Two geometric isomers of [RuCl2(PPh3)(2)(O-N)]-type complex were prepared and characterized by X-ray crystallography (PPh3 = triphenylphosphine, O-N = Hpia/pia(-), Hpia = 3-hydroxypicolinamide). The electrochemical properties of the complexes upon protonation/deprotonation were investigated. The redox potential of the Ru center was remarkably shifted by isomerization. The UV-vis and electrochemical measurements suggested that slow isomerization from trans(P,Cl), trans(P,N) geometry to trans(P,P) geometry induced the oxidation and deprotonation of the complex.