Proton transfer across liquid|liquid interfaces facilitated by the disproportionation reaction of a lutetium bisphthalocyanine: A voltammetric study at the microinterfaces between water and nitrobenzene or 1,6-dichlorohexane

Proton transfer across the water vertical bar solvent (nitrobenzene, 1,6-dichlorohexane) interface is facilitated by the presence in the organic phase of a lutetium bisphthalocyanine. The driving force of the facilitated transfer of H+ is the redox disproportionation reaction of this compound (M-0) occurring at the liquid vertical bar liquid interface in the presence of proton: 2M(s)(0) + H-w(+) HMs + M-s(+) a reaction induced by the very high affinity of M-, the reduced bisphthalocyanine, for H+ (KA 10-13-5 Mol-1 1). The lutetium bisphthalocyanine, which exits as the molecular form M-0 over similar to 0.4 V (K-d = 10(-6.4)) in the neutral solvent, disproportionates completely in acidic solutions (e.g., in nitrobenzene: K-dH = 10(7.1) mol(-1)]). At the water vertical bar nitrobenzene interface, this disproportionation reaction facilitates the proton transfer by almost 0.30 V. Voltammetry at a rotating disk electrode in nitrobenzene confirms the redox disproportionation reaction and the basicity of the reduced lutetium bisphthalocyanine. (C) 2008 Elsevier B.V. All rights reserved.