An Explanation of the Electrochromism of Lutetium Diphthalocyanine

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 g-value of 2.003. 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 g-value of 2.0022. The optical absorption spectra and extinction coefficients of three of the forms are also reported. © 1979, The Electrochemical Society, Inc. All rights reserved.