Single-molecule Magnet Behavior Research Articles

Single-Molecule Magnet Behavior in a Tb-Nitronyl Nitroxide Radical Network with [Tb3(NIT)2] Nodes.

Two rare two-dimensional Ln-radical networks, namely, [{Ln(tfa)3}3(NIT-4Py)2]n [LnIII = Gd 1 and Tb 2; tfa- = trifluoroacetylacetonato; and NIT-4Py = 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide], have been successfully constructed and characterized. In these complexes, each NIT-4Py radical functions as a tridentate ligand to ligate three Ln ions, creating a 2D network with linear five-spin [Ln3(NIT)2] nodes. Ferromagnetic Ln-NO interactions govern the characteristic magnetic behavior of a finite spin system. The Tb complex is shown to exhibit SMM behavior in a zero DC field, with an energy barrier for spin flipping of 53 K and hysteretic M-H behavior at 2.3 K, with a coercive field Hcoer = 110 Oe. This complex represents the first example of a Ln-nitronyl nitroxide SMM-based network.

Multifunctional Dy3+ Complexes with Triphenylmethanolates: Structural Diversity, Luminescence, and Magnetic Relaxation.

The coordination environment of magneto-luminescent Dy3+-based Single-Molecule Magnets (SMM) is a crucial factor influencing both magnetic and luminescent properties. In this work, we explore how triphenylmethanolate (Ph3CO-), in combination with other ligands, can modulate the structure and, therefore, the magnetic properties of Dy3+-based SMM. Using triphenylmethanolate in combination with THF and pyridine (Py) as co-ligands, we synthesized a series of mononuclear cis-[Dy(OCPh3)2(THF)4][BPh4]·(2,6-Me2C5H3N) (1), trans-Dy(OCPh3)3(THF)2 (2), fac-Dy(OCPh3)3(py)3 (3) and dinuclear [(Ph3CO)Dy(THF){(μ2-Cl)2Li(THF)2}μ2-Cl]2 (4) complexes where the Dy3+ ion presents five- or six-coordinate geometries. Dinuclear compound 4 exhibits a genuine SMM behavior with a relatively high energy barrier of 421 cm-1, while mononuclear complexes 1-3 are field-induced SMM. These complexes also present Dy3+-characteristic luminescence, highlighting their multifunctional character.

Trigonal Planar Heteroleptic Lanthanide(III) Bis(silyl)amide Complexes Containing Aminoxyl Radicals and Anions.

Modulation of the crystal field (CF) in lanthanide (Ln) complexes can enhance optical and magnetic properties, and large CF splitting can be achieved with low coordination numbers in specific geometries. We previously reported that the homoleptic near-linear Sm2+ complex [SmII{N(SiiPr3)2}2] (1-Sm) is oxidized by the 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO•) radical to give the heteroleptic, approximately trigonal planar Sm3+ complex, [SmIII{N(SiiPr3)2}2(TEMPO-)] (2-Sm). Here, we report the synthesis of homologous [LnIII{N(SiiPr3)2}2(TEMPO-)] (2-Ln; Ln = Tm, Yb) complexes by the oxidation of the parent [Ln{N(SiiPr3)2}2] (1-Ln; Ln = Tm, Yb) with TEMPO•; complexes 2-Ln all contain TEMPO- anions. The homoleptic bent Ln3+ complexes [LnIII{N(SiiPr3)2}2][B(C6F5)4] (3-Ln; Ln = Sm, Tm, Yb) were also treated with TEMPO• to yield the heteroleptic, approximately trigonal planar Ln3+ complexes [LnIII{N(SiiPr3)2}2(TEMPO•)][B(C6F5)4] (4-Ln; Ln = Sm, Tm, Yb); the cations of 4-Ln all contain TEMPO• radicals. We have compared the electronic structures of the two geometrically similar families of Ln3+ complexes with the TEMPO- anion (2-Ln) or TEMPO• radical (4-Ln) using a combination of UV-vis-NIR and EPR spectroscopy, magnetic measurements, and ab initio calculations. These studies revealed no single-molecule magnet behavior for 2-Yb despite evidence for sizable CF splitting and a high degree of purity of the ground stabilized mJ = |±7/2⟩ state, while the radical TEMPO• in 4-Yb did not significantly improve performance.

Self-Assembled Lanthanide Phosphinate Square Grids (Ln = Er, Dy, and Tb): Dy4 Shows SMM/SMT and Tb4 SMT Behavior.

Tetranuclear [2 × 2] square-grid-like LnIII clusters have been synthesized by reacting LnCl3·6H2O salts with bis[α-hydroxy(p-bromophenyl)methyl]phosphinic acid [R2PO2H, where R = CH(OH)PhBr] and pivalic acid. Single-crystal X-ray diffraction studies show the formation of [Me4N]2[Ln4(μ2-η1:η1-PO2R2)8(η2-CO2But)4(μ4-CO3)] [Ln = Er (1), Dy (2), and Tb (3)]. Direct-current studies reveal significant ferromagnetic interactions between DyIII in 2 and TbIII in 3 and an antiferromagnetic interaction between ErIII in 1. Dynamic magnetic susceptibility measurements confirm a single-molecule magnet (SMM) behavior in both 0 and 1200 Oe applied magnetic fields for 2. Complexes 2 and 3 show single molecular toroic (SMT) behavior with a mixed magnetic moment.

Triple-Decker Hexaazamacrocyclic Lanthanide(III) Complexes: Structure, Magnetic Properties, and Temperature-Dependent Luminescence.

The reaction of fluoride anions with mononuclear rare-earth(III) complexes of the hexaazamacrocycle derived from 2,6-diformylpyridine and ethylenediamine affords trinuclear coordination compounds [Ln3L3(μ2-F)4(NO3)2](NO3)3. The X-ray crystal structures of these complexes show triplex cationic complexes where the three roughly parallel macrocyclic lanthanide(III) units are linked by bis-μ2-F bridges. The detailed analysis of the photophysical properties of the [Eu3L3(μ2-F)4(NO3)2](NO3)3·2H2O and [Tb3L3(μ2-F)4(NO3)2](NO3)3·3H2O complexes reveals different temperature dependence of luminescence intensity and luminescence decay time of the Eu(III) and Tb(III) derivatives. The spectra of mixed species of average composition [Eu1.5Tb1.5L3(μ2-F)4(NO3)2](NO3)3·3H2O are in accordance with the ratiometric luminescent thermometer behavior. Measurements of the direct-current (dc) magnetic susceptibility of the [Dy3L3(μ2-F)4(NO3)2](NO3)3·2H2O complex indicate possible ferromagnetic interactions between the Dy(III) ions. Alternating current (ac) susceptibility measurements of this complex indicate single-molecule magnet behavior in zero dc field with magnetic relaxation dominated by Orbach mechanism and an effective energy barrier Ueff = 12.3 cm-1 (17.7 K) with a pre-exponential relaxation time, τ0 of 7.3 × 10-6 s. A similar reaction of mononuclear macrocyclic complexes with a higher number of fluoride equivalents results in polymeric {[Ln3L3(μ2-F)5](NO3)4}n complexes. The X-ray crystal structure of the Nd(III) derivative of this type shows trinuclear units that are additionally linked by single fluoride bridges to form a linear coordination polymer.

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.

Syntheses, structures and magnetisms of dimethyl phosphate-bridged dinuclear lanthanide complexes with pentadentate macrocyclic ligand

A series of air-stable dinuclear complexes, [HNEt3]2[Ln2(L)2((CH3O)2PO2)4](BPh4)4 (L = 2,14-dimethyl-3,6,10,13,19-pentaazabicyclo[13.3.1]nonadeca1(19), 2,13,15,17-pentene, Ln = Dy, 1-Dy; Tb, 2-Tb; Gd, 3-Gd), has been synthesized and characterized using single-crystal X-ray crystallography and magnetic measurements. The crystal structures disclose that two dimethyl phosphate anions act as bridging ligands, linking two Ln(III) ions. Each Ln(III) ion is eight-coordinated by five nitrogen atoms from a pentadentate Schiff based ligand L and three oxygen atoms from three dimethyl phosphates, forming a triangular dodecahedral coordination geometry. Direct-current magnetic susceptibility measurements indicate an extremely weak antiferromagnetic exchange between Gd(III) ions in 3-Gd. Complex 1-Dy exhibits slow magnetic relaxation with an effective energy barrier (Ueff) of 13 K under an applied field of 1000 Oe, whereas 2-Tb does not exhibit single-molecule magnet behavior. This work presents a novel strategy for constructing polynuclear single-molecular magnets by using a pentadetate macrocycle as magnetic building blocks integrated with replaceable axial ligands.

Alcohol-bridged dinuclear dysprosium single-molecule magnets

Herein we showcase triple-bridged symmetric dinuclear dysprosium complexes with the core structure of general chemical formula Dy2(L1)2(L2)2(R-OH) (R = Me, 1; Et, 2; iPr, 3; pHCH2, 4) involving bridging alcohol molecules. L1 and L2 represent the deprotonated form of oxazole 4‑tert‑butyl‑2-(7-methoxybenzo[d]oxazol-2-yl)phenol and Schiff-base (E)-2,4-di‑tert‑butyl‑6-((3,5-di‑tert‑butyl‑2-hydroxybenzylidene)amino)phenol, respectively. Single-crystal X-ray structural characterization revealed an unprecedented long Dy-O bond length for the benzyl alcohol analogue. The corresponding long Dy-O bond lengths in 1–4 are 2.7825, 2.6651, 2.6021 and 2.9955 Å, respectively. Alternating current magnetic susceptibility measurements at zero dc field revealed that all four complexes display clear frequency dependence signal peaks, indicating single-molecule magnet behavior. The spin reversal energy barrier heights for 1, 2 and 4 are 31.1, 27.6 and 17.4 K. The dynamic magnetic behavior is influenced by the different Dy-O bond lengths derived from the bridging alcohol molecules. Theoretical calculations were employed to establish magneto-structural correlations in 1–4. Magneto-structural correlations with respect to the alcohol molecule participating in triple-bridged symmetric dinuclear dysprosium complexes is established with the help of quantum-chemical calculations.

Integrating Polyoxometalate into Dy(III)-based Single-molecule Magnets with Pentagonal Bipyramidal Symmetry.

Polyoxometalates (POMs) with various coordination fashions are versatile ligands for constructing single-ion magnets (SIMs), but enforcing POM-SIMs with a specific geometry remains a synthetic challenge. Herein, we synthesized a POM-cocrystallized DyIII-SIM [Dy(OPPh3)4(H2O)3][PW12O40]·4EtOH (1Dy) and a POM-ligated DyIII-SIM [{Dy(OPPh3)3(H2O)3}{PW12O40}]·Ph3PO·H2O (2Dy) with pentagonal bipyramidal local coordination geometry. Magnetic measurements indicate that 1Dy displays field-induced single-molecule magnet (SMM) behavior and the relaxation is dominated by under-barrier processes. 2Dy exhibits spin-lattice relaxation at a broader temperature region with a reversal barrier over 300 K. Magneto-structural analysis reveals that the enhancement of SMM behavior originated from the equatorial replacement of Ph3PO by POM, which strengthens the axial anisotropy in 2Dy. Luminescent experiments indicate that the characteristic DyIII emissions of 1Dy are covered up by the strong π-π* emission of Ph3PO at low-temperature regions. As for 2Dy, partial DyIII emission persists thanks to the antenna effect between DyIII and POM.

Structures and Single-Molecule Magnet Behavior of Dy3 and Dy4 Clusters Constructed by Different Dysprosium(III) Salts.

Using the Schiff base ligand H2L-pyra (N'-(2-hydroxybenzoyl)pyrazine-2-carbohydrazonamide) with multiple dentate sites, the trinuclear DyIII-based complex [Dy3(HL-pyra)2(L-pyra)2(CH3COO)3]·2H2O (1) was synthesized. By analyzing the fragmented assembly process and fine-tuning the bridging anions, complex [Dy4(HL-pyra)2(L-pyra)4(NO3)2(H2O)2]·8H2O (2) with different nuclear numbers was successfully synthesized. Magnetic studies demonstrated that 1 did not exhibit magnetic relaxation behavior under the external field; however, 2 exhibited zero-field single-molecule magnetic relaxation behavior with an effective energy barrier (Ueff) of 197.44 K. This is attributed to the improved anisotropy of the single ion after the normalization of the crystal structure, thus realizing the molecular magnetic switching. Moreover, magnetic dilution analysis of 2 demonstrated that the weak magnetic interaction between metal ions inhibited the occurrence of quantum tunneling of magnetization (QTM), resulting in high-performance single-molecule magnet (SMM) behavior. The reasons for the magnetic difference between these two complexes were analyzed using ab initio calculation and magneto-structural correlations. This study provides a reasonable prediction of the ideal configuration of the approximately parallelogram DyIII-based SMMs, thus offering an effective approach for synthesizing Dy4 complexes with excellent properties.

Syntheses and properties of seven 3,4-dichlorobenzoate-based zinc-rare earth heterometallic complexes containing a field-induced Zn(II)-Dy(III)-Dy(III)-Zn(II) single-molecule magnet

Under solvothermal conditions of CH3CH2OH and H2O, a series of 3d-4f heterometallic complexes [Ln2Zn2(3,4-DCB)10(2,2′-bpy)2] [Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Er (6) and Yb (7), 3,4-DCB = 3,4-dichlorobenzoic acid, 2,2′-bpy = 2,2′-bipyridine] were synthesized by the reactions of Ln(NO3)3·6H2O, Zn(NO3)2·6H2O, 3,4-HDCB, 2,2′-bpy and NaOH. These complexes were characterized by single crystal X-ray diffraction, powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA) and differential thermo analysis (DTA). Complexes 1–7 show two types of different zero-dimensional (0D) structures although they have the same molecular formula. Complexes 1–5 are isomorphic, and complexes 6 and 7 are isomorphic. In 1–7, linear tetranuclear clusters are formed from 3,4-DCB connecting Ln(III) and Zn(II). They can be expanded into one-dimensional (1D) supramolecular chains or two-dimensional (2D) supramolecular layers by the intermolecular π–π interactions. The photoluminescent properties of 1, 2, 4 and 5 and the magnetic properties of 3–7 were studied in detail. Complex 5 exhibits an obvious field-induced single-molecule magnet behavior with a Ueff value of approximately 24 K.

Multifunctional Ln2 compounds with butterfly-shaped structures: Remarkable Single-Molecule Magnet behaviors, and biological activities

The efficient design and reasonable construction of multifunctional Ln(III)-based compounds with fascinating structures have always attracted great concern, and it is also an immense challenge in recent times for chemists and materials scientists. Herein, two new binuclear Ln(III)-based compounds with molecular formula [Ln2L2(dbm)2(CH3OH)2]·xCH3OH·yCHCl3 (LnIII = Tb (1), x =2, y = 0; LnIII = Dy (2), x =0, y = 2; H2L = (E)-N'-(5-bromo-2-hydroxy-3-methoxybenzylidene)nicotinohydrazide; and Hdbm = 1,3-diphenyl-1,3-propanedione) have been constructed by a polydentate Schiff base ligand (H2L) via solvothermal method. The structures, magnet behaviors, and biological activities of compounds 1 and 2 have been studied systematically. Structure studies suggest that the two Ln2 compounds 1 and 2 are isostructural and possess butterfly-shaped molecular structures. Magnetic studies exhibit that Dy2 compound 2 shows remarkable single-molecule magnet behavior under zero-field conditions with Ueff/kB = 55.91 K and τ0 = 4.02×10−7 s. Moreover, solid-state fluorescent properties research shows that the two Ln2 compounds display the characteristic Tb3+ and Dy3+ ions luminescence at room temperature. Furthermore, biological activities research reveal that the two Ln2 compounds have better antibacterial activities against four common types of bacteria (Escherichia coli, Staphylococcus aureus, Candida albicans, and Bacillus subtilis) than the polydentate Schiff base ligand (H2L) and β-diketo salts Ln(dbm)3⋅2H2O (Ln(III) = TbIII and DyIII). The interaction between Ln2 compounds (1 and 2) and calf thymus DNA have also been studied, and the result reveal that both Tb2 and Dy2 compounds were mainly intercalated with calf thymus DNA. To our knowledge, compounds 1 and 2 are rarely reported multifunctional Ln(III)-based compounds owning single-molecule magnet behavior, fluorescent properties, and biological activities simultaneously.

Single molecule magnet behaviour of CoIIILnIII (Ln = TbIII, GdIII) compounds with compartmental Schiff base ligand and sulfonate co-ligands

In this research, our team synthesized and characterized two heteronuclear 3d-4f complexes, [CoIIICl(μ-valen)(μ-4-HBS)LnIII(NO3)(H2O)(4-HBS)], with Ln representing Tb (1) and Gd (2). Achievement of this was through the utilization of a compartmental Schiff base ligand H2valen, alongside secondary co-ligands Na(4-HBS) [H2valen=6,6′-((1E,1′E)-(ethane-1,2-diylbis(azaneylylidene))bis(methaneylylidene))bis(2-methoxyphenol); Na(4-HBS)=sodium 4-hydroxybenzenesulfonate]. X-ray crystallography revealed that both complexes feature a similar [Co(III)-Ln(III)] core, connected by the phenoxo-O atoms from the compartmental Schiff base ligand and the sulfonate-O atoms from the co-ligand. In this context, Co(III) displays a distorted octahedral geometry within a CoN2O3Cl coordination sphere, while Ln(III) exhibits a muffin (MFF)-like distorted geometry in a LnO9 coordination sphere. Magnetic analysis shows that the two complexes display unique magnetic properties. Complex 1 exhibits pronounced SMM behavior, with a notable energy barrier of 14.8 K for magnetization reversal. However, complex 2 presents a minor energy barrier of 4.8 K. Additionally, complexes 1 and 2 represent uncommon examples of dinuclear Co(III)-Ln(III) SMMs.

From Dy-chain to Dy-dimer: Significant structural variation induced only by counter cations and slow magnetic relaxation behaviors

Herein we report a family of Dy complexes with 1,1,1,5,5,5-hexafluoropentane-2,4‑dione (Hhfac), [Et2MeNH][Dy(hfac)3(OAc)] (1), [Et3NH][Dy(hfac)3(OAc)] (2) and [(n-Pr)3NH]2[Dy2(hfac)6(OAc)2] (3), among which a rare structural variation has been realized by the change of organic ammonium counter cations. These complexes are all constructed from mononuclear [Dy(hfac)3] building units and OAc− linkages, while employing different protonated tertiary amines as the counter cations. The Namine-H∙∙∙Oacetate hydrogen bonds, which are formed between counter cations and OAc− bridges in all complexes, make each counter cations just wedge into the gaps between adjacent [Dy(hfac)3] building units. The hfac‒ groups of each [Dy(hfac)3] unit thus inversed to other side along with the enlarging of the steric hindrance of counter cations, resulting in a significant structural variation from infinite chain topologies of 1 and 2 to discrete dimer structure of 3. For such significant structural variation induced only by the counter cations, to our knowledge, it is the first time in the whole lanthanide complex family. The magnetic studies revealed that 1–3 all show field-induced single-molecule magnets (SMMs) behavior, with the efficient energy barriers (Ueff) of 23.9, 8.5, and 11.2 K, respectively.

Cu(II)-Ln(III) (Ln = Gd, Tb and Dy) complexes of an unsymmetrical N2O3 donor ligand: field induced SMM behaviour of Cu(II)-Tb(III) complexes.

Three new hetero-metallic CuII-LnIII complexes [(CuL)Gd(NO3)3(CH3OH)]n (1), [(CuL)Tb(NO3)3(H2O)]·[CuL] (2) and [(CuL)Dy(NO3)3(H2O)]·[CuL] (3) have been synthesized using a mono-nuclear Cu(II) complex, [CuL], of an unsymmetrically di-condensed N2O3 donor Schiff base ligand, N-(3-methoxysalicylidene)-N-(salicylidene)-1,2-ethylenediamine (H2L). Single crystal X-ray crystallography revealed that complex 1 is a nitrate bridged 1D chain of dinuclear Cu(II)-Gd(III) units whereas in 2 and 3, the dinuclear Cu(II)-Ln(III) units are co-crystallized with a [CuL] unit. The Ln(III) centers are nine coordinated with the geometry of a spherical capped square antiprism for Gd and spherical tricapped trigonal prism for Tb and Dy. The geometry of the Cu(II) center is distorted octahedral for complex 1 and distorted square planar for complexes 2 and 3. Temperature-dependent molar magnetic susceptibility measurements in 1-3 revealed the presence of overall ferromagnetic coupling between the Cu(II) and Ln(III) centers. Notably, field induced single-molecule magnet behavior was witnessed in the Tb(III) derivative (2). The ab initio calculations indicated that upon application of an external magnetic field, the tunneling in the ground state of complex 2 gets reduced and thereby field-induced SMM behaviour is observed. Besides, in the case of complex 1, BS-DFT calculations were carried out to gain further insights into the magnetic exchange coupling interactions between the Cu(II) and Gd(III) centers.

Dy4 and Dy5 complexes based on tautomeric hydrazone Schiff-base ligand regulated by temperature showing single-molecule magnet behaviour

Two dysprosium complexes [Dy4(H2L)6]⋅4H2O (Dy4) and [Dy5(H2L)(HL)2(L)(µ3OH)2Cl(H2O)(MeCN)2]⋅4MeOH⋅7H2O (Dy5) (H4L = (N',N'''E,N',N'''E)-N',N'''-(pyridine-2,6-diylbis(methanylylidene))bis(2-hydroxybenzohydrazide)) based on hydrazone Schiff-base ligand were synthesized, which could be regulated by controlling temperature (Dy4, below 293 K and Dy5, over 308 K). Magnetic studies show that complex Dy4 is a typical field-induced single-molecule magnet with an effective energy barrier (Ueff) of 42.9 K under 1 kOe dc field. Complex Dy5 is a zero dc field single-molecule magnet with an effective energy barrier (Ueff) of 4.18 K. The results indicate the synthesis of lanthanide complexes is sensitive to substitute of ligand and temperature.

Unique Double and Triple Decker Arrangements of Rare-Earth 9,10-Diborataanthracene Complexes Featuring Single-Molecule Magnet Characteristics.

Herein, we present the first report on the synthesis of rare-earth complexes featuring a 9,10-diborataanthracene ligand. This 14-π-electron ligand is highly reductive and was previously used in small-molecule activation. Salt elimination reactions between dipotassium 9,10-diethyl-9,10-diborataanthracene [K2(DEDBA)] and [LnIII(η8-CotTIPS)(BH4)(thf)x] (CotTIPS=1,4-(iPr3Si)2C8H6) in a 1 : 1 ratio yielded heteroleptic sandwich complexes [K(η8-CotTIPS)LnIII(η6-DEDBA)] (Ln=Y, Dy, Er). These compounds form Lewis-base-free one-dimensional coordination polymers when crystallised from toluene. In contrast, reaction of [K2(DEDBA)] and [LnIII(η8-CotTIPS)(BH4)(thf)x] in a 1 : 2 ratio led to the formation of heteroleptic triple-decker complexes [(η8-CotTIPS)LnIII(μ-η6:η6-DEDBA)LnIII(η8-CotTIPS)] (Ln=Y, Dy, Er). Notably, these are not only the first lanthanide triple-decker compounds featuring a six-membered ring as a deck but also the first trivalent lanthanide triple-decker featuring a heterocycle in the coordination sphere. Magnetic investigations reveal that [K(η8-CotTIPS)LnIII(η6-DEDBA)] (Ln=Dy, Er) and [(η8-CotTIPS)ErIII(μ-η6:η6-DEDBA)ErIII(η8-CotTIPS)] exhibit Single-Molecule Magnet (SMM) behaviour. In the case of [(η8-CotTIPS)LnIII(μ-η6:η6-DEDBA)LnIII(η8-CotTIPS)] (Ln=Dy, Er), the introduction of a second near lanthanide ion results in strong antiferromagnetic interactions, allowing the enhancement of the magnetic characteristic of the system, compared to the quasi isolated counterpart. This research renews the overlooked coordination chemistry of the DBA ligand and expands it to encompass rare-earth elements.

Single-Molecule Magnet Behavior of Confined Dy(III) in a Mixed Heteroatom-Substituted Polyoxotungstate.

Two heteroatom-templated Dy(III)-confined polyoxotungstates [H2N(CH3)2]7Na7[Dy2(H2O)7(W4O9)(HPSeW15O54)(α-SeW9O33)2]·31H2O (1) and [H2N(CH3)2]14K2Na18{[Dy2(H2O)13W14O40]2[α-SeW9O33]4[HPSeW15O54]2}·44H2O (2) were synthesized by a one-pot aqueous reaction and structurally characterized. The most distinctive structural feature of complexes 1 & 2 is the simultaneous presence of both trivacant Keggin [α-SeW9O33]8- and Dawson [HPSeW15O54]10- building blocks containing P(III)-Se(IV) heteroatoms. The trimeric polyanion of 1 can be represented as a fusion of two trivacant Keggin [α-SeW9O33]8- and Dawson [HPSeW15O54]10- building units encapsulating the [Dy2(H2O)7(W4O9)]12+ cluster. On the other hand, hexameric polyoxoanions of 2 are described as four trivacant Keggin [α-SeW9O33]8- and two Dawson [HPSeW15O54]10-, building units anchoring a [Dy4(H2O)26W28O80]20+ cluster. The magnetic investigation revealed the presence of significant magnetic anisotropy and slow relaxation of magnetization behavior for complex 1 with a phenomenological energy barrier, Ueff = 13.58 K in the absence of an external magnetic field, and Ueff = 24.57 K in the presence of a 500 Oe external dc magnetic field. On the other hand, complex 2 favors the QTM relaxation process in the absence of an external magnetic field and shows field-induced slow relaxation of magnetization with Ueff = 11.11 K at 1500 Oe applied dc field. The in-depth analysis of magnetic relaxation dynamics shows that the relaxation process follows the Orbach as well as Raman relaxation pathways. Further, the ab initio calculation of the studied complexes confirms that the highly axial ground and first excited energy states (containing pure highest mJ states) are responsible for the observed single-molecule magnet (SMM) behavior. Remarkably, this is the first example of a mixed heteroatom-based Dy(III)-substituted polyoxotungstate with both trimeric Keggin [α-SeW9O33]8- and Dawson [HPSeW15O54]10- building units showing SMM behavior.

Synthesis and Magnetic Properties of Bis-Halobenzene Decamethyldysprosocenium Cations.

The decamethyldysprosocenium cation, [Dy(Cp*)2]+ (Cp* = {C5Me5}), was a target single-molecule magnet (SMM) prior to the isolation of larger dysprosocenium cations, which have recently shown magnetic memory effects up to 80 K. However, the relatively short Dy···Cp*centroid distances of [Dy(Cp*)2]+, together with the reduced resonance of its vibrational modes with electronic states compared to larger dysprosocenium cations, could lead to more favorable SMM behavior. Here, we report the synthesis and magnetic properties of a series of solvated adducts containing bis-halobenzene decamethyldysprosocenium cations, namely [Dy(Cp*)2(PhX-κ-X)2][Al{OC(CF3)3}4] (X = F or Cl) and [Dy(Cp*)2(C6H4F2-κ2-F,F)(C6H4F2-κ-F)][Al{OC(CF3)3}4]. These complexes were prepared by the sequential reaction of [Dy(Cp*)2(μ-BH4)]∞ with allylmagnesium chloride and [NEt3H][Al{OC(CF3)3}4], followed by recrystallization from parent halobenzenes. The complexes were characterized by powder and single crystal X-ray diffraction, NMR and ATR-IR spectroscopy, elemental analysis, and SQUID magnetometry; experimental data were rationalized by a combination of density functional theory and ab initio calculations. We find that bis-halobenzene adducts of the [Dy(Cp*)2]+ cation exhibit highly bent Cp*···Dy···Cp* angles; these cations are also susceptible to decomposition by C-X (X = F, Cl, Br) activation and displacement of halobenzenes by O-donor ligands. The effective energy barrier to reversal of magnetization measured for [Dy(Cp*)2(PhF-κ-F)2][Al{OC(CF3)3}4] (930(6) cm-1) sets a new record for SMMs containing {Dy(Cp*)2} fragments, though all SMM parameters are lower than would be predicted for an isolated [Dy(Cp*)2]+ cation, as expected due to transverse ligand fields introduced by halobenzenes and the large deviation of the Cp*···Dy···Cp* angle from linearity promoting magnetic relaxation.

Synergism of Light-Induced [4 + 4] Cycloaddition and Electron Transfer Toward Switchable Photoluminescence and Single-Molecule Magnet Behavior in a Dy4 Cubane.

Molecular materials possessing switchable magneto-optical properties are of great interest due to their potential applications in spintronics and molecular devices. However, switching their photoluminescence (PL) and single-molecule magnet (SMM) behavior via light-induced structural changes still constitutes a formidable challenge. Here, a series of cubane structures were synthesized via self-assembly of 9-anthracene carboxylic acid (HAC) and rare-earth ions. All complexes exhibited obvious photochromic phenomena and complete PL quenching upon Xe lamp irradiation, which were realized via the synergistic effect of photogenerated radicals and [4 + 4] photocycloaddition of the AC components. The quenched PL showed the largest fluorescence intensity change (99.72%) in electron-transfer photochromic materials. A reversible decoloration process was realized via mechanical grinding, which is unexpectedly in the electron-transfer photochromic materials. Importantly, an SMM behavior of the Dy analog was observed after room-temperature irradiation due to the photocycloaddition of AC ligands and the photogenerated stable radicals changed the electrostatic ligand field and magnetic coupling. Moreover, based on the remarkably photochromic and photoluminescent properties of these compounds, 2 demos were applied to support their application in information anti-counterfeiting and inkless printing. This work, for the first time utilizing the simultaneous modulation of photocycloaddition and photogenerated radicals in one system, realizes complete PL quenching and light-induced SMM behavior, providing a dynamical switch for the construction of multifunctional polymorphic materials with optical response and optical storage devices.