The unexpected covalent contribution in the DOTADy-OH2 bond revealed by ab initio calculations of the easy axis of magnetization through simple H2O rotations.

Racemic and optically pure [Dy(hfac)(L)] complexes with L = 3-(2-pyridyl)-4-aza[6]-helicene have been synthesized and characterized. Both the racemic and enantiopure forms behave as single molecule magnets in their crystalline phase, while electronic circular dichroism activity is evidenced. Ab initio calculations on isolated complexes followed by the determination of intermolecular dipolar couplings allowed the rationalization of the different low-temperature magnetic behaviours. The enantiopure SMM differs from the racemic one by the presence of a hysteresis loop in the former system.

We report the study of a Dy-based metal-organic framework (MOF) with unprecedented magnetic properties. The compound is made of nine-coordinated Dy magnetic building blocks (MBBs) with poor intrinsic single-molecule magnet behavior. However, the MOF architecture constrains the MBBs in a one-dimensional structure that induces a ferromagnetic coupling between them. Overall, the material shows a magnetic slow relaxation in absence of external static field and a hysteretic behavior at 0.5 K. Low-temperature magnetic studies, diamagnetic doping, and ab initio calculations highlight the crucial role played by the Dy-Dy ferromagnetic interaction. Overall, we report an original magnetic object at the frontier between single-chain magnets and single-molecule magnets that host intrachain couplings that cancel quantum tunneling between the MBBs. This compound is evidence that a bottom-up approach through MOF design can induce spontaneous organization of MBBs able to produce remarkable molecular magnetic materials.

The design of a coordination complex that involves a ligand combining both a tetrathiafulvalene core and a helicene fragment was achieved thanks to the reaction between the new 2-{1-[2-methyl[6]helicene]-4,5-[4,5-bis(propylthio)tetrathiafulvalenyl]-1 H -benzimidazol-2-yl}pyridine ligand ( L ) and the Dy(hfac) 3 ·2H 2 O metalloprecursor. Magnetic investigations showed field-induced single-molecule-magnet (SMM) behavior under an applied magnetic field of 1000 Oe for [Dy(hfac) 3 ( L )]·0.5CH 2 Cl 2 , while experimentally oriented single-crystal magnetic measurements allowed for determination of the magnetic anisotropy orientation. The magnetic behavior was rationalized through ab initio CASSCF/SI-SO calculations. This redox-active chiral-field-induced SMM paves the way for the design of switchable-multiproperty SMMs.

A spiropyran-based switchable ligand isomerizes upon reaction with lanthanide(III) precursors to generate complexes with an unusual N O coordination sphere. The air-stable dysprosium(III) complex shows a hysteresis loop at 2 K and a very strong axial magnetic anisotropy generated by the merocyanine phenolate donor.

International audienceThe reaction between the 2-_TTF-fused-1H-benzimidazol-2-yl_ pyridine alkylated with either the di-( pyrazol-1-yl)-4-pyridyl (L-1) or dimethyl-2,2'-bipyridine (L-2) moiety and 1 equiv. of L-n(hfac)(3).2H(2)O (Ln(III) = Dy-III and Yb-III) leads to three dinuclear complexes of formula [Yb-2(hfac)(6)(L-1)].2(CH2Cl2).C6H14 (1) and [Ln(2)(hfac)(6)(L-2)].CH2Cl2 (Ln(III) = Yb-III (2) and Dy-III (3)). The X-ray structures highlight square antiprism (D-4d symmetry) and spherical tricapped trigonal prism (D-3h) for the eight-and nine-coordinated lanthanide ions, respectively. Irradiation of the lowest-energy HOMO -> LUMO ILCT absorption band induced a F-2(5/ 2) -> F-2(7/ 2) Yb-centered emission for 1 and 2. Both Yb-III ions displayed similar emissions in 2 while two distinct emissions, attributed to the two YbIII ions because of their different coordination environments, were observed in 1. Slow magnetic relaxation is detected by dynamic magnetic measurements for 3 with a measured relaxation time tau(0) = 3.7(1.3) x 10(-7) s and an energy barrier Delta = 39.6(2) cm(-1). Taking into account the environment of both DyIII ions in 3, it was expected that both metallic centers displayed similar dynamic magnetic behavior. The latter was rationalized by ab initio CASSCF/SI-SO calculations

Abstract:The complex [Dy(L)(tta) 3 ] with L the chiral 3-(2-pyridyl)-4-aza[6]-helicene ligand (tta − = 2-thenoyltrifluoroaacetonate) has been synthesized in its racemic form and structurally and magnetically characterized. [Dy(L)(tta) 3 ] behaves as a single molecule magnet in its crystalline phase with the opening of a hysteresis loop at 0.50 K. These magnetic properties were interpreted with ab initio calculations.

A textbook dysprosium dinuclear complex based on acetylacetone ligands, [Dy2(acac)4(μ2‐acac)2(H2O)2], has been synthesized and fully characterized. This simple dimeric lanthanide complex shows well‐resolved solid‐state luminescence and behaves as a single‐molecule magnet under zero DC field. A seminal crystal‐field approach is used to marry both magnetism and luminescence in the frame of an energetic picture.