Mononuclear Dysprosium Complexes Research Articles

Slow magnetic relaxation of a mononuclear dysprosium complex derived from 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione and 1,10-phenanthroline

A mononuclear dysprosium complex with a triangular dodecahedron geometry behaves as a single-molecule magnet with the effective barrier Ueff = 193 K.

Four mononuclear dysprosium complexes with neutral Schiff-base ligands: syntheses, crystal structures and slow magnetic relaxation behavior.

Four mononuclear 9-coordinate Dy-based complexes, [Dy(HL1)2(NO3)3(CH3OH)] (1Dy), [Dy(HL2)2(NO3)3(H2O)] (2Dy), [Dy(HL3)3(NO3)3]·CH3CN (3Dy), and [Dy(HL4)3(NO3)3] (4Dy), have been constructed by neutral Schiff-base ligands (1-[N-(4-R)aminomethylidene-2(1H)-naphthalenone, R = -Cl (HL1), -NO2 (HL2), -OCH3 (HL3), -I (HL4)). By tuning the terminal substituent group of HL ligands, the number of HL ligands coordinated to the central Dy3+ ion unexpectedly varies from 2 to 3, and the local symmetry around the Dy3+ ion reduces from D3h to Cs. Magnetic measurements reveal that 2Dy can display single-ion magnet (SIM) behavior in zero dc field, while 1Dy, 3Dy and 4Dy show field-induced slow magnetic relaxation. Ab initio calculations were employed to elucidate magnetic anisotropy in the complexes, including g-tensors, averaged transition magnetic moments and magnetic easy axes. The difference in magnetic behaviors of the four complexes can be ascribed to the terminal substituent effect of neutral Schiff-base ligands.

Eight coordinated mononuclear dysprosium complexes of heptadentate aminophenol ligands: the influence of the phenol substituents and the ancillary donors on the magnetic relaxation.

The mononuclear complexes [Dy(3Br,5Cl-H3L1,1,4)(D)]·solvate (D = H2O, solvate = 0.25MeOH, 1W·0.25MeOH; D = Py without solvate, 1Py), and [Dy(3NO2,5Br-H3L1,1,4)(H2O)] (2W) were isolated. The crystal structures of 1W·0.25MeOH, 1Py and 2W·2CH3C6H5 show that the DyIII ion is octacoordinated, in N4O4 or N5O3 environments, with distorted geometries, between square antiprism, biaugmented trigonal prism and triangular dodecahedral. A similar environment for the metal ion is shown in the chiral crystals of the diamagnetic yttrium analogue [Y(3Br,5Cl-H3L1,1,4)(MeOH)] (3M), which were spontaneously resolved. Magnetic analyses of the three dysprosium complexes, and their diluted analogous 1W@Y, 1Py@Y and 2W@Y, reveal that none of them seem to relax through an Orbach mechanism at Hdc = 0. However, the three complexes show Orbach relaxation under Hdc = 1000 Oe, and 1Py is the in-field SIM with the highest energy barrier among these complexes, with a Ueff value of 358 K. Analysis of ac magnetic data shows that the electron-withdrawing substituents on the phenol rings of the aminophenol ligands, as well as the auxiliary oxygen donors from water ligands, reduce the energy barriers of the complexes, which is attributed to a charge reduction in the coordinating atoms of the aminophenol donor. Ab initio calculations support the experimental results.

Structural Modulation of Fluorescent Rhodamine-Based Dysprosium(III) Single-Molecule Magnets.

Two rhodamine 6G-based mononuclear dysprosium complexes, [Dy(LR)(LA)2](ClO4)3·Et2O·1.5MeOH·0.5H2O (1) and [Dy(LR)(H2O)4(MeCN)](ClO4)3·2H2O·MeCN (2) (LR = salicylaldehyde rhodamine 6G hydrazone, LA = 2-pyridylcarboxaldehyde benzoyl hydrazone), are synthesized, aiming at improving the magnetic behavior by modulating their coordination environment. Both complexes own one exclusive short Dy-Ophenoxy coordination bond as the predominant bond and exhibit single-molecule magnet behavior under zero dc field with the energy barrier (Ueff/kB) of 90 K (1) and 320 K (2) and apparent hysteresis at 1.9 K. The ab initio calculations indicate that the short Dy-Ophenoxy bond determines the direction of magnetic anisotropic axis for 1 and 2. The quantum tunneling of magnetization (QTM) between the ground Kramers doublets (KDs) in 1 cannot be neglected, leading to an experimental Ueff/kB much lower than the calculated energy of the first excited state (318.2 K). For 2, the stronger magnetic anisotropy and negligible QTM between the ground KDs guarantees that the energy barrier is close to the calculated energy of first KDs (320.8 K). On the other hand, the presence of ring-opened xanthene moiety makes complexes 1 and 2 in the solid state emit red light with emission bands of 645 and 658 nm, respectively.

Mononuclear dysprosium complex with single-ion magnetic behavior and its highly selective detection of 1,4-dioxane

The organic ligand 5,7-dibromo-2-methyl-8-quinolinol (L) was used to react with Dy(NO3)3·6H2O at 60 °C to obtain the complex [Dy(L)3(CH3CH2OH)(H2O)]·CH3CN (1). Furthermore, the electrospray mass spectrometry (ESI–MS) data show that the main molecular fragment was [DyL2(DMF)2]+ under the condition of 0 eV voltage. When complex 1 was dissolved in DMF and stayed for half a month, and it also showed the main molecular fragment after measuring ESI–MS. So complex 1 was relatively stable in DMF. And magnetic susceptibilities showed that 1 exhibits a clear field-induced SIM behavior, and the energy barriers and extrapolated relaxation time was Ueff = 14.6 K and τ0 = 4.1 × 10−5 s under 1000 Oe dc field. The complex 1 was dissolved in various organic solvents and tested for fluorescence. It was found to have very high selectivity in 1,4-dioxane and the fluorescence intensity was more than 3 times that of other organic solvents.

Bifunctional Mononuclear Dysprosium Complexes: Single-Ion Magnet Behaviors and Antitumor Activities.

Two mononuclear dysprosium complexes (Et3NH)[Dy(BrMQ)4]·H2O·DMF(BrMQ-Dy) and (Et3NH)[Dy(ClMQ)4]·H2O·DMF (ClMQ-Dy) (H-BrMQ = 5,7-dibromo-2-methyl-8-quinolinol, H-ClMQ = 5,7-dichloro-2-methyl-8-quinolinol) were synthesized and characterized. The Dy(III) ions in complexes BrMQ-Dy and ClMQ-Dy have a pseudo-D4d local symmetry. Magnetic characterizations reveal that complex BrMQ-Dy is a single-ion magnet and complex ClMQ-Dy exhibits field-induced slow magnetic relaxation behaviors. The calculated effective barriers of BrMQ-Dy, BrMQ-Dya, ClMQ-Dy, and ClMQ-Dya are 47.8, 27.3, 96.0, and 65.5 cm-1, respectively (BrMQ-Dya and ClMQ-Dya represent the desolvated samples of BrMQ-Dy and ClMQ-Dy, respectively). Ab initio calculations confirmed that coordination symmetry of the Dy(III) ions, electron-withdrawing ligands, and the guest molecules is a key factor affecting the magnetic dynamics of the two complexes. The IC50 values of BrMQ-Dy and ClMQ-Dy against BEL-7404, HeLa, and Hep-G2 cancer cells were 1.01-22.06 μM. Interestingly, two Dy(III) complexes were less toxic to normal HL-7702 cells. BrMQ-Dy and ClMQ-Dy significantly induced cell arrest at G2 phase and down-regulated the G2 phase-related protein levels. Various experiments suggested that BrMQ-Dy and ClMQ-Dy also caused dysfunction of mitochondrial pathways in HeLa cells. Taken together, the different in vitro anticancer activity of complexes BrMQ-Dy and ClMQ-Dy in the order of 5,7-dichloro substitution > 5,7-dibromo substitution.

Effect of the Ligand Field Geometry on the Slow Magnetization Relaxation in Mononuclear Dysprosium Complexes

Effect of the Ligand Field Geometry on the Slow Magnetization Relaxation in Mononuclear Dysprosium Complexes

Asymmetry-unit-dominated double slow-relaxation modes of 2,6-dimethyl-3,5-heptanedione dysprosium SMMs

Two new β-diketone mononuclear dysprosium complexes exhibit two types of single and double relaxation modes under optimized DC field.

Two 1,8-naphthalenediol-based dysprosium complexes: syntheses, structures, and magnetic properties

Two mononuclear dysprosium complexes, [Dy(H2L1)2(CH3OH)2]Cl∙6CH3OH (1) and [Dy(H3L2)2(CH3OH)2]Cl∙2H2O (2), derived from 1,8-naphthalenediol-based ligands were synthesized and characterized by single-crystal X-ray diffraction and magnetic measurements. Single-crystal X-ray analyses reveal that the eight-coordinate DyIII ion exhibits distorted triangular dodecahedron geometry in both complexes. The mononuclear units in 2 are further connected into one-dimensional chains via hydrogen-bond interactions. Alternating-current magnetic susceptibility studies indicate that 2 shows slow relaxation of the magnetization with a roughly estimated activation energy of 3 K and pre-exponential factor of 10−6 s, while 1 does not show any ac signals.

Cis-trans isomerism modulates the magnetic relaxation of dysprosium single-molecule magnets.

Geometry and magnetic relaxation modulations in a series of mononuclear dysprosium complexes, [DyLz2(o-vanilin)2]·X·solvent (Lz = 6-pyridin-2-yl-[1,3,5]triazine-2,4-diamine; X = Br- (1), NO3- (2), CF3SO3- (3)), were realized by changing the nature of the counter-anion. The DyIII ions in all complexes are eight-coordinate and in approximate D4d symmetry environments. The magnetic relaxation and anisotropy of these complexes were systematically investigated, both experimentally and from ab initio calculations. All complexes exhibit excellent single-molecule magnetic behavior. Remarkably, magneto-structural studies show that the rotation of the coordinating plane of the square-antiprismatic environment in complex 2 induces a magnetic relaxation path through higher excited states, yielding a high anisotropy barrier of 615 K (696 K for a diluted sample). Additionally, obvious opening of the hysteresis loop is observed up to 7 K, which is the highest blocking temperature ever reported for dysprosium single-molecule magnets.

Azacyclo-auxiliary ligand-tuned SMMs of dibenzoylmethane Dy(iii) complexes

A series of eight-coordinate β-diketone mononuclear dysprosium complexes exhibit field-induced SMM properties which can be tuned by the azacyclo-auxiliary ligands, showing different relaxation modes.

Exploiting single-molecule magnets of β-diketone dysprosium complexes with C3v symmetry: suppression of quantum tunneling of magnetization

A series of four unique seven-coordinated β-diketone mononuclear dysprosium complexes with C3v geometry exhibit SMM properties suppressing the QTM, which was tuned by the distortion of coordination symmetry around the Dy(iii) ion.

Cover Picture: Magnetic Memory in an Isotopically Enriched and Magnetically Isolated Mononuclear Dysprosium Complex (Angew. Chem. Int. Ed. 5/2015)

Cover Picture: Magnetic Memory in an Isotopically Enriched and Magnetically Isolated Mononuclear Dysprosium Complex (Angew. Chem. Int. Ed. 5/2015)

Magnetic Memory in an Isotopically Enriched and Magnetically Isolated Mononuclear Dysprosium Complex

The influence of nuclear spin on the magnetic hysteresis of a single-molecule is evidenced. Isotopically enriched Dy(III) complexes are synthesized and an isotopic dependence of their magnetic relaxation is observed. This approach is coupled with tuning of the molecular environment through dilution in an amorphous or an isomorphous diamagnetic matrix. The combination of these approaches leads to a dramatic enhancement of the magnetic memory of the molecule. This general recipe can be efficient for rational optimization of single-molecule magnets (SMMs), and provides an important step for their integration into molecule-based devices.

Magnetic Memory in an Isotopically Enriched and Magnetically Isolated Mononuclear Dysprosium Complex

AbstractThe influence of nuclear spin on the magnetic hysteresis of a single‐molecule is evidenced. Isotopically enriched DyIII complexes are synthesized and an isotopic dependence of their magnetic relaxation is observed. This approach is coupled with tuning of the molecular environment through dilution in an amorphous or an isomorphous diamagnetic matrix. The combination of these approaches leads to a dramatic enhancement of the magnetic memory of the molecule. This general recipe can be efficient for rational optimization of single‐molecule magnets (SMMs), and provides an important step for their integration into molecule‐based devices.

Local coordination geometry perturbed β-diketone dysprosium single-ion magnets.

A series of three β-diketone mononuclear dysprosium complexes, namely, Dy(TFI)3(H2O)2 (1), Dy(TFI)3(bpy) (2), and [Dy(TFI)3(Phen)]·0.02CHCl3 (3) (TFI = 2-(2,2,2-trifluoroethyl)-1-indone, bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline) have been designed and synthesized. Crystal structure analysis reveals that complexes 1-3 have haveisomorphic structures in which the central Dy(III) ion is eight-coordinated by six oxygen atoms from three TFI ligands and two O/N atoms from auxiliary ligands, forming a distorted bicapped trigonal prismatic geometry for 1, a distorted dodecahedral geometry for 2, and a distorted square antiprismatic geometry for 3, respectively. Magnetic studies indicate that complex 2 with D(2d) symmetry and 3 with D(4d) symmetry exhibit slow magnetic relaxation with barrier heights (U(eff)/k(B)) of 48.8 K for 2 and 57.9 K for 3. Strikingly, the relaxation time (τ) of 0.0258 s for 3 is about 20 times that for 2, which is presumably associated with larger rotation of the SAP surroundings for 3. Further, complexes 2 and 3 exhibit essential magnetic hysteresis loops at 1.8 K. These extend the recent reports of the single-ion magnets (SIMs) of β-diketone mononuclear dysprosium complexes.

Single-ion magnet behavior of a new mononuclear dysprosium complex

Abstract A new mononuclear dysprosium complex formulated as [Dy(dppz) (tfnb)3]·0.375H2O (dppz = dipyrido[3,2-a:2′,3′-c]phenazine; tfnb = 4,4,4-trifluoro-1-(2-naphthyl)-1,3- butanedione) was synthesized, structurally and magnetically characterized. X-ray diffraction study reveals that the central DyIII ion in the complex adopts an approximately square-antiprismatic (SAP) geometry. The complex shows frequency-dependent ac magnetic susceptibilities, indicating single-ion magnet behavior.