Helical coordination polymers, from

Another helical coordination polymer to contain binding at A-N3 is the product isolated from the reaction between /raas-[(NH3)2Pt(9-MeA-iV7)(9-MeH N7)]2+ (H = 9-methylhypoxanthine) and an excess of AgN03, 13 59). Unusually, in this material the 9-MeA is bound by metal ions at Nl, N3, and N7 simultaneously. The chain polymer is... 

Helical coordination polymers containing large chiral cavities or charmels are interesting for stereospecific syntheses, separation of enantiomers and stereoselective catalysis. Crystals of 39 are obtained from a solution of nickel(II) acetate and benzoic acid in methanol which is covered with a solution of 4,4 -bipyridine in the presence of benzene or nitrobenzene [107]. Each helix turn contains three complex units and the chain consists of Ni(II) (with binding of benzoate) and the bipyridine. Because each helix is shifted against the next, large cavities are formed containing, for example, benzene or nitrobenzene. 

The Cu(ll) complex, [Cu2(L55)2(H20)] H20, 75 derived from L55 crystallizes as a ID helical coordination polymer assembled from the dimeric building blocks similar to 71. But, the major difference is the presence of one more water molecule in the crystal lattice of 75. Interestingly, despite the similar structures and crystal packing of helical coordination polymers in 71 and 75, a stable dehydrated complex from 75 could not be obtained because the anhydrous species rapidly gets rehydrated in the presence of air. This indicates that the formation of new Cu-0 bond by the carboxylate group is restricted in 75. Fmther, in contrast to 71, the reason why the reversible hydration takes place in the case of [Cu2(L55)2(H20)] H20, 75, can be understood by the close examination of the crystal structure of 75. ... 

The zinc complex of 1,1,1,5,5,5-hexafluoroacetylacetonate forms coordination polymers in reaction with either 2,5-bis(4-ethynylpyridyl)furan or l,2-bis(4-ethynylpyridyl)benzene. The X-ray crystal structures demonstrate an isotactic helical structure for the former and a syndio-tactic structure for the latter in the solid state. Low-temperature 1H and 19F NMR studies gave information on the solution structures of oligomers. Chiral polymers were prepared from L2Zn where L = 3-((trifluoromethyl)hydroxymethylene)-(+)-camphorate. Reaction with 2,5-bis(4-ethy-nylpyridyl)furan gave a linear zigzag structure and reaction with tris(4-pyridyl)methanol a homo-chiral helical polymer.479... 

Consequently, the mononuclear building blocks (S,S)-65 were obtained starting from (5S)-64. which during crystallization from chloroform afforded left-handed helical lD-coordination polymer (M)-fxJ Cu(L v)2 (M-66). The structure of (M)-66 was determined by X-ray crystal structure analysis (Fig. 24). In conclusion, it is demonstrated that stereogenic centers of ligands may induce stereospecifically helicity to lD-coordination polymers. Thus (R)-64 gives rise to (P)-66 and (S)-64 to mirror image (M)-66 [166, 169-172],... 

Fig. 25 Left Schematic representation of the location of the copper(I) centers of coordination polymer mei0-oo1 [Cu( -pydz)2[PF6] (73). In order to clarify the meso-helical arrangement, the positions of the copper centers were scaled along c by a factor of 0.125. Right. Generation of a helix and a mesc-helix from a circle and a lemniscate...

Figure 2.39 Fragment of the polymeric chain in [Tb2(L )3(dppe02)]n. [53b]. (Reproduced from S.N. Semenov, A.Y. Rogachev, S.V. Eliseeva, C. Pettinari, F. Marchetti, A.A. Drozdov and S.I. Troyanov, First direct assembly of molecular helical complexes into a coordination polymer, Chemical Communications, 17, 1992-1994, 2008, by permission of the Royal Society of Chemistry.)...

The construction of novel coordination polymers is a current interest in the field of supramolecular chemistry and crystal engineering, stemming from their potential applications as frinctional materials as well as their intriguing variety of architectures and molecular topologies. In particular, solid materials with either helical or chiral structures are of intense interest in chemistry and material science. Although solid materials with imusual structures are expected to increase in number, the exploration for preparing framework solids with chiral structures still remains a challenge. Thermal analysis is a fundamental tool for the characterization of these new coordination polymeric compounds. 

Representative examples of 1-D coordination polymer motifs are illustrated in Scheme 5. In these motifs, the helix remains quite rare in the context of coordination polymers, but there is additional interest because it is inherently chiral irrespective of the components. The inherent chirality of this architecture comes from spatial disposition rather than the presence of chiral atoms. [Ni(4,4 -bpy)(benzoate)2(MeOH)2] self-assembles as a helical architecture that is sustained by the linking of octahedral metal connectors with linear ligands (Scheme 5d). The helical chains pack such that they are staggered, but align in a parallel fashion. Therefore, the bulk crystal is polar as every helix in an individual crystal is of the same handedness. Other examples of 1-D coordination polymers are listed in Table j... 

Zhang, S. Yang, S. Lan, J. Yang, S. You, J. Helical nonracemic tubular coordination polymer gelators from simple achiral molecules. Chem. Commun. 2008, 6170-6172. 

In the calculations of the electronic structure of these polypeptides, we applied the all-valence electron MINDO crystal-orbital method in its MINDO/3 parametrization. The calculations involved atomic coordinates corresponding to the antiparallel-) -pleated-sheet structure of Pauling and Corey S hence we had a combined symmetry operation in the case of poly( y) each gly unit was obtained in this polymer from its neighboring one by a translation along the helical axis through 3.25 A and by a simultaneous 180° rotation around it. In order to preserve the cyclic property of the Fock hypermatrix of the whole polymer (which is... 

Argent SP, Adams H, Riis-Johannessen T, Jeffery JC, Harding LP, Clegg W, Harrington RW, Ward MD (2006) Complexes of Ag(I), Hg(I) and Hg(II) with multidentate pyrazolyl-pyridine ligands from mononuclear complexes to coordination polymers via helicates, a mesocate, a cage and a catenate. Dalton Trans 4996-5013... 

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