Electrochemical and electrochromic properties of arylene diimide dyes with N-phenylphenothiazine units

Five arylene diimides containing N-phenylphenothiazine or N-phenyl-3,7-di-tert-butylphenothiazine units as Nsubstituents, coded as PTZ-PMDI, PTZ-NTDI, tBuPTZ-PMDI, tBuPTZ-NTDI and tBuPTZ-PTDI, were synthesized from condensation of N-(4-aminophenyl)phenothiazine and N-(4-aminophenyl)-3,7-di-tert-butylphenothiazine with pyromellitic dianhydride (PMDA), naphthalene-1,4,5,8-tetracarboxylic dianhydride (NTDA) and perylene3,4,9,10-tetracarboxylic dianhydride (PTDA), respectively. Incorporation of tert-butyl substituents on the PTZ active sites reduces the oxidation potential and increases the redox stability and solubility of the PTZ-diimides. PTZ-PMDI and PTZ-NTDI without tert-butyl substituents on the PTZ units are insoluble in suitable organic solvents, therefore the characterization of their electrochemical and electrochromic properties is unavailable. All the tBuPTZ-diimide compounds were electrochemically active and underwent reversible oxidation and quasireversible reduction as evidenced by cyclic voltammetry studies. These diimide compounds changed colors when they were reduced and oxidized, demonstrating their multi-electrochromic properties. The tBuPTZdiimides gave a colored state of pink and red upon electro-oxidation, together with a low onset bias of 0.6 V and good switching stabilities. The electrochromic devices using these diimides as electroactive compounds were constructed and their electrochromic performance was studied.

Automated summary

This study synthesized five arylene diimides with multi-electrochromic properties and investigated their electrochemical activity, solubility, and switching stability. The results showed that the introduction of tert-butyl substituents on the PTZ active sites reduced the oxidation potential, increased solubility, and significantly improved the electrochromic performance. Electrochromic devices using these compounds as electroactive materials were constructed and their performance was studied.