Conformational Tuning of the Intramolecular Electronic Coupling in Molecular‐Wire Biruthenium Complexes Bridged by Biphenyl Derivatives

Abstract

The synthesis and characterization of a series of biphenyl-derived binuclear ruthenium complexes with terminal {RuCl(CO)(PMe3)3} moieties and different structural arrangements of the phenyl rings are reported. Electrochemical studies revealed that the two metal centers of the binuclear ruthenium complexes interact with each other through the biphenyl bridge, and the redox splittings ΔE1/2 show a strong linear correlation with cos(2) ϕ, where ϕ is the torsion angle between the two phenyl rings. A combination of electrochemical, UV/Vis/NIR, and in situ IR differential spectroelectrochemical analysis clearly showed that: 1) the intramolecular electronic couplings in the binuclear ruthenium complexes could be modulated by changing ϕ; 2) the electronic ground state of the mixed-valent cations changes from delocalized to localized through the biphenyl bridge with increasing torsion angle ϕ, that is, the redox processes of these complexes change from significant involvement of the bridging ligand to an oxidation behavior with less participation of the bridge.

Design of multi-functional 2D open-shell organic networks with mechanically controllable properties

“…The power of this structural parameter in π-conjugated single molecule systems has been theoretical and experimentally demonstrated. 24,25,28–30 Our work shows how this fundamental molecular level link between structure and properties can be entirely transferred to extended materials, opening thus its potential use which may give rise to unprecedented technological applications. We hope this work becomes the starting line for the exploration of a new class of functional materials where aryl ring twist angles can be internally tuned ( e.g.…”

“…24,25 Some works studying bi-phenyl molecular junctions have pointed to the possibility of using electric fields 26 or electro-chemical potentials 27 to externally manipulate dihedral angles within molecular devices. However, chemical design is, by far, the most utilized approach to finely tune this structural parameter to a certain value in order to determine the associated electrical, 24,28 magnetic, 29 optical 30 and electro-chemical properties.…”

“…However, chemical design is, by far, the most utilized approach to finely tune this structural parameter to a certain value in order to determine the associated electrical, 24,28 magnetic, 29 optical 30 and electro-chemical properties. 25 The challenging task of externally tuning aryl ring twist angles in single-molecule devices comes from the extreme difficulties associated with: (i) controlling the orientation of the molecular units within the device 15 and, (ii) the need to direct the external stimulus uniquely to twist aryl rings without causing other physico-chemical phenomena which may also interfere with the output characteristics of the system. 10 …”

Electronic Structures of Divinylchalcogenophene‐Bridged Biruthenium Complexes: Exploring Trends from O to Te

“…Binuclear ruthenium mixed‐valence complexes incorporating two “RuCl(CO)(PR 3 ) 2 L” (L = neutral two‐electron donor or free coordination site) redox‐active termini connected by a carbon‐rich unsaturated spacer display well‐behaved redox chemistry and are ideally suited for studies of the electron‐density distribution and interplay between the properties of the bridge and metal centres as well as charge‐transfer characteristics , , , , , . In particular, the synergistic nature of the bonding interactions between the Ru metal centre and ancillary CO ligand results in the v (CO) IR band being an excellent reporter group of metal electron density , , . With this in mind, we report here the synthesis, electrochemical behaviour and spectroscopic characterisation of a full series of chalcogenophene‐bridged binuclear ruthenium complexes ( 4a – 4d , see Scheme ) with the aim of exploring their electronic structures as a function of the heteroatom (O, S, Se, Te) in the bridging ligand and redox state.…”

Redox Isomeric Ferrocenyl Styrylruthenium Radical Cations with Diphenyl-Substituted β-Ketoenolato Ligands

“…The carbonyl ligand at the Ru atom provides a sensitive and convenient spectroscopic label to monitor any change of the electron density at the styrylruthenium entity accompanying a redox process. Oxidation-induced shifts of the energy of the CO stretching vibration v ̃(CO) have proven highly useful for probing the metal versus ligand contributions to the HOMO of alkenylruthenium complexes − and the degree of charge (de)­localization in the one-electron oxidized, mixed-valent forms of divinylarylene-bridged ruthenium complexes with identical ,− or chemically different ,,,− redox sites.…”