ELECTROCHEMISTRY AND ELECTROCHROMIC BEHAVIOR OF LANGMUIR-BLODGETT-FILMS OF OCTAKIS-SUBSTITUTED RARE-EARTH-METAL DIPHTHALOCYANINES

Heavy rare-earth metal diphthalocyanine complexes with alkoxy or alkyl substituents dissolved in common organic solvents formed stable Langmuir-Blodgett (L-B) films. The cyclic voltammogram of L-B films on indium-tin oxide Nesa glass electrodes showed smaller peak splitting and more symmetrical shape than those of corresponding solvent-cast films. The multicolor electrochromism was found both in L-B film and cast film systems in contact with an aqueous HCl-KCl electrolyte. For the completion of the color change, different potentials should be applied with different substituents. More than 1 V (versus SCE) was necessary for the tert-butyl-substituted complexes and less than 0.8 V for the propoxy-substituted ones. After about 7 h of repetitive cycling at 100 mV/s between 0 and 0.6 approximately 0.9 V, the relative Q-band intensity decreased by 2-5%, demonstrating good electrochemical stability.