Five-Stage Near-Infrared Electrochromism in Electropolymerized Films Composed of Alternating Cyclometalated Bisruthenium and Bis-triarylamine Segments

Oxidative electropolymerization of cyclometalated bisruthenium complexes [(Nptpy)(2)Ru-2(tppyr)](PF6)(2) and [(Nptpy)(2)Ru-2(tpb)](PF6)(2) produced adherent metal, lopolymeric films on electrode surfaces, where Nptpy is 4'.. (p-N,N-diphenylamino)pheny1-2,2':6',2-terpyridine, tppyr is the 2,7-bisdeprotonated form of 1,3,6,8-tetra(pyrid-2-yI)pyrene, and tpb is the 3,6-bisdeprotonated form of 1,2,4,5tetra(pyrid-2-yl)benzene. The resulting polymers are composed of two types of alternating constituent units: tppyr- or Apb-bridged cyclometalated bisruthenium units and biphenylbridged bis-triarylamine segments. These films exhibited four .well-defined anodic redox couples as a result of the stepwise oxidations of these two units. By manipulating the intervalence charge-transfer transitions of mixed-valent bisrutheniurn and bis-triarylamine units, five-stage near-infrared electrochromism with stepwise color, changes accompanied by good contrast ratio and coloration efficiency has been realized in these films. The film characterization by scanning electronic microscopy and X-ray photoelectron spectroscopy techniques are presented as well.