Synthesis, Structure, and Magnetic and Redox Properties of Linear Bis-Dinuclear Complexes Afforded by Schiff Base Ligands Containing Catecholate and Pyridine or Imidazole Groups
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- 作者：Sylvie Theil ; Ratnamala Yerande ; Rajeev Chikate ; Franç ; oise Dahan ; Azzedine Bousseksou ; Subhash Padhye ; and Jean-Pierre Tuchagues
- 刊名：Inorganic Chemistry
- 出版年：1997
- 出版时间：December 31, 1997
- 年：1997
- 卷：36
- 期：27
- 页码：6279 - 6286
- 全文大小：177K
- 年卷期：v.36,no.27(December 31, 1997)
- ISSN：1520-510X
文摘
Three complexes,[MnII2L1(CH3CO2)2(CH3OH)]2(1),(MnII2L2(CH3CO2)2(CH3OH))2 (2), and(MnII2HL3(CH3CO2)2(CH3OH))2(3), wherein H2L1 =3-[(((2'-pyridyl)methyl)imino)methyl]benzene-1,2-diol,H2L2 = 3-[((2-(2'-pyridyl)ethyl)imino)methyl]benzene-1,2-diol,and H3L3 =3-[((2-(4'-imidazolyl)ethyl)imino)methyl]benzene-1,2-diol, have been synthesized and studied. 1crystallizes in the monoclinic system, space groupP21/c, Z =2,a = 11.396(1) Å, b = 18.583(2) Å,c = 9.888(1) Å, and 
= 103.51(1)
.The structure was solved by directmethods and refined to conventional agreement indices R =0.028 and Rw = 0.029. The molecularstructure of1 consists of discrete[MnII2L1(CH3CO2)2(CH3OH)]2molecules. 1 is a chainlike bis-dinuclear Mn(II)complexinvolving an unprecedented arrangement of pentacoordinated(N2O3) and hexacoordinated (O6)manganese ionsas the outer and inner pairs of metal centers, respectively. Thedifferent Mn···Mn distances result fromsignificantdifferences in bridging moieties, two catecholato bridges for theshortest distance between inner manganese ions,and one catecholato and two acetato bridges for the longer distancesbetween inner and outer manganese ions.The symmetry of the N2O3 donor set aroundthe outer Mn(1) is close to a trigonal bipyramid while theO6 ligandenvironment of the inner Mn(2) can be described as a rhombicallydistorted octahedron. The synthesis, IR, EPR,and magnetic susceptibility of 1-3 suggest asimilar bis-dinuclear structure for all three complexes.Variable-temperature magnetic susceptibility studies establish the presence ofantiferromagnetic exchange interactionsbetween Mn(II) centers of 1-3 withpredominence of the interactions between inner and outer metal ions(-3.4to -5 cm-1) over the interaction betweeninner manganese ions (-0.5 to 0.5 cm-1).EPR spectroscopy indicatesthat the bis-dinuclear arrangement of complexes1-3 is retained in aprotic solvents. Asshown by EPR, O2oxidation leads to the release of the constitutive Mn(II)dinuclear units, prior to formation of mononuclearMn(II)and finally Mn(III) species. Observation of two irreversibletwo-electron oxidation waves in the CV profiles of1-3 is consistent with a similar splitting ofthe bis-dinuclear complex molecules induced byelectrochemicaloxidation. These studies suggest that complexes resulting from thereaction of manganese with the fully oxidizedform of such electroactive ligands may afford interesting new higheroxidation-state polynuclear Mn species.
= 103.51(1).The structure was solved by directmethods and refined to conventional agreement indices R =0.028 and Rw = 0.029. The molecularstructure of1 consists of discrete[MnII2L1(CH3CO2)2(CH3OH)]2molecules. 1 is a chainlike bis-dinuclear Mn(II)complexinvolving an unprecedented arrangement of pentacoordinated(N2O3) and hexacoordinated (O6)manganese ionsas the outer and inner pairs of metal centers, respectively. Thedifferent Mn···Mn distances result fromsignificantdifferences in bridging moieties, two catecholato bridges for theshortest distance between inner manganese ions,and one catecholato and two acetato bridges for the longer distancesbetween inner and outer manganese ions.The symmetry of the N2O3 donor set aroundthe outer Mn(1) is close to a trigonal bipyramid while theO6 ligandenvironment of the inner Mn(2) can be described as a rhombicallydistorted octahedron. The synthesis, IR, EPR,and magnetic susceptibility of 1-3 suggest asimilar bis-dinuclear structure for all three complexes.Variable-temperature magnetic susceptibility studies establish the presence ofantiferromagnetic exchange interactionsbetween Mn(II) centers of 1-3 withpredominence of the interactions between inner and outer metal ions(-3.4to -5 cm-1) over the interaction betweeninner manganese ions (-0.5 to 0.5 cm-1).EPR spectroscopy indicatesthat the bis-dinuclear arrangement of complexes1-3 is retained in aprotic solvents. Asshown by EPR, O2oxidation leads to the release of the constitutive Mn(II)dinuclear units, prior to formation of mononuclearMn(II)and finally Mn(III) species. Observation of two irreversibletwo-electron oxidation waves in the CV profiles of1-3 is consistent with a similar splitting ofthe bis-dinuclear complex molecules induced byelectrochemicaloxidation. These studies suggest that complexes resulting from thereaction of manganese with the fully oxidizedform of such electroactive ligands may afford interesting new higheroxidation-state polynuclear Mn species.