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Tetranuclear Polypyridyl Complexes of Ru II and Fe II : Synthesis, Electrochemical, Photophysical and Photochemical Behaviour
Author(s) -
Lombard Jean,
Romain Sophie,
Dumas Stéphane,
Chauvin Jérôme,
Collomb MarieNoëlle,
Daveloose Denis,
Deronzier Alain,
Leprêtre JeanClaude
Publication year - 2005
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200500106
Subject(s) - chemistry , ruthenium , bipyridine , redox , electrochemistry , electron transfer , luminescence , quantum yield , covalent bond , excited state , quenching (fluorescence) , ligand (biochemistry) , photochemistry , tris , crystallography , 2,2' bipyridine , inorganic chemistry , fluorescence , crystal structure , catalysis , electrode , organic chemistry , biochemistry , physics , receptor , optoelectronics , quantum mechanics , nuclear physics
Abstract Three heterotetranuclear complexes [{Ru II (bpy) 2 (LL n )} 3 Fe II ] 8+ {bpy = 2,2'‐bipyridine, n = 2, 4, 6; denoted [{Ru(LL n )} 3 Fe] 8+ }, in which one iron centre is complexed by three Ru II ‐tris‐bipyridine‐like moieties containing covalently bridging bis‐bipyridine LL n ligands, have been synthesised and characterised. The stability and the electrochemical, photophysical and photochemical properties of these complexes have been investigated in CH 3 CN. The cyclic voltammograms of all complexes exhibit two successive reversible oxidation processes in the positive region, corresponding to the Fe II /Fe III and Ru II /Ru III redox couples. These systems are clearly separated (Δ E 1/2 about 300 mV), which indicates the absence of an electronic connection between the two subunits. In the negative region, three successive reversible four‐electron systems are observed, corresponding to the ligand‐based reduction processes. The two oxidized forms of the complexes [{Ru II (LL n )} 3 Fe III ] 9+ and [{Ru III (LL n )} 3 Fe III ] 12+ , which are obtained by two successive exhaustive electrolyses, are very stable. The [{Ru(LL n )} 3 Fe] 8+ complexes are luminescent, which shows that the covalent linkage between the Ru II ‐tris‐bipyridine and Fe II ‐tris‐bipyridine subunits leads to an only partial quenching of the Ru II * excited states by energy transfer to the Fe II centre. The luminescence lifetime and quantum yield are found to be independent of the complexes’ concentration, thus indicating that the energy‐transfer process is only due to an intramolecular electron‐exchange mechanism. Quantitative photoinduced oxidation of the tetranuclear complexes has been performed by continuous photolysis experiments in the presence of a large excess of a diazonium salt, which plays the role of a sacrificial oxidant. Two successive oxidation processes (Fe II → Fe III and Ru II → Ru III ) are observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)