Magnetostructural examination of Mn(III) complexes [Mn(cyclam)X2]+ with strong axial ligands

Three novel Mn(III) cyclam complexes, [Mn(cyclam)(NCBH3)2](CF3SO3), [Mn(cyclam)(NCBPh3)2](CF3SO3), and [Mn(cyclam)(NCSe)2](CF3SO3) · H2O, have been synthesized. These complexes are in the high-spin state between 4 and 350 K, and show large zero-field splittings. The crystal structure of [Mn(cyclam)(NCBH3)2](CF3SO3) was determined where the axial elongation of Mn–N bonds is found to be the largest among the homologue complexes. Ligand field in the [Mn(cyclam)X2]+ complex series was examined by angular-overlap model calculation.

Graphical abstractThree novel Mn(III) complexes, trans-[Mn(cyclam)X2](CF3SO3) (X− = NCBH3−, NCBPh3−, NCSe−), were synthesized. Magnetic measurements showed they are in high-spin states with S = 2. Their large uniaxial zero-field splittings suggested that the axial ligand field strength in these complexes is not far from the spin-crossover boundary according to the AOM calculations.Figure optionsDownload full-size imageDownload as PowerPoint slide