69879-57-8Relevant academic research and scientific papers
Manganese(II) complexes of polydentate Schiff bases. 1. Synthesis, characterization, magnetic properties, and molecular structure
Mabad, Bouchra,Cassoux, Patrick,Tuchagues, Jean-Pierre,Hendrickson, David N.
, p. 1420 - 1431 (2008/10/08)
The synthesis, infrared spectra, EPR, and variable-temperature magnetic susceptibility of 13 manganese(II) complexes with Schiff base ligands are described. These potentially penta- or hexadentate Schiff base ligands include N2O3, N3O2, and N4O2 donor sets and result from the condensation of salicylaldehyde, or 5-nitrosalicylaldehyde, with diaminopropanol or tri- or tetraamines. The crystal molecular structure of MnII[5-NO2-sal-N(1,5,9,13)]·0.65C2H 4Cl2 has been established by X-ray diffraction methods. This complex crystallizes in the orthorhombic space group D2h6-Pnna in a cell of dimensions a = 20.732 (4) A?, b = 16.906 (2) A?, and c = 15.861 (3) A?, with Z = 8. The structure was solved by the heavy-atom method and refined by a full-matrix least-squares technique to conventional agreement indices R = 0.038 and Rw = 0.041 with 2208 unique reflections for which Fo2 > σ(Fo2). The results obtained provide evidence that all manganese(II) complexes described here are high-spin penta- or hexacoordinated species. Minor changes in the design of the polydentate ligands result in different architectural arrangements of the corresponding complexes: MnII(saldpt) and MnII(5-NO2-saldpt), characterized by the N3O2 ligand donor set with propylene units bridging the three N atoms, are monomeric. Also monomeric are MnII(salaep)2 and MnII(5-NO2-salaep)2, both of which have two tridentate N2O ligands, and MnII[sal-N(1,4,7,10)], MnII[5-NO2-sal-N(1,4,7,10)], MnII[sal-N(1,5,8,12)], MnII[5-NO2-sal-N(1,5,8,12)], MnII[sal-N-(1,5,9,13)], and MnII[5-NO2-sal-N(1,5,9,13)], which incorporate hexadentate N4O2 ligands. MnII(saldien), which has a N3O2 donor set ligand with ethylene bridges between the three nitrogen atoms, is a dimer. MnII(salprenOH), which has a N2O3 donor set ligand with an alcoholic function between the two imine nitrogen atoms, exhibits a structure with extended intermolecular magnetic exchange interactions in the solid state. MnII(5-NO2-saldien) exhibits weak extended intermolecular interactions in the solid state and is a dimer when dissolved in noncoordinating solvents. IR and EPR data indicate the presence of cis and trans isomers with respect to the phenolic oxygen atoms for all monomeric complexes. The dimeric complexes behave as spectral analogues for the active site of the photosynthetic water-splitting enzyme.
