Spin exchange coupling in asymmetric heterodinuclear complexes containing the .mu.-oxo-bis(.mu.-acetato)dimetal core

Hotzelmann, Rainer; Wieghardt, Karl; Floerke, U.; Haupt, H.‐J.; Weatherburn, David C.; Bonvoisin, Jacques; Blondin, Geneviève; Girerd, J.‐J.

doi:10.1021/ja00031a023

Cited by 181 publications

(211 citation statements)

References 1 publication

Supporting

Mentioning

199

Contrasting

Order By: Relevance

“…9,10 We recently showed that Ct RNR uses a stable Mn IV /Fe III cofactor, generated by reaction of the Mn II /Fe II -R2 complex with O 2 , for radical initiation. 11 Although heterobinuclear Mn/Fe complexes of various oxidation states, 12-14 including one example of an inorganic Mn IV /Fe III complex, 15 have been reported, Ct RNR is, to our knowledge, the first case in which an enzyme has been shown to use a Mn/Fe cluster as a redox cofactor. Here we characterize this novel cofactor by Mössbauer spectroscopy, showing that it has a triplet (S Total = 1) ground state resulting from antiferromagnetic coupling of its Mn IV (S Mn = 3/2) and high-spin Fe III (S Fe = 5/2) constituents and providing parameters to calibrate calculation of its geometric and electronic structure.…”

mentioning

confidence: 98%

The Active Form of Chlamydia trachomatis Ribonucleotide Reductase R2 Protein Contains a Heterodinuclear Mn(IV)/Fe(III) Cluster with S = 1 Ground State

2007

View full text Add to dashboard Cite

The class I ribonucleotide reductase from Chlamydia trachomatis uses a stable Mn IV /Fe III cofactor to initiate nucleotide reduction by a free-radical mechanism. The enzyme provides the first example both of a Mn-dependent ribonucleotide reductase and of a Mn/Fe redox cofactor. In this work, we have used variable-field Mössbauer spectroscopy to demonstrate that the active cofactor has an S = 1 ground state due to antiferromagnetic coupling between the Mn IV (S Mn = 3/2) and high-spin Fe III (S Fe = 5/2) sites.The reduction of nucleotides to 2′-deoxynucleotides by ribonucleotide reductases (RNRs) 1 begins with the abstraction of the 3′ hydrogen atom of the substrate by a transient cysteine thiyl radical (C•). [2][3][4] Class I, II, and III RNRs differ in subunit composition and the nature of the cofactor used to generate the 3′-H-abstracting C•. 2 A conventional class I RNR uses a stable tyrosyl radical (Y•), which is introduced into the enzyme's homodimeric R2 subunit (also denoted β 2 ) by reaction of O 2 with an adjacent carboxylate-bridged non-heme diiron cluster, 5 to generate the C• in its R1 subunit (also denoted α 2 ) via long-range (~ 35 Å) proton-coupled electron transfer (PCET). [6][7][8] The identification in Chlamydia trachomatis (Ct) and other species of pathogenic bacteria of RNRs having the class I subunit architecture but the Y•-harboring tyrosine replaced by phenylalanine raised the question of how such an RNR might function without the initiating Y•. 9,10 We recently showed that Ct RNR uses a stable Mn IV /Fe III cofactor, generated by reaction of the Mn II /Fe II -R2 complex with O 2 , for radical initiation. 11 Although heterobinuclear Mn/Fe complexes of various oxidation states, 12-14 including one example of an inorganic Mn IV /Fe III complex, 15 have been reported, Ct RNR is, to our knowledge, the first case in which an enzyme has been shown to use a Mn/Fe cluster as a redox cofactor. Here we characterize this novel cofactor by Mössbauer spectroscopy, showing that it has a triplet (S Total = 1) ground state resulting from antiferromagnetic coupling of its Mn IV (S Mn = 3/2) and high-spin Fe III (S Fe = 5/2) constituents and providing parameters to calibrate calculation of its geometric and electronic structure. Figure 2, analysis of these spectra for the hypothetical case of an S Total = 4 ground state, selected plots of the spin expectation values, and the spin Hamiltonian used for analysis of the Mössbauer spectra. This material is available free of charge from the journal website: http://pubs.acs.org. Figure S1). The derived spectra of the Mn IV / Fe III complex are shown in Figure 2. NIH Public AccessThe zero-field spectrum is a sharp quadrupole doublet with parameters (δ = 0.52 mm/s and ΔE Q = 1.32 mm/s) typical of high-spin Fe III . Spectra recorded in applied fields were analyzed with the assumption of slow relaxation and according to the spin Hamiltonian with respect to the total-spin ground state, S Total = 1, given in the Supporting Information. For this analysis, the ...

show abstract

mentioning

confidence: 98%

The Active Form of Chlamydia trachomatis Ribonucleotide Reductase R2 Protein Contains a Heterodinuclear Mn(IV)/Fe(III) Cluster with S = 1 Ground State

2007

View full text Add to dashboard Cite

show abstract

“…A large number of model compounds have been synthesized recently, among them a series of triply bridged binuclear compounds with the y-0x0-bis(y-acetato) bridging geometry (5,7). We present absorption spectra of two homobimetallic compounds of this type with the formula ' Author to whom correspondence may be addressed.…”

Section: Introductionmentioning

confidence: 99%

Single-crystal absorption spectroscopy of binuclear complexes of iron(III) and manganese(III) with the μ-oxo-bis(μ-acetato)dimetal core

Pelletier¹,

Reber

1995

Can. J. Chem.

View full text Add to dashboard Cite

Single-crystal absorption spectroscopy at variable temperature is used to determine exchange couplings between transition metal centers in both the electronic ground and excited states in two new homobimetallic complexes with the formula [LM(y-O)(y-CH3C02)2ML'](C104)2, where M is iron(II1) or manganese(II1).L and L' denote 1,4,7-triazacyclononane and 1,4,7-trimethyl-l,4,7-triazacyclononane, respectively. Values for the ground state exchange coupling constant J are -295 cm-I and +I0 cm-I for the iron and manganese compounds, respectively, using He, = -JS,.S,. Exchange interactions in excited states are qualitatively analyzed, indicating that a spin-forbidden transition of the Fe-Fe binuclear unit occurs with significant intensity by the single-ion mechanism, and not as expected by the Tanabe pair intensity mechanism for spin-forbidden transitions, the dominant mechanism for isoelectronic complexes of manganese(I1).

show abstract

“…This mechanism is in the spirit of the superexchange mechanisms proposed by Goodenough [13] in 1963. Similar mechanism is invoked recently by Tchougreeff [14] to explain the ferromagnetic ordering in decamethylferrocenium tetracyanoethenide, by Kinoshita and coworkers [15] to explain the intermolecular ferromagnetic coupling in paranitrophenyl nitronyl nitroxide and by Girerd and coworkers [16] to interpret the magnetic properties of µ-oxo Mn(II) compounds. Indeed, the interplay of direct exchange which favours parallel spin alignment on a given site (Hund's rule) and kinetic exchange which favours antiparallel alignment of spins on bonded pair of sites (by virtue of Pauli principle) is what determines the spin state of a system [17].…”

Section: Introductionmentioning

confidence: 90%

Exchange interaction in binuclear complexes with rare-earth and copper ions: A many-body model study

2002

View full text Add to dashboard Cite

We have used a many-body model Hamiltonian to study the nature of the magnetic ground state of hetero-binuclear complexes involving rare-earth and copper ions. We have taken into account all diagonal repulsions involving the rare-earth 4f and 5d orbitals and the copper 3d orbital. Besides, we have included direct exchange interaction, crystal field splitting of the rare-earth atomic levels and spin-orbit interaction in the 4f orbitals. We have identified the inter-orbital 4 f repulsion, U f f and crystal field parameter, ∆ f as the key parameters involved in controlling the type of exchange interaction between the rare earth 4 f and copper 3d spins. We have explored the nature of the ground state in the parameter space of U f f , ∆ f , spin-orbit interaction strength λ and the 4 f filling n f . We find that these systems show low-spin or high-spin ground state depending on the filling of the 4 f levels of the rare-earth ion and ground state spin is critically dependent on U f f and ∆ f . In case of half-filling (Gd(III)) we find a reentrant low-spin state as U f f is increased, for small values of ∆ f , which explains the recently reported apparent anomalous antiferromagnetic behaviour of Gd(III)-radical complexes. By varying U f f we also observe a switch over in the ground state spin for other fillings . We have introduced a spinorbit coupling scheme which goes beyond L-S or j-j coupling scheme and we find that spin-orbit coupling does not significantly alter the basic picture.

show abstract

Spin exchange coupling in asymmetric heterodinuclear complexes containing the .mu.-oxo-bis(.mu.-acetato)dimetal core

Cited by 181 publications

References 1 publication

The Active Form of Chlamydia trachomatis Ribonucleotide Reductase R2 Protein Contains a Heterodinuclear Mn(IV)/Fe(III) Cluster with S = 1 Ground State

The Active Form of Chlamydia trachomatis Ribonucleotide Reductase R2 Protein Contains a Heterodinuclear Mn(IV)/Fe(III) Cluster with S = 1 Ground State

Single-crystal absorption spectroscopy of binuclear complexes of iron(III) and manganese(III) with the μ-oxo-bis(μ-acetato)dimetal core

Exchange interaction in binuclear complexes with rare-earth and copper ions: A many-body model study

Contact Info

Product

Resources

About