Mixed valence complexes involving MM quadruple bonds (M=Mo or W)

2007 ◽  
Vol 366 (1862) ◽  
pp. 101-112 ◽  
Author(s):  
Malcolm H Chisholm
Keyword(s):  
Mixed Valence ◽  
Electronic Coupling ◽  
Organic Radical ◽  
Radical Anions ◽  
Class Iii ◽  
Mixed Valency ◽  
Bridging Ligand ◽  
Quadruple Bond ◽  
Redox Active ◽  
Quadruple Bonds

The MM quadruple bond of configuration MM σ 2 π 4 δ 2 is redox active and in many ways ideally suited for studies of mixed valency when two or more such centres are linked by a bridging ligand. In this account, the mechanism of electronic coupling is examined for complexes of the type [L 3 M 2 bridgeM 2 L 3 ] 0/+ where L, a pivalate; bridge, a dicarboxylate or related ligand and M, Mo or W. The represented examples allow us to probe electronic factors close to the class II/III border and readily distinguish between electron and hole transfer in the superexchange mechanism. The potential for mixed valence organic radical anions mediated by the M 2 centre is also raised and one specific example of class III behaviour is described.

Distinguishing the Strength of Electronic Coupling for Mo2-Containing Mixed-Valence Compounds within the Class III Regime

2014 ◽  
Vol 21 (6) ◽  
pp. 2353-2357 ◽  
Author(s):  
Tao Cheng ◽  
Ying Ning Tan ◽  
Yu Zhang ◽  
Yu Yu Zhang ◽  
Miao Meng ◽  
...  
Keyword(s):  
Mixed Valence ◽  
Electronic Coupling ◽  
Class Iii ◽  
Mixed Valence Compounds

Driving the Localized-to-Delocalized Transition in Unsymmetrical Dinuclear Ruthenium Mixed-Valence Complexes

2005 ◽  
Vol 58 (11) ◽  
pp. 767 ◽  
Author(s):  
Deanna M. D'Alessandro ◽  
F. Richard Keene
Keyword(s):  
Electronic State ◽  
Ground State ◽  
Mixed Valence ◽  
Electronic Coupling ◽  
Classical Analysis ◽  
Bridging Ligand ◽  
Dinuclear Ruthenium ◽  
State Analysis

The degree of delocalization in the symmetrical complexes [{Ru(bpy)2}2(μ-dpb′)]5+ and [{Ru(bpy)2}2(μ-dpb)]5+ (dpb = 2,3-bis(2-pyridyl)-1,4-benzoquinoxaline; dpb′ = dipyrido(2,3-a;3′,2′-c)benzophenazine; bpy = 2,2′-bipyridine) is diminished by the substitution of the terminal bpy ligands at one end of the complex. The results of a classical analysis for the diastereoisomeric forms of the series of complexes [{Ru(bpy)2}(μ-BL){Ru(pp)2}]5+ (pp = bpy, Me2bpy (4,4′-dimethyl-2,2′-bipyridine), Me4bpy (4,4′,5,5′-tetramethyl-2,2′-bipyridine)) indicate that a greater degree of ground-state delocalization exists in the complexes incorporating the bridging ligand dpb′ compared with the dpb analogue. A two-state analysis in which ΔE 0 (the redox asymmetry) is varied at constant H ab (the electronic coupling) and λ (the reorganizational energy) does not adequately describe the properties of the systems due to the importance of a third electronic state corresponding to the bridging ligand.

Resonance Raman spectroscopic study of solvent-dependent coexistence of localized and delocalized dinitroaromatic radical anions

2014 ◽  
Vol 92 (10) ◽  
pp. 940-947 ◽  
Author(s):  
Ryan M. Hoekstra ◽  
Yen-Ting Chen ◽  
Matthew D. Kiesz ◽  
João P. Telo ◽  
Rachel M. Stephenson ◽  
...  
Keyword(s):  
Broad Band ◽  
Mixed Valence ◽  
Resonance Raman ◽  
Reorganization Energy ◽  
Class Ii ◽  
Radical Anions ◽  
Class Iii ◽  
Excitation Energies ◽  
Absorption Region ◽  
Stretch Mode

Optical absorption spectra of three dinitroaromatic radical anions, 2,7-dinitro-9,9-dimethylfluorene (1•−), 4,4′-dinitrobiphenyl (2•−), and 4,4′-dinitrotolane (3•−) in solvents THF, HMPA, and MeCN show both an unresolved broad band characteristic of charge-localized mixed valence species (Robin-Day classification Class II), and a vibronically structured band of the delocalized species (Class III). With decreasing solvent reorganization energy, a greater portion of the compounds become charge-delocalized. In particular, 1•− with the greatest coupling, is almost entirely composed of the delocalized species in all solvents. An intense Raman mode is used to identify the charge-bearing unit as the nitrobenzene moiety. Resonance Raman profiles are utilized to gain detailed information of vibrational modes. The out-of-phase ring lengthening stretch mode is observed to be enhanced at higher excitation energies, corresponding to the absorption band of the Class II species, while the in-phase ring lengthening stretch mode, a totally symmetric vibration, is most strongly enhanced in the absorption region of the Class III species. Resonance Raman profiles support the solvent-dependent coexistence of Class II and Class III molecules of the same chemical composition.

Synthesis and wire-like performance of diruthenium molecular wire with a C≡C-porphyrin-C≡C linker

2015 ◽  
Vol 19 (01-03) ◽  
pp. 442-450 ◽  
Author(s):  
Yuya Tanaka ◽  
Masanori Ono ◽  
Munetaka Akita
Keyword(s):  
Mixed Valence ◽  
Chemical Oxidation ◽  
Electronic Coupling ◽  
Cyclic Voltammogram ◽  
Class Iii ◽  
Metal Centers ◽  
Intervalence Charge Transfer ◽  
Ir Study ◽  
Diruthenium Complex ◽  
Back Donation

A diruthenium complex with a free-base porphyrin linker 1 is synthesized and characterized by 1 H and 31 P NMR, IR, and ESI-TOF-MS spectroscopy. A cyclic voltammogram of 1 shows two reversible waves attributed to the redox processes at the ruthenium centers, and a compropotionation constant (K C ) has been determined to be 1.8 × 105, indicating that a mixed valence state of 1+ is thermodynamically stable. The monocationic complex 1+ obtained by chemical oxidation of 1 by [ Cp 2 Fe ] PF 6 shows an intervalence charge transfer (IVCT) band in the NIR region. On the basis of the electronic coupling ( V ab) of 2644 cm-1 obtained by analysis of the IVCT band, complex 1+• is assigned as a Class III compound according to the Robin–Day classification. DFT calculation and IR study suggest that the strength of π-back donation is one of key determinants for a strong electronic coupling between the two metal centers.

A Donor−Acceptor−Donor Bridging Ligand in a Class III Mixed-Valence Complex

2001 ◽  
Vol 40 (6) ◽  
pp. 1189-1195 ◽  
Author(s):  
Peter J. Mosher ◽  
Glenn P. A. Yap ◽  
Robert J. Crutchley
Keyword(s):  
Mixed Valence ◽  
Class Iii ◽  
Bridging Ligand ◽  
Donor Acceptor ◽  
Mixed Valence Complex

Electronic Coupling in Dimetallic Complexes with π-Conjugated Bridge

2006 ◽  
Vol 6 (11) ◽  
pp. 3347-3350 ◽  
Author(s):  
Min-Chul Chung ◽  
Ho-Geun Ahn ◽  
Chee-Hun Kwak ◽  
Munetaka Akita
Keyword(s):  
Radical Cation ◽  
Coupling Parameter ◽  
Mixed Valence ◽  
Absorption Peak ◽  
Electronic Coupling ◽  
Class Iii ◽  
Effective Coupling ◽  
Electronic Delocalization

Compound 2, [(η5-C5Me5) Fe(dppe)]2 (μ-C≡C–CH=CH–C≡C), was prepared by the reaction of compound 1, [η5-C5Me5) Fe(dppe)]+2 (μ2-C=CH–CH=CH–HC=C) · (PF 6)2–, with KOBut. Compound 2 showed two quasi-reversible one-electron oxidations at −0.674 and −0.253 V, respectively. The comproportionation constant, Kc, was calculated from these measurements. The mixed-valence(MV) radical cation 2+ showed an absorption peak at 1586 nm, which was assigned to the MV π–π band of the delocalized complex (Robin-Day Mixed-valence Class III) and the effective coupling parameter, Hab, is consistent with the presence of electronic delocalization.

ChemInform Abstract: [V16O38(CN)]9-: A Soluble Mixed-Valence Redox-Active Building Block with Strong Antiferromagnetic Coupling.

ChemInform ◽  
2012 ◽  
Vol 43 (45) ◽  
pp. no-no
Author(s):  
Tony D. Keene ◽  
Deanna M. D'Alessandro ◽  
Karl W. Kraemer ◽  
Jason R. Price ◽  
David J. Price ◽  
...  
Keyword(s):  
Building Block ◽  
Mixed Valence ◽  
Antiferromagnetic Coupling ◽  
Redox Active

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

2013 ◽  
Vol 126 (5) ◽  
pp. 1317-1320 ◽  
Author(s):  
German E. Pieslinger ◽  
Pablo Alborés ◽  
Leonardo D. Slep ◽  
Luis M. Baraldo
Keyword(s):  
Mixed Valence ◽  
Class Iii ◽  
Mixed Valence Complex
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