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Model calculations indicate that the increasement of Ueff becomes tiny when N–Dy–N angle is large. Thus, the construction of near-linear two-coordinate dysprosium(III) SMMs with high Ueff and TB using bulky imidazolin-2-iminato ligands is feasible.

The synthesis of fluoride-bridged 1Dy, 2Dy and hepta-nuclear 3Dy dysprosium complexes is reported here and a hydroxy-bridged dinuclear dysprosium complex 4Dy is synthesized for comparison.

This is the first time that circularly polarized luminescence and obvious magneto-optical effects have been observed simultaneously in a single-molecule magnet.

By the bridging action of the 6-chloro-2-hydroxypyridine (Hchp) ligand and the terminal coordination role of the homochiral ligand, (-)/(+)-3-trifluoroacetyl camphor (l-Htfc/d-Htfc), a pair of enantiomerically pure dysprosium(III) dinuclear complexes, [Dy2(l-tfc)4(chp)2(MeOH)2] (l-1) and [Dy2(d-tfc)4(chp)2(MeOH)2] (d-1), was obtained. Their circular dichroism (CD) spectra verified their enantiomeric nature. Magnetic investigation indicated that they exhibit ferromagnetic interaction and good zero field single-molecule magnet (SMM) properties. The Ueff/k values of l-1 and d-1 at 0 Oe are 180.5 and 181.3 K, respectively, which are large values for homochiral Dy(III) SMMs. A reasonable explanation for the magnetic properties of l-1 and d-1 was supplied by ab initio calculations. Remarkably, magnetic circular dichroism (MCD) investigation revealed that the chiral Dy2 enantiomers show a strong magneto-optical Faraday effect at room temperature, suggesting potential applications in magneto-optical devices.

Homoleptic tris(6,6′-dimethyl-2,2′-bipyridine) rare earth metal complexes M(κ2-dmbp)3 (M = Y, Tb, Dy, Ho, Er; dmbp = 6,6′-dimethyl-2,2′-bipyridine) were synthesized by in situ reduction of 3 equiv. of dmbp with excess KC8 in the presence of 1 equiv. of rare earth metal trihalides. All compounds were characterized by X-ray crystallography, UV-Vis-NIR spectroscopy, infrared (IR) spectroscopy, elemental analysis, and magnetic measurements. While the structural parameters and spectroscopic data confirmed the existence of the trivalent rare earth metal cation and three dmbp radical anions, the electron paramagnetic resonance (EPR) spectrum and the measured magnetic moment of Y(κ2-dmbp)3 indicated that two parallel dmbp radical anions were antiferromagnetically coupled. For paramagnetic rare earth metal ions, room temperature magnetic susceptibility values indicated a weak ferromagnetic interaction between the metal ion and the remaining dmbp radical. Density functional theory (DFT) calculations were performed on Y(κ2-dmbp)3 to gain insight into the electronic structures of these homoleptic metal complexes. The computational results were consistent with the structural, spectroscopic, and magnetic data for a S = 1/2 ground state and spin densities mostly residing on one dmbp radical anion, while the spins on the other two parallel dmbp radical anions being antiferromagnetically coupled.

The first-row transition metal compounds, [MII(L1)2](ClO4)2 (M = Ni (1); Co (2)), have been prepared by treatment of a neutral tetradentate ligand (L1 = N2,N9-dibutyl-1,10-phenanthroline-2,9-dicarboxamide) with metal perchlorate salts in MeOH. Both compounds have been structurally characterized by X-ray crystallography and it was found that the coordination numbers are 6 and 7, respectively. The reaction of 6,6′-bis(2-tbutyl-tetrazol-5-yl)-2,2′-bipyridine (L2) with hydrated FeII(ClO4)2 afforded a 8-coordinate Fe(II) compound, [FeII(L2)2](ClO4)2 (3); however its reaction with hydrated CoII(ClO4)2 resulted in 6-coordinate [CoII(L2)2](ClO4)2. It is interesting to observe field-induced slow magnetic relaxation in the 7-coordinate Co(II) compound 2 and 8-coordinate Fe(II) compound 3, which further supports the validity of designing high coordination number compounds as single-molecule magnets. Direct current magnetic studies demonstrate that 2 has a very large positive D value (56.2 cm−1) and a small E value (0.66 cm−1), indicating easy plane magnetic anisotropy. Consistent with the larger D value, an effective spin-reversal barrier of Ueff = 100 K (71.4 cm−1) is obtained, which is the highest value reported for 7-coordinate Co(II) complexes with a pentagonal bipyramidal geometry. In contrast, 8-coordinate Fe(II) compound 3 exhibits uniaxial magnetic anisotropy.

Investigating the magnetic anisotropy and magnetic interactions of lanthanide complexes is of vital importance for an in-depth understanding of their magnetic properties. Herein, we reported the synthetic, structural and magnetic studies of a triangular type dysprosium complex (1Dy3, [{(Cp)(Tp*)Ln(μ-bta)}3·2(thf)], Cp = C5H5, Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate anion, btaH = 1H-1,2,3-benzotriazole). 2Dy ([(Cp)Dy(Tp)2·C7H8], Tp = hydrotris(1-pyrazolyl)borate) was investigated by single-crystal angular-resolved susceptibility measurements and computational studies to help understand the magnetic anisotropy of 1Dy3. The easy axis of three DyIII ions in 1Dy3 was orientated out of the triangular dysprosium plane. The exchange interactions were small (−0.85 cm−1) but caused remarkable effects on magnetic relaxations at low temperature. In the temperature range from 2 K to 4 K, magnetic relaxation occurred via the exchange-coupled low-lying excited states, inhibiting magnetic hysteresis. Our study showed that weak intramolecular magnetic interactions can significantly affect the dynamic properties in the low temperature regime.

Compared with homopolymers, the copolymers exhibit improved properties, providing a broad application prospect. Herein, we report the visible-light-induced living/controlled radical copolymerizatio...

The magnetic properties of the T-shaped three-coordinate complexes, namely, [(sIMes)2Fe(THF)][BPh4] (1, sIMes: 1,3-bis(2′,4′,6′-trimethylphenyl)-imidazolin-2-ylidene) and [(cyIMes)2Fe(THF)][BPh4] (2, cyIMes: 1,3-bis(2′,4′,6′-diethylphenyl)-4,5-(CH2)4-imidazol-2-ylidene) and quasi-linear two-coordinate complexes [(sIDep)2Fe][BArF4] (3, sIDep: 1,3-bis(2′,6′-diethylphenyl)-imidazolin-2-ylidene; ArF: 3,5-di(trifluoromethyl)phenyl) and [(cyIDep)2Fe][BArF4] (4, cyIDep: 1,3-bis(2′,6′-diethylphenyl)-4,5-(CH2)4-imidazol-2-ylidene) were studied. Magnetic characterization indicated the unquenched first-order angular momentum and large zero-field splitting. AC susceptibility measurements showed that the T-shaped three-coordinate Fe(I) complexes exhibited field-induced relaxation of magnetization. The Direct, resonant quantum tunneling, and Raman processes were observed and contributed to the determination of the overall magnetic relaxations.

In the series of the adducts of tris(alkyl) HoIII complexes, Ho(CH2SiMe3)3(THF)2 (1Ho-THF, Me = methyl) can exhibit slow magnetic relaxation under a zero applied direct current (DC) field with the ...

We report the synthesis and magnetic properties of a μ2-OH− bridged dinuclear Dy(III) single-molecule magnet (SMM), [Dy2(apca)4(μ2-OH)2(H2O)2]n (Dy, Hapca = 3-aminopyrazine-2-carboxylic acid), which was assembled in a two-dimensional (2D) network. Magnetic studies reveal that Dy exhibits ferromagnetic interactions, multi-process slow relaxation of magnetization and hysteresis loops. The influence of an external magnetic field and magnetic-site dilution on the magnetic properties was also studied.

Two dinuclear dysprosium single-molecule magnets (SMMs) with a nearly identical core structure, namely [Dy2(DMOP)2(DBM)4(CHCl3)4] (1) and [Dy2(DMOP)2(DBM)4(C2H4Cl2)2] (2) (DMOP = 2,6-dimethoxyphenol, DBM = dibenzoylmethane), and their Y(III) (3) and Gd(III) (4) analogues were structurally and magnetically characterized. Despite the fact the phenoxyl of DMOP can only transfer weak exchange coupling and the local coordination environment around the individual Dy(III) ion is in a low geometrical symmetry, their joint contribution ultimately leads to significant zero-field slow magnetic relaxation behaviours. It is interesting to note that the effective energy barrier (Ueff) of the magnetization reversal was nearly doubly improved by only deliberately replacing or losing the lattice solvents while maintaining the Dy2 core structure. Ab initio calculations confirmed that changing the lattice solvents induced the intramolecular coupling change and impacted the dynamic magnetic relaxations. The significant enhancement of an SMM's performance depending on the lattice solvents indicated that it is possible to improve an SMM's properties by tuning the guest molecules.

We present two layered perovskites of the formula [CH3C(NH2)2]2[M(HCOO)4] (M = Co and Ni). The two materials are isostructural and crystallize in the orthorhombic space group Pccn. The structures consist of anionic 100-oriented perovskite or square metal-formate layers and interlayer [CH3C(NH2)2]+ cations. In each layer octahedral M2+ ions are linked by equatorial anti-anti HCOO- bridges and are further coordinated by apical monodentate HCOO- groups. The interlayer acetamidinium cations form N-HO H-bonds with the anionic layers to support the 3D structure. As the directions of most vibrations of the interlayer atoms are approximately along the a-axis, the two materials exhibit nearly zero thermal expansion (a few (MK)-1) along the b-direction perpendicularly to the layers and positive thermal expansion along the a- (∼40 (MK)-1) and c- (∼20 (MK)-1) axes parallel to the layers. They are both weak ferromagnets, and the Neel temperatures are 6.0 K and 17.0 K for M = Co and Ni, respectively. The Co compound exhibited high spontaneous magnetization of 444 cm3 G mol-1 under a field of 10 Oe and an unusually low coercive field of 38 Oe at 2 K. IR spectroscopic, thermal and dielectric properties were investigated.

An approximately equatorial three-coordinated dysprosium(iii) complex DyL2[N(SiMe3)2] (L = bis(2-(2,5-dimethyl-1H-pyrrol-1-yl)ethyl)amine) with an additional neutral auxiliary pyrrole ligand was synthesised and structurally characterized. The magnetic property measurement shows that it is an equatorial charge distributed field-induced single-molecule magnet. Ab initio calculations reveal that the neutral pyrrole ligand plays an important role in stabilizing the ground doublet and thus enhancing the magnetic anisotropy.

Hybrid compound 1-(2-fluro-4-bromobenzyl)-4-dimethylaminopyridium bis(maleonitriledithiolate) cuprate(II) [2F4BrBzDMAP]2[Cu(mnt)2] is prepared and characterized by X-ray diffraction. The compound crystallizes in the triclinic system with the space group P-1. The unit cell dimensions are a = 8.9813(11), b = 9.0794(12), c = 13.1082(17) A and α = 88.179(2)°, β = 81.397(2)°, γ = 70.736(1)° with Z = 1. The structure consists of two [2F4BrBzDMAP]+ cations and one [Cu(mnt)2]2– anion. The cations of the title compound stack into a one-dimensional column through p∙∙∙π and π∙∙∙π interactions, and the anions (A) and cations (C) are arranged alternatively into one 1D column in an ∙∙∙A–CC–A–CC–A∙∙∙ sequence through C–H∙∙∙N hydrogen bonds and S∙∙∙N interactions. The presence of functional groups is confirmed by the FT-IR spectrum, and optical absorption is ascertained by the recorded UV-Visible spectrum. The thermal stability of the compound is determined by thermogravimetric and differential thermal analyses. The variable-temperature magnetic susceptibility measurement shows that the compound exhibits a weak ferromagnetic coupling behavior when the temperature is lowered.

Bulky and strong electron-donating dibutylamino groups were incorporated onto the peripheral positions of one of the two phthalocyanine ligands in the bis(phthalocyaninato) terbium complex, resulting in the isolation of heteroleptic double-decker (Pc)Tb{Pc[N(C4H9)2]8} {Pc = phthalocyaninate; Pc[N(C4H9)2]8 = 2,3,9,10,16,17,23,24-octakis(dibutylamino)phthalocyaninate} with the nature of an unsymmetrical molecular structure, a square-antiprismatic coordination geometry, an intensified coordination field strength, and the presence of organic radical-f interaction. As a total result of all these factors, this sandwich-type tetrapyrrole lanthanide single-ion magnet (SIM) exhibits an overall enhanced magnetic performance including a high blocking temperature (TB) of 30 K and large effective spin-reversal energy barrier of Ueff = 939 K, rendering it the best sandwich-type tetrapyrrole lanthanide SIM reported thus far.

A series of AlNa bimetallic ammonium metal formate frameworks (AlNa AMFFs) have been prepared by employing various ammoniums from NH4+ to large linear polyammoniums. The series consists of six perovskites of (412 ⋅63 ) topology for mono-ammoniums, two chiral (49 ⋅66 ) frameworks incorporating polyethylene ammoniums, two niccolites with (412 ⋅63 )(49 ⋅66 ) topology containing diammoniums, and two layered compounds made of 2D (4,4) AlNa formate sheets intercalated by small diammoniums. The first ten compounds present the structural hierarchy of (412 ⋅63 )m (49 ⋅66 )n framework topologies for (m, n)=(1, 0), (0, 1), and (1, 1), respectively, in parallel to the homometallic AMFFs for divalent metals. The symmetry lowering, asymmetric formate bridges, and different hydrogen-bonding strengths appeared in the bimetallic structures owing to the different charge and size of Al3+ and Na+ seemingly inhibits the occurrence of phase transitions for more than half the AlNa AMFFs within the series, and the bimetallic members undergoing phase transitions show different transition behaviors and dielectric properties compared with the homometallic analogs. Anisotropic/negative/zero thermal expansions of the materials could be rationally attributed to the librational motion, or flip movement between different sites, of the ammonium cations, and the coupled change of AlNa formate frameworks. The thermal and IR spectroscopic properties have also been investigated.

A mononuclar six-coordinate dysprosium complex was synthesized and structurally and magnetically characterized. X-ray structural analyses show trigonal-prismatic coordination geometry of the DyIII center. Slow relaxation of magnetization in the absence of a direct-current field and magnetic hysteresis up to 3.0 K could be observed, indicating its single-ion-magnet behavior. Arrhenius fitting and ab initio calculations suggest that the magnetic relaxation process may not occur through the Orbach process at high temperatures under the experimental conditions.

Strong electron-donating dialkylamino groups were incoporated onto the phthalocyanine ligand in bis(phthalocyaninato) rare earth complexes for the first time to investigate their effects on the spectroscopic properties, electrochemistry, and electronic structure. The bis[2,3,9,10,16,17,23,24-octakis(dibutylamino)phthalocyaninate] rare earth complexes M{Pc[N(C4H9)2]8}2 {Pc[N(C4H9)2]8 = 2,3,9,10,16,17,23,24-octakis(dibutylamino)phthalocyanine, M = Y, Tb} (1, 2) were isolated from the condensation reaction of the corresponding metal free ligand in a refluxing mixture of n-octanol/1,2,4-trichrolobenzene (TCB) (1 : 5) in the presence of M(acac)3·nH2O (M = Y, Tb) in relatively good yields, with their sandwich double-decker nature revealed on the basis of their mass, 1H NMR, electronic absorption, IR, and EPR spectroscopic results in addition to elemental analysis. Their electrochemistry was investigated by cyclic voltammetry (CV). In particular, magnetic studies reveal the typical slow relaxation of the terbium double-decker, indicating its typical single-ion magnet (SIM) nature with a blocking temperature of 25 K and a spin reversal energy barrier of 752 ± 8 K, representing the sole example of sandwich-type tetrapyrrole lanthanide-based SMMs reported thus far with a blocking temperature over 20 K. Theoretical calculations disclose the effect of the bulky and strong electron-donating peripheral dialkylamino groups, which create a square-antiprismatic coordination geometry and intensified coordination field strength for the central terbium ion, resulting in the excellent magnetic performance of this terbium double-decker SIM.

Three penta-coordinate Co2+ complexes with halide substitutes were synthesized. Their zero-field splitting (ZFS) parameters were determined by fitting dc magnetic data and far-infrared magneto-transmission spectra. The results gave an unusual case that complexes with heavier halide atoms bear smaller ZFS parameters.

A series of tetrahedral Co(II) complexes with chalcogen donors were prepared, which exhibited strong magnetic uniaxial anisotropies and slow relaxations as SIMs. By substituting donors from S to Te, we realized the fine-tuning of the ligand field while keeping the coordination geometry virtually unchanged, yielding the first tellurium-coordinated SIM.

An organic material single crystal of [BzIQl][PIC] ([BzIQl]+ = benzylisoquinolinium; [PIC]− = picrate) has been grown by slow evaporation solution growth technique. Single crystal XRD studies reveal the crystal belongs to monoclinic system with C2/c. The two neighboring [PIC]− anions form a dimer through π⋯π interaction, while the cations stack to a columnar structure through C-H⋯π and π⋯π interactions. The anions (A) and cations (C) are arranged into a columnar structure in a ⋯AA-CC-AA-CC⋯sequence through C-H⋯O hydrogen bonds. The cations and anions are linked through electrostatic and other hydrogen bonding interactions form 3D network. The power XRD measurements substantiate the quality of the crystal. The presence of functional groups of the organic material was confirmed by FT-IR and FT-Raman analysis and theoretical studies. Differential thermal analysis (DTA) carried out on the grown crystal indicates that the material is stable up to 224.9 °C. Additionally, the organic material shows three main emission peaks about 385, 467 and 538 nm upon excitation at 241 nm in solid state at room temperature.

Topotactic reduction of the perovskite oxide TbBaCo2O5.5 with CaH2 leads to a new crystalline phase TbBaCo2O4.5, adopting a 2 × 2 × 1 superstructure compared to TbBaCo2O5.5. The structure consists of a corner-shared network of square pyramidal CoO5 and trigonal planar CoO3 units. Magnetic susceptibility and variable temperature neutron diffraction data reveal that TbBaCo2O4.5 adopts a G-type antiferromagnetically ordered structure (TN ∼ 322 K). The ordered moments are consistent with the presence of low-spin Co2+ (S = 1/2) in trigonal-planar coordination and high-spin Co2+ centers in square pyramidal coordination. TbBaCo2O4.5 shows lower conductivity than TbBaCo2O5.5, which is consistent with the p-type conduction behavior. The unique anion vacancy arrangements in TbBaCo2O4.5 further complement the role of A-cations in controlling the oxygen vacancy distribution in LnBaCo2O5+δ series and demonstrate more opportunity to tune the structural and physical properties based on cationic and anionic lattice coupling.

To conclude the design principle for high-performance erbium-based single-ion magnets (SIMs), two half-sandwich type erbium complexes 1Er [(LOMe)Er(COT)] (LOMe = [(η5-C5H5)Co{P([double bond, length as m-dash]O)(OMe)2}3], COT = cyclooctatetraenyl) and 2Er [(THF)2(OAr)Er(COT)] (Ar = 2,6-Dipp2C6H3, Dipp = 2,6-diisopropylphenyl) were synthesized, and structurally and magnetically characterized. Both of them exhibited SIM behavior. Their magnetic relaxation behaviours were further elucidated by ab initio calculations and near-IR emission spectroscopy. The results demonstrated that an axial ligand with a weaker electron-donating effect was preferential to construct high blocking barrier erbium-based SIMs.

Two half-sandwich organodysprosium complexes [(C7H8)Dy(AlCl4)3] and [(C7H8)Dy(AlBr4)3] were synthesized by modifying the arene ligand of the complex [(C6Me6)Dy(AlCl4)3]. Single X-ray diffraction data reveals the local geometry of Dy(III) ion is close to pentagonal bipyramid. Magnetic investigation shows both are single-ion magnets with enhanced magnetic properties.

The chemical preparation, spectroscopic characterization, and crystal structures of two new ion-pair complexes, [4NO2BzIQl]2[Ni(mnt)2](1) and [4NO2BzIQl]2[Ni(i-mnt)2] (2) ([4NO2BzIQl]+ = 4-nitrobenzyl isoquinolinium, mnt2− = maleonitriledithiolate and i-mnt2− = iso-maleonitriledithiolate), have been reported. Both 1 and 2 crystallize in the triclinic system in space group P-1. The cations of 1 stack into a 1D alternating column through C–H···π, π···π and p···π interactions, while the [4NO2BzIQl]+ cations (C) and [Ni(i-mnt)2]2− anions (A) of 2 stack into another 1D alternative column with a A–CC–A–CC–A sequence. Weak N···Ni, C–H···Ni, C–H···N, C–H···S, and p···π interactions observed in 1 and 2 consolidate a 3D network structure. Thermal analysis reveals that 1 and 2 are stable up to 211°C and 208°C, respectively, and the final decomposition product of two complexes is nickel oxide.

A series of isostructural hydrazinium lanthanide (Ln) formate framework compounds of [NH2NH3][Ln(HCOO)4] for Ln3+ ions from Tb3+ to Lu3+ and Y3+ have been successfully prepared by utilizing NH2NH3+. The compounds crystallize in orthorhombic polar space group Pca21, with cell parameters at 180 K of a = 18.2526(7)-18.1048(5) A, b = 6.5815(2)-6.5261(2) A, c = 7.6362(3)-7.5044(2) A, and V = 917.33(6)-886.67(4) A3, showing the effect of lanthanide contraction. The compounds possess polar perovskite-like structures incorporating the hydrazinium cations in the cavities of the NaCl-like framework, in which the Ln3+ ions in a bicapped trigonal prism are connected by anti-anti and syn-anti formate groups. The N-H···Oformate hydrogen-bonding interactions are between the hydrazinium cations and the anionic framework. One anti-anti formate group is frustrated by the competitive N-H···Oformate hydrogen-bonding interactions. It thus twists or flips upon warming, resulting in large anisotropic thermal expansion and negative thermal expansion below 180 K. A comparison with the transition metal and magnesium analogues revealed that the structural compactness, tighter binding of the hydrazinium cation by the framework, and symmetrically better match between the framework and ammonium cation for Ln compounds could inhibit the occurrence of phase transition in the series. The IR spectroscopic, thermal, and magnetic properties are investigated.

A niccolite series of [bnH2 (2+) ][M(HCOO)3 ]2 (bnH2 (2+) =1,4-butyldiammonium) shows four kinds of metal-dependent phase transitions, from high temperature para-electric phases to low-temperature ferro-, antiferro-, glass-like, and para-electric phases. The conformational flexibility of bnH2 (2+) and the different size, mass, and bonding character of the metal ion lead to various disorder-order transitions of bnH2 (2+) in the lattice and relevant framework modulations, thus different phase transitions and dielectric responses. The magnetic members display a coexistence or combination of electric and magnetic orderings in the low-temperature region.

In a field-induced single-ion magnet [(dtc)3Dy(phen)] (dtc(-) = diethyldithiocarbamate anion), replacing two of the S-based dtc(-) ligands with O-based dbm(-) ligands (dbm(-) = dibenzoylmethanoate anion) leads to a significant enhancement of magnetic anisotropy, yielding a rarely reported sulfur-ligated lanthanide-based single-ion magnet [(dbm)2Dy(dtc)(phen)]. Ab initio calculations reveal that the gz value of [(dbm)2Dy(dtc)(phen)] is much larger than that of [(dtc)3Dy(phen)], consistent with the experimental results.

The single-molecule magnetism of sandwich tetrapyrrole lanthanide compounds has clearly initiated a huge renaissance in the magnetochemistry of pure lanthanide coordination complexes. In this review, we focus on their structure–function relationships, their historical evolution, and preliminary efforts in surface effect on the SMM properties of multikis(tetrapyrrole) lanthanide complexes for the development of spintronic devices.

A series of new sandwich type lanthanide complexes containing both boratabenzene and cyclooctatetraenyl ligands, [(C5H5BR)Ln(COT)] (1Er: R = H, Ln = Er; 2Er: R = Me, Ln = Er; 3Er: R = NEt2, Ln = Er; 4Dy: R = H, Ln = Dy; 5Dy: R = Me, Ln = Dy; 6Dy: R = NEt2, Ln = Dy; 7Y: R = NEt2, Ln = Y), were synthesized. The structures of 1Er–7Y were all characterized by single crystal X-ray diffraction. Dynamic susceptibility experiments showed that the erbium complexes 1Er–3Er exhibited slow magnetic relaxation under zero dc field while the dysprosium complexes 4Dy–6Dy did not. For the erbium complexes, the magnetic properties were influenced by the substituent on the boron atom. 1Er exhibited hysteresis up to 8 K, and 2Er featured the highest energy barrier (300 cm−1) among all the reported erbium single-ion magnets (SIMs). The influence of the boron substituent on the magnetic properties was highlighted by ab initio calculations.

A new tripodal hexadentate ligand of tris[6-(1 H-pyrazol-1-yl)pyridin-2-yl]methanol (tppm) was synthesized and explored for constructing the trigonal-prismatic cobalt(II) complex [Co(tppm)][ClO4]2·2CH3CN·H2O (1). Magnetic study showed that 1 exhibited large uniaxial magnetic anisotropy with a zero-field-splitting parameter of -80.7 cm-1 and typical single-molecule-magnet behavior.

A series of homoleptic mononuclear 8-coordinate FeII and CoII compounds, [FeII(L2)2](ClO4)2 (2), [FeII(L3)2](ClO4)2 (3), [FeII(L4)2](ClO4)2 (4), [CoII(L1)2](ClO4)2 (5), [CoII(L2)2](ClO4)2 (6), [CoII(L3)2](ClO4)2 (7), and [CoII(L4)2](ClO4)2 (8) (L1 and L2 are 2,9-dialkylcarboxylate-1,10-phenanthroline ligands; L3 and L4 are 6,6′-dialkylcarboxylate-2,2′-bipyridine ligands), have been obtained, and their crystal structures have been determined by X-ray crystallography. The metal center in all of these compounds has an oversaturated coordination number of 8, which is completed by two neutral homoleptic tetradentate ligands and is unconventional in 3d-metal compounds. These compounds are further characterized by electronic spectroscopy, cyclic voltammetry (CV), and magnetic measurements. CV measurements of these complexes in MeCN solution exhibit rich redox properties. Magnetic measurements on these compounds demonstrate that the observed single-ion magnetic (SIM) behavior in the previously reported [FeII(L1)2...

Herein, a series of light lanthanide-based complexes, Ln(fdh)3(bpy) (Ln = CeIII, PrIII, and NdIII and fdh = 1,1,1-fluoro-5,5-dimethyl-hexa-2,4-dione, bpy = 2,2'-bipyridine), were synthesized and characterized. The angle-resolved magnetometry studies reveal that the three complexes have Ising-type anisotropy, and the magnetic easy axes orient along the negative charge dense direction in the crystal field. The results were consistent with the ab initio calculations. This research demonstrates that the crystal field electron density distribution determines the anisotropy of light lanthanides.

Using DCC as the dehydrating agent, a series of Weakley-type polyoxomolybdates [Bu4N]3{Ln[Mo5O13(OMe)4(NO)]2} (Ln = Tb, Dy, Ho, Er) were synthesized in a one-pot reaction and structurally characterized by elemental, IR, UV-vis analysis, PXRD, and single-crystal X-ray diffraction. Furthermore, the static and dynamic measurements were utilized to investigate their magnetic performances. Typically, slow relaxation of magnetization was observed for Dy analogues with an energy barrier for the reversal of the magnetization of 50 K, which is the highest barrier height observed on the polyoxomolybdates-based single-molecule magnets (SMMs). For a deep understanding of the appearance of the SMM behavior on Weakley-type polyoxomolybdates series, ab initio calculations on {Dy[Mo5O13(OMe)4(NO)]2}3- have been conducted.

A new two-dimensional (2D) lanthanide metal–organic framework, {[Dy2(HCAM)3(H2O)4]·2H2O}n (1, H3CAM = 4-hydroxypyridine-2,6-dicarboxylic acid) has been hydrothermally synthesized and structurally characterized using single-crystal X-ray diffraction. There are two crystallographically independent dysprosium atoms in 1, displaying spherical tricapped trigonal prism geometry and square antiprism geometry, respectively. The dysprosium(III) ions are connected with each other through the bridging HCAM2− anions, generating a classical 2D (4, 4) grid structure. Magnetic investigations revealed that intramolecular ferromagnetic interactions exist among the dysprosium(III) ions in 1, which shows field-induced two-step thermal magnetic relaxation, with the effective thermal barriers of 63.5 K and 57.1 K, respectively.

A dinuclear Fe(II) compound has been prepared through the reaction of 2,5-dichloride-4-phenylimino-1,2,4-triazole (L) with Fe(BF4)2·6H2O, with the formula [Fe2(L)5(SCN)4](H2O) (1). X-ray, magnetic, and 57Fe Mossbauer characterizations showed that compound 1 exhibited a spin crossover (SCO) behavior with T1/2 = 150 K. The study shows that introducing chloride groups on the ligand exerts a positive effect on increasing T1/2 and making SCO more complete. A LIESST effect was also observed for 1 through a light irradiation experiment.

We report three dinuclear cobalt(II) complexes, [Co(L)Cl2]2 (L = bpy, mbpy, and dmpbt), that are bridged solely by chloride ions. High-field electron paramagnetic resonance and magnetometric measurements were applied to investigate the magnetic intramolecular Co–Co interactions. Simulation results based on the multispin model reveal that the complexes are weakly ferromagnetically coupled and that the isotropic exchange coupling constants differ slightly for the three complexes. Moreover, the competing effects of zero-field splitting and magnetic coupling on the temperature-dependent magnetic susceptibility were analyzed.

A pair of enantiopure cubane-type CuII4O4 clusters was constructed from simple chiral ligands (R or S)-2-[(2-hydroxy-1-phenylethylimino)methyl]phenol (H2LR or S). Single-crystal X-ray diffraction studies demonstrated that complexes 1R and 1S are enantiomers. They consist of a CuII4O4 cubane core in which the four CuII centres are linked by a μ3-oxo bridge. The four CuII ions in one cluster are all in a distorted square-pyramidal geometry. Circular dichroism (CD) spectroscopy also confirmed that complexes 1R and 1S are enantiomers and that the chirality was successfully transferred and amplified from the ligand to the coordination environment of the CuII ions. Magnetic susceptibility measurements show an overall antiferromagnetic interaction which could be fitted by using MAGPACK with a two parameter model (J1 = –5.58 cm–1, J2 = 3.80 cm–1).

Until now, the expressions of the anisotropic energy barriers Δξ and ΔA, using the uniaxial magnetic anisotropy D, the intrachain coupling strength J, and the high-spin ground state S for single-chain magnets (SCMs) in the intermediate region between the Ising and the Heisenberg limits, were unknown. To explore this relationship, we used density functional theory and ab initio methods to obtain expressions of Δξ and ΔA in terms of D, J, and S of six R4Fe(II)-Re(IV)Cl4(CN)2 (R = diethylformamide (1), dibutylformamide (2), dimethylformamide (3), dimethylbutyramide (4), dimethylpropionamide (5), and diethylacetamide (6)) SCMs in the intermediate region. The ΔA value for compounds 1-3 was very similar to the magnetic anisotropic energy of a single Fe(II), while the value of Δξ was predicted using the exchange interaction of Fe(II) with the neighboring Re(IV), which could be expressed as 2JSReSFe. Similar to compounds 1-3, the anisotropy energy barrier ΔA of compounds 4 and 5 was also equal to (Di - Ei)SFe(2), but the correlation energy Δξ was closely equal to 2JSReSFe(cos 98.4 - cos 180) due to the reversal of the spins on the opposite Fe(II). For compound 6, one unit cell of Re(IV)Fe(II) was regarded as a domain wall since it had two different Re(IV)-Fe(II) couplings. Thus, the Δξ of compound 6 was expressed as 4J″SRe1Fe1SRe2Fe2, where J″ was the coupling constant of the neighboring unit cells of Re1Fe1 and Re2Fe2, and ΔA was equal to the anisotropic energy barrier of one domain wall given by DRe1Fe1(S(2)Re1Fe1 - 1/4).

A mononuclear Dysprosium(III) complex [Hex4N][Dy(DBM)4] (1) was synthesized using dibenzoylmethane (DBM) anion ligand with a tetrahexylammonium (Hex4N+) cation balancing the charge. Complex 1 was structurally and magnetically characterized. The local geometry of Dy(III) ions is close to the ideal D4d symmetry. The temperature and frequency-dependent out-of-phase ac susceptibility peaks were observed in the absence of a static dc field. The relaxation energy barrier Ueff = 27.7 K and τ0 = 1.3 × 10−7 s were obtained by Arrhenius fitting. It is interesting that the quantum tunneling of the magnetization was suppressed when two optimum dc fields (300 and 1500 Oe) were applied. Two distinct thermal relaxation processes were observed with Ueff = 56.6 K, τ0 = 6.6 × 10−10 s for 300 Oe and Ueff = 68.1 K, τ0 = 3.4 × 10−11 s and Ueff = 88.0 K, τ0 = 5.0 × 10−10 s for 1500 Oe. The two thermal relaxation processes were also recognized clearly under zero dc field for the analogue with 20 times magnetic site dilution by Y(III). Nevertheless there is only one crystallographically independent Dy(III) ion in this system. Further inspection of the crystallographic structure reveals that the benzene disorder within the conjugated system of the β-diketonate ligand could change the delocalized electron distribution on the carbonyl coordination oxygen atoms and result in small different ligand fields, which account for the multiple relaxation processes. Ab initio calculations confirm the two energy barriers derived from two disordered structures.

Presented here are the structures and magnetism of two isostructural magnetic Cl-bridged chain compounds of the type (H2mela)2[MCl5]Cl (mela melamine, M Fe(II) (1), M Mn(II) (2)). The chain structure is formed along the Jahn–Teller elongation axis of the MCl6 octahedra. In compound 1, the Cl− ion transmits an antiferromagnetic exchange interaction that, combined with the magnetic anisotropy of the Fe(II) sites, gives rise to a canted antiferromagnetic arrangement of the spins. Detailed magnetic studies revealed that 1 exhibits slow magnetic relaxation behavior like single-chain magnet (SCM), and that the finite size effects, due to naturally occurring defects, strongly influences the static and dynamic properties of 1. The contribution of the correlation length to the energy barrier has also been investigated. The Mn compound 2 is an isotropic Heisenberg chain with antiferromagnetic coupling between the Mn(II) ions. Doped crystals of Zn1, Cu1–Cu5 and Mn1–Mn5 were synthesized by introducing different contents of Zn(II), Cu(II) and Mn(II) ions to study the magnetic dilution and decoupling phenomena, respectively.

A new dysprosium(III) phosphonate dimer {Dy(notpH4)(NO3)(H2O)}2·8H2O (1) [notpH6=1,4,7-triazacyclononane-1,4,7-triyl-tris(methylenephosphonic acid)] that contains two equivalent Dy(III) ions with a three-capped trigonal prism environment is reported. Complex 1 can be transformed into {Dy(notpH4)(NO3)(H2O)}2 (2) in a reversible manner by desorption and absorption of solvent water at ambient temperature. This process is accompanied by a large dielectric response. Magnetic studies reveal that both 1 and 2 show thermally activated magnetization relaxation as expected for single-molecule magnets. Moreover, the magnetic dynamics of the two compounds can be manipulated by controlling the number of solvent molecules at room temperature.

Four azide–copper coordination polymers, [Cu2L1(N3)4]n, [Cu2L2(N3)4]n, [Cu2L3R(N3)4]n, and [Cu2L3S(N3)4]n, were synthesized by using pybox [pyridine-2,6-bis(oxazolines)] as coligands {L1: 2,6-bis(4,5-dihydrooxazol-2-yl)pyridine; L2: 2,6-bis(5,6-dihydro-4H-1,3-oxazin-2-yl)pyridine; L3R or 3S: 2,6-bis[(R or S)-4-benzyl-4,5-dihydrooxazol-2-yl]pyridine}. Compounds 1 and 2 possess similar 1D infinite azide–copper hexagonal tapes with three types of N3 bridges (two single end-on N3 bridges and one double end-on N3 bridge). Compounds 3R and 3S possess an azide–copper 2D honeycomb layer with two types of N3 bridges (a single end-to-end N3 bridge and a double end-on N3 bridge). The chirality of these enantiopure layered structures is controlled by the addition of the chiral pybox ligand in the synthesis, which is very rare for the reported azide–copper coordination polymers. The double end-on N3 bridge transfers mainly ferromagnetic exchange coupling interactions in these four compounds. Owing to the steric hindrance of the pybox ligands, the interchain and interlayer separations are broadened, which weakens the magnetic interactions between them. Thus, no long-range ferromagnetic ordering was observed above 1.8 K. A magnetostructural correlation was also discussed in detail.

Two neutral mononuclear iron(II) complexes with different spin-crossover (SCO) properties, Fe(L1)2(SCN)2 (1) and Fe(L2)2(SCN)2 (2) (L1 = 2-(thiophen-3-yl)-1H-imidazo[4,5-f][1,10]phenanthroline and L2 = 2-(thiophen-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline), were solvothermally synthesized. With the different substituted position in 1,10-phenanthroline derivatives, 1 exhibits gradual SCO around room temperature with T1/2 = 280 K, while 2 displays abrupt SCO with 10 K hysteresis at T1/2↓ = 210 K and T1/2↑ = 220 K.