Search

Four novel isostructural heterometallic dysprosium–hexacyanometallate frameworks, namely {[Dy4(L)4(H2O)4(CH3OH)4M(CN)6]·Cl·8H2O}n and {[Dy4(L)4(H2O)4(CH3OH)4M(CN)6]·Br·4CH3OH}n (M = Fe for 1 and 3, Co for 2 and 4; H2L = N′-(2-hydroxybenzylidene)picolinohydrazide) have been successfully assembled by a feasible approach employing a superparamagnetic dimeric unit as the building block and hexacyanometallates [M(CN)6]3− as bridges. Within these frameworks, hexacyanometallates serve as 4-way nodes and connect the adjacent dimeric building blocks to form a three-dimensional diamond-like structure with a Schlafli symbol of 6^6. Magnetic measurements indicate the ferromagnetic nature of intradimer Dy3+–Dy3+ interactions, the antiferromagnetic coupling between Dy3+ ions and adjacent [Fe(CN)6]3− units, as well as the dynamic magnetic behaviour under zero dc field with the effective energy barriers of 111(2), 283(8), 108(2), and 280(15) K for 1–4, respectively. Ab initio calculations and in-depth magneto-structural studies demonstrate that the magnetic anisotropy of Dy3+ ions and the intradimer ferromagnetic coupling are positive factors for slowing down the quantum tunnelling of magnetization (QTM), resulting in the highest effective energy barrier and the largest coercive field for 2 among all compounds, while the antiferromagnetic interaction between Dy3+ ions and [Fe(CN)6]3− units can accelerate the QTM and thus shut off the magnetic memory effect of 1 and 3 at low temperature.

Single-molecule magnets (SMMs) are expected to be promising candidates for the applications of high-density information storage materials and quantum information processing. Lanthanide SMMs have attracted considerable interest in recent years due to their excellent performance. It has always been interesting but not straightforward to study the relaxation and blocking mechanisms by embedding 3d ions into 4f SMMs. Here we report a family of air-stable 3d-4f ion-pair compounds, YFe (1), DyCr (2), DyFe (3), DyCo (4), and Dy0.04Y0.96Fe (5), composed of pentagonal bipyramidal (D5h) LnIII cations and transition metallocyanate anions. The ion-pair nature makes the dipole-dipole interactions almost the only component of the magnetic interactions that can be clarified and analytically resolved under proper approximation. Therefore, this family provides an intuitive opportunity to investigate the effects of 3d-4f and 4f-4f magnetic interactions on the behavior of site-resolved 4f SMMs. Dynamic magnetic measurements of 1 under a 4 kOe external field reveal slow magnetic relaxation originating from the isolated [FeIII]LS (S = 1/2) ions. Under zero dc field, compounds 2-5 show similar magnetic relaxation processes coming from the separated pentagonal bipyramidal (D5h) DyIII ions with high Orbach barriers of 592(5), 596(4), 595(3), and 606(4) K, respectively. Comparatively, both compounds 3 and 5 exhibit two distinct relaxation processes, respectively from the [FeIII]LS and DyIII [Ueff = 596(4) K for 3 and 610(7) K for 5] ions, under a 4 kOe dc field. The dipolar interactions between the neighboring TMIII (TM = transition metal, CrIII or [FeIII]LS) and DyIII ions were revealed to have little effect on the thermal relaxation in compounds 2, 3, and 5, or the coexistence of the two separate relaxation processes in compounds 3 and 5 under a 4 kOe dc field, but they significantly affect the quantum tunneling of magnetization and the magnetic hysteresis behavior of 2 and 3 at low temperatures compared to those of 4.

The study of lanthanide (Ln)-transition-metal (TM) heterometallic clusters which play key roles in various high-tech applications is a rapid growing field of research. Despite the achievement of numerous Ln-TM cluster compounds comprising one Ln atom, the synthesis of Ln-TM clusters containing multiple Ln atoms remains challenging. Here, we present the preparation and self-assembly of a series of Au-bridged heterometallic clusters containing multiple cerium (Ce) atoms via on-surface coordination. By employing different pyridine and nitrile ligands, the ordered coordination assemblies of clusters containing 2, 3 and 4 Ce atoms bridged by Au adatoms are achieved on Au(111) and Au(100), as revealed by scanning tunneling microscopy. Density functional theory calculations uncover the indispensable role of the bridging Au adatoms in constructing the multi-Ce-containing clusters by connecting the Ce atoms via unsupported Ce-Au bonds. These findings demonstrate on-surface coordination as an efficient strategy for preparation and organization of the multi-Ln-containing heterometallic clusters., The preparation of lanthanide-transition metal clusters containing multiple lanthanide atoms remains challenging. Here, the authors present the controlled on-surface formation of ligand-stabilized heterometallic Ce/Au clusters containing two, three and four Ce atoms bridged by Au adatoms.

A pair of structurally-similar and stable 8-coordinate high-spin Fe(ii) and Fe(iii) compounds have been obtained. Both compounds exhibit field-induced slow magnetic relaxation behaviour. The Fe(iii) compound represents the first example of 8-coordinate Fe(iii) single-molecule magnets (SMM).

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.

A series of mononuclear lanthanide complexes with the formula [Hex4N][Ln(DBM)4] (1Ln) (Ln = Nd and Tb), [But4N][Dy(DBM)4] (2), [Et4N][Dy(DBM)4] (3), [PhCH2N(CH3)3][Dy(DBM)4] (4) and [Hex4N][Dy(TTA)4] (5) formed by four β-diketonate ligands (i.e. DBM = dibenzoylmethane, TTA = 2-thenoyltrifluoroacetone) and four organic counter ammonium cations (i.e. Hex4N = tetrahexylammonium, But4N = tetrabutylammonium, Et4N = tetraethylammonium and PhCH2N+(CH3)3) were structurally and magnetically characterized. The organic ammonium as contactless cation pairs with [Ln(β-diketonate)4]−1 moieties, the impact of different remote organic cations and the first coordination sphere comprising distinct β-diketonates on their SMM performance were elaborately studied. This is an efficient method by virtue of the interaction of the remote organic ion pair to modulate their single-molecule magnetic (SMM) properties. More importantly, the tetrakis β-diketonate Dy(III) anion can be almost intactly grafted on functional GaN substrate through an anion exchange reaction, resulting in diminishing slow magnetic relaxation behavior, which presents potential application in future SMM devices.

A family of cyano-bridged 3d-4f 1D chain compounds, {RE[TM(CN)6(2-PNO)5]}·(H2O)4 {RE = YIII, TM = [FeIII]LS (1); RE = DyIII, TM = CoIII (3); RE = ErIII, TM = [FeIII]LS (4), CoIII (5); 2-PNO = 2-picoline-N-oxide} and {RE[TM(CN)6(2-PNO)5]} {RE = DyIII, TM = [FeIII]LS (2)}, were synthesized and characterized. Single-crystal X-ray diffraction studies reveal that compounds 1 and 3-5 are isostructural, while compound 2 has a similar 1D chain structure with a different chain to chain arrangement. An axially-elongated pentagonal bipyramidal (D5h) coordination geometry is formed with five 2-PNO ligands in the equatorial plane and two [TM(CN)6]3- on the apical sites around the rare earth ions in these compounds. A comparison of the magnetic relaxation behaviour in detail reveals that it is more favorable for the Er (4 and 5) than the Dy analogues (2 and 3) to exhibit SIM properties in this axially-elongated D5h coordination environment. Under zero dc field, ac susceptibility measurements show that the Dy analogues have no magnetic relaxation behaviour, while the Er analogues exhibit frequency dependence despite the strong QTM effect. Under a 1 kOe dc field, the Er analogues generally show 1-2 orders of magnitude longer relaxation time at each selected temperature and a higher relaxation energy barrier than the Dy analogues. And the RECo compounds (3 and 5) show a more suppressed QTM effect than the corresponding REFe (2 and 4) compounds, which may be ascribed to the elimination of the fluctuation field from the neighbouring [FeIII]LS ions. The ab initio calculations indicate the misplacement between the orientation of the main magnetic axis and the structural axis in the Dy analogues, and the relative consistency in the Er analogues, which should be the source of the Er analogues showing better SIM properties than the Dy analogues.

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.

Symmetry and axiality are thought to be guides toward the pursuit of high energy barrier and blocking temperature for the dysprosium (III) (DyIII) single-molecule magnets (SMMs). The DyIII complexe...

The thermally induced cyclodehydrofluorization of iron tetrakis(pentafluorophenyl)porphyrin proceeded highly stereoselectively to give a prochiral product on a gold surface in an ultrahigh vacuum, whereas dehydrocyclization of the respective iron tetrakisphenylporphyrin did not show such selectivity. Stereoselectivity was predominantly observed for closely packed layers, which is an indication of intermolecular cooperativity and steric constraints induced by adjacent species. Density functional theory identified intermolecular packing constraints as the origin of such selectivity during the reaction. Scanning tunneling microscopy revealed the formation of an enantiomerically pure two-dimensional self-assembly as a conglomerate of mirror domains. On-surface two-dimensional topochemistry, as reported herein, may open new routes for stereoselective synthesis.

We investigate a family of dinuclear dysprosium metallocene single-molecule magnets (SMMs) bridged by methyl and halogen groups [Cp'2 Dy(μ-X)]2 (Cp'=cyclopentadienyltrimethylsilane anion; 1: X=CH3- ; 2: X=Cl- ; 3: X=Br- ; 4: X=I- ). For the first time, the magnetic easy axes of dysprosium metallocene SMMs are experimentally determined, confirming that the orientation of them are perpendicular to the equatorial plane which is made up of dysprosium and bridging atoms. The orientation of the magnetic easy axis for 1 deviates from the normal direction (by 10.3°) due to the stronger equatorial interactions between DyIII and methyl groups. Moreover, its magnetic axes show a temperature-dependent shifting, which is caused by the competition between exchange interactions and Zeeman interactions. Studies of fluorescence and specific heat as well as ab initio calculations reveal the significant influences of the bridging ligands on their low-lying exchange-based energy levels and, consequently, low-temperature magnetic properties.

The electron spin characters of paramagnetic endohedral metallofullerenes (EMFs) are sensitive to their surroundings, which offer an opportunity to manipulate their paramagnetic properties. Here we reported the amination of paramagnetic Gd@C82 and revealed that morpholine groups can be used as a tool to fine-tune properties of Gd@C82. Changes of their paramagnetic properties have been observed under different temperatures and among three derivatives. Addition of morpholine groups eliminates the single unpaired electron on the carbon cage, and causes lower symmetry of the carbon cage and location limit of encapsulated gadolinium, leading serious restriction of Gd@C82 and gadolinium motion. The high sensitivity of spin population to chemical modification offers us the possibility to investigate the spin qubit property and further realize quantum control on a molecular level.

A novel three-dimensional porous dysprosium coordination polymer {[Dy2L2(bpdo)2(H2O)(CH3OH)]·2ClO4·2CH3CN}n (1) has been successfully assembled by combining a superparamagnetic building block of [DyLCl(CH3OH)]2 with the organic ligand 4,4′-bipyridine-N,N′-dioxide (bpdo) (H2L = N′-(2-hydroxybenzylidene)picolinohydrazide). Interestingly, upon the release and/or absorption of different solvent molecules, 1 undergoes reversible single-crystal-to-single-crystal (SCSC) transitions, resulting in the formation of another layer compound of {[DyL(bpdo)(H2O)]·ClO4·2H2O}n (2). This structural transformation involves the breaking and reforming of coordination bonds and leads to significant changes in the relaxation behaviour expected for these coordination polymers, as evidenced by the increase in effective energy barriers from 133 K (1) to 264 K (2) and the slowdown of quantum tunnelling at low temperature. The theoretical calculations indicate that the distinct relaxation behaviours arise mainly from the variation in the coordination geometry around the dysprosium ions. Our work shows that guest molecules can reversibly induce remarkable structural changes in a porous dysprosium coordination polymer and significantly affect its dynamic properties.

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.

An azo-based ligand of azotetrazolyl-2,7-dihydroxynaphthalene (H3ATD) was used to synthesize three FeIII–MII–FeIII(M = Fe, Cd) linear trinuclear complexes with different high temperature spin crossover (SCO) behaviours for the terminal FeIIIions.

The electronic [Xe]4f13 configurations of Yb(III) ions generate a variety of electronic energy levels, resulting in the fantastic optical and magnetic multifunctional properties of Yb(III) complexes. Here, 2-hydroxy-3-methoxy benzoic acid (H2MBA) was used to construct two dinuclear and one-dimensional Yb(III) complexes namely [Yb2(HMBA)2(MBA)2(DMF)2(H2O)2]·6H2O (1, DMF = N,N-dimethylformamide) and [NH4][Yb(HMBA)4] (2). Fluorescence measurements reveal that H2MBA can sensitize the characteristic near-infrared luminescence of Yb(III). Magnetic susceptibility measurements show that the two Yb(III) complexes are field-induced single-molecule magnets (SMMs) with anisotropy barriers of 18(1) cm−1 and 20(1) cm−1 for 1 and 2, respectively. The magnetism–luminescence–structure correlations as well as relaxation pathways are investigated by ab initio calculations and fluorescence spectrometry.

While assembling superparamagnetic units in a controlled manner is crucial for future applications of molecular nanomagnets, optimizing their magnetic properties while achieving directional assembly of these units still remains a formidable challenge. Herein, we demonstrate how the assembly of two dysprosium chain complexes, namely, [Dy2(L)2Cl2(CH3OH)3]n·nCH3OH (1) and [Dy(L)Cl(DMF)]n (2) (H2L = N‘-(5-bromo-2-hydroxybenzylidene)pyrazine-N-oxide-carbohydrazide), can be successfully manipulated using an appropriate bridging ligand design. Both complexes contain similar dimeric units bridged by two alkoxido oxygens from an L2− ligand, but extended by its pyrazine-N-oxide group exhibiting two distinct coordination modes, namely, single and double pyrazine-N-oxide bridges, respectively. Magnetic studies reveal that both complexes display typical slow magnetic relaxation under zero direct-current field; however, the anisotropy barrier and the coercive field at 2 K for complex 2 are twice as much as that of 1. A further theoretical study indicates that switching the coordination mode from a single pyrazine-N-oxide bridge to double bridges can enhance both the magnetic anisotropy of dysprosium ions and magnetic coupling within the dimeric cores. The synergistic effect between the magnetic anisotropy of dysprosium ions and magnetic interactions among them directly contributes to the overall better performance of complex 2.

Two ion-pair Fe(iii) complexes (PPh4)[FeIII(HATD)2]·2H2O (1, H3ATD = azotetrazolyl-2,7-dihydroxynaphthalene) and [FeII(phen)3][FeIII(HATD)2]2·3DMA·3.5H2O (2, phen = 1,10-phenanthroline, DMA = N,N-dimethylformamide) were synthesized by employing the tridentate ligand H3ATD. Crystal structure analyses reveal that complexes 1 and 2 consist of FeIII ions in an octahedral environment where a FeIII ion is coordinated by two HATD2- ligands forming the [FeIII(HATD)2]- core. The shortest cationanion distance between the phosphorus ion of the (PPh4)+ cation and the ferric ion of the [FeIII(HATD)2]- anion is 13.190 A in complex 1, whereas that between the ferrous ion of the [FeII(Phen)3]2+ cation and the ferric ion of the [FeIII(HATD)2]- anion is 7.821 A in complex 2. C-HC and C-HO hydrogen interactions between the [FeII(phen)3]2+ cation and the [FeIII(HATD)2]- anion are observed in 2. Face-to-face π-π stacking interactions between naphthalene rings with the separated interplanar center to center distances of 3.421-3.680 A were observed, which result in a one-dimensional supramolecular chain in complexes 1 and 2. Magnetic measurements show that complex 1 is in the low-spin (LS) state below 500 K, whereas 2 undergoes a high temperature spin crossover (SCO) between 360 and 500 K. Magneto-structural relationship studies reveal that π-stacking, hydrogen interactions and Coulomb interactions between the [FeIII(HATD)2]- anion and the [FeII(phen)3]2+ cation play a crucial role in the high temperature Fe(iii) SCO behaviour of complex 2.

A new microporous Ni-based metal-organic framework (Ni-MOF-1) was synthesized by reaction of Ni(NO)3·6H2O with the binary ligands of tetracarboxylic 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine (H4TCPP) and 4,4′-bipyridine under solvothermal reaction. The single crystal X-ray diffraction indicates that Ni-MOF-1 possesses a three-dimensional porous network with novel trinuclear Ni3(OH)2(COO)4(HCOO)4 clusters, exhibiting high CO2 uptakes of 37.57 cm3 g−1 and high selectivity of CO2 over N2 (42.89) at 273 K.

Two dysprosium complexes bearing unsupported Dy–Ge/Sn metal–metal bonds are reported here, wherein the Dy–Ge and Dy–Sn bonds both contain relatively large covalency. The complexes exhibit slow relaxation of magnetization at zero field with energy barriers of 485 and 620 K, respectively, and the blocking temperature of 6 K.

A novel superparamagnetic dysprosium chain complex, namely, [Dy(L)Cl(CH3OH)]n (1) (H2L = N′-(5-bromo-2-hydroxybenzylidene)pyrazine-N-oxide-carbohydrazide), has been successfully synthesized by the extension of dinuclear units through chloride bridges. Magnetic and theoretical studies indicate that dipolar magnetic interactions induced by the chloride bridges are helpful for the magnetic relaxation process to pass through the second-excited state of dysprosium ions, resulting in the higher energy barrier for 1.

To mimic the strategy used by natural photosynthesis in Photosystem II, which adopts the cubic Mn4CaO5 cluster as a natural oxygen-evolving complex, a bio-inspired cubane-like tetranuclear cluster [Cu4(pdmH)4(OAc)2](NO3)2·3H2O (1) has been synthesized successfully with pyridine-2, 6-dimethanol as the ideal ligand, and investigated by X-ray crystallography, PXRD, in situ UV-vis-NIR spectroelectrochemical analysis, and magneto- and electrochemistry. By X-ray analysis, it is shown that the distorted cubane-like core Cu4(μ3-O)4 is composed of four CuII and four μ3-O which arrange at the vertices of a slightly distorted cube. Electrochemical studies indicate that complex 1 presents potential properties as an effective molecular catalyst for electrocatalytic water oxidation under aqueous alkaline conditions at a potential of ∼1.20 V vs. NHE with a relatively low overpotential of ∼400–665 mV vs. NHE, which may result from the unique covalent metal–oxo bonding. Magnetic susceptibility measurements reveal that complex 1 displays overall antiferromagnetic exchanges between the Cu(II) ions within the clusters. Temperature dependence of in-phase (χM′) ac susceptibility signals display frequency-dependence, whereas the out-of-phase (χM′′) signals show no significant frequency-dependence for complex 1, which indicates that the complex may not be a SMM.

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.

A class of cyano-bridged 3d-4f zig-zag chain compounds, {RE[TM(CN)6] (PNO)2(H2O)4}·(H2O) {RE = YIII, TM = [FeIII]LS (1); RE = DyIII, TM = [FeIII]LS (2), CoIII (3)}, have been synthesized and characterized by single-crystal X-ray diffraction. The rare earth ions in these compounds are situated in a slightly distorted triangular dodecahedral (D2d) coordination environment. The magnetic properties of compounds 1-3 have been comparatively studied in detail. Under a zero dc field, the temperature dependence of ac susceptibility measurements for YFe (1) indicates the absence of magnetic relaxation stemming from the single anisotropic [FeIII]LS ion. The dysprosium analogue DyFe (2) shows only magnetic relaxation behavior with a prominent QTM effect, while DyCo (3) exhibits SIM properties not completely covered by QTM, with an extracted energy barrier of 73 K under a zero dc field. The ab initio calculations indicate that both compounds 2 and 3 are SMMs with well-behaved magnetic relaxation properties primarily from the individual DyIII ion. Therefore, the different magnetic behaviors exhibited by compound 2 compared to 3 may be ascribed to the stronger QTM effect caused by the extra weak interaction of [FeIII]LS ions in 2 as a fluctuating transverse field around the DyIII ion. The QTM effect for both 2 and 3 is suppressed under an applied dc field with an effective energy barrier of 134 and 150 K, respectively. Compared with compound 2, the higher extracted Ueff/kB and χ''(T) peak temperature for 3 should be further attributed to its slightly higher single-ion axiality as calculated and the elimination of the transverse field from the [FeIII]LS ion.

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 ...

It is very challenging to synthesize stable trivalent rare-earth complexes in which the coordination number is lower than 3 for the high oxidation state, there is a large ion radius and nearly non-bonding character of trivalent lanthanide ions. The bulky phenol ligand ArOH (Ar=2,6-Dipp2 C6 H3 , Dipp=2,6-diisopropylphenyl) was utilized to construct low-coordinate lanthanide compound [(ArO)Ln(OAr')] (Ar'=6-Dipp-2-(2'-i Pr-6'-CHMe(CH2- )C6 H3 )C6 H3 O- ; Ln=Tb, Dy, Ho, Er, Tm). These complexes and the free ligand ArOH were isostructural. Magnetic measurements and theoretical studies demonstrated that both the oblate-type dysprosium and prolate-type erbium analogues exhibited single-ion magnet (SIM) behavior. The bulky phenol ligands provided strong uniaxial ligand field, making the dysprosium SIM possessing blocking barrier up to 961 K.

The five heterometallic formate frameworks [EtA][GaIIIFeII(HCOO)6] (1; EtA = CH3CH2NH3+), [DMA][GaIIIFeII(HCOO)6] (2; DMA = (CH3)2NH2+), [DEtA][GaIIIFeII(HCOO)6] (3; DEtA = (CH3CH2)2NH2+), [MA][GaIIINiII(HCOO)6] (4; MA = CH3NH3+), and [DMA][GaIIINiII(HCOO)6] (5) were synthesized through solvothermal methods. Complexes 1–5 are isotructural, and all crystallize in the trigonal P31c space group. Each metal center is 6-connected, with each HCOO– bridging ligand in an anti-anti mode to build a three-dimensional niccolite-like architecture. All of the complexes exhibit weak ferromagnetism at low temperature. A variable-temperature (VT) dielectric study indicates that the dielectric anomaly is induced by the freezing of motions from the protonated amines during the freezing process.

In this present study, two Mn/Ln clusters, [Mn2Ln2(O2CMe)6(pdmH)2L](NO3)·H2O (Ln = Dy (1), Gd (2)), have been synthesized and experimentally investigated by X-ray crystallography, PXRD, magneto- and electrochemistry. By X-ray analysis, it is shown that the two complexes are isomorphous, both possessing one [MnIIMnIIILnIII2(μ3-O)2]6+ core with four metal atoms in one plane arranged in a butterfly conformation. This is the first time that mixed-valent manganese (MnII and MnIII) and LnIII heterometal tetranuclear complexes have been isolated and characterized. Magnetic susceptibility measurements reveal that compounds 1 and 2 both display overall weak ferromagnetic exchanges between the metal ions within the clusters. The temperature dependencies of the out-of-phase (χM′) and in-phase (χM′) ac susceptibility signals exhibit no significant frequency-dependency for compounds 1 and 2, which suggests that the two complexes may not be SMMs. Electrochemical studies indicate that compounds 1 and 2 can both catalyze water oxidation at a potential of ∼1.70 V with an overpotential of ∼880 mV vs. NHE, which could be due to a cooperative catalytic effect between the manganese and lanthanide ions.

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.

A new three-dimensional porous lanthanide coordination polymer {[Dy(L)(μ2-bpdo)0.5(μ4-bpdo)0.5(CH3OH)]·ClO4·3CH3OH}n (2) featuring slow magnetic relaxation has been successfully assembled by reacting a superparamagnetic chain complex{[Dy(HL)(H2O)2(CH3OH)2]·2Cl·CH3OH}n (1) with an organic bridging ligand, namely, 4,4′-bipyridine-N,N′-dioxide (bpdo) (H2L = N′-(2-hydroxybenzylidene)-picolinohydrazide). Compared with 1, complex 2 has a higher magnetic anisotropy barrier, which arises from the variation of the ligand field around dysprosium ions and/or the existence of magnetic coupling between them induced by the bpdo ligand, leading to a thermal magnetic relaxation process through the second-excited doublet. Interestingly, complex 2 can undergo a reversible single-crystal-to-single-crystal conversion accompanying the desorption and adsorption of methanol molecules. The de-solvated phase, {[Dy(L)(μ2-bpdo)0.5(μ4-bpdo)0.5(CH3OH)]·ClO4}n (3), exhibits a slow magnetic relaxation process through the first-excited doublet, presenting the first example of reversible adjustment on the magnetic relaxation pathway regulated by guest molecules. This exciting finding offers a new perspective for enhancing the magnetic relaxation barrier.

A new centrosymmetric tetranuclear aggregate [Dy4(L)2(OAc)8(CH3OH)2] (1) was assembled using a unique symmetrical Schiff base ligand 1,5-bis(salicylidene)-carbohydrazide (H2L). Magnetic studies reveal ferromagnetic interactions between dysprosium ions and two obvious relaxation processes under zero dc field with effective energy barriers Ueff of 38 K and 223 K, the highest among the reported tetranuclear dysprosium molecular nanomagnets. To obtain further evidence on the origination of the slow magnetic relaxation, a diamagnetic yttrium analogue [Y4(L)2(OAc)8(CH3OH)2] (2) and a diluted sample [(Dy0.06Y0.94)4(L)2(OAc)8(CH3OH)2] (3) were synthesized. Further magnetic studies on the diluted sample combined with theoretical calculations indicate that the two-step magnetic relaxation processes in complex 1 originate from the single-ion magnetic behaviors of dysprosium ions with different coordination environments.

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.

A single-ion magnet (Dsp)Er(COT) was obtained by replacing a carbon atom of [Cp*]– in (Cp*)Er(COT) by a soft P atom. Both relaxation barrier and blocking temperature are improved., Beyond the lanthanide organometallic single-ion magnet (SIM) (Cp*)Er(COT)1 ([Cp*]– = pentamethylcyclopentadienide; COT2– = cyclooctatetraenide) that has a good performance, we managed to replace one coordinated carbon atom on the [Cp*]– ring by a soft phosphorus atom and obtained (Dsp)Er(COT) (CCDC No. ; 1835955; Dsp– = 3,4-dimethyl-2,5-bis(trimethylsilyl)phospholyl) whose sandwich structure is reported here for the first time. This substitution results in a remarkable change of magnetic dynamics. It exhibits slow magnetic relaxation under a zero applied direct current (DC) magnetic field with an energy barrier (Δ/kB) of 358 K and magnetic hysteresis up to 9 K, both of which are higher than those of (Cp*)Er(COT). With the descended local symmetry of (Dsp)Er(COT), the energy barrier and blocking temperature (TB) both improve unexpectedly and are among the highest ones in Er(iii)-based single-molecule magnets (SMMs).

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.

Low-temperature reduction of perovskite Tb0.5Ca0.5MnO3–x yields novel crystal-structured noncentrosymmetric compound Tb0.50Ca0.50Mn0.962.33+O2.37, which unusually crystallizes in cubic lattice I23 (a ∼ 15.27 A) based on a 4ap × 4ap × 4ap expansion relative to the simple cubic perovskite unit cell. Rietveld refinements and HAADF-STEM images are used for the structure determination, revealing a rare-typed metal-anion coordination framework which consists of corner-shared tetrahedra and pyramids, and edge-shared bipyramids and octahedra. 2/64 B-site Mn-ordered vacancies are observed for the first time acting as the apex and body center of the I lattice in reduced systems. Room-temperature piezoelectricity is detected, with a quasistatic d33 value of ∼0.32 pC N–1 and inverse d33 value of ∼10.5 pm V–1. This phase primarily exhibits antiferromagnetic ordering below TN ∼ 70 K, with ferromagnetic responses resulted from spin-canting below 40 K. This work provides a new way toward synthesizing unconventional acent...

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.

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.

We herein report on the synthetic, structural, magnetic, and computational studies of six air-stable mononuclear Co(II) complexes with distorted octahedral geometry from PyBox type ligands. Magnetic and theoretical studies reveal that these complexes all exhibit field-induced type single-molecule magnet behaviour and a large energy splitting between the ground and first excited Kramers doublets. Dynamic magnetic property analysis shows that the Raman relaxation process is the predominant process in all six compounds. For complexes 1, 2, 3, 5, and 6, the contribution of the direct process also existed. Importantly, the axial zero-field splitting parameter D in this series varies from positive to negative with the increased distortion of the octahedral geometry for the Co(II) center, indicating that the fine-tuning of the molecular symmetry is an effective approach to manipulate the magnetic anisotropy in SIMs.

A hydroxide-bridged centrosymmetric DyIII dimer with each DyIII being five-coordinated has been synthesized using bulky hindered phenolate ligands. Magnetic studies revealed that this compound exhibits a slow magnetic relaxation of a single-ion origin together with a step-like magnetic hysteresis of the magnetic coupled cluster. The thermal relaxation barrier of magnetization is 721 K in the absence of a static magnetic field, while the intramolecular magnetic interaction is very large among reported 4f-only dimers. CASSCF calculations with a larger active space were performed to understand the electronic structure of the compound. The thermal relaxation regime and the quantum tunneling regime are well separated, representing a good model to study the relaxation mechanism of SMMs with intramolecular Dy–Dy magnetic interactions.

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.

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.

Two iso-structural hybrid perovskites of [(CH3)2SO][RE(HCOO)3] for RE3+ = Lu3+ and Y3+ are polar and possess neutral rare earth formate frameworks incorporating dimethyl sulfoxide locating in the framework cavities and coordinating to the RE3+ ions. The materials display reversible phase transitions at 172 K and 138 K for Lu and Y, respectively. The phase transitions are driven by the transformations of weak C–H⋯O interactions and the gradual twists of the constituents in low temperature, which control the order–disorder states of dimethyl sulfoxide and account for different anisotropic thermal expansion behaviors for the two phases and the characters of dielectric responses.

A novel two-dimensional dysprosium(III) complex, [Dy(L)(CH3COO)]·0.5DMF·H2O·2CH3OH (1), has been successfully synthesized from a new pyridine-N-oxide (PNO)-containing ligand, namely, N'-(2-hydroxy-3-methoxybenzylidene)pyridine-N-oxidecarbohydrazide (H2L). Single-crystal X-ray diffraction studies reveal that complex 1 is composed of a dinuclear dysprosium subunit, which is further extended by the PNO part of the ligand to form a two-dimensional layer. Magnetic studies indicate that complex 1 shows well-defined temperature- and frequency-dependent signals under a zero direct-current (dc) field, typical of slow magnetic relaxation with an effective energy barrier Ueff of 33.6 K under a zero dc field. Interestingly, powder X-ray diffraction and thermogravimetric analysis reveal that compound 1 undergoes a reversible phase transition that is induced by the desorption and absorption of methanol and water molecules. Moreover, the desolvated sample [Dy(L)(CH3COO)]·0.5DMF (1a) also exhibits slow magnetic relaxation but with a higher anisotropic barrier of 42.0 K, indicating the tuning effect of solvent molecules on slow magnetic relaxation.

Two three-dimensional supramolecular organic frameworks, [(H2bpdc)0.5(bipy)0.5] (1) and [(H3dpob)(bipy)·3H2O] (2), have been successfully constructed and structurally characterized (H2bpdc = 2,2′-biphenyldicarboxylic acid; H3dpob = 3-(2′,3′-dicarboxylphenoxy)benzonic acid; bipy = 4,4′-bipydine). 1 is driven by C–H···π hydrogen-bonded packing to three dimension. 2 origins form parallel-packed wavy chains and show π–π stacking-directed structure. After the SOFs are formed via weak noncovalent interaction, 1 and 2 show an enhancement in thermostability. The different conformations of bipy induced by weak noncovalent interactions are responsible for the huge dissimilarity of structural and luminescence behavior between them. Under the excitation of 365 nm ultraviolet light, 1 and 2 show stronger blue-white and green-white luminescent emissions in the solid state, respectively. In comparison with 2, supramolecular organic framework 1 shows superior performance in aggregation-induced emission (AIE) activity, wh...

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.

The use of the monodentate N-heterocyclic carbene (NHC) 1,3,4,5-tetramethylimidazol-2-ylidene (IMe2Me2) and its N,N-diethyl and N,N-diisopropyl analogues IEt2Me2 and IPr2Me2 enabled the preparation of the four-coordinate homoleptic iron(I)–NHC complexes [(NHC)4Fe][BPh4] (NHC = IMe2Me2, 1; IEt2Me2, 2; IPr2Me2, 3) and the first three-coordinate homoleptic iron(I)–NHC complex, [(IPr2Me2)3Fe][BPh4] (5). X-ray crystallographic studies revealed the tetrahedral coordination geometries of the cations in 1 and 2, the square-planar geometry in 3, and the trigonal-planar geometry in 5. 57Fe Mossbauer spectroscopy and magnetic susceptibility measurements suggested that 1, 2, and 5 are high-spin (S = 3/2) iron(I) species and that 3 is a low-spin (S = 1/2) complex. 1H NMR and UV–vis–NIR spectroscopies revealed the existence of tetrahedral–square-planar isomerization (for 2 and 3) and NHC dissociation (for 3) in solutions of 2 and 3.

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.