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Effect of the parent ligand on the photophysical properties of closely-coupled, binuclear ruthenium(II) tris(2,2′-bipyridine) complexes

Lookup NU author(s): Professor Andrew Benniston, Emeritus Professor Anthony Harriman

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Abstract

The photophysical properties of closely-coupled, binuclear complexes formed by connecting two ruthenium(II) tris(2,2′-bipyridine) complexes via an alkynylene group differ significantly from those of the relevant mononuclear complex. In particular, the energy of the first triplet excited state is lowered relative to the parent complex, because of the presence of the alkynylene substituent, while the triplet lifetime is prolonged, in part, because of extended electron delocalisation. We now report that the triplet lifetime is also affected by the nature of the spectator 2,2′-bipyridyl ligands. Thus, replacing the parent 2,2′-bipyridine ligands with the corresponding 4,4′-dinitro-substituted ligands serves to decrease the luminescence yield and lifetime. With the corresponding carboxylate ester, the luminescence yield and lifetime are increased. Perdeuteration of the parent 2,2′-bipyridine ligands also leads to a modest increase in the luminescence yield. Such observations are indicative of electronic coupling between the various metal-to-ligand, charge-transfer excited triplet states. Temperature dependence studies confirm that these excited states are closely spaced and thermally accessible at ambient temperature. For some of the binuclear complexes, the quantum yield for formation of the lowest-energy triplet state is significantly less than unity.


Publication metadata

Author(s): Benniston AC, Harriman A, Romero FM, Ziessel R

Publication type: Article

Publication status: Published

Journal: Dalton Transactions

Year: 2004

Issue: 8

Pages: 1233-1238

Date deposited: 09/07/2010

ISSN (print): 1477-9226

ISSN (electronic): 1477-9234

Publisher: Royal Society of Chemistry

URL: http://dx.doi.org/10.1039/b400933a

DOI: 10.1039/b400933a


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