Bis-Porphyrins Containing Diimine Chelates of Variable Geometry as Spacer
摘要:
Etio or meso type free base porphyrin dimers bridged by either 6,6'-diphenyl-2,2'-bipyridine or 2,9-diphenyl-1,10-phenanthroline spacers were synthesized following parallel routes. Metallation of one of the porphyrins with zinc(II) allowed to study the intramolecular fluorescence quenching of the zinc(II) porphyrin component by the free base component within the dimers, It was shown to depend on the nature of the heterocyclic spacer.
Free-base porphyrin dimers bridged by either 6,6'-diphenyl-2,2'-bipyridine or 2,9-diphenyl-1,10-phenanthroline spacers were synthesized and characterized. Metallation of one of the porphyrins with Zn-II allowed us to study intramolecular energy-transfer processes between the Zn-II-porphyrin photoreceptor and the free-base porphyrin energy acceptor by time-correlated single-photon counting. The rate of energy transfer was shown to depend strongly on the nature of the bridge, being enhanced by a factor of nearly 6 when comparing the (cis) phenanthroline bridge with the trans-bipyridine bridge. A detailed analysis of the fluorescence decays suggests the presence of two slowly interconverting conformers for the 6,6'-djphenyl-2,2'-bipyridine spacer.