In this contribution, detailed hydrogen bonding and deprotonation equilibria between a ruthenium biimidazole-like complex [Ru(bpy)2(TMBbimH2)](PF6)2 (4  , TMBbimH2 is 5,6,5',6'-Tetra-methyl-2,2'- bibenzimidazole) and acetate anion have been discussed for the first time, in which hydrogen bonded adduct is observed in absorption spectra and electrochemical measurement in the presence of a large excess of acetic acid, with a feature 1MLCT band at 491 nm and an oxidation potential of 0.57 V, different from the fully protonated species (474 nm and 0.74 V) and mono-deprotonated species (512 nm and 0.37 V). A set of circular equilibria is established. A new approach to calculate the deprotonation constant is also developed. A binding constant Log K = 6.99 and a deprotonation constant Log K = 3.78 are obtained from absorption titration experiments.

Detailed hydrogen bonding and deprotonation equilibria between a ruthenium biimidazole-like complex and acetate anion

243rd National Meeting (2012)

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