Dinuclear Dysprosium Compounds: The Importance of Rigid Bridges.

We report the synthesis, structures and magnetic behaviour of two isostructural dinuclear Dy3+ complexes where the metal ions of a previously reported monomeric building block are connected by a peroxide (O22-) or a pair of fluoride (2 x F-) bridges. The nature of the bridge determines the distance between the metal ion dipoles leading to a dipolar coupling in the peroxido bridged compound of only ca. 70% of that in the bis-fluorido bridged dimer. The sign of the overall coupling between the metals is antiferromagnetic for the peroxido bridged compound and ferromagnetic for the bis-fluorido bridged complex. This in turn influences the magnetisation dynamics. We compare the relaxation characteristics of the dimers with those of the previously reported monomeric building block. The relaxation dynamics for the bis-fluorido system are very fast. On the other hand, comparing the properties of the monomer, the peroxido bridged sample and the corresponding Y-doped sample show that the relaxation properties via a Raman process have very similar parameters. We show that a second dysprosium is important for either tuning or detuning the Single Molecule Magnet (SMM) properties of a system.

Isostructural Oxamate Complexes with Visible Luminescence (Eu3+) and Field-Induced Single-Molecule Magnet (Nd3+).

The search for new metal-organic compounds as candidates for quantum information processing technologies is in the spotlight. Several metal ions and organic linkers have been used to obtain such compounds. Herein, we describe the synthesis, crystal structures, and cryomagnetic properties of two air-stable isostructural neodymium(III) and europium(III) one-dimensional (1D) coordination polymers of formula [Nd(Hmpa)3(DMSO)2]n (1) and [Eu(Hmpa)3(DMSO)2]n (2) [Hmpa = N-(4-methylphenyl)oxamate, and DMSO = dimethylsulfoxide]. These complexes were prepared by reacting n-Bu4N(Hmpa) proligand [n-Bu4N+ = tetra-n-butylammonium] and the correspondent LnCl3·6H2O salt (Ln = Nd or Eu) in the open air and mild conditions. The crystal structures of 1 and 2 reveal the Ln3+ ion surrounded by two DMSO molecules and three oxamate ligands, one of them connecting to adjacent mononuclear entities through carboxylate bridges featuring a 1D coordination polymer, while the other two establishing double N-H···O hydrogen bonds among adjacent polymers to give a resultant supramolecular 2D network. Cryomagnetic measurements in the static (dc) and dynamic current (ac) regimes reveal that 1 behaves as a field-induced single-molecule magnet below 8.8 K. A photoluminescence study shows that Hmpa ligands efficiently sensitize the luminescence of Eu3+ complex in the visible region in the solid state at room temperature.

Enhancement of Effective Energy Barrier and Magnetic Blocking Temperature in Tetraoxolene Radical Coupled Dinuclear Dysprosium Complex.

A well-judged combination of a high axial ligand field and a bridging radical ligand in a dinuclear lanthanide complex provides a single-molecule magnet with a higher effective energy barrier for magnetic relaxation and blocking temperature compared to its non-radical analog due to significant magnetic exchange coupling between radical and Ln(III) ions. In this work, we report two chloranilate (CA) bridged dinuclear dysprosium complexes, [{(bbpen)Dy(µ2-CA)Dy(bbpen)}] (1Dy) and [{(bbpen)Dy(µ2-CA•)Dy(bbpen)}-{CoCp2}+] (2Dy), where 2Dy is the radical bridged Dy-complex obtained via the chemical reduction of bridging CA moiety (H2bbpen = N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-methylpyridyl)ethylenediamine). The presence of high electronegative phenoxide moiety enhances the axial anisotropy of pseudo-square antiprismatic Dy(III) ions. The diffused spin of radical is efficiently coupled with anisotropic Dy(III) centres and decreases the quantum tunnelling of magnetization (QTM) in the magnetic relaxation process. The magnetic relaxation of 1Dy follows Orbach, Raman, and QTM processes whereas for 2Dy it follows Orbach and Raman Processes. Due to less involvement of the QTM relaxation process, 2Dy shows a higher thermal energy barrier (Ueff = 700 K) and a high blocking temperature (6.7 K), compared to its non-radical analog. Remarkably, the radical coupled 2Dy complex shows the highest energy barrier among the radical bridged Dy(III)-based SMMs to date.

Lanthanide-Based Molecular Magnetic Semiconductors.

Magnetic semiconductors, with integrated properties of ferromagnets and semiconductors, are significant for developing next-generation spintronic devices. Herein two atomically precise clusters of dysprosium(III) tellurides, formulated respectively as [Na2(15-crown-5)3(py)][(η5-Cp*Dy)5(Te)6](py)4 (Dy5Te6, Cp* = pentamethylcyclopentadienyl; py = pyridine) and [K(2,2,2-cryptand)]2[(η5-Cp*Dy)6(Te3)(Te2)2(Te)3] (Dy6Te10), are reported. Crystallographic studies revealed the presence of multifarious tellurido ligands within the polyhedral cluster cores. Spectroscopic and magnetic studies showed that both clusters are single-molecule magnets exhibiting slow magnetic relaxation behaviors at low temperatures and semiconductors with optical bandgaps comparable to benchmark semiconductors. These clusters represent probably the first lanthanide-based molecular magnetic semiconductors.

Chiral Star-Shaped [CoIII3LnIII] Clusters with Enantiopure Schiff Bases: Synthesis, Structure, and Magnetism.

Two enantiomeric pairs of new 3d-4f heterometallic clusters have been synthesized from two enantiomer Schiff base derivatives: (R/S)-2-[(2-hydroxy-1-phenylethylimino)methyl] phenol (R-/S-H2L). The formulae of the series clusters are Co3Ln(R-L)6 (Ln = Dy (1R), Gd (2R)), Co3Ln (S-L)6 (Ln = Dy (1S), Gd (2S)), whose crystal structures and magnetic properties have been characterized. Structural analysis indicated that the above clusters crystallize in the chiral P213 group space. The central lanthanide ion has a coordination geometry of D3 surrounded by three [CoIII(L)2]- anions using six aliphatic oxygen atoms of L2- featuring a star-shaped [CoIII3LnIII] configuration. Magnetic measurements showed the presence of slow magnetic relaxation with an effective energy barrier of 22.33 K in the DyIII derivatives under a zero-dc field. Furthermore, the circular dichroism (CD) spectra of 1R and 1S confirmed their enantiomeric nature.

Six-Coordinated CoII Single-Molecule Magnets: Synthetic Strategy, Structure and Magnetic Properties.

The pursuit of molecule-based magnetic memory materials contributes significantly to high-density information storage research in the frame of the ongoing information technologies revolution. Remarkable progress has been achieved in both transition metal (TM) and lanthanide based single-molecule magnets (SMMs). Notably, six-coordinated CoII SMMs hold particular research significance owing to the economic and abundant nature of 3d TM ions compared to lanthanide ions, the substantial spin-orbit coupling of CoII ions, the potential for precise control over coordination geometry, and the air-stability of coordination-saturated structures. In this review, we will summarize the progress made in six-coordinated CoII SMMs, organized by their coordination geometry and molecular structure similarity. Valuable insights, principles, and new mechanism gleaned from this research and remaining issues that need to be addressed will also be discussed to guide future optimization.

Spin-State Control in Dysprosium(III) Metallacrown Magnets via Thioacetal Modification.

Integrating controllable spin states into single-molecule magnets (SMMs) enables precise manipulation of magnetic interactions at a molecular level, but remains a synthetic challenge. Herein, we developed a 3d-4f metallacrown (MC) magnet [DyNi5(quinha)5(Clsal)2(py)8](ClO4) ⋅ 4H2O (H2quinha=quinaldichydroxamic acid, HClsal=5-chlorosalicylaldehyde) wherein a square planar NiII is stabilized by chemical stacking. Thioacetal modification was employed via post-synthetic ligand substitutions and yielded [DyNi5(quinha)5(Clsaldt)2(py)8](ClO4) ⋅ 3H2O (HClsaldt=4-chloro-2-(1,3-dithiolan-2-yl)phenol). Thanks to the additional ligations of thioacetal onto the NiII site, coordination-induced spin state switching (CISSS) took place with spin state altering from low-spin S=0 to high-spin S=1. The synergy of CISSS effect and magnetic interactions results in distinct energy splitting and magnetic dynamics. Magnetic studies indicate prominent enhancement of reversal barrier from 57 cm-1 to 423 cm-1, along with hysteresis opening and an over 200-fold increment in coercive field at 2 K. Ab initio calculations provide deeper insights into the exchange models and rationalize the relaxation/tunnelling pathways. These results demonstrate here provide a fire-new perspective in modulating the magnetization relaxation via the incorporation of controllable spin states and magnetic interactions facilitated by the CISSS approach.

Pressure-Induced Structural, Optical and Magnetic Modifications in Lanthanide Single-Molecule Magnets.

Lanthanide Single-Molecule Magnets are fascinating objects that break magnetic performance records with observable magnetic bistability at the boiling temperature of liquid nitrogen, paving the way for potential applications in high-density data storage. The switching of lanthanide SMM has been successfully achieved using several external stimuli such as redox reaction, pH titration, light irradiation or solvation/desolvation thanks to the high sensitivity of the magnetic anisotropy to any structural change in the lanthanide surrounding. Nevertheless, the use of applied high pressure as an external stimulus is largely underused, especially considering that it can be combined with high pressure X-ray diffraction to establish a complementary structure-property relationship. This Concept article summarizes the few relevant examples of investigations of lanthanide SMMs under applied high pressure, provides conclusions on the effect of such stimulus on molecular structures and magnetic anisotropy, and finally draws perspective on the future development of magnetic measurements under applied pressure.

A Pair of Multifunctional Cu(II)-Dy(III) Enantiomers with Zero-Field Single-Molecule Magnet Behaviors, Proton Conduction Properties and Magneto-Optical Faraday Effects.

Multifunctional materials with a coexistence of proton conduction properties, single-molecule magnet (SMM) behaviors and magneto-optical Faraday effects have rarely been reported. Herein, a new pair of Cu(II)-Dy(III) enantiomers, [DyCu2(RR/SS-H2L)2(H2O)4(NO3)2]·(NO3)·(H2O) (R-1 and S-1) (H4L = [RR/SS] -N,N'-bis [3-hydroxysalicylidene] -1,2-cyclohexanediamine), has been designed and prepared using homochiral Schiff-base ligands. R-1 and S-1 contain linear Cu(II)-Dy(III)-Cu(II) trinuclear units and possess 1D stacking channels within their supramolecular networks. R-1 and S-1 display chiral optical activity and strong magneto-optical Faraday effects. Moreover, R-1 shows a zero-field SMM behavior. In addition, R-1 demonstrates humidity- and temperature-dependent proton conductivity with optimal values of 1.34 × 10-4 S·cm-1 under 50 °C and 98% relative humidity (RH), which is related to a 1D extended H-bonded chain constructed by water molecules, nitrate and phenol groups of the RR-H2L ligand.

Single-Molecule Magnet Properties in 3d4f Heterobimetallic Iron and Dysprosium Complexes Involving Hydrazone Ligand.

The reaction between the ((E)-N'-(2-hydroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide) (H2opch) ligand and the metallo-precursor [Dy(hfac)3]·2H2O led to the formation of an homometallic coordination complex with the formula [Dy2(hfac)3(H2O)(Hopch)2][Dy(hfac)4] (1). In presence of both [Dy(hfac)3] 2H2O and the Fe(II) salt, the heterobimetallic tetranuclear [FeDy3(hfac)8(H2O)2(opch)2] (2) was isolated, while the addition of the co-ligand 1,2-Bis(2-hydroxy-3-methoxybenzylidene) hydrazine (H2bmh) led to the formation of two heterobimetallic tetranuclear complexes with the formula [Fe3Dy(hfac)6(opch)2(H2bmh)] C6H14 (3) C6H14 and [Fe2Dy2(hfac)7(opch)2(H2bmh)] 0.5C7H16 (4) 0.5C7H16. Single crystal X-ray diffraction and dc magnetic investigation demonstrated that 3 and 4 involved the iron center in the +II and +III oxidation states. Dynamic magnetic measurements highlighted the single-molecule magnet behavior of 1 and 2 in a zero applied dc field primarily due to the ferromagnetic interactions taking place in these compounds.

Control of the Magnetic Interaction between Single-Molecule Magnet TbPc2 and Superconductor NbSe2 Surface by an Intercalated Co Atom.

We demonstrate that an intercalated Co atom in superconductor NbSe2 could control the magnetic interaction between the adsorbed magnetic molecule of TbPc2 and the NbSe2 substrate. An intercalated Co atom enhances the magnetic interaction between the NbSe2 and the TbPc2 spin to cause Kondo resonance at the TbPc2 position, a spin-singlet state formed by the itinerary electron. By applying a surface-normal magnetic field, we change the molecule's spin direction from the initial one directed to the Co atom to the surface normal. The change appears as a split Kondo resonance at the TbPc2, one of which is enhanced at the Tb site, which disappears when the outer magnetic field normal to the surface is applied and never appears, even if we return B to 0 T. The phenomenon suggests that the intercalated magnetic atoms can control the magnetic interaction between a magnetic molecule and the superconductor NbSe2.

Regulating Magnetic Relaxations of Cyano-Bridged {DyIII MoV } Systems by Tuning the N-Sites in ß-Diketone Ligands.

Cyano-bridged 4d-4f molecular nanomagnets have re-called increasing research interests in molecular magnetism since they offer more possibilities in achieving novel nanomagnets with versatile structures and magnetic interactions. In this work, four ß-diketone ligands bearing different substitution N-sites were designed and synthesized, namely 1-(2-pyridyl)-3-(3-pyridyl)-1,3-propanedione (HL1 ), 1,3-Bis (3-pyridyl)-1,3-propanedione (HL2 ), 1-(4-pyridyl)-3-(3-pyridyl)-1,3-propanedione (HL3 ), and 1,3-Bis (4-pyridyl)-1,3-propanedione (HL4 ), to tune the magnetic relaxation behaviors of cyano-bridged {DyIII MoV } systems. By reacting with DyCl3 ⋅ 6H2 O and K4 Mo(CN)8 ⋅ 2H2 O, four cyano-bridged complexes, namely {[Dy[MoV (CN)8 ](HL1 )2 (H2 O)3 ]} ⋅ 6H2 O (1), {[Dy[MoV (CN)8 ](HL2 )(H2 O)3 (CH3 OH)]}2 ⋅ 2CH3 OH ⋅ 3H2 O (2), {[Dy[MoV (CN)8 ](HL3 )(H2 O)2 (CH3 OH)] ⋅ H2 O}n (3), and {[Dy[MoV (CN)8 ](HL4 )2 (H2 O)3 ]} ⋅ 2H2 O⋅CH3 OH (4) were obtained. Structural analyses revealed that 1 and 4 are binuclear complexes, 2 has a tetragonal structure, and 3 exhibits a stair-like polymer chain structure. The DyIII ions in all complexes have eight-coordinated configurations with the coordination spheres DyO7 N1 for 1 and 4, DyO6 N2 for 2, and DyO5 N3 for 3. Magnetic measurements indicate that 1 is a zero-field single-molecule magnet (SMM) and complexes 2-4 are field-induced SMMs, with complex 4 featuring a two-step relaxation process. The magnetic characterizations and ab initio calculations revealed that changing the N-sites in the ß-diketone ligands can effectively alter the structures and magnetic properties of cyano-bridged 4d-4f nanomagnets by adjusting the coordination environments of the DyIII centers.

Lipoic Acid-Functionalized Hexanuclear Manganese(III) Nanomagnets Suitable for Surface Grafting.

Highly anisotropic single-molecule magnets (SMMs) have attracted much interest in the field of molecular magnetism because of their spin features and potential technological applications. Additionally, a great effort has been devoted to the functionalization of such molecule-based systems which are made with ligands containing functional groups suitable to connect SMMs to junction devices or to perform their grafting on surfaces of different substrates. We have synthesized and characterized two lipoic acid-functionalized and oxime-based Mn(III) compounds, of formula [Mn6(µ3-O)2(H2N-sao)6(lip)2(MeOH)6][Mn6(µ3-O)2(H2N-sao)6(cnph)2(MeOH)6]}·10MeOH (1) and [Mn6(µ3-O)2(H2N-sao)6(lip)2(EtOH)6]·EtOH·2H2O (2) [H2N-saoH2 = salicylamidoxime, lip = lipoate anion, cnph = 2-cyanophenolate anion]. Compound 1 crystallizes in the space group Pi of the triclinic system and 2 crystallizes in the space group C2/c of the monoclinic system. In the crystal, neighboring Mn6 entities are linked using non-coordinating solvent molecules, which are H-bonded to N atoms of -NH2 groups of amidoxime ligand. In addition, Hirshfeld surfaces of 1 and 2 were calculated to study the variety of intermolecular interactions and the different levels of importance that take place in their crystal lattice; this type of computed study is the first time performed on Mn6 complexes. The study of the magnetic properties of 1 and 2 through dc magnetic susceptibility measurements reveals the coexistence of ferromagnetic and antiferromagnetic exchange couplings between the Mn(III) metal ions in both compounds, the latter being the predominant magnetic interaction. A spin S = 4 value of the ground state was obtained using isotropic simulations of the experimental magnetic susceptibility data for both 1 and 2. Ac magnetic susceptibility measurements show features typical of slow relaxation of the magnetization in 1 and 2, which indicate that SMM behavior takes place in both compounds.

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.

Determinative Effect of Axial Linearity on Single-Molecule Magnet Performance in Dinuclear Dysprosium Complexes.

Two dichloride-bridged dinuclear dysprosium(III) complexes based on salen ligands, namely, [Dy(L1 )(µ-Cl)(thf)]2 (1; H2 L1 =N,N'-bis(3,5-di-tert-butylsalicylidene)phenylenediamine) and [Dy2 (L2 )2 (µ-Cl)2 (thf)2 ]2 (2; H2 L2 =N,N'-bis(3,5-di-tert-butylsalicylidene)ethylenediamine) are reported. These two complexes have two short Dy-O(PhO) bonds that exhibit angles of ∼90° for 1 and ∼143° for 2, leading to clear slow relaxation of the magnetization for 2 and not for 1. Compound 2 has a near-identical core to the recently reported compound [Dy2 (L3 )2 (µ-Cl)2 (thf)2 ] (3; H2 L3 =N-(2-pyridylmethyl)-N,N-bis(2'-hydroxy-3',5'-di-tert-butylbenzyl)amine). The only substantial difference is the relative angle of the two O(PhO) -Dy-O(PhO) vectors, which is collinear in 2 owing to inversion symmetry and ∼68° in 3 due to a molecular C2 axis. It is shown that this subtle structural difference leads to large differences in the dipolar ground states, giving rise to open magnetic hysteresis for 3 and not for 2.

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 (quantum tunneling of magnetization) 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.

Photo-responsive Single-Molecule Magnet Showing 0D to 1D Single-Crystal-to-Single-Crystal Structural Transition and Hysteresis Modulation.

Photo-responsive lanthanide-based single-molecule magnets (SMM) hold great promise for future switching and memory devices. Herein, we report a dysprosium phosphonate [DyIII (SCN)2 (NO3 )(depma)2 (4-hpy)2 ] (1Dy), which features a supramolecular framework containing layers of hydrogen-bonding network and pillars of π-π interacted anthracene units. The photocycloaddition reaction of anthracene pairs led to a rapid and reversible single-crystal-to-single-crystal (SC-SC) structural transition to form the 1D coordination polymer [DyIII (SCN)2 (NO3 )(depma2 )(4-hpy)2 ]n (2Dy), accompanied by photoswitchable SMM properties with the reduction of effective energy barrier by half and the narrowing of the butterfly-like hysteresis loop. The diluted sample showed a photo-induced switch of the blocking temperature (TB ) from 3.8 K for 1Dy@Y to 2.6 K for 2Dy@Y. This work may inspire the construction of lanthanide-based molecular materials with targeted photo-responsive magnetic properties.

Lanthanide Single-molecule Magnets: Synthetic Strategy, Structures, Properties and Recent Advances.

Single-molecule magnets (SMMs) show wide potential applications in the field of ultrahigh-density storage materials, quantum computing, spintronics, and so on. Lanthanide (Ln) SMMs, as an important category of SMMs, open up a promising prospect due to their large magnetic moments and huge magnetic anisotropy. However, the construction of high performance for Ln SMMs remains an enormous challenge. Although remarkable advances are focused on the topic of Ln SMMs, the research on Ln SMMs with different nuclear numbers is still deficient. Therefore, this review summarizes the design strategies for the construction of Ln SMMs, as well as the metal skeleton types. Furthermore, we collect reported Ln SMMs with mononuclearity, dinuclearity, and multinuclearity (three or more Ln spin centers) and the SMM properties including energy barrier (Ueff ) and pre-exponential factor (τ0 ) are described. Finally, Ln SMMs with low-nuclearity SMMs, especially for single-ion magnets (SIMs), are highlighted to understand the correlations between structures and magnetic behavior of the detail SMM properties are described. We expect the review can shed light on the future developments of high-performance Ln SMMs.

Aerogel-Based Single-Ion Magnets: A Case Study of a Cobalt(II) Complex Immobilized in Silica.

The chemical immobilization of cobalt(II) ions in a silica aerogel matrix enabled the synthesis of the first representative example of aerogel-based single-ion magnets. For the synthesis of the lyogels, methyl-trimethoxysilane and N-3-(trimethoxysilyl)propyl ethylenediamine were co-hydrolyzed, then the ethylenediamine groups that were immobilized on the silica matrix enabled the subsequent binding of cobalt(II) ions. Lyogels with various amounts of ethylenediamine moieties (0.1-15 mol %) were soaked in isopropanol solutions of cobalt(II) nitrate and further supercritically dried in carbon dioxide to obtain aerogels with a specific surface area of 210-596 m2·g-1, an apparent density of 0.403-0.740 cm3·g-1 and a porosity of 60-78%. The actual cobalt content in the aerogels was 0.01-1.50 mmol per 1 g of SiO2, which could easily be tuned by the concentration of ethylenediamine moieties in the silica matrix. The introduction of cobalt(II) ions into the ethylenediamine-modified silica aerogel promoted the stability of the diamine moieties at the supercritical drying stage. The molecular prototype of the immobilized cobalt(II) complex, bearing one ethylenediamine ligand [Co(en)(MeCN)(NO3)2], was synthesized and structurally characterized. Using magnetometry in the DC mode, it was shown that cobalt(II)-modified silica aerogels exhibited slow magnetic relaxation in a nonzero field. A decrease in cobalt(II) concentration in aerogels from 1.5 mmol to 0.14 mmol per 1 g of SiO2 resulted in a weakening of inter-ion interactions; the magnetization reversal energy barrier likewise increased from 4 to 18 K.

Bulky anion effect on the architecture of chiral dysprosium single-molecule magnets.

The interest for chiral tris(ß-diketonato)lanthanide complexes in coordination chemistry is huge due to its Lewis acid character, optical activity, and the control of the final compound architecture. The reaction of equimolar quantities of [Dy((-)/(+)hfc)3 (H2 O)] (hfc- = 3-(heptafluoropropylhydroxymethylene)-(+/-)-camphorate) and L led to the formation of a pair of enantiomers for dinuclear complexes [Dy((-)/(+)hfc)3 (L)]2 ⋅C7 H16 ([(-)/(+)1]⋅C7 H16 ) (L = 4'-(4'''-pyridyl-N-oxide)-1,2':6'1''-bis-(pyrazolyl)pyridine]). Starting from the previous experimental protocol with the addition of bulky BArF anions, a partial dissociation of the chiral [Dy((-)/(+)hfc)3 (H2 O)] was observed leading to the isolation of a mono-dimensional cationic chiral polymer {[Dy((-)/(+)hfc)2 (L)][BarF]}n ⋅nCH3 NO2 ([(-)/(+)2]n ⋅nCH3 NO2 ). Natural circular dichroism (NCD) highlighted an exciton CD couplet for [(-)/(+)2]n but not for (-)/(+)1. The latter behaves as a single-molecule magnet (SMM) with a blocking temperature up to 4 K, whereas [(-)/(+)2]n is a 1D assembly of field-induced SMMs with a magnetic relaxation occurring through a Raman process only.