Strong intramolecular ferromagnetic couplings in nickel(II) and copper(II) complexes chelated with tert-butyl 5-methoxy-2-pyridyl nitroxide

We successfully isolated a new paramagnetic bidentate ligand tert-butyl 5-methoxy-2-pyridyl nitroxide (meopyNO). Complexation of nickel(II) and copper(II) perchlorates with meopyNO gave the corresponding ML2-type bis-chelated compounds. The magnetic studies showed that they were ground high-spin molecules with 2J/kB = +288(5) and +178(3) K for [M(meopyNO)2(H2O)2] · (ClO4)2 (M = Ni and Cu, respectively), where the spin Hamiltonian is defined as H = −2J(S1 · S2 + S2 · S3). From the crystallographic analysis, the torsion angles (ϕ) around M–O–N–C2py were 4.2(3)° and 6.87(19)°, respectively, being so small that the orthogonality between the magnetic radical π∗ and the metal dσ orbitals would be guaranteed.

Graphical abstractNew chelated compounds [MII(meopyNO)2(H2O)2] · (ClO4)2 (M = Ni and Cu) were characterized, where meopyNO stands for tert-butyl 5-methoxy-2-pyridyl nitroxide. The magnetic studies showed that they were ground high-spin molecules with 2J/kB = +288(5) and +178(3) K, respectively.Figure optionsDownload full-size imageDownload as PowerPoint slide