The Synthesis And Electrochemical Study Of Several New Electrochromic Materials Pyridilium Analogues

Electrochromism is defined as the wonder that optical properties (transmittance, reflectance, absorption, etc.) of the materials undergo reversible and stable change when the potential is applied. The reversible change of the transmission and colors of the materials can be found in appearance. The materials are named as electrochromic materials (EC) and the devices based on these materials are called electrochromic devices (ECD).Electrochromic materials can be classified into three groups:single molecular materials, organic and polymeric materials and inorganic materials. Organic molecular and polymeric electrochromic materials have shown relatively diverse and clear colors, good response time, and accessible wet-chemical processing for the devices over the inorganic counterparts. During the past decade, the related studies have focused on organic molecular and polymeric organic materials which have well-defined reversible redox processes and superior electrochromic behaviors, such as the viologen family, anthraquinone and conducting polymers polyaniline, polythiophene. With the excellent performance, environmental protection and energy saving, electrochromic materials comply with the future trend of development of the smart materials. It has very broad application prospects in electrochromic displays, the large-screen information display, smart windows, mirrors of vehicles and electronic ink. In this paper, a series of novel single molecular electrochromic materials: monosubstituted4,4’-bipyridilium-TCNQ anion radical complexes,2,6-Di(4-pyridyl)-4-benzylpyridilium derivatives and2,4,6-Tri(pyridine-4-yl) pyridilium derivatives. The structure of these compounds was characterized by’H NMR,13C NMR, FT-IR and MS. Their electrochromic behaviors, electro-optical properties and thermal stability were investigated by cyclic voltammetry, thermogravimetric analysis and UV-vis absorption spectra. It was found these compounds presented superior electrochemical and electrochromic properties. By comparing these materials, several compounds with excellent electrochromic properties were screened out to assemble a simple summary of electrochromic device. The results show that these ECDs exhibited multicolor (red, green, blue) electrochromic behaviors, high optical contrast and they may be expected to apply in commercial large electrochromic displays by further improvement and optimization.