Ruthenium molecular wires

The construction of well-defined DNA assemblies containing donors and acceptors at discrete sites on the helix allows the probing of DNA as a model of molecular wire. Barton et al. have designed a DNA duplex with a [Ru(bpy/phen)2(dppz)]2+ derivative as an electron donor and [Rh(phi)2(bpy/phen)]3+ derivative as an electron acceptor tethered by flexible linker to the opposite ends of the assembles [91,96, 97]. Both complexes were free to intercalate but separated by a fixed distance. The intercalation sites for both complexes were characterized by employing duplex DNA bearing a tethered ruthenium or rhodium complex. For ruthenium complexes... 

A doubly metallated 15 base-pair double helix containing ruthenium and rhodium at each end of the strands [106] showed the efficiency of DNA for coupling electron donors and acceptors over a very long range, greater than 40 A. The DNA double helix was found to behave like a piece of molecular wire with fast electron-transfer rates (>1010 s l) for the photoinduced electron transfer between the metallointercalators [107-109] and semiempirical Hartree-Fock calculations of HAB for DNA mediated electron transfer [110] were described. 

One interesting example of Dexter-type energy transfer in literature would be the one shown in Figure 4(c). These ligand-metal-based systems provide unidirectional energy transfer in a linear array of systems, which would be used in the production of molecular wires. In this simple example, efficient energy transfer from ruthenium and osmium complexes to anthracene was observed. 

XPS analysis [117] allowed for determining the length of the molecular wire through the evaluation of the ruthenium/nitrogen atomic ratio and for evaluation of the film thickness from which the authors claim the tilting of the molecules. 

The development of polynuclear ruthenium(II) terpyridine molecular wire molecules based on the biferrocene building block bfc were recently reported by Dong et al. [91]. The multinuclear supramolecules assembled from r,r -bis(terpyridyl) biferrocene redox-active sub-units attached to Ru(II) ions were prepared by, for example, the reaction of bfc-terpy (133) and bfc(terpy)2 (134), respectively, with LRuCls (L = terpy, fc-terpy), LRuCl2(dmso) (L = bfc-terpy, dmso = dimethylsulfoxide) or RuCl2(dmso) in the appropriate ratios as outlined in Figure 11 [91], Complexes Ru(bifc-terpy)(dmso)Cl2 (135), [Ru(terpy)(bifc-terpy)](PFg)2... 

E., and Taube, H. (1981). Determination of E20-E10 in Multistep Charge Transfer by Stationary-Electrode Pulse and Cyclic Voltammetry Application to Binuclear Ruthenium Ammines. Inorg. Chem., 20, 1278-1285. (c) Cotton, F. A. Donohue, J. P., and Murillo, C. A. (2003). Polyunsaturated Dicarboxylate Tethers Connecting Dimolybdenum Redox and Chromophoric Centers Syntheses, Structures, and Electrochemistry. J. Am. Chem. Soc., 125, 5436-5450. (d) Berry, J. F. Cotton, F. A., and Murillo, C. A. (2004). A Trinuclear EMAC-Type Molecular Wire with Redox-Active Ferroeenylaeetylide "Alligator Clips" Attaehed. Organometallics, 23, 2503-2506. (e) Sheng, T. Appelt, R. Comte, V., and Vahrenkamp, H. (2003). Chain-Like... 

Fig. 2.16 Different approaches to the realization of molecular wires, a) Polyene compound designed by Jean-Marie Lehn and coworkers and proven to conduct electrons between the Ruthenium centers, b) Polyphenylene compound synthesized by Barigelletti et al. In contrast to appearance, the benzene rings in the spacer cannot be positioned in the same plane, as their hydrogen atoms would touch. Hence the possibilities for continuous overlaps of electronic orbitals are limited and it came as a surprise that luminescence energy can be electronically transported from the ruthenium to the osmium center.

Plate II Schematic representation of a DNA derivative constructed to test the conductivity of double-stranded DNA. As in the molecular wire shown in Fig. 2.16, both the light-inducible electron donor (right) and the receptor which emits a photon on arrival of the electron, are metalloorganic complexes containing ruthenium. 

Fig. 4. 30 Molecular structures (a) and schematic representations of the CP-AFM (b) and the X-wire (c) junction test structures, in both test structures, the top Au electrode was brought into contact with a SAM of ruthenium complexes formed on the bottom Au electrode. 1-V traces were obtained over 1.0 V (Reprinted with permission from Kim et al. [116]. Copyright (2009) American Chemical Society)...

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