TY - JOUR
T1 - Tuning reductive and oxidative photoinduced electron transfer in amide-linked anthraquinone-porphyrin-ferrocene architectures
AU - Melomedov, Jascha
AU - Ochsmann, Julian Robert
AU - Meister, Michael
AU - Laquai, Frederic
AU - Heinze, Katja
PY - 2014/1/1
Y1 - 2014/1/1
N2 - Porphyrin amino acids 3a-3h with meso substituents Ar of tunable electron-donating power (Ar = 4-C6H4OnBu, 4-C 6H4OMe, 4-C6H4Me, Mes, C 6H5, 4-C6H4F, 4-C6H 4CF3, C6F5) have been linked at the N terminus to anthraquinone Q as electron acceptor through amide bonds to give Q-PAr dyads 4a-4h. These were conjugated to ferrocene Fc at the C terminus as electron donor to give the acceptor-chromophore-donor Q-P Ar-Fc triads 6a-6h. To further modify the energies of the electronically excited and charge-separated states, the triads 6a-6h were metallated with zinc(II) to give the corresponding Q-(Zn)PAr-Fc triads Zn-6a-Zn-6h. The Q-PAr1 dyad (Ar1 = C 6H5) was further extended with a second porphyrin P Ar2 (Ar2 = 4-C6H4Me) as well as appended to a ferrocene to give the tetrad Q-PAr1-PAr2-Fc 9. Almost all the conjugates show strongly reduced fluorescence quantum yields and excited-state lifetimes, which has been interpreted as photoinduced electron transfer (PET) either from the excited porphyrin to the quinone (oxidative PET) or from the ferrocene to the excited porphyrin (reductive PET). Electrochemical data, absorption spectroscopy, steady-state emission, time-resolved fluorescence, transient absorption pump-probe spectroscopy as well as DFT calculations have been used to elaborate the preferred PET pathway (reductive vs. oxidative PET) in these architectures with systematically varied electron-donating substituents at the central chromophore.
AB - Porphyrin amino acids 3a-3h with meso substituents Ar of tunable electron-donating power (Ar = 4-C6H4OnBu, 4-C 6H4OMe, 4-C6H4Me, Mes, C 6H5, 4-C6H4F, 4-C6H 4CF3, C6F5) have been linked at the N terminus to anthraquinone Q as electron acceptor through amide bonds to give Q-PAr dyads 4a-4h. These were conjugated to ferrocene Fc at the C terminus as electron donor to give the acceptor-chromophore-donor Q-P Ar-Fc triads 6a-6h. To further modify the energies of the electronically excited and charge-separated states, the triads 6a-6h were metallated with zinc(II) to give the corresponding Q-(Zn)PAr-Fc triads Zn-6a-Zn-6h. The Q-PAr1 dyad (Ar1 = C 6H5) was further extended with a second porphyrin P Ar2 (Ar2 = 4-C6H4Me) as well as appended to a ferrocene to give the tetrad Q-PAr1-PAr2-Fc 9. Almost all the conjugates show strongly reduced fluorescence quantum yields and excited-state lifetimes, which has been interpreted as photoinduced electron transfer (PET) either from the excited porphyrin to the quinone (oxidative PET) or from the ferrocene to the excited porphyrin (reductive PET). Electrochemical data, absorption spectroscopy, steady-state emission, time-resolved fluorescence, transient absorption pump-probe spectroscopy as well as DFT calculations have been used to elaborate the preferred PET pathway (reductive vs. oxidative PET) in these architectures with systematically varied electron-donating substituents at the central chromophore.
KW - Density functional calculations
KW - Electron transfer
KW - Porphyrinoids
KW - Quinones
KW - Substituent effects
UR - http://www.scopus.com/inward/record.url?scp=84898544466&partnerID=8YFLogxK
U2 - 10.1002/ejic.201400118
DO - 10.1002/ejic.201400118
M3 - Article
AN - SCOPUS:84898544466
SP - 1984
EP - 2001
JO - European Journal of Inorganic Chemistry
JF - European Journal of Inorganic Chemistry
SN - 1434-1948
IS - 11
ER -