Slow Magnetic Relaxation in Condensed versus Dispersed Dysprosium(III) Mononuclear Complexes

Abstract

Reaction of the ligands 4,5-bis(propylthio)tetrathiafulvalene-2-(2-pyridyl)benzimidazole (L(1)) and 4,5-bis(propylthio)tetrathiafulvalene-2-(2-pyridyl)-3-(2-pyridinylmethyl)benzimidazole (L(2)) with Dy(hfac)3⋅2 H2O (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate) gave mononuclear complexes [Dy(hfac)3(L(1))] (1) and [Dy(hfac)3(L(2))] (2). In both compounds the Dy(III) ion is surrounded by six oxygen and two nitrogen atoms. Complex 1 displays single-ion magnet (SIM) behaviour only in solution (Δ=12(1) K and τ0 =1.9(4)×10(-6) s), while complex 2 is a SIM in both solution (Δ=15(2) K and τ0 =1.5(3)×10(-6) s) and solid state (Δ=17(2) K and τ0 =9.5(2)×10(-6) s). The SIM behaviour is obtained if the hydrogen bond is broken by dissolution (1 in solution) or by alkylation (2). Multiple relaxation processes were identified for 2 with two competing processes: a fast one in zero field and a slow one for fields higher than 500 Oe. The two processes coexist for intermediate applied magnetic field. Magnetic-dilution and frozen-solution measurements led to the conclusion that the origin of these multiple relaxation processes is not due to the property of a single molecule.

Slow Magnetic Relaxation in Chiral Helicene-Based Coordination Complex of Dysprosium

“…Thus, the replacement of the 1,1,1,5,5,5-hexafluoroacetylacetonate anions with tta − ones confers an higher symmetry for the coordination environment [27]. As already noted, such observation was already done for another complex stemming from this group and a significant positive impact on the magnetic properties was observed [37,38]. Starting from the racemic mixture of L, both enantiomers are present in the cell (P-1 space group symmetry).…”

“…Indeed, it is well known that the swapping of these two ligands in such specific N 2 O 6 environment enhances the magnetic properties [36][37][38], even if in other coordination environments the opposite effect has been recently observed [39]. Therefore, we report the synthesis, the single crystal X-ray structural analysis and the magnetic characterization along with extensive ab initio calculations of the novel compound [Dy(L)(tta) 3 ] (1).…”

Magnetic Studies of Redox‐Active Tetrathiafulvalene‐Based Complexes: Dysprosium vs. Ytterbium Analogues

“…We actually focused our attention on a TTF‐based ligand named 2‐{1‐methylpyridyl‐4,5‐[4,5‐bis(propylthio)tetrathiafulvalenyl]‐1 H ‐benzimidazol‐2‐yl}pyridine (L) (Scheme ) 17. It was first coordinated to the precursor Dy(hfac) 3 · 2H 2 O (hfac – = 1,1,1,5,5,5‐hexafluoroacetylacetonate) to give a mononuclear complex that behaves as a SMM in both solid state and solution 17. Then, the β‐diketonate anion hfac – was replaced by tta – (tta – = 2‐thenoyltrifluoroacetonate, Scheme ) to optimize the SMM behaviour.…”

Tetrathiafulvalene-Supported Triple-Decker Phthalocyaninato Dysprosium(III) Complex: Synthesis, Properties and Surface Assembly

“…Their cationic radical salts constitute an important class of conducting molecular materials26272829, and have been incorporated as units on molecular machines3031. Absorbing redox-active TTF organic units on surfaces, and assembling SMMs systems comprised of these molecules with the paramagnetic metal ions may lead to new multifunctional materials with interesting structures and properties26323334353637383940.…”