Electrochemical crystallisation and characterisation of platinum phthalocyanine charge transfer salts in non-aqueous media

Abstract

Partially oxidised platinum phthalocyanine (PtPc) has been electrochemically crystallised from a solution of PtPc in 1-chloronaphthalene (CN) containing tetrabutylammonium perchlorate supporting electrolyte at high temperature. The crystallisation process was investigated by chronoamperometry. The formation of partially oxidised PtPc occurs by a three-dimensional instantaneous nucleation and growth mechanism. SEM images show that the deposit is composed of many fibre-like crystallites with an average diameter of about 20 nm. Voltammetry and AC impedance were used to study the electrochemical behaviour of the partially oxidised PtPc at both high and room temperature. The electrochemical intercalation of anions into this partially oxidised PtPc in acetonitrile at room temperature is characterised by a reversible electrochemical process followed by a reversible phase transformation. A large capacitance is observed during the oxidation cycle. The phase transformation is responsible for the switching of the doped PtPc from a semi-conducting to metal-like conductive state. The kinetic parameters of the intercalation process depend greatly upon the doping potential.