Abstract
The use of non-covalent binding has recently merited increasing attention as a simpler but more elegant way to construct electron donor-acceptor ensembles mimicking the efficient biological electron transfer systems as compared with the use of covalent bonding. We report herein the two supramolecular donor-acceptor dyads. One is supramolecular pyridylferrocene (PyFc)-zinc(II) tetrakis(perfluorophenyl)porphyrin (ZnTFPP) dyad, and the other one is supramolecular zinc(II) tetraphenylporphyrin (ZnTPP)-pyridylnaphthalenediimide (PyNIm) dyad. The pyridylferrocene (PyFc) or pyridylnaphthalenediimide (PyNIm) forms a supramolecular complex with zinc porphyrin derivatives in polar or non-polar solvents. In the PyFc-ZnTFPP supramolecular comples, the singlet excited state of ZnTFPP is quenched by photoinduced electron transfer from PyFc to the singlet excited state of ZnTFPP. The charge-separated state formed by the photoinduced electron transfer has extremely short lifetime by the fast back electron transfer from ZnTFPP radical anion to PyFc cation. In the ZnTPP-PyNIm supramolecular comples, the singlet excited atets of ZnTPP is quenched by photoinduced electron transfer from the singlet excited state of ZnTPP to PyNIm. The lifetime of the charge-separated state was determined as 610 micro second at 278 K. This is the first example of the direct detection of charge-separeted state in supramolecular dyad. And this is the longest lifetime of the charge-separated state ever reported for covalently or non-covalently donor-acceptor dyad oin solution.
