Coordinative Supramolecular Assembly of Electrochromic Films Based on Metal Ion Complexes of Polyiminofluorene with Terpyridine Substituent Groups

The formation and characteristic properties of organized films that are based on metal ion complexes of poly(4-(2,2′:6,2′′-terpyridyl)phenyliminofluorene) ( P1 ) with thickness control in the nanometer range are reported. The films were obtained upon multiple sequential assembly of divalent metal ions (Zn, Co, Ni) and the terpyridine(tpy)-substituted polymer P1 on solid supports via coordinative interactions between metal ions and tpy ligands. The influence of deposition parameters is described, and the optical, electrochemical, and electrochromic properties of the polymer films are compared. Under optimized conditions, 12 dipping cycles and a time period of <5 min are sufficient to obtain a homogeneous film of 100 nm in thickness. Films containing Zn(II) and Ni(II) ions are yellow in the neutral state and change color to red and finally blue if anodically oxidized up to 560 mV vs FOC. Films containing Co(II) ions are purple in the neutral state and change to blue in the oxidized state. All color changes are highly reversible, even under ambient conditions. For films prepared upon 12 dipping cycles, the switching from the neutral to the fully oxidized state proceeds within 300 and 700 ms, and the contrast at 800 nm is up to 18%. The films might be useful as active layers in electrochromic devices.