Diruthenium–Polyyn-diyl–Diruthenium Wires: Electronic Coupling in the Long Distance Regime

Abstract

Reported herein is a series of Ru2(Xap)4 capped polyyn-diyl compounds, where Xap is either 2-anilinopyridinate (ap) or its aniline substituted derivatives. Symmetric [Ru2(Xap)4](μ-C4k)[Ru2(Xap)4] (compounds 4ka (X = 3-isobutoxy) and 4kc (X = 3,5-dimethoxy) with k = 2, 3, 4, and 5) was obtained from the Glaser coupling reaction of Ru2(Xap)4(C2kH). Unsymmetric [Ru2(Xap)4](μ-C(4k+2))[Ru2(ap)4] (compounds 4k+2b with k = 2, 3, and 4) were prepared from the Glaser coupling reaction between Ru2(Xap)4(C(2k+2)H) and Ru2(ap)4(C2kH). X-ray diffraction study of compound 12c revealed both the sigmoidal topology of the polyyn-diyl bridge and the fine structural detail about the Ru2 cores. Cyclic and differential pulse voltammetric (CV and DPV) measurements and spectroelectrochemical studies revealed that (i) the reduced monoanions [Ru2-C2m-Ru2](-1) (m = 4-8) belong to the Robin-Day class II mixed valent ions and (ii) the electronic coupling between Ru2 termini depends on the length of the polyyn-diyl bridge with an attenuation constant (γ) between 0.12 and 0.15 Å(-1). In addition, spin-unrestricted DFT calculations provide insight about the nature of orbitals that mediate the long distance electronic coupling.

Elaborately Tuning Intramolecular Electron Transfer Through Varying Oligoacene Linkers in the Bis(diarylamino) Systems

“…The linear correlation confirms that [ 1e ] + still belongs to the class II MV system and provides good evidence for a superexchange electron transfer mechanism52. More importantly, the β value was comparable to that found for the oligophenylene-bridged ruthenium-amine series ( β  = 0.14 Å −1 )56 and polyyn-diyl bridged diruthenium systems ( β  = 0.12 and 0.15 Å −1 )3, and was slightly larger than that found for oligofuran- (0.066 Å −1 ) and thiophene-bridged diferrocenyl systems (0.070 Å −1 )52. However, it’s smaller than that observed for similar single-bond linked oligophenylene bis-triarylamine systems (0.32 Å −1 )46 and much smaller than those observed in biomacromolecule systems57.…”

“…Recently, mixed-valence (MV) compounds with two identical redox-active groups have attracted continuous attention because they are one of the most widely exploited model systems used to study intramolecular electron transfer processes and can provide important and broad prospects for constructing highly functionalized molecules with interesting electronic and photophysical properties essential for molecular devices12345. Accordingly, numerous studies have focused on elaborately screening rigid and π -conjugated bridging ligands linking two redox termini to subtly tune the intramolecular electron-transfer properties in MV systems678910.…”

Gas Phase Formation of the Interstellar Molecule Methyltriacetylene

“…Polyynes end‐capped with gold nanoclusters or ruthenium‐based organometallic fragments also define molecular wires, in which the transition from insulators via semiconductors to metals can be selectively tuned by adjusting the length of the carbon chain (Scheme ) . In deep space, since hydrocarbon molecules carrying linear carbon chain backbones constitute nearly one third of all detected interstellar organic molecules, the elucidation of their formation routes will unravel the most fundamental processes that drive the hitherto poorly understood exotic organic chemistry in low temperature interstellar environments.…”

“…[19] This system is also stimulating for the physical organic and computational chemistry communities from the fundamental point of view of chemical bonding and material sciences as it represents a benchmark to understand the reactivity and electronic structure of polyynes versus cummulenic π systems with allene (H 2 CCCH 2 ) -methylacetylene (CH 3 CCH) being the prototype system. [20][21] Polyynes end-capped with gold nanoclusters [24] or ruthenium-based organometallic fragments [25] also define molecular wires, [26] in which the transition from insulators via semiconductors to metals can be selectively tuned by adjusting the length of the carbon chain (Scheme 2). [25,[27][28][29] In deep space, since hydrocarbon molecules carrying linear carbon chain backbones constitute nearly one third of all detected interstellar organic molecules, [30] the elucidation of their formation routes will unravel the most fundamental processes that drive the hitherto poorly understood exotic organic chemistry in low temperature interstellar environments.…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…Metal vinylidene complexes were suggested as likely M a n u s c r i p t 106 intermediates in the ruthenium-catalyzed reductive anti-Markovnikov hydration of terminal alkynes and formic acid [1017]. Electrochemical oxidations of alkynylmetal complexes likely produce species with substantial metal carbon multiple bonding character [1018,1019,1020,1021,1022]. Enhanced resonance interaction from a vinylidene resonance form was noted when the phosphine group of a diphenylphosphinoethynyliron complex was ligated to palladium [1023].…”