Influence of synthesis conditions on the preparation of mononuclear Dy(III) compounds based on β-diketone ligands: Synthesis, structure, magnetic behavior and theoretical analysis

Two mononuclear Dy(III) compounds, [Dy(fbta)3(HCOOH)2] (1) and [Dy(fbta)4]∙C5H6N (2) (fbta ​= ​3-(4-Fluorobenzoyl)-1,1,1-trifluoroacetone), were synthesized based on different pH control reagents including HCOOH and C5H5N. Dy(III) ions in compounds 1 and 2 belong to square antiprism (D4d) configurations with DyO8 coordination environments. Two coordinated carboxyl oxygen atoms of two different HCOOH molecules in 1 are replaced by two coordinated oxygen atoms of one β-diketone anion ligand in 2. One protonated C5H6N guest as a monovalent cation is found to reside in 2, resulting in charge balance. The different synthetic conditions have an important in determining the final structures and magnetic behaviors in 1 and 2. Compound 1 displays SMM behavior under zero dc field, while compound 2 shows neither peak nor frequency dependence at zero dc field. The efficient ON/OFF switching of SMM behavior was interpreted by the theoretical calculations of quantum tunneling of magnetization (QTM) time.