DyIII Complexes Research Articles

Exploring the structural variations and magnetic properties of three hexanuclear dysprosium(III) complexes exhibiting single-molecule magnetism behavior

Three novel hexanuclear DyIII complexes supported by polyhydroxy Schiff-base ligands, [Dy6(hmc)3(μ-acac)2(acac)3(μ3-OH)4(H2O)2]·2MeCN (1·2MeCN), [Dy6K2(hmc)3(μ-CO3)6(μ3-CO3)4(H2O)2]·8MeOH (2·8MeOH) and [Dy6(hmc)3(μ-OAc)6(μ3-OH)3(H2O)3] (3) (H3hmc: 1,5-bis(2-hydroxy-3-methoxybenzylidene)carbonhydrazide), have been prepared and structurally characterized by single-crystal X-ray diffraction, elemental analysis, and IR spectroscopy. Each of the hexanuclear complexes is constructed from triangular Dy3 building blocks, with the six DyIII ions are arranged in three different conformations. The magnetic properties of three dinuclear DyIII complexes have also been investigated (Fig. S2). The frequency-dependent ac susceptibility is indicative of Single-Molecule Magnet behavior without and/or with optimum dc field for complexes 2 and 3.

Exploring the Spatial Arrangement of Simple 18-Membered Hexaazatetraamine Macrocyclic Ligands in Their Metal Complexes.

Hexaazamacrocyclic Schiff bases have been extensively combined with lanthanoid (Ln) ions to obtain complexes with a highly axial geometry. However, the use of flexible hexaazatetraamine macrocycles containing two pyridines and acyclic spacers is rather uncommon. Accordingly, we obtained [DyL(OAc)2]OAc·7H2O·EtOH and [DyLMe2(Cl)2]Cl·2H2O, where L and LMe2 are the 18-membered macrocycles 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane and 3,10-dimethyl-3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane, respectively, which contain ethylene and methylethylene spacers between their N3 moieties. [DyL(OAc)2]OAc·7H2O·EtOH represents the first crystallographically characterized lanthanoid complex of L, while [DyLMe2(Cl)2]Cl·2H2O contributes to increasing the scarce number of LnIII compounds containing LMe2. Furthermore, the crystal structure of L·12H2O was solved, and it was compared with those of other related macrocycles previously published. Likewise, the crystal structures of the DyIII complexes were compared with those of the lanthanoid and d-metal complexes of other 18-membered N6 donor macrocycles. This comparison showed some effect of the spacers employed, as well as the influence of the size of the ancillary ligands and the metal ion. Additionally, the distinct folding behaviors of these macrocycles influenced their coordination geometries. Moreover, the luminescent properties of [DyL(OAc)2]OAc·7H2O·EtOH and [DyLMe2(Cl)2]Cl·2H2O were also investigated, showing that both complexes are fluorescent, with the emission being sensitized by the ligands.

The effect of magnetic coupling along the magnetic axis on slow magnetic relaxation in DyIII complexes with D5h configuration based on an aggregation-induced-emission-active ligand.

The adjustment of crystal symmetry and intramolecular magnetic coupling is of great importance for the construction of high-performance single-molecule magnets. By using an aggregation-induced-emission-active pyridine-carbohydrazone-based Schiff base ligand and phosphine oxides, four dinuclear and one one-dimensional DyIII-based complexes, [Dy2(TPE-pc)2(Bu3PO)2Cl2]·2CH3CN·2H2O (1), [Dy2(TPE-pc)2(Cy3PO)2Cl2] (2), [Dy2(TPE-pc)2(MePA)2Cl2]·2CH3OH (3), [Dy2(TPE-pc)2(Ph3PO)2Cl2]2 (4) and [Dy2(TPE-pc)2(DPPO)Cl2]n (5) (H2TPE-pc = (E)-N'-(2-hydroxy-5-(1,2,2-triphenylvinyl)benzylidene)picolinohydrazide, MePA = N-phenyl-N',N''-bis(morpholinyl) phosphoric triamide, DPPO = piperazine-1,4-diylbis(diphenyl phosphine oxide)), were isolated. All complexes are made up of an enol oxygen-bridged Dy2 unit, where DyIII ions possess a pentagonal bipyramidal geometry with pseudo D5h symmetry. Magnetic measurements reveal that intramolecular DyIII-DyIII couplings are ferromagnetic and all complexes display a significant slow magnetic relaxation phenomenon below 30 K under a zero dc field. Ab initio calculations indicate that the anisotropic magnetic axes of all DyIII ions are approximately perpendicular to the higher-order symmetric axes in all complexes, and that DyIII-DyIII magnetic couplings along the magnetic axes effectively suppress the ground state quantum tunneling effect of magnetization and promote the occurrence of slow magnetic relaxation. Raman relaxation prevails in all complexes. In addition, the H2TPE-pc ligand shows an aggregation-induced emission (AIE) effect; however, all complexes exhibit an aggregation-caused quenching (ACQ) phenomenon.

Understanding Single-Molecule Magnet properties of lanthanide complexes from 4f orbital splitting.

We present an approach for connecting the magnetic anisotropy of lanthanide mononuclear complexes with their f-orbital splitting for both idealized and real coordination environments. Our proposal is straightforward to apply and provides sensible estimations of the energy spacing of the ground multiplet for axial magnetic systems. This energy splitting controls Single-Molecule Magnet properties of lanthanide complexes, determining key parameters such as the demagnetization energy barrier (Ueff). Importantly, this approach is consistent with the current paradigm of oblate and prolate preferences for the distribution of the f-electron density, but delivers a finer description for ions belonging to the same group (e.g. the oblates TbIII and DyIII). The model provides simple explanations for some general trends observed experimentally (e.g. the low barriers for ErIII complexes in comparison to DyIII or the large barriers observed for cyclopentadienyl DyIII complexes in comparison with other ligands based on organometallic rings), contributing as a valuable tool to expand our description of ligand field effects in lanthanide-based SMMs.

Tuning the slow magnetic relaxation with the substituents in anilate bridged bis(dysprosium) complexes.

Dinuclear lanthanide complexes [((HB(pz)3)2Dy)2(μ-Th2An)] (1Dy) and [((HB(pz)3)2Dy)2(μ-ClCNAn)] (2Dy), based on the hydrotris(pyrazol-1-yl)borate (HBpz3-) scorpionate capping ligand and anilate (An2-) bridging linkers, namely homosubstituted dithiophene- and heterosubstituted chlorocyanoanilate, bearing electron-donating and withdrawing substituents at the 3,6-positions of the benzoquinone core, are reported. 1Dy shows an octacoordinated {N6O2} DyIII ion within a D4h distorted square antiprismatic coordination, an ideal geometry for Single-Molecule Magnet (SMM) behavior, given its oblate nature, whereas in 2Dy the octacoordinated DyIII ion adopts a D2d triangular dodecahedron geometry, while maintaining the same {N6O2} coordination sphere. Both complexes show field-induced single molecule magnet (SMM) behaviour, with tuning of the slow magnetic relaxation as a function of the nature of the substituents at the 3,6-positions of the anilate moiety. A comparison of the Arrhenius fitting parameters for 1Dy and 2Dy supports the hypothesis that square antiprismatic DyIII complexes, as 1Dy, exhibit higher energy barriers. This interpretation is supported by ab initio calculations that also shed light on the crucial role of intermolecular dipolar interactions.

Apparently improved energy barrier of Dy(iii) SMMs by adopting the bridging bipyrimidine ligand

By strategically selecting appropriate ligands, we have designed mononuclear and dimeric DyIII complexes in order to gain valuable insights into the impact of magnetic coupling on the magnetic properties of single-molecule magnets (SMMs).

From a Dy2 single-molecule magnet (SMM) to a 1D triangle-based Dy(III) chain SMM utilizing formate ions as bridging units

The reaction of Dy(NO3)2·6H2O with a Schiff base ligand N1,N3-bis(5-chlorosalicyladehyde)diethylenetriamine (H2bcsdt) afforded a dinuclear DyIII complex [Dy2(bcsdt)2(NO3)2] (1). The addition of HCOOH to the reaction system from which 1 was prepared generated a coordination polymer with the formula {[Dy3(bcsdt)3(HCOOH)(HCOO)(CO3)]·EtOH}n (2). Single-crystal X-ray diffraction analysis revealed that complex 2 possesses a one-dimensional chain structure based on a {[Dy3(bcsdt)3(HCOOH)(HCOO)(CO3)]·EtOH} repeating unit. In this unit, the three DyIII ions are connected by three oxygen atoms of one CO32– ion and display a nearly perfect triangle topology. The magnetic properties of 1 and 2 were investigated. They both exhibited slow relaxation of magnetization, indicative of single molecule magnet (SMM) behavior.

A spherical capped square antiprismatic DyIII complex encapsulated three acylhydrazone Schiff base ligands behaving field-induced single-ion magnet behaviour

One mononuclear DyIII based complex, [Dy(L)3]·0·25H2O (1) (HL= N'-(2-hydroxybenzoyl)pyridine-2-carbohydrazonamide) has been successfully synthesized and systematically characterized. Single-crystal X-ray diffraction reveals that 1 crystallizes in the orthorhombic system with space group P/21. The nine-coordinated DyIII ion in 1 adopts distorted spherical capped square antiprism configuration (C4v-CSAPR) with three tridentate coordination pockets. In addition, the alternating-current (ac) magnetic susceptibility investigations show that 1 exhibits slow magnetic relaxation behavior under an applied 1000 Oe field with effective energy barrier (Ueff) of 83.10 K. To understand the magnetic behaviour in depth, the magnetic axes and magneto-structural correlations are analyzed to reveal that the coordination of three ligands effectively enhances the axiality of the nine-coordinated mononuclear DyIII complexes, thereby exhibiting the slow magnetic relaxation behaviour. This work provides a strategy to effectively improve the performance of single-ion magnets (SIMs) by introducing more ligands around the DyIII ion, and regularizing the coordination configuration of the DyIII ion towards an axial-type structure.

Significant Control on Zero-field Quantum Tunneling of Magnetization in Dysprosium Based Single-Molecule Magnets via Orientation of the Anilato Ligand.

Tuning the bridging fashion of anilato ligand in dinuclear DyIII complexes, reveals a sizable effect on the slow relaxation of magnetization. Combined experimental and theoretical studies divulge that the geometry with high order axial symmetry (pseudo square antiprism) reduces the transverse crystal fields corresponding to QTM resulting in a significant increase in energy barrier (Ueff = 518 cm-1) through the Orbach relaxation process whereas the geometry with lower symmetry (triangular dodecahedron, pseudo D2d) enhances the transverse crystal fields that accelerate the ground state QTM process. Notably, the value 518 cm-1 represents the highest energy barrier among anilato ligand based SMMs.

A DyIII Complex of a Pentadentate Schiff Base with Field-Induced Single-Ion Magnet Behaviour

The influence of the solvent in the reaction of dysprosium(III) chloride hydrate with the N3O2 ligand H2L (2,6-bis(2-hydroxyphenyliminomethyl)pyridine) was studied To this end, the new mononuclear chloride complex [Dy(L)Cl(H2O)2] (1) was isolated in absolute ethanol as solvent, without any evidence of the hydrolysis of the ligand. This clearly contrasts with previous results, where a similar reaction in methanol proceeds with the partial hydrolysis of the Schiff base, and the formation of a new hemiacetal donor to yield [Dy(HL’)2)][Dy(L)(Cl2)] (H2L’ = (6-(2-hydroxyphenyliminomethyl)-2-methoxyhydroxymethyl)pyridine). The single crystal X-ray structure of the chloride complex 1 shows that the DyIII ion is octacoordinated in a highly distorted N3O4Cl environment between triangular dodecahedral and biaugmented trigonal prisms. The full magnetic characterisation of 1 shows that it presents field-induced single ion magnet behaviour, with a thermal energy barrier Ueff of 113.5 K, which is the highest among dysprosium complexes derived from H2L.

Interesting chemical and physical features of the products of the reactions between trivalent lanthanoids and a tetradentate Schiff base derived from cyclohexane-1,2-diamine.

The initial use of a tetradentate Schiff base (LH2) derived from the 2 : 1 condensation between 2-hydroxyacetophenone and cyclohexane-1,2-diamine in 4f-metal chemistry is described. The 1 : 2 reaction of Ln(NO3)3·xH2O (Ln = lanthanoid or yttrium) and LH2 in MeOH/CH2Cl2 has provided access to isostructural complexes [Ln(NO3)3(L'H2)(MeOH)] in moderate to good yields. Surprisingly, the products contain the corresponding Schiff base ligand L'H2 possessing six aliphatic -CH2- groups instead of the -CH-(CH2)4-CH- unit of the cyclohexane ring, i.e. an unusual ring-opening of the latter has occurred. A mechanism for this LnIII-assisted/promoted LH2 → L'H2 transformation has been proposed assuming transient LnII species and a second LH2 molecule as the H2 source for the reduction of the cyclohexane moiety. DFT calculations provide strong evidence for the great thermodynamic stability of the products in comparison with analogous complexes containing the original intact ligand. The structures of the PrIII, SmIII, GdIII, TbIII, and HoIII complexes have been determined by single-crystal X-ray crystallography. The 9-coordinate LnIII centre in the molecules is bound to six oxygen atoms from the three bidentate chelating nitrato groups, two oxygen atoms that belong to the bidentate chelating organic ligand, and one oxygen atom from the coordinated MeOH group. In the overall neutral bis(zwitterionic) L'H2 ligand, the acidic H atoms are clearly located on the imino nitrogen atoms and this results in the formation of an unusual 16-membered chelating ring. The coordination polyhedra defined by the nine donor atoms around the 4f-metal-ion centres can be best described as distorted, spherical capped square antiprisms. The EuIII, TbIII, and DyIII complexes exhibit LnIII-based luminescence in the visible region, with the coordinated L'H2 molecule acting as the antenna. Ac magnetometry experiments show that the DyIII member of the family behaves as an SIM at zero field and under external dc fields of 0.1 and 0.2 T without the enhancement of the peaks' maxima, suggesting that QTM is not the relaxation path. The GdIII complex behaves, rather unexpectedly, as a SIM with two different magnetic relaxation paths occurring at very close temperatures; this behaviour is tentatively attributed to a very small axial zero-field splitting (D ∼ 0.1 cm-1), which cannot be detected by magnetization or susceptibility experiments. The prospects of the present, first results in the lanthanoid(III)-LH2 chemistry are discussed.

Luminescence of Macrocyclic Mononuclear DyIII Complexes and Their Immobilization on Functionalized Silicon-Based Surfaces.

Two mononuclear DyIII complexes, [Dy(L1)(NCS)3] (Dy-EDA) and [Dy(L2)(NCS)3] (Dy-DAP), where Ln (n = 1-2) corresponds to a macrocyclic ligand derived from 2,6-pyridinedicarboxaldehyde and ethylenediamine (L1) and 1,3-diaminepropane (L2) were immobilized on functionalized silicon-based surfaces. This was achieved by the microcontact printing (μCP) technique, generating patterns on a functionalized surface via covalent bond formation through the auxiliary -NCS ligands present in the macrocyclic complex species. With this strategy, it was possible to control the position of the immobilized molecules on the surface. Water contact angle measurements, X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectra (IRRAS), and atomic force microscopy (AFM) confirmed that the surfaces were successfully functionalized. Furthermore, the optical properties in a broad temperature range were investigated for the as-prepared compounds. At room temperature, Dy-EDA was shown to emit in the deep blue region (Commission Internationald'Eclairage (CIE): (0.175, 0.128)), while Dy-DAP in the white region (CIE: (0.252, 0.312)). The different CIE values were due to the contribution of the strong emission of the ligand in the case of Dy-EDA. Besides, surface photoluminescence measurements showed that the immobilized complexes retained their bulk emissive properties.

Multifunctional Dy@PVP and Ho@PVP one-dimensional nanofibers: Electrospinning synthesis, luminescent and magnetic properties

In this paper, different concentrations of DyIII complex of {[Dy(2-stp)2(H2O)6].2(4,4′-bipy).5(H2O)}, and HoIII complex of {[Ho(2-stp)2(H2O)6].2(4,4′-bipy).5(H2O)} (2-stp= 2-sulfoterephthalate and 4,4′-bipy=4,4′-bipyridine), were doped into the polymer matrix of Poly(vinylpyrrolidinone) (PVP) using the electrospinning technique, forming a series of orangish-yellow and purish-yellow luminescent nanofibers of Dy@PVP and Ho@PVP. It was observed that DyIII/HoIII ions showed strong characteristic emission in the luminescent spectra of the composite nanofibers. Simultaneously, in comparison with the precursor DyIII/HoIII complex, the Dy@PVP or Ho@PVP nanofibers has a great improvement in the photo and thermal stability

Synthesis, Structure, and Zero-Field SMM Behavior of Homometallic Dy2, Dy4, and Dy6 Complexes.

The synthesis, structure, and magnetic properties of three DyIII complexes of different nuclearity, [Dy2(H2L)2(NO3)] [NO3]·2H2O·CH3OH (1), [Dy4(HL)2(piv)4(OH)2] (2), and [Dy6(H2L)3(μ3-OH)(μ3-CO3)3(CH3OH)4(H2O)8] 5Cl·3H2O (3) [(H4L) = 6-((bis(2-hydroxyethyl)amino)-N'-(2-hydroxybenzylidene)picolinohydrazide)], are described. This variety of complexes with the same ligand could be obtained by playing with the metal-to-ligand molar ratio, the type of DyIII salt, the kind of base, and the presence/absence of coligand. 1 is a dinuclear complex, while 2 is a tetranuclear assembly with a butterfly-shaped topology. 3 is a homometallic hexanuclear complex that exhibits a propeller-shaped topology. Interestingly, in this complex 3, three atmospheric carbon dioxide molecules are trapped in the form of carbonate ions, which assist in holding the hexanuclear complex together. All of the complexes reveal a slow relaxation of magnetization even in zero applied field. Complex 1 is a zero-field SMM with an effective energy barrier (Ueff) of magnetization reversal equal to 87(1) K and a relaxation time of τ0 = 6.4(3) × 10-9 s. Under an applied magnetic field of 0.1 T, these parameters change to Ueff = 101(3) K, τ0 = 2.5(1) × 10-9 s. Complex 2 shows zero-field SMM behavior with Ueff = 31(2) K, τ0 = 4.2(1) × 10-7 s or τ01 = 2(1) × 10-7 s, Ueff1 = 37(8) K, τ02 = 5(6) × 10-5 s, and Ueff2 = 8(4) by considering two Orbach relaxation processes, while 3, also a zero-field SMM, shows a double relaxation of magnetization [Ueff1 = 62.4(3) K, τ01 = 4.6(3) × 10-8 s, and Ueff1 = 2(1) K, τ02 = 4.6(2) × 10-5 s]. The ab initio calculations indicated that in these complexes, the Kramer's ground doublet is characterized by an axial g-tensor with the prevalence of the mJ = ±15/2 component, as well as that due to the weak magnetic coupling between the metal centers, the magnetic relaxation, which is dominated by the single DyIII centers rather than by the exchange-coupled states, takes place via Raman/Orbach or TA-QTM. Moreover, theoretical calculations support a toroidal magnetic state for complex 2.

Bis[μ3-2-(pyridin-3-yl)acetato-κ3 O:O:O']bis-[μ2-2-(pyridin-3-yl)acetato-κ2 O:O']bis-[chlorido-(1,10-phenanthroline-κ2 N,N')dysprosium(III)

The title DyIII complex, [Dy2(C7H6NO2)4Cl2(C12H8N2)2] or [Dy2(μ 3-PAA)4(Cl)2(phen)2] (PAA = 3-pyridyl-acetate, phen = 1,10-phenanthroline), obtained by reaction of Dy(ClO4)3, 3-pyridyl-acetic acid ligands and 1,10-phenanthroline, exhibits a dinuclear structure. Adjacent binuclear dimers are further connected via face-to-face π-π stacking inter-actions resulting in supra-molecular chains along the c-axis direction.

A Sodium Sodate as Precursor for Lanthanide Bis(4-R-benzoxazol-2-yl)methanide Single-Molecule Magnets.

From the sodium sodate precursor [(Na(thf)6][Na{(4-Me-NCOC6H3)2CH}2] (1) three isostructural dinuclear lanthanide complexes [(μ-Cl)LnIII{(4-MeNCOC6H3)2CH}2]2 with Ln = Gd (2), Dy (3), and Er (4) based on the N,N'-chelating monoanionic bis(4-methylbenzoxazol-2-yl)methanide ligand (titled "Mebox") were synthesized and characterized by X-ray diffraction and magnetic measurements. The sodium precursor 1 was analyzed via X-ray diffraction and diffusion-ordered NMR spectroscopy experiments (DOSY-NMR) in order to investigate its aggregation in solution and the solid state. The sodium analog [(thf)3Na(NCOC6H4)2CH] (1') based on the bis(benzoxazol-2-yl)-methanide ligand (titled "box") was prepared and analyzed for comparison reasons. From the lanthanide derivatives 2-4, the DyIII complex 3 displays slow relaxation of magnetization at zero field, with a relaxation barrier of U = 315.7 cm-1. The coupling strength between the two lanthanide centers was estimated with the GdIII equivalent 2, giving a weak antiferromagnetic coupling of J = -0.035 cm-1.

Modulating the Structures and Magnetic Properties of Dy(III) Single-Molecule Magnets through Acid-Base Regulation.

Chemical modulation on the structures and physical properties of the coordination complexes is of great interest for the preparation of new functional materials. By changing the acidity or basicity of the reaction medium, the deprotonation degree of a multidentate ligand with multiple active protons, H4daps (H4daps = N',N'″-((1E,1'E)-pyridine-2,6-diylbis(ethan-1-yl-1-ylidene))bis(2-hydroxybenzohydrazide)), can be regulated on purpose. With this ligand of different deprotonation and charges, three new DyIII complexes ([Dy(H3daps)(CH3COO)2(EtOH)]·CH3COOH (1Dy), [Dy2(H2daps)2(EtOH)2(H2O)2(MeOH)2](CF3SO3)2·(H2O)2 (2Dy), and [Dy3(H1daps)2(H2daps)(μ3-OH)(EtOH)(H2O)] (3Dy)) of different nuclearities (mono-, di-, and trinuclear for 1Dy to 3Dy, respectively) have been synthesized and characterized structurally and magnetically. Analyses on the related bond lengths and resulting hydrogen bond modes in the complexes provide the details of the deprotonation position and the charge of the ligands, which can be in the form of H3daps-, H2daps2-, and H1daps3-. Interestingly, the more deprotonated ligand can act as a bridging ligand between the DyIII centers using the phenol and/or carbonyl oxygen atoms, which leads to the multinuclear structures. Magnetic studies on these complexes revealed that complex 1Dy is a field-induced single-molecule magnet (SMM), while complexes 2Dy and 3Dy show SMM behavior under a zero dc field.

Role of the Templating Heteroatom on Both Structural and Magnetic Properties of POM‐Based SIM Lanthanoid Complexes

AbstractThe plasticity of the coordination chemistry of Lanthanoid ions (LnIII) has allow the design of novel coordination compounds with slow relaxation of the magnetization since the first Single Ion Magnet (SIMs) was reported by Ishikawa, who used the phthalocyaninate ligand to make a “sandwich type” complex. The coordination chemistry has allowed the possibility to design different types of molecular complexes with SIMs behaviour based on organic ligands. There is also SIMs based on inorganic ligands, using different types of lacunary polyoxometalates (LPOM) like, [XW11O39]n−. The combination of both types of ligands can produce hybrid inorganic‐organic LnIII complexes with SIM behaviour. This is an attractive approach since these hybrid materials could benefit from the combination of the ease of functionalization of the organic ligands with the robustness of the inorganic moieties. There are reports that a hybrid mononuclear DyIII complex could improve the relaxation dynamics when it is compared to the inorganic analogues. Thus, in this review we present a study and comparison on the improvement that inorganic and organic ligands can cause to the geometry of the metal centres of fully inorganic and hybrid (mononuclear and dinuclear) lanthanoid complexes (for DyIII, ErIII and YbIII). Moreover, we will discuss which of these changes can modify the magnetic properties of the Lanthanoid Complexes.

Incorporation of expanded organic cations in dysprosium(III) borohydrides for achieving luminescent molecular nanomagnets

Luminescent single-molecule magnets (SMMs) constitute a class of molecular materials offering optical insight into magnetic anisotropy, magnetic switching of emission, and magnetic luminescent thermometry. They are accessible using lanthanide(III) complexes with advanced organic ligands or metalloligands. We present a simple route to luminescent SMMs realized by the insertion of well-known organic cations, tetrabutylammonium and tetraphenylphosphonium, into dysprosium(III) borohydrides, the representatives of metal borohydrides investigated due to their hydrogen storage properties. We report two novel compounds, [n-Bu4N][DyIII(BH4)4] (1) and [Ph4P][DyIII(BH4)4] (2), involving DyIII centers surrounded by four pseudo-tetrahedrally arranged BH4– ions. While 2 has higher symmetry and adopts a tetragonal unit cell (I41/a), 1 crystallizes in a less symmetric monoclinic unit cell (P21/c). They exhibit yellow room-temperature photoluminescence related to the f–f electronic transitions. Moreover, they reveal DyIII-centered magnetic anisotropy generated by the distorted arrangement of four borohydride anions. It leads to field-induced slow magnetic relaxation, well-observed for the magnetically diluted samples, [n-Bu4N][YIII0.9DyIII0.1(BH4)4] (1@Y) and [Ph4P][YIII0.9DyIII0.1(BH4)4] (2@Y). 1@Y exhibits an Orbach-type relaxation with an energy barrier of 26.4(5) K while only the onset of SMM features was found in 2@Y. The more pronounced single-ion anisotropy of DyIII complexes of 1 was confirmed by the results of the ab initio calculations performed for both 1–2 and the highly symmetrical inorganic DyIII borohydrides, α/β-Dy(BH4)3, 3 and 4. The magneto-luminescent character was achieved by the implementation of large organic cations that lower the symmetry of DyIII centers inducing single-ion anisotropy and separate them in the crystal lattice enabling the emission property. These findings are supported by the comparison with 3 and 4, crystalizing in cubic unit cells, which are not emissive and do not exhibit SMM behavior.

Molecular magnetic properties of a dysprosium(III) complex coordinated to a nonadentate bispidine ligand

AbstractThe DyIII complex of the nonadentate bispidine L1 (bispidine=3,7‐diazabicyclo[3.3.1]nonane) has a capped square antiprismatic structure, known to lead to suppressed quantum relaxation of magnetization by quantum tunneling. [DyIIIL1]OTf indeed is an SMM with a modest barrier to magnetization relaxation. The experimentally determined barrier of 46 cm−1 is confirmed by ab initio calculations (43.5 cm−1), and the quantum‐chemical analysis indicates that ligand modifications, leading to a higher symmetry and a stronger axial ligand field should significantly increase the effective barrier to magnetization relaxation.