Slow Magnetic Relaxation Research Articles

The slow magnetic relaxation in Dy-phthalocyanine single-molecule magnet induced by CH2Cl2 solvent molecules

DyPc2 and DyPc2•CH2Cl2 were prepared using the solvent thermal method. The x-ray diffractometer and the Fourier transform infrared spectrometer were used to explore the structure changes between DyPc2 and DyPc2•CH2Cl2. The results clearly demonstrate that the CH2Cl2 molecule can alter the crystal structures and, thus, change the molecular stacking structures of DyPc2 without destroying molecular integrity. Geometry optimization further proved that DyPc2 belongs to the space group P212121, while DyPc2•CH2Cl2 crystallizes in the space group Pnma. It is clearly demonstrated that the different molecular environment affects the structure of a single DyPc2 molecule to some extent, such as the twist angles of two Pc rings and the Pc−Dy−Pc angles. The molar magnetic susceptibility and hysteresis loops for DyPc2 and DyPc2•CH2Cl2 were also measured and compared. The negative Weiss constants were obtained by the Curie−Weiss law fitting above 50 K. The hysteresis loop for DyPc2•CH2Cl2 is wider than that of DyPc2, implying that the magnetic relaxation of DyPc2 slowed down, while quantum tunneling of the magnetization is prevented efficiently after absorbing CH2Cl2 molecules. This work clarifies the correlation between the molecular environment and magnetism of single-molecule magnets, which is helpful for their design guideline and future applications.

Russian Doll-like 3d-4f Cluster Wheels with Slow Relaxation of Magnetization.

The solvothermal reactions of LnCl3·6H2O and MCl2·6H2O (M = Co, Ni) with 2,2'-diphenol (H2L1) and 5,7-dichloro-8-hydroxyquinoline (HL2) gave three 3d-4f heterometallic wheel-like nano-clusters [Ln7M6(L1)6(L2)6(µ3-OH)6(OCH3)6Cl(CH3CN)6]Cl2·xH2O (Ln = Dy, M = Co, x = 3 for 1; Ln = Dy, M = Ni, x = 0 for 2; Ln = Tb, M = Ni, x = 0 for 3) with similar cluster structure. The innermost Ln(III) ion is encapsulated in a planar Ln6 ring which is further embedded in a chair-conformation M6 ring, constructing a Russian doll-like 3d-4f cluster wheel Ln(III)⸦Ln6⸦M6. 2 and 3 show obvious slow magnetic relaxation behavior with negligible opening of the magnetic hysteresis loop. Such a Russian doll-like 3d-4f cluster wheel with the lanthanide disc isolated by transition metallo-ring is rarely reported.

Observation of High Magnetic Bistability in Lanthanide (Ln = Gd, Tb and Dy)-Grafted Carbon Nanotube Hybrid Molecular System.

There is an immense research interest in molecular hybrid materials posing novel magnetic properties for usage in spintronic devices and quantum technological applications. Although grafting magnetic molecules onto carbon nanotubes (CNTs) is nontrivial, there is a need to explore their single molecule magnetic (SMM) properties post-grafting to a greater degree. Here, we report a one-step chemical approach for lanthanide-EDTA (Ln = GdIII, 1; TbIII, 2 and DyIII, 3) chelate synthesis and their effective grafting onto MWCNT surfaces with high magnetic bistability retention. The magnetic anisotropy of an Ln-CNT hybrid molecular system by replacing the central ions in the hybrid complex was studied and it was found that system 1 exhibited a magnetization reversal from positive to negative values at 70 K with quasi-anti-ferromagnetic ordering, 2 showed diamagnetism to quasi-ferromagnetism and 3 displayed anti-ferromagnetic ordering as the temperature was lowered at an applied field of 200 Oe. A further analysis of magnetization (M) vs. field (H) revealed 1 displaying superparamagnetic behavior, and 2 and 3 displaying smooth hysteresis loops with zero-field slow magnetic relaxation. The present work highlights the importance of the selection of lanthanide ions in designing SMM-CNT hybrid molecular systems with multi-functionalities for building spin valves, molecular transistors, switches, etc.

A cobalt(II) hydrogen-bonded organic framework exhibiting uniaxial negative thermal expansion and field-induced slow magnetic relaxation

The magnetic and thermal expansion properties of a cobalt(II) hydrogen-bonded organic framework (CoHOF), [Co(H2O)6](NPS)2 (1, HNPS = naphthalene-2-sulphonic acid), constructed by hexaaquacobalt(II) and organsulfonate were reported. Single-crystal X-ray diffraction reveals a porous 2D hydrogen-bonded framework of 1 sustained by multiple and charge-assisted intermolecular hydrogen bonding interactions. Variable-temperature single-crystal combined with powder X-ray diffraction and thermal gravimetric analyses confirms the high thermal stability of the CoHOF. The dynamic changes of the crystal lattice indicate uniaxial negative thermal expansion (NTE) behavior along the c-axis direction through a possible slippage motion. Magnetic measurements indicate the Co2+ ions show uniaxial magnetic anisotropy with D = −92.5 cm−1. A.C. susceptibility measurements reveal field-driven slow magnetic relaxation of 1. These results provide a rare cobalt(II) hydrogen-bonded organic framework showing single-ion magnetism and negative thermal expansion properties.

Syntheses of new di-nuclear and tetra-nuclear lanthanide 9-anthracenecarboxylates: Magnetocaloric effect, slow magnetic relaxation and luminescent properties

Lanthanide complex-based materials with magnetic and luminescent properties have received a great deal of attention, owing to their importantly potential applications in diverse fields. In this work, the 9-anthracenecarboxylic acid (9-Haca) as bridging ligand was applied in combination with optically active π-conjugated 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tptz) to construct a series of new di-nuclear and tetra-nuclear lanthanide 9-anthracenecarboxylates [La2(9-aca)6(tptz)2(μ-H2O)]·0.25H2O (1), [Ln2(9-aca)6(tptz)2(H2O)2]·0.5AQ·CH3COOH2H2O [Ln = Sm (2a), Eu (2b), Gd (2c), Tb (2d), Dy (2e), Tm (2f); AQ = 9,10-anthracenedione] and [Ln4(9-aca)10(tptz)2(CH3COO)2]·H2O [Ln = Eu (3a), Gd (3b), Dy (3c)]. 1 displays a di-nuclear centrosymmetric moiety [La2(9-aca)6(tptz)2(μ-H2O)] built up from two complex [La(9-aca)2(tptz)] groups bridged by one H2O molecule and two syn-syn-μ2-η1:η1-9-aca‒ bridging ligands, while 2a‒2f are isostructural and comprise another di-nuclear centrosymmetric moieties [Ln2(9-aca)6(tptz)2(H2O)2] based on two complex [Ln(9-aca)2(tptz)(H2O)] groups connected by two syn-syn-μ2-η1:η1-9-aca– bridging ligands. 3a‒3c are isostructural and show tetra-nuclear centrosymmetric moieties [Ln4(9-aca)10(tptz)2(CH3COO)2] containing three types of coordination modes of 9-aca– ligands. The present compounds offer the only examples of lanthanide 9-anthracenecarboxylates decorated by optically active tptz. Magnetic investigations of 2a, 2c‒2f, and 3b‒3c indicate that 3c is typical of slow relaxation of the magnetization, while 2c and 3b show significant magnetocaloric effect (MCE) with the value of –ΔSm of 5.26 J/(kg·K) at 4 K and 15.65 J/(kg·K) at 2 K (ΔH = 7 T), respectively. The luminescent properties were also studied and reveal that the characteristic luminescent properties of the π-conjugated aromatic ligands are introduced into magnetic lanthanide 9-anthracenecarboxylates, simultaneously exhibiting slow magnetic relaxation (or MCE) and luminescent properties.

Synthesis, crystal structures and magnetic properties of two Ni-Dy heterometallic complexes with the structural topologies regulated by employing different Schiff base ligands

Regulation of the structural topologies of single molecule magnets (SMMs) is one of the most important approach for enhancing their SMM performance. In this work, we first obtained a Ni2Dy trinuclear complex, [Ni2Dy(Hhmmp)2{(py)2CO2}(CH3COO)2]OH (1, H2hmmp = 2-[(2-hydroxyethylimino)methyl]-6-methoxyphenol, (py)2C(OH)2 = the gem-diol form of di-2-pyridyl ketone (dpk)) by employing H2hmmp and dpk reacting with Dy(NO3)3·5H2O and Ni(CH3COO)2·4H2O in the MeCN solution containing triethylamine. However, when H2hmmp, triethylamine and MeCN in the reaction system of 1 were replaced by 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H4L), N(Me)4OH·5H2O and the mixture of MeCN and N,N-dimethylformamide (DMF), a Ni2Dy2 complex, [Ni2Dy2(HL)2{(py)2CO(OH)}2(CH3COO)2]·2H2O (2), was obtained. Structural analysis revealed that two NiII and one DyIII in 1 formed a “V-shaped” topology, while two NiII and two DyIII ions in 2 formed a butterfly-like topology with Ni and DyIII ions occupied on the body positions and the wing positions, respectively. Additionally, the coordination geometries of DyIII ion in 1 and 2 square antiprism geometry (D4d) and capped octahedron (C3v), respectively. Magnetic investigation indicated that 1 exhibits obviously slow magnetic relaxation behavior, with an energy barrier Ueff of ∼6 K. The orientations of the magnetic anisotropy of DyIII in 1 and 2 were estimated by Magellan software; the results indicate that few coordination atoms were located on the equatorial plane of DyIII in 1 and 2, which result in 1 and 2 exhibiting poor SMM performance.

Lattice Solvent Engineering Improves the Stability of a Cobalt Pyrenylnitronylnitroxide Ferrimagnetic Chain.

Reaction of 2-(1'-pyrenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (PyrNN) with [Co(hfac)2(H2O)2] (hfac = hexafluoroacetylacetonate) in n-heptane solvent (hep) with a small amount of bromoform (CHBr3 = bf) gives the 1D ferrimagnetic complex [Co(hfac)2PyrNN]n·0.5bf·0.5hep (Co-PyrNN·bf). This chain exhibits slow magnetic relaxation with magnetic blocking below 13.4 K, presenting a magnetic hysteresis with high coercive field (51 kOe at 5.0 K) as a hard magnet. It also shows frequency-dependent behavior consistent with one dominant relaxation process with an activation barrier of Δτ/kB = (365 ± 24) K. The compound is an isomorphous variant of a previously reported ambient unstable chain made by using chloroform (CHCl3 = cf), [Co(hfac)2PyrNN]n·0.5cf·0.5hep (Co-PyrNN·cf). This shows that the variation of a magnetically inactive lattice solvent can improve the stability of analogous, void space containing single-chain magnets.

Hydrogen-bonded nickel(II)-organosulfonate framework: Thermal expansion behavior, proton conduction, and magnetic properties

Metalo Hydrogen-bonded organic frameworks are emerging supramolecular platforms for designing functional molecular materials. Herein, we reported the supramolecular structure, thermal, magnetic, and proton conduction properties of a hydrogen-bonded nickel(II)-organosulfonate framework, [Ni(H2O)6][NPS]2 (NiHOF, HNPS = naphthalene-2-sulphonic acid). Single-crystal X-ray diffraction studies reveal a two-dimensional hydrogen-bonded network sustained by multiple and charge-assisted OH···O H bonds between hexaaquanickel(II) cations and organosulfonate anions. Additionally, continuous ca. 0.47 × 0.70 nm2 windows were formed within the framework. The thermal stability of the NiHOF was confirmed by thermal gravimetric analysis and variable temperature single-crystal and powder X-ray diffraction patterns. N2 sorption isotherms suggest an ultramicroporous supramolecular framework of NiHOF with permanent porosity. The anisotropic positive thermal expansion behavior of NiHOF was evidenced by the dynamic crystallography experiments. Magnetic measurements indicate easy-axis magnetic anisotropy (D = -10.5 cm−1) of the NiHOF while no slow magnetic relaxation behavior. Electrochemical impedance spectroscopy indicates the temperature and humidity dependence of conductivities of NiHOF. At 50 °C and 70% relative humidity, the conductivity is 1.13 × 10−4 S·cm−1, revealing a supramolecular proton conductor of NiHOF. This work provides a potential way for designing novel thermal, magnetic, and electrical molecular materials through the supramolecular assembly of inorganic and organosulfonate synthons.

Desolvation‐Induced Highly Symmetrical Terbium(III) Single‐Molecule Magnet Exhibiting Luminescent Self‐Monitoring of Temperature

AbstractA conjunction of Single‐Molecule Magnet (SMM) behavior and luminescence thermometry is an emerging research line aiming at contactless read‐out of temperature in future SMM‐based devices. The shared working range between slow magnetic relaxation and the thermometric response is typically narrow or absent. We report TbIII‐based emissive SMMs formed in a cyanido‐bridged framework whose properties are governed by the reversible structural transformation from [TbIII(H2O)2][CoIII(CN)6] ⋅ 2.7H2O (1) to its dehydrated phase, TbIII[CoIII(CN)6] (2). The 8‐coordinated complexes in 1 show the moderate SMM effect but it is enhanced for trigonal‐prismatic TbIII complexes in 2, showing the SMM features up to 42 K. They are governed by the combination of QTM, Raman, and Orbach relaxation with the energy barrier of 594(18) cm−1 (854(26) K), one of the highest among the TbIII‐based molecular nanomagnets. Both systems exhibit emission related to the f–f electronic transitions, with the temperature variations resulting in the optical thermometry below 100 K. The dehydration leads to a wide temperature overlap between the SMM behavior and thermometry, from 6 K to 42 K. These functionalities are further enriched after the magnetic dilution. The role of post‐synthetic formation of high‐symmetry TbIII complexes in achieving the SMM effect and hot‐bands‐based optical thermometry is discussed.

Desolvation-Induced Highly Symmetrical Terbium(III) Single-Molecule Magnet Exhibiting Luminescent Self-Monitoring of Temperature.

A conjunction of Single-Molecule Magnet (SMM) behavior and luminescence thermometry is an emerging research line aiming at contactless read-out of temperature in future SMM-based devices. The shared working range between slow magnetic relaxation and the thermometric response is typically narrow or absent. We report TbIII -based emissive SMMs formed in a cyanido-bridged framework whose properties are governed by the reversible structural transformation from [TbIII (H2 O)2 ][CoIII (CN)6 ] ⋅ 2.7H2 O (1) to its dehydrated phase, TbIII [CoIII (CN)6 ] (2). The 8-coordinated complexes in 1 show the moderate SMM effect but it is enhanced for trigonal-prismatic TbIII complexes in 2, showing the SMM features up to 42 K. They are governed by the combination of QTM, Raman, and Orbach relaxation with the energy barrier of 594(18) cm-1 (854(26) K), one of the highest among the TbIII -based molecular nanomagnets. Both systems exhibit emission related to the f-f electronic transitions, with the temperature variations resulting in the optical thermometry below 100 K. The dehydration leads to a wide temperature overlap between the SMM behavior and thermometry, from 6 K to 42 K. These functionalities are further enriched after the magnetic dilution. The role of post-synthetic formation of high-symmetry TbIII complexes in achieving the SMM effect and hot-bands-based optical thermometry is discussed.

Tuning Crystal Packing and Magnetic Properties in a Series of [Dy12] Metallocubanes Based on Azobenzene Derivatives of Salicylic Acid.

A series of four new Dy12 dodecanuclear clusters based on azobenzene derivative ligands of salicylic acid (L1-L4) has been synthesized and characterized in the crystalline phase using X-ray diffraction on single crystal and powder, IR spectroscopy, elemental analysis, and DSC-TGA methods. It was revealed that all obtained clusters exhibit the formation of the similar metallic cluster nodes, as vertex-sharing heterocubanes, obtained from four Dy3+ cations, three bridging hydroxyl groups, and O atoms from the salicylic ligands. The coordination geometry around the Dy(III) centers has been carefully analyzed. Whereas Dy12-L1 and Dy12-L2 with L1 and L2 containing Me and OMe groups in para positions of the phenyl rings, respectively, form similar porous 3D diamond-like molecular networks due to CH-π interactions, for Dy12-L3 with L3 bearing NO2-electron-withdrawing group, the generation of 2D molecular grids assembled by π-π staking is observed, and for Dy12-L4 with L4 bearing phenyl substituent, 3D hexagonal channels have been generated. The complexes Dy12-L1, Dy12-L2, and Dy12-L3 exhibit a zero-field slow magnetic relaxation effect. After UV irradiation of Dy12-L1, a decrease of the magnetic anisotropy energy barrier displaying the possibility of control over magnetic properties by the external stimulus has been observed.

Solvatotuning of the Field-Induced Slow Magnetic Relaxation through a Single-Crystal-to-Single-Crystal Transformation in Pentanuclear Gadolinium(III)-Nickel(II) Complexes

Solvatotuning of the Field-Induced Slow Magnetic Relaxation through a Single-Crystal-to-Single-Crystal Transformation in Pentanuclear Gadolinium(III)-Nickel(II) Complexes

The Organic Ammonium Counterion Effect on Slow Magnetic Relaxation of the [Er(hfac)4]− Complexes

The first mononuclear anionic erbium complex [Er(hfac)4]− (hfac = hexafluoroacetylacetone) with an organic ammonium cation [(CH3)4N+] as the counterion was synthesized and structurally and magnetically characterized. The coordination geometries around the Er ions are square antiprisms with pseudo-D4d symmetry. The complex shows distinct field-induced slow magnetization relaxation, which is described by a combination of Orbach (Ueff/kB~28.54(8) K.) and direct mechanisms. Quantum chemical calculations were performed to analyze the magnetic properties of the complex under consideration.

A Combined Synthetic, Magnetic, and Theoretical Study on Enhancing Ligand-Field Axiality for Dy(III) Single-Molecule Magnets Supported by Ferrocene Diamide Ligands.

Molecular design is crucial for improving the performance of single-molecule magnets (SMMs). For dysprosium(III) SMMs, enhancing ligand-field axiality is a well-suited strategy to achieve high-performance SMMs. We synthesized a series of dysprosium(III) complexes, (NNTIPS)DyBr(THF)2 (1, NNTIPS = fc(NSiiPr3)2; fc = 1,1'-ferrocenediyl, THF = tetrahydrofuran), [(NNTIPS)Dy(THF)3][BPh4] (2), (NNTIPS)DyI(THF)2 (3), and [(NNTBS)Dy(THF)3][BPh4] (4, NNTBS = fc(NSitBuMe2)2), supported by ferrocene diamide ligands. X-ray crystallography shows that the rigid ferrocene backbone enforces a nearly axial ligand field with weakly coordinating equatorial ligands. Dysprosium(III) complexes 1-4 all exhibit slow magnetic relaxation under zero fields and possess high effective barriers (Ueff) around 1000 K, comparable to previously reported (NNTBS)DyI(THF)2 (5). We probed the influences of structural variations on SMM behaviors by theoretical calculations and found that the distribution of negative charges defined by rq, i.e., the ratio of the charges on the axial ligands to the charges on the equatorial ligands, plays a decisive role. Moreover, theoretical calculations on a series of model complexes 1'-5' without equatorial ligands unveil that the axial crystal-field parameters B20 are directly proportional to the N-Dy-N angles and support the hypothesis that enhancing the ligand-field axiality could improve SMM performance.

Tailored Lewis Acid Sites for High-Temperature Supported Single-Molecule Magnetism.

Generating or even retaining slow magnetic relaxation in surface immobilized single-molecule magnets (SMMs) from promising molecular precursors remains a great challenge. Illustrative examples are organolanthanide compounds that show promising SMM properties in molecular systems, though surface immobilization generally diminishes their magnetic performance. Here, we show how tailored Lewis acidic Al(III) sites on a silica surface enable generation of a material with SMM characteristics via chemisorption of (Cpttt)2DyCl ((Cpttt)- = 1,2,4-tri(tert-butyl)-cyclopentadienide). Detailed studies of this system and its diamagnetic Y analogue indicate that the interaction of the metal chloride with surface Al sites results in a change of the coordination sphere around the metal center inducing for the dysprosium-containing material slow magnetic relaxation up to 51 K with hysteresis up to 8 K and an effective energy barrier (Ueff) of 449 cm-1, the highest reported thus far for a supported SMM.

A trivalent 4f complex with two bis-silylamide ligands displaying slow magnetic relaxation.

The best-performing single-molecule magnets (SMMs) have historically relied on pseudoaxial ligands delocalized across several coordinated atoms. This coordination environment has been found to elicit strong magnetic anisotropy, but lanthanide-based SMMs with low coordination numbers have remained synthetically elusive species. Here we report a cationic 4f complex bearing only two bis-silylamide ligands, Yb(III)[{N(SiMePh2)2}2][Al{OC(CF3)3}4], which exhibits slow relaxation of its magnetization. The combination of the bulky silylamide ligands and weakly coordinating [Al{OC(CF3)3}4]- anion provides a sterically hindered environment that suitably stabilizes the pseudotrigonal geometry necessary to elicit strong ground-state magnetic anisotropy. The resolution of the mJ states by luminescence spectroscopy is supported by ab initio calculations, which show a large ground-state splitting of approximately 1,850 cm-1. These results provide a facile route to access a bis-silylamido Yb(III) complex, and further underline the desirability of axially coordinated ligands with well-localized charges for high-performing SMMs.

A Chain of Vertex-Sharing {CoIII2CoII2}n Squares with Single-Ion Magnet Behavior

A new mixed-valence one-dimensional coordination polymer of formula {[CoII(MeOH)2][(μ-NC)2CoIII(dmphen)(CN)2]2}n·2nH2O (1) was obtained by reacting the Ph4P[CoII(dmphen)(CN)3] metalloligand (dmphen = 2,9-dimethyl-1,10-phenanthroline and Ph4P+ = tetraphenylphosphonium ion) with cobalt(II) acetate tetrahydrate. The structural analysis shows the formation of a neutral 4,2-ribbon-like chain of vertex-sharing cyanido-bridged {CoIII2CoII2} squares in which the metalloligand underwent an oxidation process and a reorganization to form {CoIII(dmphen)(CN)4}− linkers that coordinate to the [CoII(MeOH)2]2+ units through single cyanido ligands. Both cobalt(II) and Co(III) cations are six-coordinated in distorted octahedral environments. The shortest intrachain distance between the paramagnetic cobalt(II) ions is 7.36 Å, a value which is shorter than the shortest interchain one (10.36 Å). Variable-temperature (1.9–300 K) static (dc) magnetic measurements for 1 indicate the occurrence of magnetically isolated high-spin cobalt(II) ions with a D value of +67.0 cm−1. Dynamic alternating current (ac) magnetic measurements between 2.0–13 K reveal that 1 exhibits slow magnetic relaxation under non-zero applied dc fields, being thus a new example of field-induced SIM with easy-plane magnetic anisotropy. Theoretical calculations by CASSCF/NEVPT2 on 1 support the results from magnetometry. The relaxation of the magnetization occurs in the ground state under external dc fields through a two-phonon Raman process and one intra-Kramers mechanism.

Reversible Pressure-Magnetic Modulation in a Tetrathiafulvalene-Based Dyad Piezochromic Dysprosium Single-Molecule Magnet.

The extreme sensitivity of trivalent lanthanide ions to crystal field variations led to the emergence of single-molecule magnetic switching under various stimuli. The use of pressure as an external stimulus instead of classic light irradiation, oxidation or any chemical reactions allows a fine tuning of the magnetic modulation. Here the well-known pure isotopically enriched [162 Dy(tta)3 (L)]⋅C6 H14 (162 Dy) Single-Molecule Magnet (SMM) (tta- =2-2-thenoyltrifluoroacetonate and L=4,5-bis(propylthio)-tetrathiafulvalene-2-(2-pyridyl)benzimidazole-methyl-2-pyridine) was experimentally investigated by single-crystal diffraction and squid magnetometry under high applied pressures. Both reversible piezochromic properties and pressure modulation of the slow magnetic relaxation behavior were demonstrated and supported by ab initio calculations. The magnetic study of the diluted sample [162 Dy0.05 Y0.95 (tta)3 (L)]⋅C6 H14 (162 Dy@Y) indicated that variations in the electronic structure have mainly intermolecular origin with weak intramolecular contribution. Quantitative magnetic interpretation concludes to a deterioration of the Orbach process for the benefit of both Raman and QTM mechanisms under applied pressure.

A tetranuclear Er(III)-based cluster with bifunctional properties: Efficient conversion of CO2 and slow magnetic relaxation behavior

A new Er4 cluster [Er4(NO3)2(acac)4(L)2(CH3OH)2]·2CH3CN (1) (H4L = (E)-2-(hydroxymethyl)-2-(((2-hydroxynaphthalen-1-yl)methylene)amino)propane-1,3-diol, and Hacac = acetylacetone) were synthesized by employing a polydentate Schiff-base ligand (H4L) and a β-diketonate co-ligand and further characterized structurally. Alternating current (ac) magnetic susceptibility measurements indicated that cluster 1 shows slow relaxation of magnetization behavior. More importantly, cluster 1 shows high catalytic activity of the cycloaddition reaction of CO2 and epichlorohydrin under mild conditions; and cluster 1 as heterogenous catalyst can be reused at least three times without any obvious loss in catalytic activity. It is worth mentioning that cluster 1 is a rare bifunctional Ln(III)-based material for both molecular based magnetic material and heterogenous catalyst.

Slow Magnetic Relaxation of Ni(III) Complexes toward Molecular Spin Qubits

AbstractMolecule‐based magnetic materials are promising candidates for molecular spin qubits, which utilize spin relaxation behavior. Various kinds of transition metal complexes with S=1/2 have been reported to act as spin qubits with long spin‐spin relaxation times (T2). However, the spin qubit properties of low‐spin Ni(III) complexes are not as well known since Ni(III) compounds are often unstable. We report here the slow magnetic relaxation behavior and T2 values for three kinds of low‐spin Ni(III) based complexes with S=1/2 under magnetically diluted conditions. [Ni(cyclam)X2]Y (cyclam=1,4,8,11‐tetraazacyclotetradecane) with octahedral structures and [Ni(mnt)2]− (mnt=maleonitriledithiolate) with a square‐planar structure underwent slow magnetic relaxations in the presence of a dc magnetic bias field. From electron spin resonance (ESR) spectroscopy, the Ni(III) complexes exhibited observable T2, indicating that Ni(III) complexes are promising candidates for use as molecule‐based spin qubits.