Synthesis of bridged dinaphthoviologen derivatives for enhanced electrochromic performance and picric acid detection

Electrochromic materials represent a class of highly promising smart materials in contemporary research. Viologen, as a prevalent organic small molecule in smart chromic materials, has garnered extensive attention due to its tunable intermediate structure involving pyridine units and diverse nitrogen atom substituents. In this investigation, the molecular structure of dinaphthoviologen (DNV2+) were modified, and various groups were introduced to ionize nitrogen atoms. This structural modification aimed to decrease the molecular energy gap and enhance the electron acceptability of nitrogen atoms. The results demonstrate robust redox ability in DNV2+. To explore the practical applications, a straightforward DNV2+-based electrochromic device was fabricated, incorporating ferrocene as an electronic supplement. This device exhibited commendable cycling performance (exceeding 1000 cycles) and rapid response times (8 s for coloring and 10 s for fading) without the need for additional electrolytes. Additionally, the transmittance changes by more than 45 %. Moreover, owing to the presence of conjugated structures, DNV2+ exhibited noteworthy fluorescence properties. In fluorescence-based picric acid detection experiments, the synthesized molecules exhibited high selectivity and sensitivity, as evidenced by the determined Stern-Volmer constants (K6b = 2.17 x 104 L/mol, K6c = 3.87 x 104 L/mol). The findings highlight the potential of the developed dinaphthoviologen derivatives for advanced applications in electrochromic devices and sensitive detection of picric acid.