Photoinduced Electron and Energy Transfer in Metal-mediated Multi-porphyrin arrays

Interesting supramolecular architectures can be obtained exploiting the exocyclic coordination ability of pyridylporphyrins. Thus, coordination to metal centers can be used to build metal-bridged porphyrin assemblies (e.g., 1). On the other hand, axial coordination to metalloporphyrins can be used to produce a variety of side-to-face porphyrin assemblies (e.g., 2). The two structural motifs can be combined in higher order assemblies (e.g., 3). Other interesting supramolecular systems can be designed along the same lines using pyridyl-functionalized perylene bisimides (e.g., 4). Within this framework, several discrete assemblies of various nuclearities have been recently constructed in our laboratories.1,2 The photophysics of these multichromophoric assemblies is characterized by the occurrence of fast intercomponent energy and electron transfer processes. Experimental studies leading to the identification and kinetic characterization of the photoinduced processes have been performed by fast (nanoseconds) and ultrafast (femtoseconds) time resolved techniques. Recent examples will be discussed. 1 E. Iengo, F. Scandola, E. Alessio Struct. Bond., 2006, 121, 105. 2 F. Scandola, C. Chiorboli, A. Prodi, E. Iengo, E. Alessio, Coord. Chem. Rev. 2006, 250, 1471.