Heterochelates of ruthenium(II): Electrochemistry, absorption spectra, and luminescence properties

Article abstract of DOI:10.1016/S0277-5387(97)00174-5

A series of heterochelates [Ru(bpy)²(L-X)](ClO₄) (1-6) derived from the schiff bases of o-aminophenol and p-substituted (X) benzaldehydes, HL-X (X = NO₂, Cl, F, Me, OMe and NMe₂) have been synthesized and characterized. Cyclic voltammograms of all the complexes, except 6 (X = NMe₂), exhibit a reversible Ru^II/Ru^III and an irreversible Ru^III/Ru^IV oxidation processes. In the case of 6, both the oxidation processes take place reversibly. A linear correlation is obtained by plotting the E_1/2 value of Ru^II/Ru^III couple against the Hammett σ⁺ parameters. The absorption spectra of the complexes are similar showing absorption bands due to dπ-π* (bpy), Schiff base n-π* and π-π* intraligand transitions. A linear correlation is also obtained between v_max (MLCT) and ΔE_1/2 (separation between the first oxidation and first reduction couples). The effect of solvents on the MLCT and n-π* absorption bands have been studied. Fluorescent spectral studies have shown that all the complexes luminesce at room temperature and the observed emission bands are due to metal-perturbed ligand-centred transitions.