Tuning of electrochromic properties of electrogenerated polythiophenes through Ru(II) complex tethering and backbone derivatization

Herein, we present electrochromic properties of polythiophenes (PEDOT-Ru, PProDOT-Ru, PSNS-Ru) which were synthesized through electrochemical polymerization of thiophene derivatives tethered to [Ru(bpy)₂pytri]²⁺ complexes via alkyl chain. The unconjugated spacer hinders the effective electronic interaction between the metal center and polymer backbone provided explicitly different multichromic and ambipolar nature to polythiophenes from their metal free counterparts (PEDOT, PProDOT and PSNS). The cathodic behavior of all polymers was mainly dominated by the redox and optical properties of the tethered Ru complex whereas their anodic behavior depended on properties of both the conjugated backbone and the Ru complex. Modification of conjugated backbone from SNS, ProDOT to EDOT led to a distinct variation of band gap from 2.44 eV, 1.94 eV to 1.84 eV and provided a wide span of colors at neutral state (yellow, orange, green, respectively) which are all evidently different from their metal free counterparts. PEDOT based metallopolymer reached as high as 46.24% optical contrast and 2.52 s switching time. The coloration efficiency of SNS, ProDOT and EDOT based polymers were calculated as 69.42, 298.70, 365.22 cm²/C, respectively. The polymers displayed distinct colors from various hues of red, green and blue legs of RGB color-space upon sequential anodic and cathodic polarization indicating the rewarding effect of tethering of Ru(II) complex and backbone derivatization in refinement of electrochromic properties of polythiophenes.