Precursor molecules for cobalt(II) single molecule magnets – Synthesis and magnetic properties

Molecular magnetic materials based on 1,2-diamidobenzenes are well known and have been intensively studied both experimentally and computationally. They feature interesting magnetic properties as well as redox activity. In this work, we present the synthesis and investigation of potent synthons for constructing discrete metal-organic architectures featuring 1,2-diamidobenzene-coordinated metal centers. The synthons feature weakly bound dimethoxyethane (DME) ligands in addition to the 1,2-diamidobenzene. We characterize these complexes and investigate their magnetic properties by means of static and dynamic magnetometry and high-field electron paramagnetic resonance (HFEPR). Interestingly, the magnetic and magnetic resonance data strongly suggest a dimeric formulation of these complexes, viz. [M(II)(bmsab)DME]2 (bmsab = 1,2-bis(methanesulfonamido)benzene) with M = Co, Ni, Zn. This formulation is supported by ab initio calculations. A large negative D-value of −60 cm-1 was found for the Co(II) synthon and an equally large negative D of -50 cm-1 for the Ni(II) synthon. For Co(II), this D-value is in line to what was found for the known bis-diamidobenzene complexes of this ion. In contrast, the negative D-value for the nickel(II) complex is inexpected, which we explain in terms of increased effective coordination numbers. In contrast to the homoleptic Co(II) 1,2-diamidobenzene complex, the heteroleptic Co(II) complex presented here does not feature slow relaxation of the magnetization.