Molecular string complexes

We realized that improvement in the yields of trefoil knots would be determined by (i) the proportion of double helix precursor formed compared with face-to-face open chain complex (Figure 18) (ii) the spatial arrangement of the four reacting ends of the helical dinuclear complex. This latter factor will reflect the extent of winding of the two molecular strings interlaced around the copper atoms. The various complexes synthesized and studied are depicted in Figure 21 [96]. 

Yoshikawa, K. (1997) Complexity in a molecular string Hierarchical structure as is exemplified in a DNA chain. In Complexity and Diversity. Springer-Verlag, Tokyo, pp. 81-90. 

Another particularity of knotted molecules is that the double-helical multimetallic complex that has been used as a templating core will be more or less frozen. In other words, the stability of the double helix will be insured by tying the molecular string used to make the knot in such a way as to make ligand exchange, helicity inversion, etc... 

Linear multinuclear metal complexes are attracting attention in the context of molecular electronics due to their projected use as molecular wires. 01igo(pyridyl)amido ligands are efficient scaffolds for lining up several Ni11 ions like a string. The first structurally characterized trinickel complex of this type, [Ni3(dpa)4Cl2] (dpa = bis(2-pyridyl)amide), showed a nearly linear Ni3 unit with Ni—Ni distances of around 244 pm.209 Penta-, hepta-, and nonanuclear systems have... 

Fibrillin microfibrils are widely distributed extracellular matrix assemblies that endow elastic and non elastic connective tissues with long-range elasticity. They direct tropoelastin deposition during elastic fibrillogenesis and form an outer mantle for mature elastic fibers. Microfibril arrays are also abundant in dynamic tissues that do not express elastin, such as the ciliary zonules of the eye. Mutations in fibrillin-1—the principal structural component of microfibrils—cause Marfan syndrome, a heritable disease with severe aortic, ocular, and skeletal defects. Isolated fibrillin-rich microfibrils have a complex 56 nm beads-on-a-string appearance the molecular basis of their assembly and... 

Figure 2.35. Diagram of the molecular motions in copper(I)-complexed [2]-rotaxane 101 controlled by the redox state dependence of the stereoelectronic requirements of Cu. Cu(I) and Cu(II) are represented by black and white circles, respectively. Chelating sites are represented by thick lines. Initially, the string coordinates Cu(I) together with the bidentate site of the macrocycle in a tetrahedral geometry, affording the state 101(4). Electrochemical oxidation of Cu(I) to Cu(II) produces the state 101+(4), which slowly converts into the state 101+(5) after rotation of the Cu(II)-complexed macrocycle. The cycle is completed by reduction of Cu(II), which produces the state 101(5), converting to the initial state by back motion of the Cu(I)-complexed macrocycle.

This logic type proved particularly difficult to emulate at the molecular scale until Credi et al. provided the breakthrough [48]. Following a mechanochemical line of attack (see Section 5.3.1), an electron-rich macrocycle 12 serves as a bead sliding on a string which is made from an electron-deficient heteroaromatic 13. The complex 12-13 is held together by charge transfer (CT) interactions. This same CT... 

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