Electrochemical properties of dinuclear [Ru([n]aneS<sub>4</sub>)] complexes of 2,3-bis(2-pyridyl)pyrazine

Newell, Mike; Thomas, Jim A.

doi:10.1039/b509733a

Cited by 15 publications

(12 citation statements)

References 36 publications

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“…In both the 1 + – 3 + series and the 4 + – 6 + series, the band energy is highest for the [14]aneS 4 -based complex. Again, this trend is also consistent with previous work − showing that [14]aneS 4 is most preorganized to bind to octahedral centers with the minimum of steric strain. This stabilization of the Ru II [14]aneS 4 unit, which supplies the occupied orbitals for the Ru II →SQ charge-transfer, results in the observed shift to lower wavelength of the low energy band.…”

Section: Resultssupporting

confidence: 92%

“…A similar trend for ligand-centered couples is observed when complex 4 + is compared to 5 + and 6 + : the relevant oxidation couples for the [12]aneS 4 complex are between 50 and 120 mV less positive than comparable oxidations for the other two complexes. These data are consistent with previous experimental and DFT studies showing that, because of its smaller coordination cavity, back-bonding interactions are weaker in [12]aneS 4 than in the larger thiacrowns, ,− which results in less stabilization of the Ru d(π) orbitals and hence less positive Ru III/II couples.…”

Section: Resultssupporting

confidence: 92%

“…Related to this topic, the Thomas and Félix groups have investigated the effect of a series of thiacrown ligands on the redox properties of ruthenium(II) centers , and used these fragments in the construction of mixed valence, MV, complexes. − Generally, it was found that, because of back bonding interactions involving overlap of C–S σ* orbitals that are in-plane with occupied t 2g metal orbitals, the thiacrowns stabilize the Ru II state more than even polypyridyl ligands, and this effect increases as the number of S donors within the thiacrown increases. However, comparisons of MV systems containing macrocycles with the same number of S donors, revealed that changes in the size of the macrocycle also tune the intermetallic interaction and the overall redox chemistry of the entire system, presumably by changing the extent of the C–S σ*/t 2g overlap.…”

Section: Introductionmentioning

confidence: 99%

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Ruthenium(II) Thiacrown Complexes Incorporating Noninnocent Redox Active Ligands: Synthesis, Electrochemical Properties, and Theoretical Studies

et al. 2012

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The synthesis and characterization of a series of nine new complexes incorporating [Ru II Cl([n]aneS 3 )] (n = 12,14, 16) metal centers coordinated to redox active catechol ligands is reported. The solid-state structure of one of these complexes has been determined by X-ray crystallography. The redox properties of these complexes have been probed experimentally through absorption spectroscopy, cyclic voltammetry, and spectroelectrochemistry, as well as computationally through density functional theory calculations. These studies reveal that, whereas the tetrachlorocatechol-based complexes are isolated with the dioxolene unit in the catechol form, the rest of the complexes are isolated in the semiquinone oxidation state. It was also found that the Ru III/II -based couple for the complexes is dependent on the nature of the thiacrown ligand coordinated to the metal center. A combination of optical and theoretical studies revealed that the absorption spectra of the complexes contain contributions from a variety of charge transfer processes; in the case of the tetrachlorocatechol complexes these transitions include catechol-to-thiacrown ligand-to-ligand charge transfer. ■ INTRODUCTIONIn metal complexes, noninnocent redox behavior occurs when the oxidation states of the metal and a coordinated ligand cannot be defined without ambiguity. 1 Noninnocence arises when the frontier orbitals of the metal and the ligand are close enough in energy for mixing to occur, and is therefore dependent on both the ligand and the metal. This phenomenon has been observed in the active site of metallo-enzymes 2 and is also exploited in the construction of novel redox-active catalysts. 3 Although this phenomenon was first studied in detail in dithiolene complexes, 1,4 transition metal complexes of another redox active ligand, catechol, have also attracted much interest. 5−15 The redox properties of catechol (1,2-dihydroxybenzene) are well-known: deprotonation of both hydroxy groups yields a dianion, which can then be oxidized by two electrons to obenzoquinone. The oxidation from catecholate (CAT) to quinone (Q) is fully reversible and takes place via two consecutive one-electron processes; the intermediate between CAT and Q states is the radical anion semiquinone (SQ), Scheme 1.Early work on the redox behavior of these coordinated ligands concerned the properties of dioxolene complexes of chromium, molybdenum, and tungsten. 5,6 Following initial work by Balch and Sohn using Ru 0 centers, 7 the Lever group carried out related studies on complexes containing Ru II -based moieties coordinated to a variety of catechol derivatives. 8 Electrochemical studies on these systems revealed that although the redox couples for the CAT-SQ and SQ-Q processes were all at more negative potentials than the Ru III/II oxidation, the exact position of the ligand-centered processes varied depending on the ligand used. The same group has also studied the properties of similar complexes containing coordinated catechol derivatives with a range of O-, N-, and S-do...

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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Ruthenium(II) Thiacrown Complexes Incorporating Noninnocent Redox Active Ligands: Synthesis, Electrochemical Properties, and Theoretical Studies

et al. 2012

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“…9,10 In more recent work, using the same ligands, we extended these studies to [Ru([n]aneS 4 )] 2+ based systems (where n ) 12, 14, and 16). 11,12 In these complexes it was found that oxidation of the Ru II centers is considerably anodically shifted and interactions between metal centers in the MV states is less intense than that of their [RuCl( [9]aneS 3 )] + analogues. This was because the substitution of the π-donor chloride ligand of the S 3 systems with an electron-accepting macrocyclic sulfur ligand 11,12 results in a decrease of electron density on the metal center, thus stabilizing the Ru II oxidation state and lowering the electron density available for delocalization over the bridging ligand.…”

Section: Thementioning

confidence: 99%

Mixed Valence Creutz−Taube Ion Analogues Incorporating Thiacrowns: Synthesis, Structure, Physical Properties, and Computational Studies

et al. 2008

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A series of nine new complexes incorporating [Ru(II)Cl([n]aneS(3))] (n = 12, 14, 16) metal centers bridged by three ditopic ligands containing two monodentate sites (pyrazine, 4,4'-bipyridine, and 3,6-bis(4-pyridyl)-1,2,4,5-tetrazine) have been synthesized and fully characterized. The solid-state structures of three of the complexes have been further characterized by X-ray crystallography studies. Intermetallic interactions within the new systems have been probed using electrochemistry and optical spectroscopy. Cyclic voltammetry reveals that the three pyrazine bridged systems display two separate Ru(III)/(II) redox couples. Using spectroelectrochemistry, we have investigated the optical properties of these mixed valence, Creutz-Taube ion analogues. An analysis of the intervalence charge transfer bands for the complexes revealed that, despite possessing the same donor sets, the electronic delocalization within these systems is modulated by the nature of the coordinated thiacrown. Computational modeling using density function theory offers further evidence of interaction between metal centers and provides insights into how these interactions are mediated.

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“…110 [Ru II ([n]aneS 4 )] (n = 12, 14) complexes with 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine bridges are reported, 111 as have [Ru II ([n]aneS 4 )] (n = 12, 14, 16) species with 2,3bis(2-pyridyl)pyrazine bridges. 112 trans-[Ru VI O 2 (L)] 2+ (L = 1,12-dimethyl-3,4:9,10dibenzo-1,12-diaza-5,8-dioxacyclopentadecane) reacts with nitrite forming trans-[Ru IV (L)(O)(ONO 2 )] + , which on aquation affords trans-[Ru IV (L)(O)(OH 2 )] 2+ . Scrambling of the oxygens from the oxo groups occurs, possibly via linkage isomerization of the nitrate group.…”

Section: Hydrides and Other Ru Complexesmentioning

confidence: 99%

Iron, ruthenium and osmium

Cotton¹

2007

Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem.

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The aryl [Li(thf) 4 ][Fe(C 6 Cl 5 ) 4 ] is notable, as is the nitride [Fe(N)(Me 3cyclam-OAc)] 2+ , the first Fe VI compound apart from the ferrate ion. Interest continues in Fe nitrosyl, oxo-and imide species; there is compelling work on three-and four-coordinate iron. In the case of ruthenium, interest continues in olefin metathesis and complexes of ligands such as bipy, phen and terpy, on account of their photochemical properties.

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Electrochemical properties of dinuclear [Ru([n]aneS₄)] complexes of 2,3-bis(2-pyridyl)pyrazine

Cited by 15 publications

References 36 publications

Ruthenium(II) Thiacrown Complexes Incorporating Noninnocent Redox Active Ligands: Synthesis, Electrochemical Properties, and Theoretical Studies

Ruthenium(II) Thiacrown Complexes Incorporating Noninnocent Redox Active Ligands: Synthesis, Electrochemical Properties, and Theoretical Studies

Mixed Valence Creutz−Taube Ion Analogues Incorporating Thiacrowns: Synthesis, Structure, Physical Properties, and Computational Studies

Iron, ruthenium and osmium

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Electrochemical properties of dinuclear [Ru([n]aneS4)] complexes of 2,3-bis(2-pyridyl)pyrazine

Cited by 15 publications

References 36 publications

Ruthenium(II) Thiacrown Complexes Incorporating Noninnocent Redox Active Ligands: Synthesis, Electrochemical Properties, and Theoretical Studies

Ruthenium(II) Thiacrown Complexes Incorporating Noninnocent Redox Active Ligands: Synthesis, Electrochemical Properties, and Theoretical Studies

Mixed Valence Creutz−Taube Ion Analogues Incorporating Thiacrowns: Synthesis, Structure, Physical Properties, and Computational Studies

Iron, ruthenium and osmium

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Electrochemical properties of dinuclear [Ru([n]aneS₄)] complexes of 2,3-bis(2-pyridyl)pyrazine