Helical polymer-metal complexes

Abstract New helical poly(phenylacetylene)s have been successfully designed and synthesised and their properties checked. The new polymers behave as sensors of metal cation valences and/or the polar and draior character of solvents. In the presence of metal salts, poly(phenylacetylene)s form helical polymer-metal complexes (HPMCs) that, in the case of a-methoxyphenylacetic acid (MPA)-containing poly(phenylacetylene), has led to a new family of nanospheres made by complex-ation between the polymer and divalent metal ions. These HPMC nanostructures present properties such as (1) their diameter can be tuned to different sizes, (2) the helicity of the polymeric material can be tuned to either of the two helical senses, and (3) they can encapsulate a number of inorganic and organic substances. These polymers also display phenomena such as helical inversion, chiral amplification and axial chirality selection, making them versatile materials. 

Keywords Chiral amplification Helical inversion Helical polymer-metal complexes Metal cations Methoxyphenylacetic acid Nanospheres Poly(phenylacetylene)s... 

Helical Polymer-Metal Complexes The Role of Metal Ions on the Helicity and... 

Methods based on the formation of complexes of CDAs with metal cations seem especially interesting for testing using PPAs, due both to the possibility of controlling the conformational equilibria at the pendants that will transmit further effects to the backbone, and to the potential role that metal ions could play in the establishment of supramolecular networks between the polymer chains (interchain bonding), giving birth to new types of nanostructures (i.e. helical polymer-metal complexes, HPMCs). 

Freire F, Seco JM, Quinoa E, Riguera R (2012) Nanospheres with tunable size and chirality from helical polymer-metal complexes. J Am Chem Soc 134(47) 19374-19383. doi 10.1021/ja3061112... 

Double helical DNA is a water-soluble polymer that contains an electronically well-coupled stack of aromatic heterocyclic base pairs. This review describes efforts in our laboratory to characterize electron-transfer reactions between transition metal complexes bound by intercalation within the 7r-stack of DNA. Much information is available concerning the structure, synthesis, and methods of characterization of this polymer. Also, research in our laboratories has been directed toward describing the photophysical and photochemical properties of metal complexes bound to DNA. Using these metal complexes to probe the DNA 7r-way, we are now in a position to ask Is DNA a molecular wire ... 

Screening of an impressive series of polymers derived from different bulky methacrylate esters, e.g., 42 (Chart 8), and using a variety of chiral ligands has revealed the scope of the process of forming helical poly(methacrylate ester)s and their applicability in, for example, the separation of chiral compounds.151 These polymers were prepared not only by anionic polymerization, but also by cationic, free-radical, and Ziegler—Natta techniques. Recently, Nakano and Okamoto reported the use of a co-balt(II)—salophen complex (43) in the polymerization of methacrylate ester 41.155 The free-radical polymerization in the presence of this optically active metal complex resulted in the formation of an almost completely isotactic polymer with an excess of one helical sense. 

Keywords Transition metal complexes Living polymerization Rigid rod helical structure Optically active polymer Asymmetric polymerization... 

Pirkle or brush type bonded phases Helical chiral polymers (polysaccharides) Cyclodextrins and crown ethers Immobilised enzymes Amino acid metal complexes Three-point interaction Attractive hydrophobic bonding Host guest interaction within chiral cavity Chiral affinity Diastereomeric complexation... 

No unusual initiators, such as transition metal complexes or heterogeneous catalysts, are needed for perhaloacetaldehyde polymerizations, the polarization of the carbonyl group of the aldehyde monomer is well defined and does not cause the formation of head to head linkages in the polymer. The shorter carbon oxygen single bond (1.43 A) which is formed by ring opening of the carbonyl double bond (1.21 A) has a beneficial effect for the formation of a helical structure for the isotactic polymer and should, consequently, favor the formation of isotactic polymer. 

Optically active polymers play a very important role in our modem society. The specialities of optically active polymers are known with their various characteristics as occurred naturally in mimicry. The present review describes the monomers and synthesis of optically active polymers from its helicity, internal compounds nature, dendronization, copolymerization, side chromophoric groups, chiral, metal complex and stereo-specific behaviour. The various properties like nonlinear optical properties of azo-polymers, thermal analysis, chiroptical properties, vapochromic behaviour, absorption and emission properties, thermosensitivity, chiral separation, fabrication and photochromic property are explained in detail. This review is expected to be interesting and useful to the researchers and industry personnel who are actively engaged in research on optically active polymers for versatile applications. 

---