Toward the Development of Molecular Wires: Ruthenium(II) Terpyridine Complexes Containing Polyferrocenyl as a Spacer

Abstract

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 (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. 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*tpyRu)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*tpyRu)1] MMLCT transition.