Electrochromic and energy storage properties of novel terpyridine-Fe(II) coordination polymers: Improving performance by molecular engineering of nonconjugated linkers from linear to three-arm star configuration

In this work, two novel terpyridine-Fe(II) coordination polymers (DTP-Fe and TTP-Fe) with nonconjugated linkers were developed for electrochromism and energy storage. Both coordination polymers exhibited efficient electrochromic switch between purple and pale yellow with optical contrast over 60%, short coloring time around 2 s, high coloration efficiency over 440 cm(2) C-1, and good cycle stability. Moreover, the electrodes based on polymers DTP-Fe and TTP-Fe showed a specific capacitance of 21.42 and 35.84 mAh.g(-1) at 1 A g(-1), respectively. More important, we demonstrated that the three-arm star configuration may be superior to the conventional linear configuration for efficient electrochemical process, which resulted in the improved performance of the coordination polymer TTP-Fe. An asymmetric electrochromic supercapacitor based on TTP-Fe thin film and Prussian blue thin film was fabricated and possessed potential application in energy saving smart windows.