title: Synthesis, characterization, and structures of Mn(DMHP)3 x 12H2O and Mn(DMHP)2Cl x 0.5H2O.
abstract: This report describes the synthesis, characterization, and X-ray crystal structures of two Mn(III) complexes, Mn(DMHP)3 x 12H2O and Mn(DMHP)2Cl x 0.5H2O (DMHP = 1,2-dimethyl-3-hydroxy-4-pyridinone). Mn(DMHP)2Cl was prepared from the reaction of Mn(II) chloride with 2 equiv of DMHP under reflux in the presence of triethylamine. Mn(DMHP)3 was obtained by reacting Mn(II) acetate with 3 equiv of DMHP in the presence of sodium acetate. Mn(DMHP)3 could also be prepared by reacting Mn(OAc)3 x 2H2O with 3 equiv of DMHP in the presence of triethylamine. Both Mn(III) complexes have been characterized by elemental analysis, infrared spectroscopy, electronic paramagnetic resonance, electrospray ionization spectroscopy, electrochemical method, and X-ray crystallography. The X-ray crystal structure of Mn(DMHP)2Cl x 0.5H2O revealed a rare example of five-coordinated Mn(III) complexes with two bidentate ligands and a square pyramidal coordination geometry. Surprisingly, the average Mn-O (hydroxy) bond distance in Mn(DMHP)2Cl x 0.5H2O is approximately 0.025 A longer than that of the average Mn-O (carbonyl) bond, suggesting an extensive delocalization of electrons in the two pyridinone rings. The structure of Mn(DMHP)3 x 12H2O, a rare example of six-coordinate high-spin Mn(III) complexes without Jahn-Teller distortion, is isostructural to M(DMHP)3 x 12H2O (M = Al, Ga, Fe, and In). The electrochemical data for Mn(DMHP)3 suggests that the Mn(III) oxidation state is highly stabilized by three DMHP ligands. DMHP has the potential as a chelator for the removal of excess intracellular Mn and the treatment of chronic Mn toxicity.
authors.affiliation: Department of Industrial and Physical Pharmacy, School of Pharmacy, Purdue University, 575 Stadium Mall Drive, West Lafayette, Indiana 47907, USA.
authors.forename: Wen-Yuan
authors.initials: WY
authors.lastname: Hsieh
authors.forename: Shuang
authors.initials: S
authors.lastname: Liu
mesh_terms: D002614:Chelating Agents / Q000138:chemical synthesis*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D008345:Manganese / Q000737:chemistry*; D008968:Molecular Conformation; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D011728:Pyridones / Q000737:chemistry
chemical_list: D002614:Chelating Agents; D009942:Organometallic Compounds; D011728:Pyridones; D008345:Manganese