MAGNETIC-PROPERTIES AND ELECTRONIC-STRUCTURE OF 5-COORDINATE AND 6-COORDINATE MANGANESE(II)2,6-BIS(BENZIMIDAZOL-2-YL)PYRIDINE COMPLEXES

Two manganese(II) complexes with the terdentate ligand 2,6-bis(benzimi dazol-2-yl)pyridine, namely [Mn(bzimpy)(2)(ClO4)(2)], 1 and [Mn(bzimpy )Cl-2]. 0.5MeOH, 2 have been investigated by magnetic susceptibility m easurements in the temperature range 18 to 300 K. Electron spin resona nce has been measured in solid state and frozen solution at 77 K. Para meters for the magnetic contributions to the Hamiltonian obtained by t hese techniques confirm axial magnetic anisotropy. ACS data are: g(av) = 1.92 +/- 0.04, \D/hc\ = 0.9 +/- 1.3 cm(-1) and g(av) = 1.89, \D/hc\ = 1.4 cm(-1) for 1 and 2, respectively. The three found ESR resonance s correspond to g(eff)(1) = 1.99, g(eff)(2) = 3.3 and g(eff)(3) = 4.3. The highest field resonance exhibits a hyperfine sextet splitting of \A(av)/hc\ = 92 x 10(-4) cm(-1) for both complexes. Well resolved forb idden transitions allow for an estimation of the zero-field splitting parameter being D/hc = -0.09 and 0.13 cm(-1) for the two complexes, re spectively. Ab initio MO-LCAO-SCF calculations on a double-zeta basis set indicate that complex 2 should be more stable than 1. The calculat ions also yielded information on electronic structure, bond-strengths and charge distribution within the complexes.