Synthesis and near infrared electrochromic properties of metallodithiolene complexes

Four metallodithiolene complexes [4,8-bis(octyloxy)-1,3,5,7-tetrathia]·di[1,1′-bis(diphenylphosphino)ferrocene·palladium(II)] (3), [4,8-bis(octyloxy)-1,3,5,7-tetrathia]di[1,3-bis(diphenylphosphino)propane·nickel(II)] (4), [4,8-bis(octyloxy)-1,3,5,7-tetrathia] ·[1,1′-bis(diphenylphosphino)ferrocene·palladium(II)]·[1,3-bis(diphenylphosphino)propane·nickel(II)] (5) and di[4,8-bis (octyloxy)-1,3,5,7-tetrathia]·[1,1′-bis(diphenylphosphino)ferrocene·palladium(II)]·nickel(II) (6) were synthesized and the near-infrared (NIR) electrochromic properties were studied. The spectroelectrochemical spectra and the electrochromic parameters such as optical contrast, switching time, optical density change, electrochromic efficiency and optical attenuation of complexes 3–6 were investigated in detail. The symmetric binuclear complex 4 showed relatively high electrochromic efficiency of 63.0 and 75.4 cm2/C both in the two oxidation states. The complexes exhibited excellent electroactive/electrochromic stability characterized by chronoamperometry (>4000 cyclic switches).