title: Structural and electronic dependence of the single-molecule-magnet behavior of dysprosium(III) complexes.
abstract: We investigate and compare the magnetic properties of two isostructural Dy(III)-containing complexes. The Dy(III) ions are chelated by hexadentate ligands and possess two apical bidendate nitrate anions. In dysprosium(III) N,N'-bis(imine-2-yl)methylene-1,8-diamino-3,6-dioxaoctane (1), the ligand's donor atoms are two alkoxo, two pyridine, and two imine nitrogen atoms. Dysprosium(III) N,N'-bis(amine-2-yl)methylene-1,8-diamino-3,6-dioxaoctane (2) is identical with 1 except for one modification: the two imine groups have been replaced by amine groups. This change has a minute effect on the structure and a larger effect the magnetic behavior. The two complexes possess slow relaxation of the magnetization in the presence of an applied field of 1000 Oe but with a larger barrier for reorientation of the magnetization for 1 (Ueff/kB = 50 K) than for 2 (Ueff/kB = 34 K). First-principles calculations using the spin-orbit complete active-space self-consistent-field method were performed and allowed to fit the experimental magnetization data. The calculations gave the energy spectrum of the 2J + 1 sublevels issued from the J = 15/2 free-ion ground state. The lowest-lying sublevels were found to have a large contribution of MJ = ±15/2 for 1, while for 2, MJ = ±13/2 was dominant. The observed differences were attributed to a synergistic effect between the electron density of the ligand and the small structural changes provoked by a slight alteration of the coordination environment. It was observed that the stronger ligand field (imine) resulted in complex 1 with a larger energy barrier for reorientation of the magnetization than 2.
authors.affiliation: ICMMO, Université de Paris Sud , 15 rue Georges Clemenceau, 91405 Orsay, France.
authors.forename: Victoria E
authors.initials: VE
authors.lastname: Campbell
authors.forename: Hélène
authors.initials: H
authors.lastname: Bolvin
authors.forename: Eric
authors.initials: E
authors.lastname: Rivière
authors.forename: Regis
authors.initials: R
authors.lastname: Guillot
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wernsdorfer
authors.forename: Talal
authors.initials: T
authors.lastname: Mallah