Strong intramolecular ferromagnetic couplings in nickel(II) and copper(II) complexes chelated with tert-butyl 5-methoxy-2-pyridyl nitroxide
摘要:
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/k(B) = +288(5) and +178(3) K for [M(meopyNO)(2)(H2O)(2)]center dot(ClO4)(2) (M = Ni and Cu, respectively), where the spin Hamiltonian is defined as H = -2J(S-1 center dot S-2 + S-2 center dot S-3). From the crystallographic analysis, the torsion angles (phi) around M-O-N-C-2py were 4.2(3)degrees and 6.87(19)degrees, respectively, being so small that the orthogonality between the magnetic radical pi* and the metal d sigma orbitals would be guaranteed. (C) 2008 Elsevier Ltd. All rights reserved.