Metallopolymer

Metallopolymer films have also been prepared by oxidative polymerization of complexes of the type [M(phen)2(4,4 -bipy)2]2+ (M = Fe, Ru, or Os phen= 1,10-phenanthroline, 4,4 -bipy = 4,4 -bipyridine).23 Such films are both oxidatively and reductively electrochromic reversible film-based reduction at potentials below —IV lead to dark purple films,23 the color and potential region being consistent with the viologen dication/radical cation electrochromic response. A purple state at high negative potentials has also been observed for polymeric films prepared from [Ru(L13)3]2+.24 Electropolymerized films prepared from the complexes [Ru(L16)-(bipy)2][PF6]22 and [Ru(L17)3][PF6]226,27 exhibit reversible orange/transparent electrochromic behavior associated with the Run/Ruin interconversion. 

El-Ghayoury A, Schenning APHJ, Meijer EW. Synthesis of ir-conjugated oligomer that can form metallopolymers. J Polym Sci Part A Polym Chem 2002 40 4020-4023. 

Finally, when the methylated ligands bpz prz and bpz qnox are self-assembled with Cu or Ag ions, metallopolymers with an M hgand ratio of 1 1 are formed. In one case [Eq. (12), (122)], the structure was determined by X-ray diffraction (see below) and consists of a sequential arrangement of metal and organic components. 

Magnetic susceptibility, nickel 7]5-ligands, 8, 159—160 Magnetization, in dynamic NMR, 1, 409 Main-chain metallopolymers, with -coordinated metals and long spacers, characteristics, 12, 347... 

Metalloorganic liquids, characteristics, 1, 853 Metallopolymers, with n-coordinated metals, 12, 311 Metallosilanes, preparation methods, 3, 521 Metallostannation, in tin-carbon bond formation, 3, 817 Metal-metal bonds... 

Upon irradiation by UV light (Xexcit = 325 nm), the metallopolymer 45 exhibits a bright green emission (Xem = 525 nm) in the solid state. In contrast, a non-emissive 2D brick-wall type coordination polymer of composition [Cu2I2(L46)2]ra 46 with rhomboid dinuclear Cu—12—Cu nodes resulted from the reaction of 2-(benzylthio)-l-thiomorpholinoethanone L46 with Cul. Compared to the short Cu-Cu distance in 45, the metal metal contacts within the rhomboids of 46 are much longer and reach 2.856(2) A. 

Owing to the intrinsic optical and photophysical features discussed for metallopolyynes, it is expected that they have great potential as active materials in optical and photonic devices. Over the years, numerous studies have shown that these metallopolymers can be exploited for a collection of electronic and optoelectronic applications. 

After publication of our work,22 new self-assembled Zn(II) terpyridine polymers were prepared and used in PLEDs. Following the methodology reported by us, Lin et al. similarly prepared a series metallopolymers by self-assembled reaction containing Zn(II) terpyridine units, including a metallo-homopolymer and metallo-u/t-copolymer containing carbazole pendants attached to the C-9 position of fluorene by long alkyl spacers.27... 

The analogous osmium polymers have also been studied in great detail. The synthetic procedures required for these metallopolymers are the same as those described above for ruthenium however, the reaction times are longer. The similarity between the analogous mononuclear and polymeric species is further illustrated by the fact that the corresponding osmium polymers have considerably lower redox potentials and are also photostable, as expected on the basis of the behavior observed for osmium polypyridyl complexes. 

The example considered is the redox polymer, [Os(bpy)2(PVP)ioCl]Cl, where PVP is poly(4-vinylpyridine) and 10 signifies the ratio of pyridine monomer units to metal centers. Figure 5.66 illustrates the structure of this metallopolymer. As discussed previously in Chapter 4, thin films of this material on electrode surfaces can be prepared by solvent evaporation or spin-coating. The voltammetric properties of the polymer-modified electrodes made by using this material are well-defined and are consistent with electrochemically reversible processes [90,91]. The redox properties of these polymers are based on the presence of the pendent redox-active groups, typically those associated with the Os(n/m) couple, since the polymer backbone is not redox-active. In sensing applications, the redox-active site, the osmium complex in this present example, acts as a mediator between a redox-active substrate in solution and the electrode. In this way, such redox-active layers can be used as electrocatalysts, thus giving them widespread use in biosensors. 

Vandermeulen, G.W.M., Kim, K.T., Wang, Z., and Manners, I. "Metallopolymer-peptide conjugates synthesis and self-assembly of polyferrocenylsilane graft and block copolymers containing a beta-sheet forming Gly-Ala-Gly-Ala tetrapeptide segment". Biomacromolecules 7(4), 1005-1010 (2006). 

Interestedly that this metallopolymer is distinguished by strong fluorescence which is proportional to metal content as distinct from complexes produced by the interaction of EuC13 with macroligands containing 2-carboxybenzoyl (14) or 2-carboxynaphthoyl (15) groups (Fig. 7) [67]. A similar method was used to copolymerize MMA and MCM of Eu(III) with l-(vinylphenyl)-3-phenyl-l,3-propandione [89]. 

The principal disadvantages of the methods of PCMU assemblage consist in the occurence of various side processes, insufficient reproducibility and problems with the preparation of structurally pure metallopolymers. 

Fig. 7 Conceptual cartoon of film of ds-DNA and the catalytic metallopolymer [Ru(bpy)2(PVP)10](ClO4)2 designed for simultaneous electrochemiluminescent (610 nm) and voltammetric detection of DNA. (From Ref. [53] with permission. Copyright American Chemical Society.) (View this art in color at www. dekker.com.)...

Mugweru, A. Rusling, J.F. Catalytic square-wave voltammetric detection of DNA with reversible metallopolymer-coated electrodes. Electrochem. Commun. 2001, 3, 406-409. 

More recently, there has been growing interest in a new type of redox polymer that is a hybrid of materials from PTs and will be referred to as conjugated metallopolymers. The key feature of this class of material is that the metal is coordinated directly to the conjugated backbone of the polymer, or forms a link in the backbone, such that there is an electronic interaction between the electroactive metal centers and the electroactive polymer backbone. This can enhance electron transport in the polymer, enhance its electrocatalytic activity, and lead to novel electronic and electrochemical properties <1999JMC1641>. 

V.M. Gryaznov, M.M. Ermilova, S.I. Zavodchenko, and N.V. Orekhova, Hydrogen permeability of some metallopolymer membranes. Polymer Science (Russia) 35 265 (1993). 

The mechanism of the initiation of the radical polymerisation of polar monomers in systems comprising organometallic compounds Homogeneous anionic polymerisation of unsaturated monomers Metallopolymers... 

---