A novel μ-oxo- and μ-carboxylato-bridged dimanganese(III) complex, [Mn2O(TMIMA)2(OAc)](ClO4)3·2CH3CN (1), where TMIMA is tris(1-methylimidazol-2-yl)methyl)amine and OAc is the acetate ion, has been synthesized and characterized by X-ray crystallography, visible spectroscopy, variable-temperature magnetism, and electrochemical methods. X-ray crystallographic parameters are as follows for compound 1: C36H51N16O15Cl3Mn2, 1164.14 g mol−1, triclinic space group (P1̄), a = 14.909(3) Å, b = 15.544(3) Å, c = 12.530(3) Å, α = 104.74(1)°, β = 112.98(1)°, γ = 87.46(2)°, V = 2580.5 Å3, Z = 2; 5334 independent reflections with I > 3σ|I| to max 2θ of 45°, R = 0.045, and Rw = 0.049. The structure consists of a discrete μ-oxo- and μ-acetato-bridged dimanganese(III) cation and the three perchlorate counterions as well as two acetonitrile solvate molecules. The two acetonitrile solvate molecules and one perchlorate anion were found to be ordered, while the other perchlorate ions were found to be disordered. The coordination environment around each MnIII ion is best described as a distorted octahedron as expected for Jahn-Teller d4 metal ions. Imidazole donors bond trans to the bridging oxo ligand and have short Mn-N bond lengths. The remaining imidazoles and amine ligands are bonded cis to the oxo bridge. The electronic spectral properties of the complex are consistent with other high-spin MnIII complexes. Variable-temperature magnetic susceptibility data indicate that the two MnIII ions are ferromagnetically coupled. Diagonalization of the full Hamiltonian matrix including zero-field interactions [formula omitted] and isotropic Zeeman interactions of the MnIII ions gives g = 2.05, D1 = D2 = 0.40 cm−1, and J = 1.33 cm−1. Compound 1 displays two one-electron redox processes in acetonitrile at a glassy-carbon electrode corresponding to the MnIII2 ↔ MnIV2 interconversion. The first step is electrochemically irreversible, while the second step is quasireversible (ΔE = 70 mV).
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry