A new class of DyIII-SIMs associated with a guanidine-based ligand

Abstract

A family of four mononuclear Dy^III complexes of the guanidine-based ligand L [L = tris(2-hydroxybenzylidene)triaminoguanidine] with formulas [DyLCl₂(DMF)₂]·DMF·CH₃OH (1), [DyL₂(CH₃OH)₂]Br·H₂O·3CH₃OH (2), [DyL₂(H₂O)₂]SCN·3H₂O·CH₃OH (3) and [DyL₂(CH₃OH)₂]SCN·CH₃CN·CH₃OH (4) were successfully prepared by varying reaction conditions. Complex 1 is seven-coordinate, with three N₂O from ligand L along with two equatorially trapped DMF molecules and two axial Cl⁻ anions, adopting pentagonal bipyramidal D_5h symmetry. Complexes 2–4 have somewhat similar structures with six donor N₄O₂ sites from two ligands and two O from corresponding solvent molecules, featuring a N₄O₄ octa-coordinate environment with triangular dodecahedron D_2d symmetry. Magnetic investigations indicated that complex 1 did not demonstrate single-molecule magnetic behavior, while complexes 2–4 were single-ion magnets (SIMs) under zero applied DC field with the effective energy barriers (U_eff) of 207.3 (2), 222.5 (3) and 311.7 K (4), respectively. The different types of coordinated solvent molecules and counter anions caused changes in intermolecular interactions and coordination geometries that severely affected their magnetic dynamics. The magnetic behaviors of these complexes were investigated through complete-active space self-consistent field (CASSCF) calculations with the inclusion of spin–orbit effects. Calculations revealed that the measured differences in magnetic behaviors originated mainly from intermolecular and crystal-packing effects as isolated complexes 1–4 have almost identical electronic and magnetic properties.