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Tuning Reductive and Oxidative Photoinduced Electron Transfer in Amide‐Linked Anthraquinone–Porphyrin–Ferrocene Architectures
Author(s) -
Melomedov Jascha,
Ochsmann Julian Robert,
Meister Michael,
Laquai Frédéric,
Heinze Katja
Publication year - 2014
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201400118
Subject(s) - chemistry , porphyrin , ferrocene , photochemistry , excited state , electron transfer , photoinduced electron transfer , electron acceptor , chromophore , amide , electrochemistry , organic chemistry , nuclear physics , physics , electrode
Porphyrin amino acids 3a – 3h with meso substituents Ar of tunable electron‐donating power (Ar = 4‐C 6 H 4 O n Bu, 4‐C 6 H 4 OMe, 4‐C 6 H 4 Me, Mes, C 6 H 5 , 4‐C 6 H 4 F, 4‐C 6 H 4 CF 3 , C 6 F 5 ) have been linked at the N terminus to anthraquinone Q as electron acceptor through amide bonds to give Q‐P Ar 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)P Ar ‐Fc triads Zn‐6a – Zn‐6h . The Q‐P Ar1 dyad (Ar 1 = C 6 H 5 ) was further extended with a second porphyrin P Ar2 (Ar 2 = 4‐C 6 H 4 Me) as well as appended to a ferrocene to give the tetrad Q‐P Ar1 ‐P Ar2 ‐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.