Photocurrent Generation in Thin SnO2 Nanocrystalline Semiconductor Film Electrodes from Electron Donor-Acceptor Metallodiporphyrin and Porphyrin-C60 Dyads

”. M. GERVALDO, L. OTERO, E. N. DURANTINI, J. J. SILBER, AND L. SERENO.

Venecia, Italia

Otro; Summer School on Green Chemistry; 2002

Interuniversity National Consortium "Chemistry for the Environment" (INCA)

Over the basis of modern organic chemistry, one approach to mimic the photosynthetic energy conversion system in nature is the use of complex synthetic molecular arrays containing chromophores, electron donors and electron acceptors linked by covalent and non covalent bonds. The energy stored in this systems as photoinduced intramolecular charge separation sate can be converted in electric work trough an external circuit in a suitable photoelectrochemical cell. In this work we designed and synthesized a novel porphyrin-porphyrin supramolecular system (ZnP-P) with particular electronic properties, and a Porpyrin-C60 dyad (P-C60). We are interested in the use of these systems as light receptors in the spectral sensitization of nanostructured wide band gap semiconductor electrodes. The asymmetrical dyad ZnP-P was designed in order to increase the intramolecular electron transfer capacity; one porphyrin moiety (ZnP) bears electron-donating methoxy groups, which help to stabilize the radical cation. The second porphyrin moiety (P) features electron-withdrawing nitro subsistent, which stabilize the porphyrin radical anion. On the other hand the functionalization of C60 buckminsterfullerene allows the linkage of this good energy and electron acceptor to many chromophores and has opened the possibility of constructing artificial photosynthetic systems. We report here the efficient generation of photoelectrical effects in the spectral sensitization of SnO2 nanoestructured semiconductor electrodes from the excitation of both dyads, and a mechanism involving the formation of an intramolecular photoinduced charge transfer state is proposed.