Pyrazinephosphonate-Bridged Dysprosium(III) Cyclic Coordination Clusters

Abstract

Noncentered paramagnetic metal rings are widely regarded as ideal prototypes for exploring one-dimensional magnetic systems. Herein, we report the synthesis of three giant hollow hexagons, Dy6, Dy24a, and Dy24b. Dy6 hexagon is assembled from a single pyrazinyl hydrazone ligand, without ring-expanding agents. The coalescence of the pyrazinephosphonate and C2-symmetric di-o-vanilloyl hydrazones enables access to two hexagonal nuts, Dy24a and Dy24b, with large cavities, in which six hydrazone ligands capture 18 DyIII ions to construct the outer hexagons, while the pyrazinephosphonate ring-expanding agents fix the inner hexagons, enabling high metal center density. Replacing the key pyridyl group of the hydrazone ligand with a pyrazinyl group transforms Dy24a into Dy24b. The structural changes substantially influence the zero-field single-molecule magnet behavior. This work demonstrates the feasibility of building giant noncentered paramagnetic metal rings and precisely tuning their size and shape, thereby paving new avenues for the design and synthesis of advanced materials.