Protonation equilibria of [Ru(LL)(CN)4]2- complexes possessing electron donating sites on the diimine ligand

Acid-base equilibria of two [Ru(LL)(CN)4]2− complexes with protonatable LL ligand, dcb and bppz (dcb = 4,4′-dicarboxy-2,2′-bipyridine, bppz = 2,3-(bis(2-pyridyl)pyrazine)) have been investigated. The assignation of protonating sites is supported by 13C NMR spectra. Both complexes are protonated first on the LL ligand and this process gives rise to significant decrease or complete quenching of the triplet luminescence.