Over the last few years, polymetallic coordination compounds have drawn much interest in terms of their architectural beauty, symmetry and high nuclearity. Specifically, molecular wheels are of interest in terms of their single type of exchange interaction that helps in understanding one-dimensional magnetism. Similarly, metal-centered wheels (disks) are also of interest for their high symmetry. The paramagnetic nature of iron and manganese in their common oxidation states often leads to polynuclear clusters with interesting magnetic properties such as a high ground state spin. This spin (S), coupled with significant magnetoanisotropy of the easy-axis type (negative zero-field splitting parameter, D) can result in a single-molecule magnet (SMM). In the present work, potentially new synthetic methodologies to high nuclearity manganese and iron clusters have been investigated employing three alcohol-based chelates: a tetradentate (O,O,O,O) chelate (tegH2), and two tridentate (O,O,O and O,O,N) chelates (degH2 and dapdH2). These have given Fe7, Fe8 and Mn7 molecular wheel compounds, of which the Fe7 and Mn7 clusters are disks whose cores are without exact precedent in the literature. The ground state spins of the compounds have been determined, and the values rationalized on the basis of the antiferromagnetic coupling among the metal ions and the degree of spin frustration present. Detailed AC studies on Mn7 reveal frequency-dependent signals indicating the slow magnetization relaxation of an SMM.
- Single-molecule magnent