Donor-π-acceptor tetraaniline derivatives with tunable electrochromic performance

Abstract Tetraaniline (TANI) and the benzene ring modified by different groups (-OH, -NR2) are connected by the π bond (C=N). A series of TANI derivatives with D-π-A structure are easily synthesized by the Schiff-base reaction and named as TANI-2OH-BA, TANI-4DEA-BA, TANI-4DEA-2OH-BA and TANI-4DMA-2OH-BA, according to the type and location of substituent groups. The introduction of D-π-A structure can not only reduce the redox potential, but also regulate the electrochromic properties of materials by changing the substituent groups. TANI-4DEA-2OH-BA and TANI-4DMA-2OH-BA films show the khaki (reduction state) to green (oxidation state) color change, which are obviously different from that of TANI (colorless to blue). TANI-4DMA-2OH-BA has the shortest switching time (tb/tc =1.6 s/2.6 s) and best cycling stability (charge retention of 93.3% after 500 CV cycles), attributed to the reduction of intermolecular forces and film compactness. Moreover, the TANI-4DMA-2OH-BA/WO3 electrochromic device presents similar color changes with the TANI-4DMA-2OH-BA film, and also has good cycling stability and short switching time. In short, constructing D-π-A structure is an effective method to design the color of oligoaniline, and TANI-4DMA-2OH-BA will be a promising material in camouflage and other aspects.