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 (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.

1,1′‐Diaryl‐Substituted Ferrocenes: Up to Three Hinges in Oligophenyleneethynylene‐Type Molecular Wires

“…[9][10][11][12][13] A precondition for this development is the possibility of electron-transfer through the ferrocene unit along a molecular wire. Such conductivity has recently been established by Engtrakul and Sita [12,13] as well as by Dong and coworkers [14,15] and is presumably a result of the redox activity of ferrocene. [16] The ferrocene subunits render the wire three-dimensional and thereby make π-π stacking less likely.…”

Long-distance electronic interaction in a molecular wire consisting of a ferrocenyl–ethynyl unit bridging two [(η5-C5H5)(dppe)M] metal centers

“…Samples of 1 and (g 5 -C 5 H 5 )(dppe)MCl were prepared according to the literature procedure [44][45][46]. Preparations of the ferrocenyl-ethynyl spacers (8-10) were described in our previous paper [26][27][28]. As shown in Schemes 1 and 2, complexes of 1-7 could be prepared.…”

“…doi:10.1016/j.jorganchem.2008. 12.056 bis-(2,2 0 :6 0 ,2 00 -terpyridyl)polyferrocene redox-active spacers endcapped with photoactive and redox-active Ru 2+ -terpyridine terminals ([(tpy)Ru II -(tpy-(fc) n -tpy)-Ru II (tpy)] 4+ (tpy = terpyridine, fc = ferrocenyl, n = 1-3) and [(tpy)Ru II -(tpy-C"C-(fc) n -C"C-tpy)-Ru II (tpy)] 4+ (n = 2-3)) to study the electronic interaction between the end-capped Ru 2+ metal centers [26][27][28]. In our previous papers, the CV electrochemical measurements for these binuclear Ru 2+ complexes were dominated by the Ru 2+ /Ru 3+ redox couple (E 1/2 from 1.35 to 1.38 V), Fe 2+ /Fe 3+ redox couples (E 1/2 from 0.4 to 1.0 V) and tpy/tpy À /tpy 2À redox couples (E 1/2 from À1.3 to À1.5 V).…”

Synthesis, electrochemistry, and photophysical properties of binuclear ruthenium(II)–terpyridine complexes comprising redox-active ferrocenyl spacer

“…Our design principle for a wire-like molecule has to fulfill following criteria: (i) organometallic redox-active spacer to enhance the capability of transfer information along the molecular axis and (ii) modular synthetic approach to control the length of the wire [21,22]. We have earlier published electrochemical and photophysical studies for a series of complexes containing bis-(2,2 0 :6 0 ,2 00 -terpyridyl)polyferrocene redox-active spacers end-capped with photoactive Ru 2+ -terpyridine terminals to address these issues ([(tpy)Ru II -(tpy-(fc) n -tpy)-Ru II (tpy)] 4+ complexes 1a-c in Scheme 1; fc = ferrocenyl; n = 1-3) [22].…”