Influence of lattice water molecules on the magnetization dynamics of binuclear dysprosium(III) compounds: insights from magnetic and calculations.

Lattice water effects on the structures and magnetic properties of single-molecule magnets (SMMs) have attracted considerable attention. Herein, we have successfully synthesized two centrosymmetric binuclear compounds [Dy(2,3'-ppcad)(CHO)(HO)] (1) and [Dy(2,3'-ppcad)(CHO)(HO)]·6HO (2) (2,3'-Hppcad = -(2-pyrazinyl)-3-pyridinecarboxamidrazone) by elaborately varying the amount of the base (LiOH·HO). Through isothermal titration calorimetry (ITC), the interactions between Dy ions and 2,3'-Hppcad with different amounts of LiOH·HO were monitored in real time. Magnetic studies reveal that two compounds exhibit the typical zero-field single-molecule magnet behavior with different energy barrier () values of 103.43 K for 1 and 386.48 K for 2, wherein the SMM performance for 2 stands out among the reported nine-coordinated Dy-SMMs systems with spherical capped square antiprism () geometries. To rationalize the observed difference in the magnetic properties of 1 and 2, calculations have been performed. The introduction of lattice water molecules leads to differences in the values observed for 1 and 2. The stronger antiferromagnetic Dy-Dy couplings in 2 were presented and the fast quantum tunneling of magnetization was further suppressed, thereby achieving a higher value. This work provides an effective strategy to enhance the SMM performance, and combines with calculations to explain how lattice water molecules can affect the magnetic interactions of Dy-SMMs.