5271-38-5Relevant articles and documents
Davies
, p. 84 (1972)
Vinokurova,Khaletskii
, (1969)
Spontaneous formation in the dark, and visible light-induced cleavage, of a Ru-S bond in water: A thermodynamic and kinetic study
Bahreman, Azadeh,Limburg, Bart,Siegler, Maxime A.,Bouwman, Elisabeth,Bonnet, Sylvestre
, p. 9456 - 9469 (2013)
In this work the thermal and photochemical reactivity of a series of ruthenium complexes [Ru(terpy)(N-N)(L)](X)2 (terpy = 2,2′;6′,2″-terpyridine, L = 2-(methylthio)ethanol (Hmte) or water, and X is Cl- or PF6-) with four different bidentate chelates N-N = bpy (2,2′-bipyridine), biq (2,2′-biquinoline), dcbpy (6,6′-dichloro-2,2′-bipyridine), or dmbpy (6,6′-dimethyl-2,2′-bipyridine), is described. For each chelate N-N the thermodynamic constant of the dark equilibrium between the aqua-and Hmte-complexes, the Hmte photosubstitution quantum yield, and the rate constants of the thermal interconversion between the aqua and Hmte complexes were measured at room temperature. By changing the steric hindrance and electronic properties of the spectator N-N ligand along the series bpy, biq, dcbpy, dmbpy the dark reactivity clearly shifts from a nonlabile equilibrium with N-N = bpy to a very labile thermal equilibrium with N-N = dmbpy. According to variable-temperature rate constant measurements in the dark near pH = 7 the activation enthalpies for the thermal substitution of H2O by Hmte are comparable for all ruthenium complexes, whereas the activation entropies are negative for bpy and biq, and positive for dcbpy and dmbpy complexes. These data are indicative of a change in the substitution mechanism, being interchange associative with nonhindered or poorly hindered chelates (bpy, biq), and interchange dissociative for more bulky ligands (dcbpy, dmbpy). For the most labile dmbpy system, the thermal equilibrium is too fast to allow significant modification of the composition of the mixture using light, and for the nonhindered bpy complex the photosubstitution of Hmte by H2O is possible but thermal binding of Hmte to the aqua complex does not occur at room temperature. By contrast, with N-N = biq or dcbpy the thermodynamic and kinetic parameters describing the formation and breakage of the Ru-S bond lie in a range where the bond forms spontaneously in the dark, but is efficiently cleaved under light irradiation. Thus, the ratio between the aqua and Hmte complex in solution can be efficiently controlled at room temperature using visible light irradiation.
Yellow-light sensitization of a ligand photosubstitution reaction in a ruthenium polypyridyl complex covalently bound to a rhodamine dye
Bahreman, Azadeh,Cuello-Garibo, Jordi-Amat,Bonnet, Sylvestre
, p. 4494 - 4505 (2014/03/21)
The ruthenium complex [Ru(terpy)(bpy)(Hmte)]2+ ([1] 2+), where terpy is 2,2′;6′,2′′-terpyridine, bpy is 2,2′-bipyridine, and Hmte is 2-methylthioethan-1-ol, poorly absorbs yellow light, and although its quantum yield for the photosubstitution of Hmte by water is comparable at 570 nm and at 452 nm (0.011(4) vs. 0.016(4) at 298 K at neutral pH), the photoreaction using yellow photons is very slow. Complex [1]2+ was thus functionalized with rhodamine B, an organic dye known for its high extinction coefficient for yellow light. Complex [Ru(Rterpy)(bpy)(Hmte)]3+ ([2]3+) was synthesized, where Rterpy is a terpyridine ligand covalently bound to rhodamine B via a short saturated linker. [2]Cl3 shows a very high extinction coefficient at 570 nm (44000 M-1 cm-1), but its luminescence upon irradiation at 570 nm is completely quenched in aqueous solution. The quantum yield for the photosubstitution of Hmte by water in [2]3+ was comparable to that in [1]2+ at 570 nm (0.0085(6) vs. 0.011(4), respectively), which, in combination with the much better photon collection, resulted in a higher photosubstitution rate constant for [2]3+ than for [1]2+. The energy of yellow photons is thus transferred efficiently from the rhodamine antenna to the ruthenium center, leading to efficient photosubstitution of Hmte. These results bring new opportunities for extending the photoactivation of polypyridyl ruthenium complexes towards longer wavelengths.
