An Explanation of the Electrochromism of Lutetium Diphthalocyanine

Abstract

Lutetium diphthalocyanine can be electrolyzed reversibly in dimethylformamide to give four different colored solutions: violet, blue, green, and yellow‐red. Two of these solutions, the violet and the green, also exhibit electron paramagnetic resonance (EPR) signals indicative of organic‐free radicals. The blue and the yellow‐red solutions are EPR silent. The oxidation state of the phthalocyanine nucleus is responsible for the electrochromism of this rare‐earth complex. The EPR signal of the violet form, which is produced by electrolytic reduction and which is probably the anion radical of the complex, has a . The signal of the green form, which is the initially prepared material and which is probably a salt containing the cation radical of the complex, has a . The optical absorption spectra and extinction coefficients of three of the forms are also reported.