Polypyridine complexes covalently linked

P. R. Ashton, R. Ballardini, V. Balzani, E. C. Constable, A. Credi, O. Kocian, S. J. Langford, J. A. Preece, L. Prodi, E. R. Schofield, N. Spencer, J. E Stoddart, S. Wenger, Ru(II)-Polypyridine Complexes Covalently Linked to Electron Acceptors as Wires for Light-Driven Pseudorotaxane-Type Molecular Machines , Chem. Eur. J. 1998, 4, 2411-2422. 

Rotaxane 316+ was specifically designed36 to achieve photoinduced ring shuttling in solution,37 but it also behaves as an electrochemically driven molecular shuttle. This compound has a modular structure its ring component is the electron donor macrocycle 2, whereas its dumbbell component is made of several covalently linked units. They are a Ru(II) polypyridine complex (P2+), ap-terpheny 1-type rigid spacer... 

Several systematic studies of the driving force dependence of the rate of forward and back ET in type 1 dyads (see Fig. 1) were carried out during the past decade. As might be expected, the type 1 dyads used in these investigations consist of covalently linked assemblies of metal complexes and organic quenchers used in early studies of bimolecular photoinduced ET reactions. Thus, the type 1 dyads consist of polypyridine Ru(II) complexes linked to pyridinium acceptors such as paraquat and diquat (quatemized 2,2 -bipyridine). 

Chromophore quencher systems where the organic molecular components are aryl hydrocarbons are under intense study [67, 190-205], In these systems an inorganic moiety (based on polypyridine complexes of Ru(II), Os(II), Re(I)) and an aryl hydrocarbon (naphthalene, anthracene, pyrene) are covalently linked by flexible aliphatic [187-201] or rigid conjugated bridges [49, 190, 191, 193). 

The rate and activation parameters for the intramolecular electron transfers from Os(II)(NH3)5 to Ru(III)(NH3)5 across oligoproline peptide bridges have been determined. The rate constants decrease from 3.1 x 10 s to 50 s as the number of proline units is increase from 1 to 4, and the metal-metal separation distance increases from 12 to 21 A. A time-correlated single photon counting method was employed to investigate the kinetics of the forward [ Ru(II)- Rh(III)] and reverse [Ru(III)<-Rh(II)] intramolecular electron transfer reactions within covalently linked Ru/Rh polypyridine complexes in aqueous, acetonitrile, and methanol solvents. The rate constants for the outer-sphere electron transfer reactions of [Ru(edta)pyz] and... 

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