MODELS OF THE MANGANESE CATALASE ENZYMES - DINUCLEAR MANGANESE(III) COMPLEXES WITH THE [MN2(MU-O)(MU-O2CR)2]2+ CORE AND TERMINAL MONODENTATE LIGANDS - PREPARATION AND PROPERTIES OF [MN2O(O2CR)2X2(BPY)2] (X = C1-, N3-, H2O)

被引:89
作者
VINCENT, JB
TSAI, HL
BLACKMAN, AG
WANG, SY
BOYD, PDW
FOLTING, K
HUFFMAN, JC
LOBKOVSKY, EB
HENDERICKSON, DN
CHRISTOU, G
机构
[1] UNIV CALIF SAN DIEGO, DEPT CHEM, 0506, LA JOLLA, CA 92093 USA
[2] INDIANA UNIV, DEPT CHEM, BLOOMINGTON, IN 47405 USA
[3] INDIANA UNIV, CTR MOLEC STRUCT, BLOOMINGTON, IN 47405 USA
关键词
D O I
10.1021/ja00079a016
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Procedures are reported that allow access to dinuclear Mn(III) complexes possessing the [Mn2O(mu-O2CR)2]2+ core. The complexes have the general formulation [Mn2O(O2CR)2X2(bpy)2] (X = Cl-, N3-, H2O; bpy = 2,2'-bipyridine) and are potential models of the Mn catalase enzymes. Treatment of MnCl2/bpy/acetic acid reaction mixtures in MeCN with NBun4MnO4 in MeCN leads to subsequent isolation of [Mn2O(OAc)2Cl2(bpy)2].AcOH.H2O(1). Analogous reactions allow the preparation of [Mn2O(O2CPh)2Cl2(bpy)2].2H2O (2) and [Mn2O(O2CEt)2Cl2(bpy)2].3EtCO2H.H2O (3). In the presence of N3-, the complex [Mn2O(O2CPh)2(N3)2(bpy)2] (5) is obtained; use of AcO- and a greater MnO4- amount yields [Mn2O2(N3)4(bpy)2] (6). Complex 1 can also be prepared from a reaction in which a solution of Cl2 in MeCN is employed as the oxidizing agent instead of NBun4MnO4. If, however, aqueous HOAc is employed as the reaction medium, oxidation with an excess of C12 leads to [Mn2O(OAC)2(H2O)2(bpy)2](ClO4)2 (7). The three Mn2 units are extremely similar and differ only in the identity of the terminal ligands X (Cl-, N3-, or H2O). They each contain a triply-bridged [Mn2(mu-O)(mu-O2CR)2]2+ core with chelating bpy and terminal X groups completing near-octahedral geometry at each Mn atom. In each case, the X group and an oxygen atom from a bridging RCO2- group lie on a Jahn-Teller elongation axis (high-spin d4 Mn(III)). Complexes 1, 2, 3, and 5 have been studied by cyclic voltammetry in DMF; they each display a quasi-reversible oxidation at -0.4 V (1, 2, and 3) and 0.18 V (5) vs ferrocene, assigned to the 2Mn(III)/Mn(III)Mn(IV) couple. Variable-temperature solid-state magnetic susceptibilities of 1 and 5 were measured in the temperature range 5.0 to ca. 330 K. The effective magnetic moment per Mn2III (mu(eff)) for 1 decreases gradually from 6.33 mu(B) at 327.7 K to 5.85 mu(B) at 100 K and then more steeply to 2.09, mu(B) at 5.0 K. For 5, mu(eff) increases steadily from 6.96 mu(B) at 320 K to a maximum of 8.12 mu(B) at 30 K and then decreases to 7.45 mu(B) at 5.0 K. The data were fit to a model that included an isotropic Heisenberg exchange interaction, an isotropic Zeeman interaction, and axial zero-field splitting terms for both ions. For complex 1, a good fit was found with J = -4.1 cm-1, g = 1.88, D1 = D2 = -0.07 cm-1, and 0.8% by weight of a paramagnetic S = 2 impurity. For complex 5, the corresponding values are J = +8.8 cm-1, g = 1.86 and D1 = D2 = 0.3 cm-1; the quality of the fit is less than that for 1, and this was concluded to be due to the presence of intermolecular exchange interactions propagated by the intermolecular hydrogen-bonding network observed in the crystal structure of 5-MeCN-4H2O. Thus, 5 is ferromagnetically coupled and has an S = 4 ground state. The J values for all available complexes containing the [Mn2O(O2CR)2]2+ core are compared, and a rationalization is suggested for the differences between 1/7 (negative J) and 5 (positive J). The relevance of these results to Mn catalase are discussed as well as to the observed difference in sign of the J values for deoxyhemerythrin (negative J) versus deoxy-N3--hemerythrin (positive J).
引用
收藏
页码:12353 / 12361
页数:9
相关论文
共 50 条
[1]   CHARACTERIZATION OF A MANGANESE-CONTAINING CATALASE FROM THE OBLIGATE THERMOPHILE THERMOLEOPHILUM-ALBUM [J].
ALLGOOD, GS ;
PERRY, JJ .
JOURNAL OF BACTERIOLOGY, 1986, 168 (02) :563-567
[2]  
BARYNIN VV, 1986, DOKL AKAD NAUK SSSR+, V288, P877
[3]  
BARYNIN VV, 1986, DOKL AKAD NAUK SSSR+, V286, P461
[4]   MIXED-VALENCE MANGANESE-(II, III) AND MANGANESE-(III, IV) DINUCLEAR COMPLEXES - PREPARATION, STRUCTURE, MAGNETOCHEMISTRY, AND ELECTRON-SPIN-RESONANCE SPECTRA OF MN2(BIPHEN)2(BIPHENH)(BPY)2 AND MN2O2CL2(OAC)(BPY)2 (BIPHENH2 = 2,2'-BIPHENOL, BPY = 2,2'-BIPYRIDINE) [J].
BASHKIN, JS ;
SCHAKE, AR ;
VINCENT, JB ;
CHANG, HR ;
LI, QY ;
HUFFMAN, JC ;
CHRISTOU, G ;
HENDRICKSON, DN .
JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, 1988, (11) :700-702
[5]   EFFECTS OF A BRIDGING DICARBOXYLATE LIGAND ON THE SYNTHESIS AND PHYSICAL-PROPERTIES OF (MU-OXO)BIS(MU-CARBOXYLATO)DIIRON(III) COMPLEXES [J].
BEER, RH ;
TOLMAN, WB ;
BOTT, SG ;
LIPPARD, SJ .
INORGANIC CHEMISTRY, 1991, 30 (09) :2082-2092
[6]   LOW-TEMPERATURE MAGNETIZATION STUDY ON MANGANESE(III) PORPHYRINS [J].
BEHERE, DV ;
MARATHE, VR ;
MITRA, S .
CHEMICAL PHYSICS LETTERS, 1981, 81 (01) :57-61
[7]   MAGNETIC-SUSCEPTIBILITY STUDY AND GROUND-STATE ZERO-FIELD SPLITTING IN MANGANESE(III) PORPHYRINS [J].
BEHERE, DV ;
MITRA, S .
INORGANIC CHEMISTRY, 1980, 19 (04) :992-995
[8]   PSEUDOCATALASE FROM LACTOBACILLUS-PLANTARUM - EVIDENCE FOR A HOMOPENTAMERIC STRUCTURE CONTAINING 2 ATOMS OF MANGANESE PER SUBUNIT [J].
BEYER, WF ;
FRIDOVICH, I .
BIOCHEMISTRY, 1985, 24 (23) :6460-6467
[9]   TOWARDS FUNCTIONAL MODELS OF THE PHOTOSYNTHETIC WATER OXIDATION CENTER - SYNTHESIS AND STRUCTURE OF THE ASYMMETRIC COMPLEX [MN2O(O2CME)2(BPY)2(H2O)(S2O8)].H2O (BPY = 2,2'-BIPYRIDINE), CONTAINING COORDINATED H2O AND S2O8(2-) [J].
BLACKMAN, AG ;
HUFFMAN, JC ;
LOBKOVSKY, EB ;
CHRISTOU, G .
JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, 1991, (15) :989-991
[10]   BIOINORGANIC MODEL COMPLEXES FOR THE ACTIVE-SITE IN MANGANESE CONTAINING CATALASES - THE CRYSTAL-STRUCTURES OF [L2MNII2(MU-OH)(MU-O2CCH3)2](PF6).CH3OH AND [L'2MNIII2(MU-O)(MU-O2CCH3)2](I3)I.H2O [J].
BOSSEK, U ;
WIEGHARDT, K ;
NUBER, B ;
WEISS, J .
INORGANICA CHIMICA ACTA, 1989, 165 (01) :123-129