Modulation of iron reduction potential by deprotonation at a remote site

Carina, Riccardo F.; Verzegnassi, Ludovica; Williams, Alan F.; Bérnardinelli, Gerald

doi:10.1039/a807321j

Cited by 72 publications

(52 citation statements)

References 14 publications

(19 reference statements)

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“…This wave falls in the same potential window as the Ni III/II couple for other tetraanionic ligands. [1,[22][23][24][25] Therefore the difference of about 600 mV between the first anodic waves is consistent with the previously reported values for the deprotonation of a coordinated imidazole group [9,11] ( % 300 mV drop per proton). The corollary to this downshift of the first oxidation wave is the concomitant disappearance of the reduction wave observed at À1.88 V. Both of these changes observed for the electrochemical behaviour of the nickel(II) complex upon deprotonation demonstrate the higher field strength generated by the deprotonated imidazole groups.…”

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confidence: 89%

“…In the case of non-heme complexes, Williams and co-workers were the first to show a drastic drop in the redox potential of a non-porphyrinic iron complex upon deprotonation of four ligated imidazole moieties. [11] Analysis of the electrochemical data revealed a drop of around 300 mV shift per proton. However, attempts to elucidate the processes involved have been realised by using a coordinatively saturated iron complex to prevent any structural change in the coordination sphere of the metal ion.…”

Section: Introductionmentioning

confidence: 99%

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Proton‐Mediated Redox Control in a Nickel(II)–Bisimidazolate Complex: Spectroscopic Characterisation and Density Functional Analysis

Lassalle‐Kaiser¹,

Guillot²,

Sainton³

et al. 2008

Chemistry A European J

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The synthesis and characterisation of the pro-ligand LH4, in which L is the o-phenylenebisamide-2-imidazole and its nickel(II) complexes are reported. The X-ray structures of the fully protonated [NiLH2] and deprotonated [NiL] complexes are presented. The effects of the deprotonation of the imidazole functions on the electronic structure of the complexes are analysed by (1)H NMR, UV/Vis and IR spectroscopy and cyclic voltammetry. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations support the analysis based on experimental data. The singly oxidised form of the deprotonated complex [NiL] was generated by preparative electrolysis and its electronic structure was investigated. Spectroelectrochemistry shows the appearance of intense transitions in the region lambda = 600-900 nm with several isosbestic points. X-band EPR spectroscopy presents an isotropic signal at g = 2.03, whereas the Q-band EPR reveals a weak anisotropic signal characteristic of a metalloradical species. DFT and TDDFT data support the description of the species as a nickel(II)-radical form, with a major contribution of the spin density on the phenylene ring and the amidate functions with a negligible participation of the imidazolate groups. This finding is in sharp contrast with those obtained from the one-electron-oxidised form of nickel(II) complexes containing phenolate groups.

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confidence: 89%

Section: Introductionmentioning

confidence: 99%

Proton‐Mediated Redox Control in a Nickel(II)–Bisimidazolate Complex: Spectroscopic Characterisation and Density Functional Analysis

Lassalle‐Kaiser¹,

Guillot²,

Sainton³

et al. 2008

Chemistry A European J

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“…In an extensive study of redox reactions of complexes of ruthenium and osmium containing benzimidazole subunits, Haga et al 19,20 measured the effect of deprotonation of a coordinated benzimidazole ligand on the M(III)/M(II) reduction potential to be a shift of ~300 mV/proton in the negative direction. Williams et al 21 have recently reported the structure and electrochemistry of an iron(II) complex of a 2,6-diimidazolyl pyridine, [Fe(H 2 (6)) 2 ] 2+ (see Figure 1). The potential for the Fe(III)/Fe(II)couple of [Fe(H 2 (6)) 2 ] 2+ is found at +0.920 mV vs NHE in acetonitrile.…”

Section: Introductionmentioning

confidence: 99%

Proton Control of Oxidation and Spin State in a Series of Iron Tripodal Imidazole Complexes

Brewer¹,

Brewer²,

Luckett³

et al. 2004

Inorg. Chem.

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“…Six-coordinatedsodium(I)environments are present in the most of the comparativelyf ew sodium(I)c omplexes, such as in 1,7-bis(2,2¢ -dihydroxybiphen-3-yl)-4,10-dimethyl-1,4,7,10-tetraazacyclododecane)sodium acetonitrile solvate [1], tetrakis(acetonitrile) bis(tetrahydrofuran)sodium bis(2,6-bis-benzimidazol-2-yl)pyridine)iron [2] and bis(2-(4¢ -thiazolyl)benzimidazole-N , N ¢ ) bis(octadeuterofuran)sodium [3]. Inthe course of studies of phenanthroline complexes, we have synthesized the title mononuclear …”

Section: Discussionmentioning

confidence: 99%

Crystal structure of diaquabis(1,10-phenanthroline-k2N, N')sodium chloride, [Na(H2O)2(C12H8N2)2]Cl

B.-S.¹

2006

Zeitschrift Für Kristallographie - New Crystal Structures

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C 24H 20ClN 4 NaO 2 ,monoclinic, P 121 / c 1(no. 14), a =16.352(3) Å, b =15.579(3) Å, c =9.132(2) Å, b =104.54(3)°, V =2251.8 Å 3 , Z =4, R gt (F) =0.056, wRref(F 2 ) =0.161, T =293 K. Source of materialThe title compound was obtainedserendipitously from the reaction of manganic dichloride dihydrate (0.40 g, 2.47 mmol), 1,10-phenanthroline monohydrate (0.13 g, 0.66 mmol), phthalic acid (0.43 g, 2.59 mmol) in water (10 mL), and then the pHwas raised to about 8.5 with 1.0 Msolutionofsodium carbonate. The mixture was stirred for ca. 4h.Subsequently, the resultingsuspension was heated in a2 5m lTeflon-lined stainless steel autoclavea t 453 Kfor 5days. After the autoclave was cooled to room temperature, the solid was filtered off. The resulting yellow filtrate was allowed to stand at room temperature and slow evaporation for two years afforded yellowish block-shapedcrystals. DiscussionSix-coordinatedsodium(I)environments are present in the most of the comparativelyf ew sodium(I)c omplexes, such as in 1,7-bis(2,2¢ -dihydroxybiphen-3-yl)-4,10-dimethyl-1,4,7,10-tetraazacyclododecane)sodium acetonitrile solvate figure, top). The Na-Nbond distances are in the range of 2.460(2) Åto 2.563(2) Å.The Na-O2and Na-O1bond lengths are 2.358(2) Åand 2.401(2) Å,r espectively. The monovalent [Na(H 2 O) 2 (phen) 2 ] + complex cations are interlinked via hydrogen bonds between the Cl -anions and Oatoms of the coordinated water molecules. The chelating phen ligands exhibit nearly perfect co-planarity, each phen ligand is sandwiched by two phen ligands from two neighboring mononuclear complex cations. The mean interplanar distances are 3.469 Åand 3.566 Å,a lternatively, indicating p -p stacking interactions along [010] direction (figure, bottom). Moreover, there are weak hydrogen bonds between Cl -anions and o -phenanthroline H3atoms ( d (C3···Cl1) = 3.706 Å, Ð C3-H3···Cl1 =146.5°). Through the hydrogen bonds and p -p stacking interactions, athree-dimensional supramolecular network is constructed.

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Modulation of iron reduction potential by deprotonation at a remote site

Abstract: Remote site deprotonation of a coordinated imidazole ligand switches the reduction potential of coordinated iron over a narrow pH range from +0.920 to 20.460 V.

Cited by 72 publications

References 14 publications

Proton‐Mediated Redox Control in a Nickel(II)–Bisimidazolate Complex: Spectroscopic Characterisation and Density Functional Analysis

Proton‐Mediated Redox Control in a Nickel(II)–Bisimidazolate Complex: Spectroscopic Characterisation and Density Functional Analysis

Proton Control of Oxidation and Spin State in a Series of Iron Tripodal Imidazole Complexes

Crystal structure of diaquabis(1,10-phenanthroline-k2N, N')sodium chloride, [Na(H2O)2(C12H8N2)2]Cl

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