Structure and magnetic properties of copper(II) carboxylate with pyridyl-substituted nitronyl nitroxides

Abstract

The synthesis, crystal structure and magnetic properties of four new copper(II) carboxylate complexes with pyridyl-substituted nitronyl nitroxides, [Cu 2(μ-ClCH 2CO 2) 2(ClCH 2CO 2) 2(NITpPy) 2(H 2O) 2]CH 3OH ( 1), [Cu(Cl 2CHCO 2) 2(NITpPy) 2(H 2O)] ( 2), [Cu(Cl 3CCO 2) 2(NITpPy) 2(H 2O)] ( 3) and [Cu(Cl 2CHCO 2) 2(NITmPy) 2(H 2O) 2] ( 4) (NITpPy=4,4,5,5-tetramethyl-2-(4-pyridyl)-2-imidazoline- N 1-oxy N 3-oxide, NITmPy=4,4,5,5-tetramethyl-2-(3-pyridyl)-2-imidazoline- N 1-oxy N 3-oxide) are reported. Complex 1 has a dimeric structure where two copper ions are doubly bridged by four oxygen atoms from two μ-ClCH 2CO 2 − ions. Complexes 2 and 3 are mononuclear, the copper(II) ion has five coordination with square-pyramidal symmetry. In complex 4, the copper(II) ion has distorted-octahedral six coordination. Temperature dependence studies of the χ m T values of complexes 1– 4 revealed that 1 exhibits a strong intramolecular metal–metal antiferromagnetic interaction and a weak intramolecular metal–nitroxide antiferromagnetic coupling, 2 and 3 exhibit a weak intramolecular metal–nitroxide antiferromagnetic coupling, while 4 possesses weak ferromagnetic exchange interactions between metal and NITmPy. A simple spin polarization model has been used to justify the observed magnetic exchange interactions between Cu(II) and radical ligands.