In attempting to modulate the electronic properties of molecular-wire Ru(II) complexes, we now describe an interesting example of X-tpy-Ru2+-tpy-(fc)2-tpy-Ru2+-tpy -X ( fc = ferrocenyl ; tpy = terpyridyl ; X=Cl, OMe, OH ) complexes comprising electronic donor or withdrawing group attached directly to the 4¡¦-position of the terminal tpy moiety. The ground-state HOMO and LUMO energies were probed by electrochemical measurements and the excited-state photophysical properties were probed by absorption spectroscopy.

Structural determinations and electrochemical properties in the series of multinuclear ferrocenyl¡Vethynyl complexes with formula [(£b5-C5H5)(P2)MII-C¡ÝC-(fc)n-C¡ÝC-MII(P2)(£b5-C5H5)] (fc = ferrocenyl; M = Fe(II), Os(II); P2 = Ph2PCH2CH2PPh2 (dppe)) are reported. These complexes undergo sequential reversible oxidation events from 0.0 to 1.0 V referred to the Ag/AgCl electrode in anhydrous CH2Cl2 solution and the low-potential waves have been assigned to the two end-capped metallic centers. The magnitude of the electronic coupling between the two terminal metallic centers in the series of complexes was estimated by the electrochemical technique. Based on the correlation between the ¡µE1/2 values and the second redox potentials of the end-capping metallic centers in the series of complexes, a qualitative explanation for the difference of the electronic coupling is given. Furthermore, we attempt to fabricate the SAMs of ferrocenyl-ethynyl molecules on gold surface and confirmed by XPS spectrum and the RAIR spectrum. CV and CA electrochemistry technique was employed in studied electron transfer rate (k).

The preparations of multinuclear supramolecules assembled from 1,1¡¬-bis(terpyridyl)ferrocene, 1,1¡¬-bis(terpyridyl)biferrocene and 1,1¡¬-bis(terpyridyl)triferrocene (tpy-(fc)n-tpy, n =1-3) redox-active moieties with Ru2+ metal centers are described. The electrochemical measurements of the Ru2+ coordinated tpy-(fc)n-tpy complexes (1a (n=1); 1b (n=2); 1c (n=3)) are dominated by the Ru2+/Ru3+ redox couple (E1/2 from 1.35 to 1.38 V), Fe2+/Fe3+ redox couples (E1/2 from ∼0.4 to ∼1.0 V) and tpy/tpy-/tpy2- redox couples (E1/2 from 1.3 to 1.5 V). The appreciable variations detected in the Fe2+/Fe3+ oxidation potentials indicate that there is an interaction between the spacer and the Ru2+ metal centers. On the coordination of Ru2+ metal centers with tpy-(fc)n-tpy rises to a red-shifted and more intense 1[(d(£k)Fe)6] ¡÷ 1[d(£k)Fe)5(£k*tpyRu)1] transition in the visible region. The observed red-shifted absorption from 526 nm in monomeric [Ru(fctpy)2]2+ complex to ~560 nm in 1b and 1c reveals that there is a qualitative electronic coupling within the ferrocenyl array. The Fe-Fe interactions result in a red characteristic of the 1[(d(£k)Fe)6] ¡÷ 1[d(£k)Fe)5(£k*tpyRu)1] MMLCT transition.

The development of molecular wires where photoactive and electroactive terminals are linked by a large size molecular spacer may open new path in the field of storage and utilization of light energy. An important issue concerns how best to design the spacer that permit controlled transfer of electron along the molecular axis. Our design principle for a molecular wire has to fulfill following criteria : (i) an organometallic redox-active spacer to enhance the capability of transfer information along the molecular axis and (ii) modular synthetic approach to control length. The preparations of multinuclear supramolecular assembled from redox-active biferrocencyl spacer and ruthenium(II) terpyridine chromophore are described. Interestingly, substitution of a methoxy group on terminal terpyridine 4'-position of complex 13 will enhance the electronic coupling between the spacer and Ru2+ metal centers. The detailed properties about complex 13 are described in electrochemical results, UV-visible spectral data, and photo luminescent investigation.

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The synthesis and characterizations together with the electrochemical behavior, UV-Vis spectroscopy, and photophysical properties of the multinuclear supramolecule assembled from the 1,1'-bis(terpyridylethynyl)triferrocene (tpy-C¡ÝC-(fc)3-C¡ÝC-tpy) redox-active spacer with ruthenium centers are described.

The ruthenium dinuclear complexes with end-caping of pyridinedicarboxylate complexes of terpyridine (2,2':6',2'-terpyridine) and (tBu)3-terpyridine (4,4¡¦,4¡¦¡¦-tri-tert-butyl-2,2¡¦:6¡¦,2¡¦¡¦-terpyridine) bridging with carbon-rich alkynyl group are reported. These novel complexes are characterized by NMR, MALDI-MS, FT-IR, UV, and electrochemistry. In comparison with the system of tpy-Ru-tpy-(¡Ý)n-tpy-Ru-tpy, we found some interesting characteristics in the studies of electronic spectra and electrochemical measurements. Furthermore, one reversible and one irreversible electrochemical redox waves in positive wave were observed (E1/2 at 0.59 and 1.15 V (irrev.) for the complex with ethynyl spacer and E1/2 at 0.62 and 1.10 V (irrev.) for the complex with butynyl spacer), indicating a strong electronic interaction between two Ru metal centers. However, in the tpy-Ru-tpy-(¡Ý)n-tpy-Ru-tpy system, only one electrochemical redox wave at ~1.3 V was found. From the electronic and electrochemical analysis , the electronic interaction between two metal centers decreases as the number of alkynyl group increases.

Very recently, Rotello¡¦s research group synthesized nanoparticles bearing terpyridine (terpy) ligands and studied their self-assembly using a variety of transition metals. This paper describes a synthetic pathway to ferrocene- and biferrocene-functionalized terpyridine octanethiols, and the studies of self-organization of ferrocene- and biferrocene-functionalized terpyridine octanethiols chemisorbed on Au nanoparticles.

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The preparations of multinuclear supramolecules assembled from ethynylferrocene(s) redox-active subunit end-capping with [(£b5-C5H5)(dppe)Ru] metal centers are described. Electrochemical measurements indicate that ferrocenyl-ethynyl spacers appear to be promising spacers which can ensure fast and quantitative transfer of information between two Ru2+ metal centers.