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∣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 (M0) occurring at the liquid∣liquid interface in the presence of proton: 2 M S 0 + H W + ⇄ HM S + M S + a reaction induced by the very high affinity of M−, the reduced bisphthalocyanine, for H+ (KA = 10−13.5 mol−1 l). The lutetium bisphthalocyanine, which exits as the molecular form M0 over ∼0.4 V (Kd = 10−6.4) in the neutral solvent, disproportionates completely in acidic solutions (e.g., in nitrobenzene: KdH = 107.1 mol−1 l). At the water∣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.