A fluorescence study of tetraphenylporphyrinatozinc(II)/imidazolyl-linked porphyrinatoiron(III) systems.

The fluorescence spectra of porphyrinatozinc(II)/iron(III) systems which consisted of tetraphenylporphyrinatozinc(II) and three kinds of imidazolyl-linked porphyrinatoiron(III) have been studied. An efficient fluorescence quenching of tetraphenylporphyrinatozinc(II) in the system was observed. Addition of a stronger organic base, such as piperdine, to the system can displace imidazolyl-linked porphyrinatoiron(III) and the fluorescence of the system restored partly. All these indicate the formation of porphyrinatozinc(II)/iron(III) supramolecular complex and coordination bonding formed by the coordination of imidazolyl group in imidazolyl-linked porphyrinatoiron(III) to Zn(II) in tetraphenyl-porphyrinatozinc(II) is the driving force of the supramolecular self-assembly. The association constants of the supramolecular complexes were calculated from the fluorescence spectroscopic titration data, and the differences among the association constants of the supramolecular complexes are discussed on the basis of the conformations which are dependent on the length of alkoxy chain linking imidazolyl group to porphyrinatoiron(III).