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Photoinduced Electron Transfer in Bisporphyrin–Diimide Complexes
Author(s) -
Flamigni Lucia,
Johnston Martin R.,
Giribabu Lingamallu
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020902)8:17<3938::aid-chem3938>3.0.co;2-3
Subject(s) - diimide , photochemistry , luminescence , quenching (fluorescence) , chemistry , singlet state , photoinduced electron transfer , triplet state , quantum yield , molecule , excited state , electron transfer , materials science , fluorescence , optoelectronics , atomic physics , organic chemistry , optics , perylene , physics
The bisporphyrin host ZnH was synthesized, and its complexation with two aromatic diimide guest molecules, bis(pyridyl)naphthalenediimide NIN and bis(pyridyl)phenyldiimide PIN , was investigated by 1 H NMR and UV/Vis spectroscopy. The diimide guests were complexed simultaneously with both metalloporphyrins of the host, with association constants on the order of 10 8 M −1 . The processes occurring in the complex after excitation of the porphyrinic host were studied by steady‐state and time‐resolved emission and transient absorption spectroscopy. Complexation alters the photophysical properties of the host ZnH ; the luminescence bands shift to the red by 30 nm in the complexed forms, while the emission quantum yield and the lifetime decrease. Comparison of a complex between ZnH and a model guest unable to undergo photoinduced processes allowed us to establish that, in the diimide complexes, quenching of the porphyrinic luminescence occurs with a rate of 1.1×10 10 s −1 . The process is identified as an electron transfer from the excited singlet of the porphyrinic host to the imide guest, which yields charge‐separated states with a lifetime of 710 ps for ZnH + ‐ NIN − and 260 ps for ZnH + ‐ PIN − .