Properties and kinetics of dihydroxy- and diaminoanthraquinone ruthenium bipyridyl dimers

Gooden, Velton M.; Dasgupta, Tara P.; Gordon, Nancy; Sadler, Garfield G.

doi:10.1016/s0020-1693(97)05707-1

Cited by 7 publications

(11 citation statements)

References 43 publications

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“…After oxidation of 2 + at room temperature, a single EPR line is observed at g ≈ 2.00, with very slight g anisotropy in the frozen state (see Figure S13, and Table in the Supporting Information). These features suggest almost exclusively ligand-based spin, and the calculations (see Table , as well as Figure S16 in the Supporting Information) either of 2 2+ or of ( 2 -H) + confirm the formation of an anthrasemiquinone ligand. ,, After reduction of 2 + , the resulting compound is EPR silent at room temperature but displays a notable g anisotropy between 1.97 and 2.01 at 115 K (Figure S13, Table in the Supporting Information). Spin density calculation on 2 suggest reduction of one of the pap ligands, and the possible spin hopping between equivalent reduced and nonreduced ligands may explain the absence of detectable EPR intensity at room temperature (dynamic line broadening , ).…”

Section: Resultsmentioning

confidence: 99%

“…The potential spectator ligands in the present series are σ-donating acetylacetonate (acac – ), moderately π-accepting 2,2′-bipyridine (bpy), and strongly π-accepting 2-phenylazopyridine (pap). Our study on the asymmetric combinations in dinuclear [ 3 ]ClO 4 , [ 4 ]ClO 4 , and [ 5 ](ClO 4 ) 2 complements previous investigations of symmetrical compounds [(acac) 2 Ru III (μ-H 2 L 2– )Ru III (acac) 2 ], [(bpy) 2 Ru II (μ-H 2 L • – )Ru II (bpy) 2 ](ClO 4 ) 3 , [(pap) 2 Ru II (μ-H 2 L 2– )Ru II (pap) 2 ](ClO 4 ) 2 , [(bpy) 2 Os II (μ-H 2 L • – )Os II (bpy) 2 ](ClO 4 ) 3 , and [(pap) 2 Os II (μ-H 2 L 2– )Os II (pap) 2 ](ClO 4 ) 2 . ,, …”

Section: Introductionmentioning

confidence: 99%

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Analysis of Redox Series of Unsymmetrical 1,4-Diamido-9,10-anthraquinone-Bridged Diruthenium Compounds

et al. 2016

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The unsymmetrical diruthenium complexes [(bpy)2Ru(II)(μ-H2L(2-))Ru(III)(acac)2]ClO4 ([3]ClO4), [(pap)2RuII(μ-H2L(2-))Ru(III)(acac)2]ClO4 ([4]ClO4), and [(bpy)2Ru(II)(μ-H2L(2-))Ru(II)(pap)2](ClO4)2 ([5](ClO4)2) have been obtained by way of the mononuclear precursors [(bpy)2Ru(II)(H3L(-))]ClO4 ([1]ClO4) and [(pap)2Ru(II)(H3L(-))]ClO4 ([2]ClO4) (where bpy = 2,2′-bipyridine, pap = 2-phenylazopyridine, acac(-) = 2,4-pentanedionate, and H4L = 1,4-diamino-9,10-anthraquinone). Structural characterization by single-crystal X-ray diffraction and magnetic resonance (nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR)) were used to establish the oxidation state situation in each of the isolated materials. Cyclic voltammetry, EPR, and ultraviolet-visible-near-infrared (UV-vis-NIR) spectroelectrochemistry were used to analyze the multielectron transfer series of the potentially class I mixed-valent dinuclear compounds, considering the redox activities of differently coordinated metals, of the noninnocent bridge and of the terminal ligands. Comparison with symmetrical analogues [L2′Ru(μ-H2L)RuL2′](n) (where L′ = bpy, pap, or acac(-)) shows that the redox processes in the unsymmetrical dinuclear compounds are not averaged, with respect to the corresponding symmetrical systems, because of intramolecular charge rearrangements involving the metals, the noninnocent bridge, and the ancillary ligands.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of Redox Series of Unsymmetrical 1,4-Diamido-9,10-anthraquinone-Bridged Diruthenium Compounds

et al. 2016

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“…The redox activity of the metals and of anthraquinone in the bridging ligands should give rise to several redox transitions. − However, the presence of potentially labile hydrogen centers in NH could affect the reversibility of these redox processes . Both voltammetric (CV, DPV) and spectro-electrochemical studies (see below) indicated that such effects do indeed occur for the NH 2 containing mononuclear compounds, especially for system 2 n , which limits the significance of corresponding data.…”

Section: Resultsmentioning

confidence: 99%

“…Whereas the ortho -quinone/catecholate redox system involves a “natural” chelate ligand situation, the para -quinones, including AQ, require additional coordinating groups if chelation is desired. Diorganophosphine substituents have been employed for that purpose, but the most frequently used substituents supporting p -quinone O atoms for metal chelation are deprotonated OH and also NHR groups …”

Section: Introductionmentioning

confidence: 99%

“…Taking quinizarin as a dihydroxo-substituted model, we have previously used the doubly deprotonated form of 1,4-diamino-9,10-anthraquinone (4-DAAQ = H 4 L′) with the more basic amine/amide functions as a bis-chelating bridging ligand for ruthenium complex fragments RuL 2 , L = bpy, pap, acac – . Like the bridging ligand, the metals can undergo redox reactions with Ru II , Ru III , and Ru IV as accessible oxidation states, , and ruthenium complexes of other anthraquinone derivatives have been reported . Within those studies the question of electron distribution in symmetric versus asymmetric configurations has emerged …”

Section: Introductionmentioning

confidence: 99%

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1,5-Diamido-9,10-anthraquinone, a Centrosymmetric Redox-Active Bridge with Two Coupled β-Ketiminato Chelate Functions: Symmetric and Asymmetric Diruthenium Complexes

et al. 2016

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The dinuclear complexes {(μ-H2L)[Ru(bpy)2]2}(ClO4)2 ([3](ClO4)2), {(μ-H2L)[Ru(pap)2]2}(ClO4)2 ([4](ClO4)2), and the asymmetric [(bpy)2Ru(μ-H2L)Ru(pap)2](ClO4)2 ([5](ClO4)2) were synthesized via the mononuclear species [Ru(H3L)(bpy)2]ClO4 ([1]ClO4) and [Ru(H3L)(pap)2]ClO4 ([2]ClO4), where H4L is the centrosymmetric 1,5-diamino-9,10-anthraquinone, bpy is 2,2'-bipyridine, and pap is 2-phenylazopyridine. Electrochemistry of the structurally characterized [1]ClO4, [2]ClO4, [3](ClO4)2, [4](ClO4)2, and [5](ClO4)2 reveals multistep oxidation and reduction processes, which were analyzed by electron paramagnetic resonance (EPR) of paramagnetic intermediates and by UV-vis-NIR spectro-electrochemistry. With support by time-dependent density functional theory (DFT) calculations the redox processes could be assigned. Significant results include the dimetal/bridging ligand mixed spin distribution in 3(3+) versus largely bridge-centered spin in 4(3+)-a result of the presence of Ru(II)-stabilizig pap coligands. In addition to the metal/ligand alternative for electron transfer and spin location, the dinuclear systems allow for the observation of ligand/ligand and metal/metal site differentiation within the multistep redox series. DFT-supported EPR and NIR absorption spectroscopy of the latter case revealed class II mixed-valence behavior of the oxidized asymmetric system 5(3+) with about equal contributions from a radical bridge formulation. In comparison to the analogues with the deprotonated 1,4-diaminoanthraquinone isomer the centrosymmetric H2L(2-) bridge shows anodically shifted redox potentials and weaker electronic coupling between the chelate sites.

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Ruthenium and Osmium: Low Oxidation States

Housecroft

2003

Comprehensive Coordination Chemistry II

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Properties and kinetics of dihydroxy- and diaminoanthraquinone ruthenium bipyridyl dimers

Cited by 7 publications

References 43 publications

Analysis of Redox Series of Unsymmetrical 1,4-Diamido-9,10-anthraquinone-Bridged Diruthenium Compounds

Analysis of Redox Series of Unsymmetrical 1,4-Diamido-9,10-anthraquinone-Bridged Diruthenium Compounds

1,5-Diamido-9,10-anthraquinone, a Centrosymmetric Redox-Active Bridge with Two Coupled β-Ketiminato Chelate Functions: Symmetric and Asymmetric Diruthenium Complexes

Ruthenium and Osmium: Low Oxidation States

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