The formation and characteristic properties of organized films that are based on metal ion complexes of poly(4-(2,2 0 :6,2 00 -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.

Poly(N‐(4‐(2,2′:6,2″‐terpyridyl)phenyl)imino‐2,7‐fluorenylene P1‐2 was prepared upon palladium‐catalyzed polycondensation of 2,7‐dibromo‐9,9‐di‐n‐hexylfluorene 1 and 4′‐(4‐aminophenyl)‐2,2′:6,2″‐terpyridine 2 with 80% yield. MALDI–TOF spectroscopy indicated a maximum degree of polymerization of 14, the most abundant species being the pentamer and the hexamer. P1‐2 is highly fluorescent in solution. The emission maximum in chloroform is 510 nm, and the quantum yield Φf is 55%. UV/Vis titration of P1‐2 with zinc acetate and iron(II) perchlorate indicates formation of metal–terpyridine (tpy) 1:2 (bis)complexes. Since formation of the (bis)complex is accompanied by cross‐linking, the polymer slowly precipitates, especially in non‐polar solvents. Comparative titration of monomer 2 with zinc acetate proceeds under sharp increase of photoluminescence intensity until a metal–tpy 2:1 ratio is reached. We assume the formation of two zinc (mono)complexes, one with the tpy and the other one with the amino group of 2. CV analysis of P1‐2 in acetonitrile indicates three quasi‐reversible oxidation processes with mid‐potentials of 0.45, 0.50 and 0.95 V versus SCE due to oxidation of the backbone nitrogen atoms, while the reduction at −2.6 V is irreversible. The strong ionochromism renders P1‐2 useful as highly sensitive and specific fluorimetric chemosensor.

Organic and inorganic materials with redox-controllable coloration and two or more stable valence states are of interest for applications in electrochromic and sensing devices. [1][2][3] Commercial applications require materials with film-forming properties, high stability, high contrast, and switching speed. Film formation can be achieved via spin-coating, solvent evaporation, electrochemical deposition, or layer-by-layer assembly.[4] The latter method is advantageous because it can be used to assemble ultrathin films of a variety of organic and inorganic compounds in a simple and inexpensive manner, with thickness control in the nanometer range.Previous work on preparation of electrochromic layer-by-layer assemblies was based on the use of polymers containing redoxactive viologen [5,6] or triphenylamine units, [7] conjugated polyelectrolytes, such as polythiophene derivatives [8][9][10] and polyaniline (PANI), [11] or colloidal solutions of Prussian Blue nanoparticles. [11,12] In most cases, film formation was brought about by alternating electrostatic assembly of electroactive components and nonactive counter-polyelectrolytes, utilizing the layer-by-layer technique first reported by Decher and coworkers. [13] Our contribution differs from the previous ones in that a crosslinked organic-inorganic coordination polymer is built up stepwise on a solid support, and no counter-polyelectrolyte is needed. The preparation method is similar to Decher's technique, in that the substrate is alternately dipped into two different solutions causing the sequential buildup of the polymer film at the substrate surface. However, in our case the two solutions contain a) a metal salt, such as zinc hexafluorophosphate, and b) a polymeric polytopic ligand, such as P1-2, which is composed of a polyiminofluorene backbone [14] with phenylterpyridine substituent groups attached to the nitrogen atom of the backbone. Synthesis and molecular structure are shown in Scheme 1a, and the self-assembly process is depicted in Scheme 2. The terpyridine (tpy) groups are capable of forming metal complexes of D 2d -symmetry with divalent zinc ions [15,16] (Scheme 1b). Due to the polytopic nature of the ligand P1-2, a network structure is formed, and the resulting coordination polymer is insoluble, so that it is easily immobilized at the substrate surface. Since the polytopic ligand is neutral, the buildup of the films proceeds exclusively via coordinative interactions. There is a similarity to the ''reactive self-assembly'' of previously reported films of coordination polymers, such as zinc bisquinoline, [17] metal tetrathiooxalates, [18] metal(IV)diphosphonates [19] metal hexacyanoferrates, [20] metal Schiff-base coordination polymers, [21] and others, [22,23] but in these cases the self-assembly is brought about by coordinative and electrostatic interactions simultaneously. There is also some analogy to functional metallo-supramolecular polyelectrolyte films and multilayers, reported by Kurth and coworkers.[24] However, in their work, first a line...

Formation and characteristic properties of organized double-electrochromic films consisting of electrochromic poly(4-(2,2':6,2″-terpyridyl)phenyliminofluorene) (P-1)-zinc ion complexes and electrochromic anions are reported. The anions are 2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulfonate) (ABTS) and poly((4-sulfonatophenyl)iminofluorene) (P-2). The films were prepared upon multiple sequential adsorption of P-1 and the zinc salts of ABTS and P-2 on solid supports using coordinative interactions between the Zn ions and the terpyridine (tpy) ligands. The ABTS and P-2 ions are incorporated in the films via electrostatic forces neutralizing the charge of the complexed divalent zinc (Zn(2+)) ions. The optical, electrochemical, and electrochromic properties of the films are described. Films consisting of the Zn ion complex of P-1 and ABTS are yellow in the neutral state and change their color to brownish gray and finally blue, if anodically oxidized at ∼640 mV vs FOC. Films containing the Zn ion complex of P-1, with P-2 as a counterion, are yellow in the neutral state and change color to dark red and finally blue, if anodically oxidized at ∼450 mV vs FOC. Compared with previously reported films of the Zn ion complex of P-1 with nonelectroactive hexafluorophosphate as the counterion, the new films exhibit faster response times, as well as higher contrast, and the colors in the oxidized state are modified. The films are stable under ambient conditions and might be useful as active layers in electrochromic devices.

Preparation, metal ion complexation, and coordinative assembly into organized electro-chromic films of a polyaniline derivative P1 substituted with tert-butyloxycarbonyl (boc) and terpyridine (tpy) substituent groups in alternating sequence are described. Cleavage of the boc groups after processing into thin films is also described. P1 is prepared upon Pd-catalyzed polycondensation of N-tert-butyloxycarbonyl-4,4'-dibromodiphenylamine and 4'(4-aminophenyl)-2,2':6,2''-terpyridine. The molecular weight is in the range of oligomers, the tetramer and pentamer being the most abundant species. P1 is soluble in common organic solvents. Solutions are pale yellow with blue or green fluorescence depending on the solvent. Fluorescence quantum yields up to 68% are found. P1 is able to complex divalent metal salts such as zinc(II) chloride, for example. Titration experiments indicate the formation of 2:1 tpy:metal ion complexes. Layer-by-layer (LbL) assembled films of metal ion complexes of P1 can be prepared, if negatively charged substrates are alternately dipped into solutions of metal(II) hexafluorophosphates and P1. Films of the zinc and nickel ion complex of P1 are lemon yellow in the neutral state and change color into greenish gray upon anodic oxidation, while Co-containing films are purple and change color into grayish blue upon oxidation. All color changes are reversible under ambient conditions. ATR-IR studies indicate that thermal treatment of the films at 180 °C, or acid treatment, e.g. with 5% aqueous trifluoroacetic acid solution, results in cleavage of the boc groups. P1 is transformed into the polyaniline derivative P2 with tpy substituent groups at every second N atom in the backbone. Films of metal ion complexes of P2 are also electrochromic albeit the colors differ slightly from those of P1. For example, the absorption maximum of the Zn-P2 film is at 456 nm, whereas it is at 446 nm for the corresponding Zn-P1 film. Prior to cleavage of the boc group, electrochromic switching times are 1.1 to 2.0 s for 30 to 40 nm thick films, while after the cleavage 0.5 to 1.2 s are found. The contrast is 13 to 19%, and not affected by the cleavage. Because of high stability, fast switching, and high contrast, the films might be useful as active materials in electrochromic devices.