High-spin chloro mononuclear MnIII complexes: a multifrequency high-field EPR study

Chemphyschem. 2005 Mar;6(3):541-6. doi: 10.1002/cphc.200400484.

Abstract

The isolation, structural characterization, and electronic properties of two six-coordinated chloromanganese (III) complexes, [Mn(terpy)(Cl)3] (1) and [Mn(Phterpy)(Cl)3] (2), are reported (terpy = 2,2':6'2"-terpyridine, Phterpy = 4'-phenyl-2,2':6',2"-terpyridine). These complexes complement a series of mononuclear azide and fluoride Mn(lll) complexes synthesized with neutral N-tridentate ligands, [Mn(L)(X)3] (X = F- or N3 and L = terpy or bpea [N,N-bis(2-pyridylmethyl)-ethylamine)], previously described. Similar to these previous complexes, 1 and 2 exhibit a Jahn-Teller distortion of the octahedron, characteristic of a high-spin Mn(III) complex (S = 2). The analysis of the crystallographic data shows that, in both cases, the manganese ion lies in the center of a distorted octahedron characterized by an elongation along the tetragonal axis. Their electronic properties were investigated by multifrequency EPR (190-475 GHz) performed in the solid state at different temperatures (5-15 K). This study confirms our previous results and further shows that: i) the sign of D is correlated with the nature of the tetragonal distortion; ii) the magnitude of D is not sensitive to the nature of the anions in our series of rhombic complexes, contrary to the porphyrinic systems; iii) the [E/D] values (0.124 for 1 and 0.085 for 2) are smaller compared to those found for the [Mn(L)(X)3] complexes (in the range of 0.146 to 0.234); and iv) the E term increases when the ligand-field strength of the equatorial ligands decreases.

MeSH terms

  • Anions
  • Biophysics / methods
  • Chemical Phenomena
  • Chemistry, Physical
  • Chlorine / chemistry*
  • Crystallography, X-Ray
  • Electron Spin Resonance Spectroscopy / methods*
  • Electrons
  • Fluorides / chemistry
  • Hydrogen Bonding
  • Ions
  • Ligands
  • Manganese / chemistry*
  • Manganese Compounds / chemistry
  • Models, Chemical
  • Models, Molecular
  • Molecular Conformation
  • Molecular Structure
  • Temperature

Substances

  • Anions
  • Ions
  • Ligands
  • Manganese Compounds
  • Manganese
  • Chlorine
  • Fluorides