Synthesis, crystal structures and magnetic properties of six coordination compounds constructed with pyridine iminomethyl–TEMPO radicals and [M(hfac)2] (M = CuII and MnII)

Abstract

In the present work, we describe the synthesis, crystal structures and magnetic properties of six coordination compounds obtained by assembling pyridine iminomethyl with a TEMPO moiety, R-[(2,2,6,6-tetramethyl-4-piperidyl-l-oxy)iminomethyl]pyridine radical (R = 3, 1 and R = 2, 2), and M^II(hfac)₂ building blocks (where M = Cu and Mn and hfac = hexafluoroacetylacetonate). The crystal structures of the coordination compounds revealed the usefulness of the functionalized radical to provide discrete or extended architectures. In the copper and manganese compounds 3 and 4, the ligand is coordinated through the oxygen atom of NO˙ and the N atom of the pyridine linkage to the metal, and the metals adopt a distorted octahedral geometry, leading to one dimensional zigzag chain systems. For the copper and manganese complexes 5 and 6, the pyridine nitrogen atoms are involved in coordination to the metal, leading to discrete mononuclear complexes. For the copper and manganese complexes 7 and 8, the pyridine nitrogen atom and iminomethyl nitrogen atom are both involved in coordination to the metal, leading to molecular systems. The magnetic susceptibility studies of the copper coordination compounds 3 and 7 show ferromagnetic interactions, and for 5, antiferromagnetic interactions involving the metal ion and the organic radical are evident. And the magnetic behavior of the manganese coordination compounds (4, 6, and 8) shows overall antiferromagnetic interactions.