Electrochromism and electrochemical properties of complexes of transition metal ions with benzimidazole-based ligand

• Published in: RSC advances Vol. 7; no. 80; pp. 50858 - 50867
• Main Authors: Wałęsa-Chorab, Monika, Banasz, Radosław, Marcinkowski, Damian, Kubicki, Maciej, Patroniak, Violetta
• Format: Journal Article
• Language: English
• Published: 2017
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C7RA10451K

Six new mononuclear complexes of transition metal ions ( 1–6 ) with ( E )-2-(1-methyl-2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)-1 H -benzoimidazole L were synthesized and characterized by spectroscopic methods as well as X-ray diffraction analysis. Structures of these complexes can be divided into three groups depending on the coordination number and environment of the metallic center: the first one of general formula [ML 2 ]X 2 , the second one - [MLX 3 ] and the third one - [MLX 2 ], where X is anion or solvent molecule. Electrochemical and electrochromic properties of complexes were investigated. Complexes Fe( ii ) 1 , Cu( ii ) 2–4 and Co( ii ) 5 were found to be electroactive and their colors depend on the oxidation state of metal center and ligand molecule. Fe( ii ) complex 1 exhibits purple color in the neutral state and its color changes to yellow after Fe( ii ) → Fe( iii ) oxidation, followed by pale-yellow after further oxidation of ligand molecule and to green when the metal center is reduced to Fe( i ). The original color can be restored after electrochemical oxidation Fe( i ) to Fe( ii ). It was found that this complex exhibits high color stability in solution during multiple oxidation/reduction cycles. This complex can be therefore regarded as very interesting material for the construction of multielectrochromic devices.