Ester-functionalized pyrene derivatives: Effects of ester substituents on photophysical, electrochemical, electrochromic, and electrofluorochromic properties

Abstract

Multifunctional electrochromic materials are widely used in optoelectronic devices. Pyrene is a π-electron-rich group with fluorescence properties. Ester-functionalized pyrene derivatives potentially have interesting multifunctional properties such as electrochromic and electrofluorochromic characteristics. In this work, mono-, di-, tri-, and tetra-ester-substituted pyrene derivatives were synthesized, and the effects of the number of ester substituents on their photophysical, electrochemical, electrochromic, and electrofluorochromic properties were investigated. The number of ester substituents significantly affected these properties. An increase in the number of ester substituents on the pyrene caused red shifts in the absorption and emission spectra, a decrease in the driving voltage, and changes in the electrochromic colored states and electrofluorochromic performance. Mono-, di-, and tri-ester-functionalized pyrene derivatives showed good electrochromic properties, namely good switching stabilities, high optical contrasts, rapid responses, and high coloration efficiencies. Mono- and tri-ester-functionalized pyrenes gave good electrofluorochromic performances with reversible fluorescence quenching–fluorescence restoring between colored and bleached states during the electrochromic process. Ester-functionalized pyrene derivatives were successfully used in two functional digital displays with vivid colors. These results show that ester-functionalized pyrene derivatives with good electrochromic and electrofluorochromic properties are promising candidates for use in various applications, e.g., digital displays, organic electroluminescence displays, electronic shelf labels, energy-saving windows, and electronic paper.