Modulating the Magnetic Interaction in New Triple-Decker Dysprosium(III) Single-Molecule Magnets

A new type of dinuclear dysprosium(III) complex based on phthalocyanine and salicylaldehyde derivatives (HL-R), [Dy-2(Pc)(2)(L-R)(2)(H2O)]center dot 2THF (R = OCH3 (1), OC2H5 (2); H2Pc = phthalocyanine; HL-OCH3 = 2-hydroxy-3-methoxybenzaldehyde; HL-OC2H5 = 3-ethoxy2-hydroxybenzaldehyde), was successfully synthesized and structurally characterized. Complex 1 features a sandwich type triple-decker structure, where two coplanar L-OCH3 ligands lie in the middle layer shared by two eight-coordinated Dy-III ions and two Pc ligands are located in the outer layer. In 2, the introduction of an ethoxy group generates a non coordination mode for the O-alkoxy atom. Magnetic studies indicate that complex 1 behaves as a zero-field single-molecule magnet with a higher energy barrier, while 2 exhibits a fast tunneling relaxation process. Theoretical calculations revealed that changes in the ligand field environment around Dy-III ions can significantly affect the arrangement of the main magnetic axes and further result in distinct magnetic interactions as well as different relaxation behaviors.