- Photoinduced electron transfer in supramolecular assemblies composed of dialkoxybenzene-tethered ruthenium(II) trisbipyridine and bipyridinium salts
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Ruthenium(II) tris{4,4′-bis[(methyleneoxy)tris(ethyleneoxy)(4-methoxybenzene)]-2, 2′-bipyridine}(1), forms supramolecular complexes with N,N′-dimethyl-4,4′-bipyridinium, MV2+ (2), and with cyclo[bis(N,N′-p-xylylene-4,4′-bipyridinium)], BXV4+ (3). The association constants of the complexes generated between the dialkoxybenzenetethered units of 1 and the electron acceptors 2 and 3 correspond to Ka = 28 ± 1 M-1 for MV2+ and Ka = 1200 ± 100 M-1 for BXV4+. Time-resolved laser flash photolysis and steady-state emission studies show that electron transfer from excited 1 proceeds by an intramolecular pathway to the electron acceptors organized in the supramolecular assemblies, kiq = 1.7 × 108 s-1 for MV2+ and kiq = 2.9 × 108 s-1 for BXV4+, and by a diffusional route from free-uncomplexed 1, kdq = 1.9 × 108 M-1 s-1 for MV2+ and kdq = 3.4 × 108 M-1 s-1 for BXV4+. Formation of the supramolecular assemblies between 1 and 2 or 3 is supported by the intramolecular electron-transfer quenching of 1 and by the fact that the assemblies dissociate upon addition of β-cyclodextrin.
- Seiler,Dürr,Willner,Joselevich,Doron,Stoddart
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