Structural and Magnetic Studies on Nickel(II) and Cobalt(II) Complexes with Polychlorinated Diphenyl(4-pyridyl)methyl Radical Ligands

New magnetic metal complexes with organic radical ligands, [M(hfac)(2)(PyBTM)(2)] (M = Ni-II, Co-II; hfac = hexafluoroacetylacetonato, PyBTM = (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical), were prepared and their crystal structures, magnetic properties, and electronic structures were investigated. Metal ions in [M(hfac)(2)(PyBTM)(2)] constructed distorted octahedral coordination geometry, where the two PyBTM molecules ligated in the trans configuration. Magnetic investigation using a SQUID magnetometer revealed that chi T increased with decreasing temperature from 300 K in the two complexes, indicating an efficient intramolecular ferromagnetic exchange interaction taking place between the spins on PyBTM and M with J/k(B) of 21.8 K and 11.8 K for [Ni-II(hfac)(2)(PyBTM)(2)] and [Co-II(hfac)(2)(PyBTM)(2)]. The intramolecular ferromagnetic couplings in the two complexes could be explained by density functional theory calculations, and would be attributed to a nearly orthogonal relationship between the spin orbitals on PyBTM and the metal ions. These results demonstrate that pyridyl-containing triarylmethyl radicals are key building blocks for magnetic molecular materials with controllable/predictable magnetic interactions.

Automated summary

New magnetic metal complexes with organic radical ligands were synthesized and investigated for their crystal structures, magnetic properties, and electronic structures. The study demonstrated efficient intramolecular ferromagnetic exchange interactions in the complexes, which could be explained by density functional theory calculations.