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Capping N-Donor Ligands Modulate the Magnetic Dynamics of ß-Diketonate-DyIII Single-Ion Magnets with D4d Symmetry.

Chemistry; 2018 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-30525257
A family of four mononuclear ß-diketonate-DyIII complexes, with formulas Dy(tmhd)3(Br2-bpy) (1), Dy(tmhd)3(Br-bpy) (2), Dy(tmhd)3(dppz) (3) and Dy(tmhd)3(mcdpq) (4) (tmhd = 2,2,6,6-tetramethyl-3,5-heptanedione, Br2-bpy = 5,5'-dibromo-2,2'-bipyridine, Br-bpy = 5-bromo-2,2'-bipyridine, dppz = dipyrido [3,2-a:2',3'-c]phenazine and mcdpq = 2-methoxyl-3-cyano-dipyrido-[3,2-f:2,3'-h] quinoxaline), have been prepared by modifying the capping N-donor coligands. DyIII centers in these complexes feature a N2O6 octa-coordinated environment with a distorted square antiprismatic D4d symmetry. Magnetic investigations evidence a SIM behavior in all complexes with the energy barriers (Ueff) of 42.10 K (1), 61.47 K, (2), 77.53 K (3) and 2.51 K (4) in the absence of static field, as well as 206.03 K (1), 224.13 K (2), 247.76 K (3) and 49.70 K (4) under applied dc fields (Hdc = 1500 Oe for 1 and 2, and 1200 Oe for 3 and 4). The different nature of the N-donor ligand induces changes on both the coordination geometry and their intermolecular interactions, which severely impact on their magnetic dynamics. The disparities in their magnetic behaviors and the uniaxial anisotropies are also explained and substantiated by theoretical calculations.