Nearest- and Next-Nearest-Neighbor Ru(II)/Ru(III) Electronic Coupling in Cyanide-Bridged Tetra-Ruthenium Square Complexes.

Lin, Ju-Ling; Tsai, Chia-Nung; Huang, Sheng-Yi; Endicott, John F.; Chen, Yuan-Jang; Chen, Hsing-Yin

doi:10.1021/ic200806a

Cited by 33 publications

(18 citation statements)

References 39 publications

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“…It is known that DFT methods can predict very accurately the properties of Class III systems, 21,[78][79][80] but they often overestimate charge delocalization in Class II mixed-valence complexes. 79,81,82 Figure 5 shows the spin density distribution for the four mixed-valence complexes. For complexes 1 3+ and 2 3+ , the DFT calculations predict the hole located almost entirely in the Ru b2 moiety.…”

Section: Electrochemistrymentioning

confidence: 99%

Exploring the localized to delocalized transition in non-symmetric bimetallic ruthenium polypyridines

et al. 2017

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In this work, we report the evolution of the properties of the inter-valence charge transfer (IVCT) transition in a family of cyanide-bridged ruthenium polypyridines of general formula [Ru(tpy)(bpy)(μ-CN)Ru(bpy)(L)] (tpy = 2,2',6',2''-terpyridine; bpy = 2,2'-bipyridine; L = Cl, NCS, 4-dimethylaminopyridine or acetonitrile). In these complexes, the redox potential difference between both ruthenium centers (ΔE) is systematically modified. A decrease in ΔE causes a red shift of the energy and an intensity enhancement of the observed IVCT transitions. For L = acetonitrile, the IVCT band becomes narrower and asymmetrical, and shows very little dependence on the nature of the solvent, suggesting a delocalized configuration, although a non-symmetrical one. Also, additional electronic transitions of low energy are clearly resolved in this complex. The observed variation in the properties of the IVCT transitions can be understood on the basis of DFT calculations, that point to increasing mixing between the dπ orbitals of both Ru ions.

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Section: Electrochemistrymentioning

confidence: 99%

Exploring the localized to delocalized transition in non-symmetric bimetallic ruthenium polypyridines

et al. 2017

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“…In many of these nearly delocalized mixed‐valence systems, the bridge plays an important role in the spectroscopy,11–13 which requires a three‐state model for an accurate interpretation 14. 15 Another focus has been the characterization of higher nuclearity systems,16 which also present challenging spectroscopy 17–19…”

Section: Structures Of the Ruthenium Complexes Discussed In This Workmentioning

confidence: 99%

“…To gain a better understanding of the electronic structure of 3 3+ , we performed a standard density functional calculation of this redox state. DFT calculations have shown a strong tendency to afford a delocalized ground state,37–39 and hence they perform poorly when predicting the experimental spectroscopic properties of localized systems 17. In spite of this limitation, the calculation yields the expected spectra of the delocalized configuration, which becomes a useful reference.…”

Section: Structures Of the Ruthenium Complexes Discussed In This Workmentioning

confidence: 99%

Solvent‐Enabled Nonenyzmatic Sugar Production from Biomass for Chemical and Biological Upgrading

et al. 2015

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We recently reported an onenzymatic biomass deconstruction process for producing carbohydrates using homogeneous mixtures of g-valerolactone (GVL) and water as as olvent. Ak ey step in this process is the separation of the GVL from the aqueous phase, enabling GVL recycling and the production of ac oncentrated aqueous carbohydrate solution.I nt his study, we demonstrate that phenolic solvents-sec-butylphenol, nonylphenol, and lignin-derived propylg uaiacol-are effective at separating GVL from the aqueous phase using only small amountso fs olvent (0.5 gp er go ft he originalw ater,G VL, and sugar hydrolysate). Furthermore, using nonylphenol, we produced ah ydrolysate that supported robustg rowth and high yields of ethanol (0.49 gE tOH per gg lucose) at an industrially relevant concentration (50.8 gL À1 EtOH). These resultss uggest that using phenolic solvents could be an interesting solution for separating and/or detoxifying aqueous carbohydrate solutions produced using GVL-based biomass deconstruction processes.Lignocellulosic biomass is emerging as ap otentialr enewable feedstock to replace crude oil as as ource of fuels and commodity chemicals. For this reason,t argeted upgrading routes are being sought to convert biomass to these valuablep roducts. In this context, soluble carbohydrates are an attractive intermediate for biomass upgrading. By weight, structuralp olysaccharides typically represent between 60 and 80 wt %o f lignocellulosic biomass.I na ddition, many chemical [1][2][3][4] and biological [5][6][7][8] processes exist for upgrading carbohydrates to fuels and chemicals.Different strategies exist for deconstructing biomass hemicellulose (a polymer of C 5 sugars; mostly xylose) and cellulose (a polymer of cellobiose, ad imer of glucose) to their soluble counterparts. Concentrated mineral acids such as sulfuric or hydrochloric acid have been used to hydrolyze hemicellulose and cellulose to soluble oligomers almost quantitatively. [9][10][11][12][13] Recently,atwo-stage process consisting of at hermochemical or pretreatment stage followed by enzymatic hydrolysis has been one of the most prominently researched biomass depolymerization methods. [14][15][16][17] Both of these methods can achieve soluble carbohydrate yields upwards of 90 %a nd produce concentrated solutionso fc arbohydrates (> 100 gL À1 ). [10,13,18] Ionic liquids are also attractive solvents for cellulose dissolution and soluble carbohydrate production. [19,20] Although these processes can be used to produce sugars from biomass,t he cost of producing and/or recovering the enzyme, mineral acid, or solvent still represents as ignificant portion of the final process. [21][22][23] For this reason,a lternate systems using significantly less catalyst have also been explored, including dilute acid hydrolysis [24,25] or hydrothermalb iomass depolymerization. [13,[26][27][28] However,a tm ost temperatures (below 510-570 K) and low acid contents( >3%), the rate of sugar degradation and dehydration to furans or other degradation products is of the sam...

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“…DFT calculations have shown a strong tendency to afford a delocalized ground state, [37][38][39] and hence they perform poorly when predicting the experimental spectroscopic properties of localized systems. [17] In spite of this limitation, the calculation yields the expected spectra of the delocalized configuration, which becomes a useful reference. For example, the calculations of the electronic structures of 1 3+ and 2 3+ yield a delocalized ground state.…”

Section: +mentioning

confidence: 99%

“…[14,15] Another focus has been the characterization of higher nuclearity systems, [16] which also present challenging spectroscopy. [17][18][19] We have recently reported [18] the spectroscopy of two trimetallic cyanide-bridged mixed-valence complexes of formula trans-[Ru(L) 4 {(m-CN)Ru(py) 4 Cl} 2 ] 3+ (1 3+ , where L = pyridine and 2 3+ , where L = 4-methoxypyridine; Table 1). These systems exhibit two transitions in the near infrared (NIR) that correspond to a charge transfer from the central ruthenium(II) unit to the neighboring terminal {-Ru III (py) 4 Cl} fragment (MM'CT), and a charge transfer between the distant {-Ru(py) 4 Cl} fragments (MMCT).…”

mentioning

confidence: 99%

Class III Delocalization in a Cyanide‐Bridged Trimetallic Mixed‐Valence Complex

Pieslinger¹,

Alborés²,

Slep³

et al. 2013

Angewandte Chemie

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The NIR and IR spectroscopic properties of the cyanide-bridged complex, trans-[Ru(dmap) 4 {(m-CN)Ru-(py) 4 Cl} 2 ] 3+ (py = pyridine, dmap = 4-dimethylaminopyridine) provide strong evidence that this trimetallic ion behaves as a Class III mixed-valence species, the first example reported of a cyanide-bridged system. This has been accomplished by tuning the energy of the fragments in the trimetallic complex to compensate for the intrinsic asymmetry of the cyanide bridge. Moreover, (TD)DFT calculations accurately predict the spectra of the trans-[Ru(dmap) 4 {(m-CN)Ru(py) 4 Cl} 2 ] 3+ ion and confirms its delocalized nature.Mixed-valence chemistry has been the focus of attention of inorganic chemists for more than 40 years, since the first example of a deliberate synthesis of a discrete binuclear system was reported by Creutz and Taube.[1] An early survey of the reported mixed-valence systems gave to rise to the Robin-Day classification, which consisted of three distinctive categories:[2] Class I, not interacting; Class II, interacting, but localized; and Class III, delocalized. A strong effort in the characterization of the inter-valence charge transfer (IVCT) of Class II systems was fueled by the two-state model proposed by Hush [3,4] and Sutin, [5,6] which provided an easy route to obtain valuable information about the parameters governing the electron transfer process. Later, the focus shifted to the exploration of systems close to delocalization, somewhere in the transition between Class II and Class III. Hence, a new Class, II/III, was proposed, [7] which comprises systems still localized, but solvent-averaged. The potential energy surface describing these systems possesses two minima of similar energy separated by a small barrier, so that both mixed-valence isomers coexist and interconvert into each other. This behavior has been demonstrated experimentally, [8,9] and the rate constant for electron transfer between the isomers has been measured. [10] In many of these nearly delocalized mixed-valence systems, the bridge plays an important role in the spectroscopy, [11][12][13] which requires a three-state model for an accurate interpretation. [14,15] Another focus has been the characterization of higher nuclearity systems, [16] which also present challenging spectroscopy. [17][18][19] We have recently reported [18] the spectroscopy of two trimetallic cyanide-bridged mixed-valence complexes of formula trans-[Ru(L) 4 {(m-CN)Ru(py) 4 Cl} 2 ] 3+ (1 3+ , where L = pyridine and 2 3+ , where L = 4-methoxypyridine; Table 1). These systems exhibit two transitions in the near infrared (NIR) that correspond to a charge transfer from the central ruthenium(II) unit to the neighboring terminal {-Ru III (py) 4 Cl} fragment (MM'CT), and a charge transfer between the distant {-Ru(py) 4 Cl} fragments (MMCT). The latter is the most intense, which suggests a strong interaction between the three metallic ions. These species demonstrate that diminishing the energy of the state located at the central Ru II (the "bridge") r...

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Nearest- and Next-Nearest-Neighbor Ru(II)/Ru(III) Electronic Coupling in Cyanide-Bridged Tetra-Ruthenium Square Complexes.

Cited by 33 publications

References 39 publications

Exploring the localized to delocalized transition in non-symmetric bimetallic ruthenium polypyridines

Exploring the localized to delocalized transition in non-symmetric bimetallic ruthenium polypyridines

Solvent‐Enabled Nonenyzmatic Sugar Production from Biomass for Chemical and Biological Upgrading

Class III Delocalization in a Cyanide‐Bridged Trimetallic Mixed‐Valence Complex

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