A Bis-Polydentate Oxamate-Based Achiral Ligand That Can Stabilize a Macrocyclic Mixed Valence Compound or Induce a 1D Helical Chain

The reaction of theN-(2-hydroxyphenyl)oxamate ligand (ohpma) has been investigated with cobalt(II) and copper(II) ions. It has led to two coordination compounds, (TMA)(3)[{Co-III(ohpma)(2)Co-II(MeOH)(2)}(3)]center dot 10H(2)O center dot 5MeOH (1) and (HNEt3)[Cu(ohpma)] (2). Both compounds have been characterized by single-crystal X-ray diffraction and magnetometry. The X-ray diffraction studies have revealed atypical structures that are not commonly observed in oxamate coordination chemistry with a macrocyclic arrangement for the mixed-valence cobalt-based complex1, and a helical chiral chain for compound2. In the latter, the bis-polydentate nature of the (ohpma)(3-)ligand with distinct tridentate and bidentate coordination sites creates a chirogenic center on the copper ion. The investigation of the magnetic properties shows for complex1a single-molecule magnet behavior detectable under static field, while antiferromagnetic interactions dominate the behavior of2.