Electrochromism in sandwich-type diphthalocyanines: electrochemical and spectroscopic behaviour of bis(phthalocyaninato)titanium(IV) (Ti(Pc)2) film

Bis(phthalocyaninato)titanium(IV) (Ti(Pc)2) films deposited on a transparent conductive electrode show a colour change upon electrochemical oxidation in aqueous electrolyte; the film colour changes from yellow to reddish-brown passing from the neutral to the di-oxidized form and from reddish-brown to green, to yellow again passing from the di-oxidized to the mono-oxidized and to the neutral form, respectively. The phenomenon is reversible and rapid, and the system seems to be interesting for application. Cyclic voltammetry and square-wave pulse experiments were analysed together with electronic spectra and X-ray photoelectron spectroscopy (XPS) surface analysis.