly quenched but the C.+-Pc.- transient was not spectroscopically detected. A semiclassical analysis of the data in hexane at temperatures ranging from 180 to 320 K was used to demonstrate that photoinduced electron transfer could occur. The model bearing the 10 double bond carotenoids exhibits biexponential fluorescence decay in toluene and in hexane, which is interpreted in terms of an equilibrium mixture of two isomers comprising s-cis and s-trans conformers of the carotenoid. The shorter fluorescence lifetime is associated with an s-cis carotenoid conformer where the close approach between the donor and acceptor moieties provides through-space electronic coupling in addition to the through-bond component.
UR - http://www.scopus.com/inward/record.url?scp=33846669021&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33846669021&partnerID=8YFLogxK
U2 - 10.1021/jp0645317
DO - 10.1021/jp0645317
M3 - Article
C2 - 17165988
AN - SCOPUS:33846669021
SN - 1520-6106
VL - 110
SP - 25411
EP - 25420
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 50
ER -