Multipurpose acetic acid functionalized carbazole derivatives: Synthesis, electrochemical properties and electrochromic device applications

Abstract

In this study, synthesis of two multifunctional acetic acid functionalized carbazole bearing monomers; 2-(3,6-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9H-carbazol-9-yl)acetic acid (M1) and 3,6-dithien-2-yl-9H-carbazol-9-ylaceticacid (M2) via Stille cross-coupling reaction was reported. Obtained monomers were electrochemically polymerized in 0.1 M TBAPF6/DCM/ACN (5:95, v:v) solution and characterized in terms of electrochemical, spectroelectrochemical and electrochromic switching behaviors. When poly-2-(3,6-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9H-carbazol-9-yl)acetic acid (P1) and poly-3,6-dithien-2-yl-9H-carbazol-9-ylaceticacid (P2) were compared in terms of electrochemical behaviors, by virtue of the electron-rich EDOT units in the P1 chains, the polymer film exhibited lower monomer oxidation potential at around 1.05 V. Both polymers exhibited neutral state yellow color with similar optical band gaps and multi-electrochromic behaviors under different applied potentials. Insertion of thiophene unit instead of ethylene dioxythiophene (EDOT) unit on the polymer backbone enhanced the electrochromic and optical contrast properties and P2 showed the higher optical contrast then P1. Furthermore, owing to the promising electrochromic properties of P2 like red shifted absorption and higher optical contrast, a prototype P2 and PEDOT bearing solid state electrochromic devices (ECDs) were constructed and characterized. P2 and PEDOT comprising ECD works between yellow and blue colors at −2.0 V and at 2.0 V respectively, with 41% optical contrast and 1.3 s switching time at 580 nm. Furthermore, P2 was used for energy storage applications before and in the present study it was used for ECD applications with promising results which make acetic acid functionalized carbazole derivatives multi-purpose new generation materials.