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

The reaction of the N ‐(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 ] · 10H 2 O · 5MeOH ( 1 ) and (HNEt 3 )[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 complex 1 , and a helical chiral chain for compound 2 . 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 complex 1 a single‐molecule magnet behavior detectable under static field, while antiferromagnetic interactions dominate the behavior of 2 .