Synthesis, Aggregation, Electrocatalytic Activity, and Redox Properties of Tetranuclear Cobalt Phthalocyanine

摘要

Using pentaerythritol as a framework, it has been possible to synthesize a tetranuclear phthalocyanine with a spiro type linkage. Electrochemical and spectro-electrochemical data are presented for the cobalt complex in the Co(III)Pc(-2), Co(II)Pc(-2), Co(III)Pc(-1) and Co(I)Pc(-3) oxidation levels. The Co(II) species aggregates very strongly, dimerising with an aggregation constant, in o-dichlorobenzene of 240,000/m, two orders of magnitude greater than for the parent Co (II)TNPc.Monolayers of the cobalt (II) species laid upon an ordinary pyrolytic graphite electrode are shown to electrocatalytically reduce oxygen more efficiently than previously described analogous mononuclear and binuclear phthalocyanines. The Co (II) tetranuclear species disproportionates into a 1:1 mixture of Co (I) and Co (II) species upon reaction with hydroxide ion in a non- or weakly donating solvent. A film containing Co (I) TrNPc (-2)44- reduces nitrite ion in NaOH slowly, with oxidation to the Co (II) tetranuclear species.