The preparations of multinuclear supramolecules assembled from 1‘,1‘ ‘‘-bis(terpyridyl)biferrocene redox-active subunits with Ru2+ metal centers are described. The electrochemical measurements of the series of Ru2+-coordinated 1‘,1‘ ‘‘-bis(terpyridyl)biferrocene complexes are dominated by the Ru2+/Ru3+ redox couple (E 1/2 at ∼1.35 V), Fe2+/Fe3+ redox couples (E 1/2 from ∼0.4 to ∼0.9 V), and terpy/terpy-/terpy2- redox couples (E 1/2 at ∼−1.2 and ∼−1.4 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 1‘,1‘ ‘‘-bis(terpyridyl)biferrocene, there is a rise to a red-shifted and more intense 1[(d(π)Fe)6] → 1[d(π)Fe)5(π*terpy Ru)1] transition in the visible region. The observed red-shifted absorption from ∼510 nm in monomeric [Ru(terpy)2]2+ and [Ru(terpy)(fcterpy)]2+ complexes to ∼570 nm in polynuclear Ru2+ 1‘,1‘ ‘‘-bis(terpyridyl)biferrocene complexes reveals that there is a qualitative electronic coupling within the array. The coordination of Ru2+ transition-metal centers lowers the energy of the π*terpy orbitals, giving a more red-shifted transition.

The preparation, characterizations, and electrochemical measurements of the terpyridine-ferrocenylalkyne spacers (tpy−C⋮C−(fc) n −C⋮C−tpy; tpy = terpyridyl; fc = ferrocenyl; n = 2, 3) are described. In the electrochemical measurements, the charge could be delocalized to the cyclopentadienyl and ethynyl moieties caused by the built-up charge density upon oxidation of the ferrocenyl moiety.

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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+ complexes of tpy-(fc) n -tpy (1a (n = 1); 1b (n = 2); 1c (n = 3)) are dominated by the Ru2+/Ru3+ redox couple (E 1/2 from 1.35 to 1.38 V), Fe2+/Fe3+ redox couples (E 1/2 from ∼0.4 to ∼1.0 V), and tpy/tpy-/tpy2- redox couples (E 1/2 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. Coordination of Ru2+ metal centers to tpy-(fc) n -tpy results in a red-shifted and more intense 1[(d(π)Fe)6] → 1[(d(π)Fe)5(π*tpy Ru)1] transition in the visible region. The observed red-shifted absorption from 526 nm in the 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(π)Fe)6] → 1[(d(π)Fe)5(π*tpy Ru)1] MMLCT transition.