Transition from a Metal‐Localized Mixed‐Valence Compound to a Fully Delocalized and Bridge‐Biased Electrophore in a Ruthenium–Amine–Ruthenium Tricenter System

Abstract

A series of cyclometalated diruthenium complexes with a redox-active amine bridge were synthesized. Depending on the terminal ligands of the ruthenium components and the substituent on the amine unit, the one-electron-oxidized state can be either in the form of a weakly or strongly coupled mixed-valence diruthenium complex, a fully charge-delocalized three-center system, or a bridge-biased electrophore. This transition among different electronic forms was supported by electrochemistry, near-infrared absorption, electron paramagnetic resonance, and density functional theory analysis.

Multistate Redox Switching and Near-Infrared Electrochromism Based on a Star-Shaped Triruthenium Complex with a Triarylamine Core

“…The film formation of these complexes can be realized by electropolymerization 30 , layer-by-layer assembly 31 , and self-assembly monolayers 32 . Recently, a cyclometalated diruthenium system bridged by a redox-active amine unit was reported by us 33 34 , which showed the presence of four redox states at a low potential region. We present in this contribution the synthesis and study of a star-shaped tris-cyclometalated ruthenium complex with an amine core.…”

Different Degrees of Electron Delocalization in Mixed Valence Ru‐Ru‐Ru Compounds by Cyanido‐/Isocyanido‐Bridge Isomerism

“…Such an isotropic feature in compound 1 3+ is in stark contrast to previously reported MV trinuclear cyanide‐bridged compounds, which exhibit anisotropic features . The characters of free electron and temperature‐independent behavior of the EPR spectra between 150 and 291 K further confirm the fully delocalized class III nature of 1 3+ . In contrast, the EPR spectra of 2 3+ exhibit anisotropic features at low temperatures (Figure b; Figure S13b), suggesting the unpaired electron on 2 3+ may be localized or the rate of ET is slower than the EPR timescale.…”

“…[7e] Thec haracters of free electron and temperature-independent behavior of the EPR spectra between 150 and 291 Kfurther confirm the fully delocalized class III nature of 1 3+ . [19,20] In contrast, the EPR spectra of 2 3+ exhibit anisotropic features at low temperatures (Figure 5b; Figure S13b), suggesting the unpaired electron on 2 3+ may be localized or the rate of ET is slower than the EPR timescale.T he anisotropic feature fades away as the temperature increases,a nd at 291 Kt he anisotropic feature disappears and only the isotropic signal is observed. Moreover, the g value (2.005) at 291 Ki sc lose to that of free electron (g = 2.0023).…”

Photofunction‐Directed Coordination Molecular Engineering

“…[ 26 ] When two ruthenium components are connected to the triarylamine unit, the obtained three‐center complex 9 2+ shows three consecutive redox processes at +0.21, +0.44, and +1.03 V vs Ag/AgCl, respectively (Figure 4). [ 27 ] Each of the available three higher oxidation states 9 3+ — 9 5+ is characterized by a NIR absorption band at 1680, 1170, and 750 nm, respectively. These features make them useful in mimicking ternary logic gate functions by using the electrochemical potential as input signals and NIR absorption at different wavelengths as the output signals.…”