A Photosensitizer Dinuclear Ruthenium Complex: Intramolecular Energy Transfer to a Covalently Linked Fullerene Acceptor

• Published in: Chemistry : a European journal 2001-04, Vol.7 (8), p.1597-1605
• Main Authors: Guldi, Dirk M., Maggini, Michele, Menna, Enzo, Scorrano, Gianfranco, Ceroni, Paola, Marcaccio, Massimo, Paolucci, Francesco, Roffia, Sergio
• Format: Article
• Language: English
• Subjects: Carbon; dyads; Electrochemistry; Energy Transfer; Fullerenes; Metalloporphyrins - chemistry; Molecular Structure; Oxygen - chemistry; Photolysis; Photosensitizing Agents - chemistry; ruthenium; Ruthenium - chemistry; sensitizers; Singlet Oxygen; Spectrophotometry, Atomic; Spectrophotometry, Ultraviolet
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/1521-3765(20010417)7:8<1597::AID-CHEM15970>3.0.CO;2-#

A fullerene derivative (5) in which a dinuclear ruthenium complex is covalently linked to a fulleropyrrolidine (FP) through a rigid spacer has been prepared through azomethine ylide cycloaddition to C60. Electrochemical and photophysical studies revealed that ground‐state electronic interactions between the bimetallic ruthenium chromophore and the FP moiety are small. The absorption spectrum of 5 displays a metal‐to‐ligand charge transfer (MLCT) transition at about 620 nm in CH2Cl2 which is shifted by nearly 160 nm relative to that of a previously reported mononuclear dyad (8). The photophysical investigations have also shown that both in dichloromethane and acetonitrile the photoexcited MLCT state of dyad 5 transforms into the fullerene triplet excited state with a quantum yield of 0.19 and that, contrary to mononuclear dyad 8, electron transfer, if any under the applied conditions, is negligible relative to energy transfer. Photoinduced energy transfer and not electron transfer from the ruthenium chromophore to C60 occurs in a novel dinuclear ruthenium(II)‐based dyad in which a fulleropyrrolidine covalently linked to a 2,3‐bipyridin‐2‐yl‐quinoxaline ligand was incorporated (see picture).