Transition Metal Complexes Containing an Optically Active Macrocyclic Ligand. Manganese(III), Nickel(II), and Copper(II)

The synthetic macrocyclic ligand rac-5,7,7,12,12,14-hexamethy 1-1,4,8,11 -tetraazacyclotetradecane (rac-5,14-[14]aneN₄) has been resolved via its nickel(ll) complex. The optically active ligand has been removed from Ni(II) and transferred to copper(II) and manganese(III). A circular dichroism analysis of (+)[Mn((–)5,14-[14]aneN₄)X₂]PF₆, where X^- is Cl^- or Br^-, has been very useful in interpreting the electronic spectrum of this tetragonally distorted high-spin d⁴ system. The macrocyclic crystal field (10Dq) for Mn(III) as measured by the position of the ⁵B_1g → ⁵B_2g electronic transition was found to be about 23 kK.