Mixed valency and metal–metal quadruple bonds

Chisholm, Malcolm H.

doi:10.1016/j.ccr.2012.10.021

Cited by 28 publications

(15 citation statements)

References 31 publications

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“…As a prerequisite for studies on binuclear MV systems, a number of computational studies focused on spin-density delocalisation as a function of conformation in mononuclear Fe and Ru complexes bearing a diethynylaromatic ligand that becomes the bridge in corresponding dinuclear species. 54,243,277,[281][282][283] This provides insight into the coupling between metal d-orbitals and the ligand p-system as a function of rotation angle.…”

Section: Rotamers: the Importance Of Conformational Motionmentioning

confidence: 99%

Quantum-chemical insights into mixed-valence systems: within and beyond the Robin–Day scheme

2014

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In mixed-valence (MV) systems essentially identical, more or less electronically coupled, redox centres are brought into formally different oxidation states by removal or addition of an electron. Depending on the strength of electronic coupling, an electron or a hole is either concentrated on one of the redox centres, or it is symmetrically delocalised onto several sites, or the situation is somewhere in between, which leads to the classification system for MV systems introduced by Melvin Robin and Peter Day. These different characteristics are of fundamental importance for the understanding of electron transfer processes. Applications of quantum-chemical methods to aid the classification and to unravel the nature of the electronic structure and spectroscopic data of both organic and transition-metal MV systems, have gained tremendous importance over the last two decades. In this review, we emphasise the prerequisites the quantum-chemical methods need to fulfill to successfully describe MV systems close to the borderline between Robin-Day classes II and III. These are, in particular, a balanced treatment of exchange, dynamical and non-dynamical correlation effects, as well as consideration of the crucial influence of the (solvent or solid-state) environment on the partial localisation of charge. A large variety of applications of quantum-chemical methods to both organic and inorganic MV systems are critically appraised here in view of these prerequisites. Practical protocols based on a combination of suitable density functional methods with continuum or non-continuum solvent models provided good agreement with experimental data for the ground states and the electronic excitations of a large range of MV systems close to the borderline. Recent applications of such methods have highlighted the crucial importance of conformational effects on electronic coupling, all the way to systems where conformational motion may cause a thermal mixing of class II and class III situations in one system.

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Section: Rotamers: the Importance Of Conformational Motionmentioning

confidence: 99%

Quantum-chemical insights into mixed-valence systems: within and beyond the Robin–Day scheme

2014

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“…[1] Furthermore,s uch complexes may have potential in molecular electronics and spintronics, [2] high-temperature superconductors, [3] and switchable molecular magnetism. [5] According to Robin and Day,m ixed valence compounds can be classified into three distinctive categories:C lass I, not interacting;C lass II, interacting,b ut localized;a nd Class III, delocalized. [5] According to Robin and Day,m ixed valence compounds can be classified into three distinctive categories:C lass I, not interacting;C lass II, interacting,b ut localized;a nd Class III, delocalized.…”

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confidence: 99%

“…[4] To understand the essential electron transfer process,ahuge amount of mixed valence compounds as simple models have been studied. [5] According to Robin and Day,m ixed valence compounds can be classified into three distinctive categories:C lass I, not interacting;C lass II, interacting,b ut localized;a nd Class III, delocalized. [6] Meantime, some important theory models have also been built.…”

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confidence: 99%

An Unusually Delocalized Mixed‐Valence State of a Cyanidometal‐Bridged Compound Induced by Thermal Electron Transfer

Lin

Zhu

et al. 2017

Angew Chem Int Ed

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The heterometallic complexes trans-[Cp(dppe)FeNCRu(o-bpy)CNFe(dppe)Cp][PF ] (1[PF ] , n=2, 3, 4; o-bpy=1,2-bis(2,2'-bipyridyl-6-yl)ethane, dppe=1,2-bis(diphenylphosphino)ethane, Cp=1,3-cyclopentadiene) in three distinct states have been synthesized and fully characterized. 1 [PF ] and 1 [PF ] are the one- and two-electron oxidation products of 1 [PF ] , respectively. The investigated results suggest that 1[PF ] is a Class II mixed valence compound. 1[PF ] after a thermal treatment at 400 K shows an unusually delocalized mixed valence state of [Fe -NC-Ru -CN-Fe ], which is induced by electron transfer from the central Ru to the terminal Fe in 1[PF ] , which was confirmed by IR spectroscopy, magnetic data, and EPR and Mössbauer spectroscopy.

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“…The fundamental photoinduced electron transfer process has been investigated for many years, including those studied in mixed valency chemistry as pioneered by Creutz and Taube 11 12 13 14 15 . However, it remains a challenge to examine the degree of electronic communication between redox sites separated by a long molecular wire 16 17 18 .…”

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Long-Range Ruthenium-Amine Electronic Communication through the para-Oligophenylene Wire

Shen

Zhong

2015

Sci Rep

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The studies of long-range electronic communication are hampered by solubility and potential-splitting issues. A “hybridized redox-asymmetry” method using a combination of organic and inorganic redox species is proposed and exemplified to overcome these two issues. Complexes 1(PF6)–6(PF6) (from short to long in length) with the organic redox-active amine and inorganic cyclometalated ruthenium termini bridged by the para-oligophenylene wire have been prepared. Complex 6 has the longest Ru-amine geometrical distance of 27.85 Å. Complexes 3(PF6) and 4(PF6) show lamellar crystal packing on the basis of a head-to-tail anti-parallelly aligned dimeric structure. Two redox waves are observed for all complexes in the potential region between +0.2 and +0.9 V vs Ag/AgCl. The electrochemical potential splitting is 410, 220, 143, 112, 107, and 105 mV for 1(PF6) through 6(PF6), respectively. Ruthenium (+2) to aminium (N•+) charge transfer transitions have been identified for the odd-electron compounds 12+–62+ by spectroelectrochemical measurements. The electronic communication between amine and ruthenium decreases exponentially with a decay slope of −0.137 Å−1. DFT calculations have been performed to complement these experimental results.

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Mixed valency and metal–metal quadruple bonds

Cited by 28 publications

References 31 publications

Quantum-chemical insights into mixed-valence systems: within and beyond the Robin–Day scheme

Quantum-chemical insights into mixed-valence systems: within and beyond the Robin–Day scheme

An Unusually Delocalized Mixed‐Valence State of a Cyanidometal‐Bridged Compound Induced by Thermal Electron Transfer

Long-Range Ruthenium-Amine Electronic Communication through the para-Oligophenylene Wire

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