Multichromic metallopolymers of poly(2,5-dithienylpyrrole)s derived through tethering of ruthenium(II) bipiridyl complex

In this study, 2,5-dithienylpyrrole (SNS) units were tethered to ruthenium(II) bipiridyl complexes and electrochemically polymerized to obtain a new class of electrochromic metallopolymers. The Ru-complexes were designed by altering the number of polymerizable SNS units per redox active metal center and the length of non-conjugated spacer, where the relationship between the monomer structure and optoelectronic properties of the resultant metallopolymers was investigated. Tuning of the native properties of poly(2,5-dithienylpyrrole)s (PSNS) through introduction of electrochromic Ru complex as a side chain substituent presented a viable approach where the metallopolymers revealed not only ambipolar but also vibrantly multichromic behavior displaying a wide color pallet ranging from reddish brown to orange to khaki to gray. Mechanism that derive the ambipolar/multichromic activity was disclosed by investigation of optoelectronic properties of analogous poly(2,5-dithienylpyrrole)s (PSNSs) having bipyridine functionality. It was found that number of polymerizable units in the monomers primarily influences the electrochromic properties and enhances the optical contrast and coloration efficiency of the SNS based metallopolymers. Electrochromic properties of SNS-based metallopolymers described here were further improved by introduction of EDOT units into the conjugated backbone via copolymerization. Copolymers exhibited color variation from brownish yellow to greenish yellow to green and blue with lower bandgaps and shorter switching times.