Studies of iron(II) and iron(III) complexes with fac-N2O, cis-N2O2 and N2O3 donor ligands: models for the 2-His 1-carboxylate motif of non-heme iron monooxygenases

被引：16

作者：

Cappillino, Patrick J. ^{[1
]}

Miecznikowski, John R. ^{[2
]}

Tyler, Laurie A. ^{[3
]}

Tarves, Paul C. ^{[1
]}

McNally, Joshua S. ^{[1
]}

Lo, Wayne ^{[4
]}

Kasibhatla, Bala Sundari T. ^{[1
]}

Krzyaniak, Matthew D. ^{[5
]}

McCracken, John ^{[5
]}

Wang, Feng ^{[1
]}

Armstrong, William H. ^{[4
]}

Caradonna, John P. ^{[1
]}

机构：

[1] Boston Univ, Dept Chem, Boston, MA 02215 USA

[2] Fairfield Univ, Dept Chem, Fairfield, CT 06824 USA

[3] Union Coll, Dept Chem, Schenectady, NY 12308 USA

[4] Boston Coll, Dept Chem, Chestnut Hill, MA 02467 USA

[5] Michigan State Univ, Dept Chem, E Lansing, MI 48824 USA

来源：

DALTON TRANSACTIONS | 2012年 / 41卷 / 18期

基金：

美国国家科学基金会; 美国国家卫生研究院;

关键词：

DENSITY-FUNCTIONAL THERMOCHEMISTRY; 2-HIS-1-CARBOXYLATE FACIAL TRIAD; FE-IV=O COMPLEX; SPECTROSCOPIC CHARACTERIZATION; ELECTRONIC-STRUCTURE; ALPHA-KETOGLUTARATE; ACTIVE-SITES; CATECHOL DIOXYGENASES; FERROUS COMPLEXES; ESCHERICHIA-COLI;

D O I：

10.1039/c2dt11096b

中图分类号：

O61 [无机化学];

学科分类号：

070301 ; 081704 ;

摘要：

Enzymes in the oxygen-activating class of mononuclear non-heme iron oxygenases (MNOs) contain a highly conserved iron center facially ligated by two histidine nitrogen atoms and one carboxylate oxygen atom that leave one face of the metal center (three binding sites) open for coordination to cofactor, substrate, and/or dioxygen. A comparative family of [Fe-II/III(N2On)(L)(4-n))](+/- x), n = 1-3, L = solvent or Cl-, model complexes, based on a ligand series that supports a facially ligated N,N,O core that is then modified to contain either one or two additional carboxylate chelate arms, has been structurally and spectroscopically characterized. EPR studies demonstrate that the high-spin d(5) Fe-III g = 4.3 signal becomes more symmetrical as the number of carboxylate ligands decreases across the series Fe(N2O3), Fe(N2O2), and Fe(N2O1), reflecting an increase in the E/D strain of these complexes as the number of exchangeable/solvent coordination sites increases, paralleling the enhanced distribution of electronic structures that contribute to the spectral line shape. The observed systematic variations in the Fe-II-Fe-III oxidation-reduction potentials illustrate the fundamental influence of differential carboxylate ligation. The trend towards lower reduction potential for the iron center across the [Fe-III(N2O1)Cl-3](-), [Fe-III(N2O2)Cl-2](-) and [Fe-III(N2O3)Cl](-) series is consistent with replacement of the chloride anions with the more strongly donating anionic O-donor carboxylate ligands that are expected to stabilize the oxidized ferric state. This electrochemical trend parallels the observed dioxygen sensitivity of the three ferrous complexes (Fe-II(N2O1) < Fe-II(N2O2) < Fe-II(N2O3)), which form mu-oxo bridged ferric species upon exposure to air or oxygen atom donor (OAD) molecules. The observed oxygen sensitivity is particularly interesting and discussed in the context of alpha-ketoglutarate-dependent MNO enzyme mechanisms.

引用

页码：5662 / 5677

页数：16

共 88 条

[1]

[Anonymous], 1997, PROGRAM REFINEMENT C

[2]

Bakir E. W. B., 2007, J AM CHEM SOC, V129, P11334

[3] Spectroscopic characterization of an FeIV intermediate generated by reaction of XO- (X = Cl, Br) with an FeII complex bearing a pentadentate non-porphyrinic ligand -: Hydroxylation and epoxidation activity [J].