Near infrared electrochromic polymers based on phenazine moieties

New fused-aromatic quinoxaline and thieno[3,4-b]pyrazine based monomers; 10,12-bis(4-hexylthiophen-2-yl)dibenzo[f,h]thieno[3,4-b]quinoxaline (HTBQ) and 10,13-bis(4-hexylthiophen-2-yl)dipyrido[3,2-a:2′,3′-c]phenazine (HTPP) were synthesized. Electrochemical polymerization of HTBQ and HTPP were performed in acetonitrile/dichloromethane (ACN/DCM) solution containing LiClO4/NaClO4. Spectroelectrochemical behavior and switching ability of PHTBQ and PHTPP films were investigated by UV–vis spectroscopy. The polymer films showed reversible electrochemical oxidation with high contrast ratios in the NIR region with low switching times. PHTBQ revealed color changes between brick color and green in the reduced and oxidized states. PHTPP changed color from green to gray when the polymer film was switched between its redox states.

► The polymers are multichromic which is rare in literature.
► Yet another one switches between green and gray/transparent regime.
► Green to transparent switching polymers only go back to 2007.
► One of the polymers reveals a switching time of less than 1 s both in visible and near IR regions, quite an important feature for display applications.