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A quantum spin liquid (QSL) is an elusive state of matter characterized by the absence of long-range magnetic order, even at zero temperature, and by the presence of exotic quasiparticle excitations. In spite of their relevance for quantum communication, topological quantum computation and the understanding of strongly correlated systems, like high-temperature superconductors, the unequivocal experimental identification of materials behaving as QSLs remains challenging. Here, we present a novel 2D heterometallic oxalate complex formed by high-spin Co(II) ions alternating with diamagnetic Rh(III) in a honeycomb lattice. This complex meets the key requirements to become a QSL: a spin ½ ground state for Co(II), determined by spin–orbit coupling and crystal field, a magnetically-frustrated triangular lattice due to the presence of antiferromagnetic correlations, strongly suppressed direct exchange interactions and the presence of equivalent interfering superexchange paths between Co centres. A combination of electronic paramagnetic resonance, specific heat and ac magnetic susceptibility measurements in a wide range of frequencies and temperatures shows the presence of strong antiferromagnetic correlations concomitant with no signs of magnetic ordering down to 15 mK. These results show that bimetallic oxalates are appealing QSL candidates as well as versatile systems to chemically fine tune key aspects of a QSL, like magnetic frustration and superexchange path geometries.

This article is part of the themed collection: Chemical Communications HOT Articles 2023., Self-assembly of trans-{EuI2} nodes and ditopic ligands leads to isoreticular 2D frameworks featuring a rare, non-kagome Archimedean tessellation. The topology and intra-layer Eu(II)–Eu(II) antiferromagnetic interactions provide the prerequisites for geometrical spin frustration, which, due to the spin state degeneracy, is key for novel phenomena such as enhanced magnetic refrigeration., The authors acknowledge support from the VILLUM Foundation, the Independent Research Fund Denmark, ESS Lighthouses “SMART” and “Q-MAT”, MICINN (PID2021-124734OB-C21), DGA, Danscatt, and the ESRF (ID12 beamline).

Reaction of Gd(OAc)3·4H2O, salicylaldehyde and CH3ONa in MeCN/MeOH affords [Gd12Na6(OAc)25(HCO2)5(CO3)6(H2O)12]·9H2O.0.5MeCN (1·9H2O.0.5MeCN), whose structure describes a quadruple-wheel consisting of two {Na3} and two {Gd6} rings. The magnetic properties of 1 reveal very weak antiferromagnetic interactions between the GdIII ions, which give rise to a record magnetocaloric effect at low applied magnetic fields and low temperatures. The magnetic entropy change reaches −ΔSm= 29.3 J kg–1 K–1 for full demagnetization from B = 1 T at T = 0.5 K.

A family of Mn(II)Ln(III) dinuclear and tetranuclear complexes (Ln = Gd and Dy) has been prepared from the compartmental ligands N,N′-dimethyl-N,N′-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylenediamine (H2L1) and N,N′,N′′-trimethyl-N,N′′-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2L2). The Mn(II)Gd(III) complexes exhibit antiferromagnetic interactions between Mn(II) and Gd(III) ions in most cases, which are supported by Density Functional Theory (DFT) calculations. Experimental magneto-structural correlations carried out for the reported complexes and other related complexes found in bibliography show that the highest ferromagnetic coupling constants are observed in di-μ-phenoxido bridged complexes, which is due to the planarity of the Mn–(μ-O)2–Gd bridging fragment and to the high Mn–O–Gd angles. The effect of these angles has been studied by DFT calculations performed on a di-μ-phenoxido doubly bridged model. The magneto-thermal properties of the Mn(II)Gd(III) based complexes have also been measured, concluding that the magnitude of the Magneto-Caloric Effect (MCE) is due to the strength rather than to the nature of the magnetic coupling. Moreover, when two Mn(II)Gd(III) dinuclear units are connected by two carbonato-bridging ligands the MCE is enhanced, obtaining a maximum magnetic entropy change of 36.4 Jkg−1 K−1 at ΔB = 7 T and T = 2.2 K. On the other hand, one of the dinuclear Mn(II)Dy(III) complexes displays Single-Molecule Magnet (SMM) behaviour with an energy barrier of 14.8 K under an applied external field of 1000 Oe., This work was supported by the Junta de Andalucía (FQM-195 and the Project I + D + i FEDER 2018, A-FQM-172-UGR), MICIU of Spain (Projects PGC2018-102052-B-C21 and RTI2018-098537-B-C22), the University of Granada, the University of The Basque Country UPV/EHU (GIU20/028) and the Gobierno de Aragón (E11 20R). We would like to thank the Centro de Supercomputación de la Universidad de Granada for computational resources. The authors acknowledge the technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF).

Use of the 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane ligand, LH

The combination of two different Fe

The combination of two different FeIII salts in a solvothermal reaction with triethanolamine results in the formation of a high symmetry [FeIII15] cluster whose structure conforms to a centred, tetrakis hexahedron., EKB and LC thank U21/EPSRC for funding a studentship (DJC). MKS would like to thank Edinburgh Compute and Data Facility (ECDF), and the European Union Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 832488. ME thanks the Spanish Ministry of Science and Innovation (Project RTI2018-098537-B-C22).

Reaction between NiCl2·6H2O, 2-hydroxy-4-methyl-6-phenyl-pyridine-3-amidoxime (H2L), benzoic acid, and M(NO3)3·6H2O (M = Gd, Y) in MeCN under basic conditions yields the complexes [NiII4GdIII5(PhCOO)10(HL)4(HLzw)4(OH)2(NO3)2]Cl·13.6MeCN·H2O (1·13.6MeCN·H2O) and [NiII4YIII5(PhCOO)10(HL)4(HLzw)4(OH)2(NO3)1.5(H2O)0.5]0.5Cl(NO3)·3H2O (2·3H2O). Both clusters display similar structures, consisting of a bell-shaped {NiII4MIII5} unit, in which a linear "zigzag" {Ni4} subunit bisects the central {MIII5} "ring". Direct (dc) and alternating current (ac) magnetic susceptibility measurements carried out in the 2-300 K temperature range for complexes 1 and 2 revealed ferromagnetic intermolecular interactions, while heat-capacity measurements for the Gd analogue suggest that complex 1 lowers its temperature from T = 9.6 K down to 2.3 K by adiabatically demagnetizing from Bi = 7 T to Bf = 0., E.K.B. thanks the EPSRC for funding grants EP/N01331X/1 and EP/P025986/1.

The combination of two different FeIII salts in a solvothermal reaction with triethanolamine results in the formation of a high symmetry [FeIII15] cluster whose structure conforms to a centred, tetrakis hexahedron.

Highly sensitive magnetometry reveals paramagnetism in dendrimer-coated gold nanoparticles. Different types of such nanoparticles, as a result of (i) functionalizing with two distinct Percec-type dendrons, linked to gold via dodecanethiol groups, and (ii) postsynthesis annealing in a solvent-free environment that further promotes their growth have been prepared. Ultimately, for each of the two functionalization configurations, we obtain highly monodisperse and stable nanoparticles of two different sizes, with spherical shape. These characteristics allow singling out the source of the measured paramagnetic signals as exclusively arising from the undercoordinated gold atoms on the surfaces of the nanoparticles. Bulk gold and the functional groups of the ligands contribute only diamagnetically., This work was supported by the MINECO-FEDER funds (project PGC2018-097583-B-I00 and RTI2018-094909-J-I00) and Gobierno de Aragón-FSE (Research Group E47_17R). The authors acknowledge the use of SAI (UZ), CEQMA (UZ-CSIC), and LMA (UZ-CSIC) services. J.A.U. thanks the Becas-Chile program of the National Commission for Scientific and Technological Research (CONICYT, Chile) for his PhD grant.

Ligand design remains key to the synthesis of coordination compounds possessing specific topologies, nuclearities and symmetries that direct targeted physical properties. N,O-chelates based on ethanolamine have been particularly prolific in constructing a variety of paramagnetic 3d transition metal complexes with fascinating magnetic properties. Here, we show that combining three ethanolamine moieties within the same organic framework in the form of the pro-ligand 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane (LH3) leads to the formation of two highly unusual Mn wheels. Reaction of Mn(NO3)2·6H2O with LH3 in basic methanolic solutions leads to the formation of [MnIII12MnII4(μ3-O)6(μ-OH)4(μ3-OMe)2(μ-OMe)2(L)4(LH)2(H2O)10](NO3)6(OH)2 (1) and [MnIII10(μ3-O)4(μ-OH)4(μ-OMe)4(L)4(H2O)4](NO3)2 (2), the only difference in the synthesis being the ratio of metal:ligand employed. The structure of the former describes two offset [MnIII6MnII2] square wheels, linked through a common centre, and the latter a single [MnIII10] wheel twisted at its centre, such that the top half is orientated perpendicular to the bottom half. In both cases the L3−/LH2− ligands dictate the orientation of the Jahn-Teller axes of the MnIII ions which lie perpendicular to the triazacyclohexane plane. Direct current magnetic susceptibility and magnetisation data reveal the presence of competing exchange interactions in 1 and strong antiferromagnetic interactions in 2. Given the simplicity of the reactions employed and the paucity of previous work, the formation of these two compounds suggests that LH3 will prove to be a profitable ligand for the synthesis of a multitude of novel 3d transition metal complexes., CJM and TGT thank the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the “First Call for H.F.R.I. Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant” (Project Number: 400). EKB thanks the EPSRC for financial support under grant reference numbers EP/I03255X/1 and EP/I031421/1. GL and ME thank the Ministerio de Ciencia e Innovación (RTI2018-094909-J-I00) and CSIC (PIE 201960E002).

Ligand design remains key to the synthesis of coordination compounds possessing specific topologies, nuclearities and symmetries that direct targeted physical properties. N,O-chelates based on ethanolamine have been particularly prolific in constructing a variety of paramagnetic 3d transition metal complexes with fascinating magnetic properties. Here, we show that combining three ethanolamine moieties within the same organic framework in the form of the ligand 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane (LH3) leads to the formation of two highly unusual Mn wheels. Reaction of Mn(NO3)2·6H2O with LH3 in basic methanolic solutions leads to the formation of [MnIII 12MnII 4(µ3-O)6(µ-OH)4(µ3-OMe)2(µOMe)2(L)4(LH)2(H2O)10](NO3)6(OH)2 (1) and [MnIII 10(µ3-O)4(µ-OH)4(µ-OMe)4(L)4(H2O)4](NO3)2 (2); the only difference in the synthesis being the ratio of metal:ligand employed. The structure of the former describes two offset [MnIII 6MnII 2] square wheels, linked through a common centre, and the latter a single [MnIII 10] wheel twisted at its centre, such that the top half is orientated perpendicular to the bottom half. In both cases the L 3- /LH2- ligands dictate the orientation of the Jahn-Teller axes of the MnIII ions which lie perpendicular to the triazacyclohexane plane. Direct current magnetic susceptibility and magnetisation data reveal the presence of competing exchange interactions in 1 and strong antiferromagnetic interactions in 2. Given the simplicity of the reactions employed and the paucity of previous work, the formation of these two compounds suggests that LH3 will prove to be a profitable ligand for the synthesis of a multitude of novel 3d transition metal complexes

Certain magnetic molecules and molecular-based frameworks are considered as alternative materials for cryogenic cooling due to their large magneto-caloric effect. This potential is particularly appealing for applications requiring local refrigeration, but so far no study has been aimed at making thin films of efficient molecular coolers on a typical device substrate and evaluating their cooling potential. In this work, the growth of a dense gadolinium metal–organic framework on oxide-free silicon covered by either self-assembled or covalent monolayers with carboxylic end groups is explored. A continuous coverage with nanosized crystallites of the selected gadolinium formate framework is successfully formed on covalent monolayers obtained by hydrosilylation with either undecenoic acid or undecynoic acid. The thickness of the magnetocaloric deposit can be increased by increasing the growth time, as shown by the surface densities derived through determination of the film magnetic properties. An estimation of the cooling potential of the thicker film obtained shows that it would refrigerate a 2 μm thick Si membrane from 5 to 0.8 K, by adiabatic demagnetization from 2 T to zero field. Altogether, this study demonstrates the potential of molecular cooler thin films to develop on-chip magnetic refrigeration at cryogenic temperatures., The authors acknowledge funding from the Spanish MINECO and FEDER through projects MAT2014-53961-R (GL, EN and OR), MAT2015-70868-ERC (OR), MAT2015-68204-R (GL and ME) and MAT2017-86826-R (OR and EN), as well as from the Aragon government (DGA, consolidated groups MOLCHIP E98, PLATON E31_17R and M4 E13_17R).

Magnetization, heat capacity and direct measurements of the magnetocaloric effect show that EuGd2O4 and EuDy2O4 have a remarkably large magnetocaloric effect at cryogenic temperatures, owing to their high magnetic density and low ordering temperatures. The Gd derivative orders antiferromagnetically at TN = 4.6 K, while its magnetocaloric effect largely exceeds that of the reference refrigerant Gadolinium Gallium Garnet (GGG) above 5 K. The Dy derivative undergoes two phase transitions at TC1 = 3.65 K and TC2 = 4.7 K, respectively, which are the result of a peculiar magnetic arrangement: the first Dy sublattice is parallel to the crystallographic c-axis, while the Eu sublattice makes a variable angle from 0o to 45o with the direction of the second Dy sublattice that lies in the ab-plane. EuDy2O4 has a lower magnetocaloric effect than EuGd2O4, yet larger than GGG. Both ordering mechanisms are semi-quantitatively explained within the frame of a mean-field simulation, which takes into account the magnetic anisotropy strength of the participating magnetic ions., This work has been funded by Spanish Ministry of Science and Innovation (Projects MAT2017–86019-R, MAT2017–84385-R, RTI2018–098537-B-C22), Gobierno de Aragón (Consolidated Group E11_20R) and Comunidad de Madrid (Project S2009/PPQ-1626).

Correction for ‘The coordination chemistry of p-tert-butylcalix[4]arene with paramagnetic transition and lanthanide metal ions: an Edinburgh Perspective’ by Lucinda R. B. Wilson et al., Dalton Trans., 2022, DOI: 10.1039/d2dt00152g.

The dissolution of anhydrous iron bromide in a mixture of pyridine and acetonitrile, in the presence of an organic amine, results in the formation of an [Fe34] metal oxide molecule, structurally characterised by alternate layers of tetrahedral and octahedral FeIII ions connected by oxide and hydroxide ions. The outer shell of the complex is capped by a combination of pyridine molecules and bromide ions. Magnetic data, measured at temperatures as low as 0.4 K and fields up to 35 T, reveal competing antiferromagnetic exchange interactions; DFT calculations showing that the magnitudes of the coupling constants are highly dependent on both the Fe‐O‐Fe angles and Fe−O distances. The simplicity of the synthetic methodology, and the structural similarity between [Fe34], bulk iron oxides, previous FeIII–oxo cages, and polyoxometalates (POMs), hints that much larger molecular FeIII oxides can be made., E.K.B. thanks the EPSRC for funding (grants EP/N01331X/1 and EP/P025986/1). G.R. thanks UGC‐UKIERI grant number 184‐1/2018(lC) and SERB (CRG/2018/000430). S.D. thanks the UGC for an SRF fellowship. M.E. thanks MICINN (RTI2018‐094909‐J‐I00). J.S. thanks the Deutsche Forschungsgemeinschaft DFG (314331397 (SCHN 615/23‐1).

The dissolution of anhydrous iron bromide in a mixture of pyridine and acetonitrile, in the presence of an organic amine, results in the formation of an [Fe34] metal oxide molecule, structurally characterised by alternate layers of tetrahedral and octahedral FeIII ions connected by oxide and hydroxide ions. The outer shell of the complex is capped by a combination of pyridine molecules and bromide ions. Magnetic data, measured at temperatures as low as 0.4 K and fields up to 35 T, reveal competing antiferromagnetic exchange interactions; DFT calculations showing that the magnitudes of the coupling constants are highly dependent on both the Fe‐O‐Fe angles and Fe−O distances. The simplicity of the synthetic methodology, and the structural similarity between [Fe34], bulk iron oxides, previous FeIII–oxo cages, and polyoxometalates (POMs), hints that much larger molecular FeIII oxides can be made., Fe Maiden: An [Fe34] molecular metal oxide consists of an [Fe4] tetrahedron encapsulated in a [Fe18] truncated tetrahedron, face‐capped by four [Fe3] triangles, and is characterised by alternate layers of tetrahedral and octahedral Fe ions linked by oxide and hydroxide anions.

Reaction between NiCl

ortho-Vanillin in the presence of nickel and lanthanide ions yields three types of heteronuclear NiII-GdIII complexes, ranging from dinuclear to tetranuclear defect dicubane complexes, as demonstrated by their structural determinations. These complexes are dependent on the solvents used during the reaction processes and on the retained lanthanide ions, as characterized by an increase in their Lewis acid character on moving from lighter to heavier lanthanide ions. Intramolecular ferromagnetic NiII-GdIII interactions are present in the heterodinuclear NiII-GdIII entities, whereas ferromagnetic NiII-NiII and NiII-GdIII interactions dominate above 2 K in the tetranuclear Ni-Gd compounds, devoid of any GdIII-GdIII interaction. The effect of a magnetic field on the magnetic entropy and adiabatic temperature changes is maximum near the liquid-helium boiling temperature, mainly determined by the relative weakness of the magnetic interactions., This work was n supported by Spanish MINECO through grant MAT2015-68204-R (to M. E. and G. L.) and a postdoctoral contract (to G. L.), by CNRS and MAGMANet (Grant NMP3-CT-2005-515767).

An octahedral {DyIII6} cage within a diamagnetic {ZnII4} rectangle is reported, with magnetic relaxation studies revealing single-molecule magnet behaviour for the complex under zero external dc field with Ueff = 43 K and τo = 1 × 10-5 s.

et al., The family of compounds of general formula [Ln TM (OH)(L)(OCR)(MeOH)](ClO) {[GdZn(OH)(hmp)(OCPr)](ClO) (1a); [YZn(OH)(hmp)(OCPr)](ClO) (1b); [GdCu(OH)(hmp)(OCPr)](ClO) (2a); [YCu(OH)(hmp)(OCPr)](ClO) (2b); [GdCu(OH)(hep)(OCPr)](ClO) (3a); [GdCu(OH)(Hpdm)(OCBu)](ClO) (4a); [GdCu(OH)(ea)(OCMe)](ClO) (5a); [GdNi(OH)(hmp)(OCEt)(MeOH)](ClO) (6a); [YNi(OH)(hmp)(OCEt)(MeOH)](ClO) (6b); [GdCo(OH)(hmp)(OCEt)(MeOH)](ClO) (7a); [YCo(OH)(hmp)(OCEt)(MeOH)](ClO) (7b)} can be formed very simply and in high yields from the reaction of Ln(NO)·6HO and TM(ClO)·6HO and the appropriate ligand blend in a mixture of CHCl and MeOH in the presence of a suitable base. Remarkably, almost all the constituent parts, namely the lanthanide (or rare earth) ions Ln (here Ln = Gd or Y), the transition metal ions TM (here TM = Zn, Cu, Ni, Co), the bridging ligand L (Hhmp = 2-(hydroxymethyl)pyridine; Hhep = 2-(hydroxyethyl)pyridine; Hpdm = pyridine-2,6-dimethanol; Hea = 2-ethanolamine), and the carboxylates can be exchanged while maintaining the structural integrity of the molecule. NMR spectroscopy of diamagnetic complex 1b reveals the complex to be fully intact in solution with all signals from the hydroxide, ligand L, and the carboxylates equivalent on the NMR time scale, suggesting the complex possesses greater symmetry in solution than in the solid state. High resolution nano-ESI mass spectrometry on dichloromethane solutions of 2a and 2b shows both complexes are present in two charge states with little fragmentation; with the most intense peak in each spectrum corresponding to [LnCu(OH)(hmp)(OCPr)](ClO) . This family of compounds offers an excellent playground for probing how the magnetocaloric effect evolves by introducing either antiferromagnetic or ferromagnetic interactions, or magnetic anisotropy, by substituting the nonmagnetic Zn (1a) with Cu (2a), Ni (6a) or Co (7a), respectively. The largest magnetocaloric effect is found for the ferromagnetically coupled complex 6a, while the predominant antiferromagnetic interactions in 2a yield an inverse magnetocaloric effect; that is, the temperature increases on lowering the applied field, under the proper experimental conditions. In spite of increasing the magnetic density by adding ions that bring in antiferromagnetic interactions (2a) or magnetic anisotropy (7a), the magnetocaloric effect is overall smaller in 2a and 7a than in 1a, where only four Gd spins per molecule contribute to the magnetocaloric properties., EKB thanks the EPSRC for financial support and the Velux Foundation for a Villum Visiting Professor Program grant. JS thanks the Deutsche Forschungsgemeinschaft (SCHN 615/23-1) for continuous support. Supercomputing time at the LRZ Garching (Germany) is gratefully acknowledged. GL and ME thank MINECO/FEDER (MAT2015-68204-R).

In contrast to the mainstream research on molecular refrigerants that seeks magnetically isotropic molecules, we show that the magnetic anisotropy of dysprosium acetate tetrahydrate, [{Dy(OAc)(HO)}]·4 HO (1), can be efficiently used for cooling below liquid-helium temperature. This is attained by rotating aligned single-crystal samples in a constant applied magnetic field. The envisioned advantages are fast cooling cycles and potentially compact refrigerators., We are grateful to Spanish MINECO for financial support (grand number FEDER-MAT2012-38318-C03-01) and for a postdoctoral contract (to G.L.).

We study the magnetic susceptibility, electrical resistivity, Hall effect, and heat capacity of single crystals of ${\mathrm{Sm}}_{x}{\mathrm{B}}_{6}$ for $x=1,0.94,0.8,$ and 0.75. Remarkably, the overall properties of the crystals do not qualitatively depend on the density of vacancies. The topological surface states are seen at low temperatures in the electrical transport properties as the bulk conductivity freezes out. Even a large number of Sm vacancies does not close the hybridization gap. The linear term in the specific heat $\ensuremath{\gamma}$, of unclear origin, remains large but decreases gradually with $x$. The shoulder in the density of states, brought by the hybridized $4f$ states and observed in the susceptibility and the specific heat, does not move but decreases its height with decreasing $x$. The specific heat also displays a weak Schottky anomaly at about 1.5 K for all $x$, except for the $x$ = 0.75 sample. This Schottky anomaly is only slightly field dependent and of unknown origin.

An octahedral {DyIII6} cage within a diamagnetic {ZnII4} rectangle is reported, with magnetic relaxation studies revealing single-molecule magnet behaviour for the complex under zero external dc field with Ueff = 43 K and τo = 1 × 10−5 s., GL and ME thank MINECO for funding (MAT2015-68204-R).

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY)., The magnetic ordering structure of GdPO4 is determined at T=60 mK by the diffraction of hot neutrons with wavelength λ=0.4696 Å. It corresponds to a noncollinear antiferromagnetic arrangement of the Gd moments with propagation vector k=(1/2,0,1/2). This arrangement is found to minimize the dipole-dipole interaction and the crystal-field anisotropy energy, the magnetic superexchange being much smaller. The intensity of the magnetic reflections decreases with increasing temperature and vanishes at T≈0.8 K, in agreement with the magnetic ordering temperature TN=0.77 K, as reported in previous works based on heat capacity and magnetic susceptibility measurements. The magnetocaloric parameters have been determined from heat capacity data at constant applied fields up to 7 T, as well as from isothermal magnetization data. The magnetocaloric effect, for a field change ΔB=0-7T, reaches -ΔST=375.8mJ/cm3K-1 at T=2.1 K, largely exceeding the maximum values reported to date for Gd-based magnetic refrigerants., We acknowledge the Spanish MINECO for funding this research through Grant Nos. MAT2012-38318-C03-01 and MAT2013-44063-R. Research at the Oak Ridge National Laboratory for one author (L.A.B.) was sponsored by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division.

We report the magnetic properties and magnetic structure of the zircon-type compound GdVO4, together with the magnetic structure of the isostructural NdVO4. At T≃2.5 K, GdVO4 undergoes a phase transition to antiferromagnetic Gz, driven mainly by the exchange interactions, while the magnetic anisotropy and dipolar interactions are minor contributions. Near the liquid-helium boiling temperature, the magnetocaloric effect of GdVO4 is nearly as large as that of the structurally closely related GdPO4. It is noteworthy that GdVO4 has been recently proposed as a good passive regenerator in Gifford-McMahon cryocoolers, since adding a magnetization-demagnetization stage to the cryocooler refrigeration cycle would increase its efficiency for liquefying helium. NdVO4 is a canted Gz-type antiferromagnet and shows enhancement of the magnetic reflections in neutron diffraction below ca. 500 mK, due to the polarization of the Nd nuclei by the hyperfine field., M.E. thanks the Donostia International Physics Center (DIPC) for the support of his stay in San Sebastián. This work has been funded by the Spanish Ministerio de Economía, Industria y Competitividad through Projects No. MAT2017-86019-R and No. MAT2015-68204-R, DGA Consolidated Group E100, and Comunidad de Madrid Project S2009/PPQ1626.

A family of heterometallic Anderson-type 'wheels' of general formula [MIII2MII5(hmp)12](ClO4)4 (where MIII = Cr or Al and MII = Ni or Zn giving [Cr2Ni5] (1), [Cr2Zn5] (2), [Al2Ni5] (3) and [Al2Zn5] (4); hmpH = 2-pyridinemethanol) have been synthesised solvothermally. The metallic skeleton common to all structures describes a centred hexagon with the MIII sites disordered around the outer wheel. The structural disorder has been characterised via single crystal X-ray crystallography, 1-3D 1H and 13C solution-state NMR spectroscopy of the diamagnetic analogue (4), and solid-state 27Al MAS NMR spectroscopy of compounds (3) and (4). Alongside ESI mass spectrometry, these techniques show that structure is retained in solution, and that the disorder is present in both the solution and solid-state. Solid-state dc susceptibility and magnetisation measurements on (2) and (3) reveal the Cr-Cr and Ni-Ni exchange interactions to be JCr-Cr = -1 cm-1 and JNi-Ni,r = -5 cm-1, JNi-Ni,c = 10 cm-1. Fixing these values allows us to extract JCr-Ni,r = -1.2 cm-1, JCr-Ni,c = 2.6 cm-1 for (1), the exchange between adjacent Ni and Cr ions on the ring is antiferromagnetic and between Cr ions on the ring and the central Ni ion is ferromagnetic.

et al., A solvothermal reaction between Ln(NO)·6HO (Ln: Gd, Tb and Dy), 2-hydroxy-1-naphthaldehyde, 2-OH-naphth, and ethylenediamine, en, in MeOH in the presence of a base, NEt, led to the formation of the 1D coordination polymers [Ln(L)(MeO)(MeOH)]·MeOH (Ln = Gd (1·MeOH), Tb(2), Dy (3·MeOH); HL = 1,1′-((1E,1′E)-(ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(naphthalen-2-ol), the Schiff-base ligand derived from the condensation of 2-OH-naphth and en), while a similar reaction in an excess of NaN yielded 1D coordination polymers [Ln(L)(N)(MeO)(MeOH)] (Ln = Gd (4), Tb (5), Dy (6)). Finally, upon replacing ethylenediamine with o-phenylenediamine, o-phen, we managed to isolate the discrete dimers [Dy(L′)(MeOH)]·2MeOH (7·2MeOH) and [Gd(L′)(MeOH)]·2MeOH (8·2MeOH) (HL′ = 1,1′-((1E,1′E)-(1,2-phenylenebis(azanylylidene))bis(methanylylidene))bis (naphthalen-2-ol), the Schiff-base ligand from the condensation of 2-OH-naphth and o-phen). Polymers 1-3 describe one-dimensional chains, containing alternating seven- and eight-coordinate Ln metal centers, polymers 4-6 contain eight-coordinate lanthanide ions, while in both 7 and 8 the two Ln centers are eight- and seven-coordinate, adopting square antiprismatic and “piano-stool” geometry, respectively. The magnetocaloric properties of the three Gd analogues were determined from magnetic measurements, yielding the magnetic entropy change-ΔS = 21.8, 23.0 and 16.0 J kg K at T = 3.0 K on demagnetization of 7 T to 0, for 1, 4 and 8, respectively. The study of the magnetic properties also revealed that all three Dy analogues (3, 6 and 7) display out-of-phase signals, therefore suggesting slow magnetic relaxation, while such behaviour was not established in the Tb analogues., The research fund for CJM and ABC has been co-financed by the European Union (European Social Fund – ESF) and Greek national funds through the Operational Program “Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF) – Research Funding Program: THALES. Investing in knowledge society through the European Social Fund. GL and ME thank Spanish MINECO (MAT2015-68204-R). MS, MO and TL: “Project partially supported by Wroclaw Centre of Biotechnology, programme The Leading National Research Centre (KNOW) for years 2014–2018”

The use of pyridine-2-amidoxime (pyaoxH2) in Ni chemistry has provided access to a dodecanuclear complex and a hexadecanuclear Ni cluster, namely [Ni12(pyaox)6(pyaoxH)6(MeOH)2Cl2]Cl4·5MeOH (1·5MeOH) and [Ni16(pyaox)8(pyaoxH)8(MeOH)4](SO4)4·10H2O·26MeOH (2·10H2O·26MeOH). Complex 1·5MeOH was isolated by the reaction of NiCl2·6H2O, pyaoxH2 and NaOMe in a 1 : 1 : 2 molar ratio in MeOH in 60% yield. Treatment of NiSO4·6H2O with pyaoxH2 and NEt3 in a 1 : 1 : 2 molar ratio in MeOH afforded 2·10H2O·26MeOH in good yield (65%). The two compounds display a multi-decker configuration based on stacked Ni4 layers, {Ni4(pyaox)2(pyaoxH)2}2+x (x = 3, 1·5MeOH; x = 4, 2·10H2O·26MeOH); each deck consists of two square planar and two octahedral NiII centres. The number of decks observed in 1·5MeOH and 2·10H2O·26MeOH depends on the nature of the inorganic anion that is present in the reaction system, which provides elements of synthetic control towards new high nuclearity NiII species. 2·10H2O·26MeOH is the first structurally characterized complex of any metal displaying a quadruple-decker configuration, being also the highest nuclearity metal cluster bearing pyaoxH2 and the highest nuclearity NiII cluster with any type of 2-pyridyl oxime. Each cluster cation displays ferromagnetic exchange between the octahedral NiII ions resulting in a spin ground state of S = 6 for 1 and S = 8 for 2. Magnetothermal studies have been performed and discussed for both clusters., CP and CE thank the School of Chemistry, NUI Galway, for the financial support. RI thanks the Royal Society of Edinburgh and ME thanks Spanish MINECO (MAT2015-68204-R) for funding. LCS acknowledges the financial support by FEDER (Fundo Europeu de Desenvolvimento Regional) through PT2020, by FCT (Fundação para a Ciência e a Tecnologia) for the research centre REQUIMTE/LAQV (UID/QUI/50006/2013) and for the grant SFRH/BPD/111899/2015.

A family of interwoven molecular inorganic knots, shaped like the 'Star of David', was prepared by the employment of naphthalene-2,3-diol in 3d/4f-metal cluster chemistry; the isoskeletal dodecanuclear compounds exhibit slow relaxation of the magnetization and magnetocaloric properties, depending on the metal ion., This work was supported by Brock University, NSERC-DG and ERA (to Th.C.S), the Ontario Trillium Foundation (graduate scholarship to D.I.A), the Fundaçao para a Ciencia e a Tecnologia (FCT, Portugal) financial support to REQUIMTE/LAQV (UID/ QUI/50006/2013), the European Synchrotron Radiation Facility (Grenoble, France) (for granting access time to the Swiss Norwegian BM01a beamline under the CH-3613 and CH-3849 research proposals), MINECO (FEDER-MAT2012-38318-C03 to M. E and postdoctoral contract to G. L), and the National Natural Science Foundation of China (grants 21371166, 21331003 and 21221061 to J. T).

A family of heterometallic Anderson-type ‘wheels’ of general formula [MIII2MII5(hmp)12](ClO4)4 (where MIII = Cr or Al and MII = Ni or Zn giving [Cr2Ni5] (1), [Cr2Zn5] (2), [Al2Ni5] (3) and [Al2Zn5] (4); hmpH = 2-pyridinemethanol) have been synthesised solvothermally. The metallic skeleton common to all structures describes a centred hexagon with the MIII sites disordered around the outer wheel. The structural disorder has been characterised via single crystal X-ray crystallography, 1–3D 1H and 13C solution-state NMR spectroscopy of the diamagnetic analogue (4), and solid-state 27Al MAS NMR spectroscopy of compounds (3) and (4). Alongside ESI mass spectrometry, these techniques show that structure is retained in solution, and that the disorder is present in both the solution and solid-state. Solid-state dc susceptibility and magnetisation measurements on (2) and (3) reveal the Cr–Cr and Ni–Ni exchange interactions to be JCr–Cr = −1 cm−1 and JNi–Ni,r = −5 cm−1, JNi–Ni,c = 10 cm−1. Fixing these values allows us to extract JCr–Ni,r = −1.2 cm−1, JCr–Ni,c = 2.6 cm−1 for (1), the exchange between adjacent Ni and Cr ions on the ring is antiferromagnetic and between Cr ions on the ring and the central Ni ion is ferromagnetic., EKB thanks the EPSRC for funding (EP/N01331X/1, EP/P025986/1). UGN acknowledges funding from the Villum Young Investigator (VKR022364) and the Danish Council for Independent Research – Natural Sciences (DFF – 7014-00198). ME thanks MINECO for funding (MAT2015-68204-R)

The reaction of [Cr3IIIO(OAc)6(H2O)3]NO3·AcOH with 2-hydroxynaphthaldehyde, 2-amino-isobutyric acid and NiCl2·6H2O in MeOH, under basic and solvothermal conditions, led to the formation of the quasi-1D coordination polymer {[CrIII2NiII(L)4(MeOH)2]}n (where L = the dianion of the Schiff base between 2-hydroxynaphthaldehyde and 2-amino-isobutyric acid), which behaves as a ferromagnetic chain, displaying slow relaxation of magnetization., ME thanks DIPC for the support of his stay at San Sebastián and MINECO for funding (MAT2015-68204-R). JML thanks the Excellence Unit ‘‘Maria de Maeztu’’ [MDM-2015-0538].

Layered gadolinium hydroxides have revealed to be excellent candidates for cryogenic magnetic refrigeration. These materials behave as pure 2D magnetic systems with a Heisenberg-Ising critical crossover, induced by dipolar interactions. This 2D character and the possibility offered by these materials to be delaminated open the possibility of rapid heat dissipation upon substrate deposition., We are grateful to the EU (ERC Advanced Grant SPINMOL), the Spanish MINECO (Projects MAT-2014-56143-R, CTQ-2014-59209-P and FEDER-MAT2012-38318-C03-01), and the Generalitat Valenciana (Prometeo Program and ISIC-Nano). Support from INNCIDE program through Vicerectorat d’lnvestigacio i Política Científica of the University of Valencia is also acknowledged. G. A. thanks the EU for a Marie Curie Fellowship (FP7/2013-IEF-627386). G.M.E. thanks the Spanish MINECO for a Ramón y Cajal Fellowship.

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.-- et al., The reaction of the pro-ligand H4L, which combines the complementary phenolic oxime and diethanolamine moieties within the same organic framework, with Zn(NO3)2·6H2O and Ln(NO3)3·6H2O in a basic methanolic solution generates a family of isostructural heterometallic coordination compounds of general formula [Ln6Zn2(CO3)5(OH)(H2L)4(H3L)2(H4L)]NO3·xMeOH [Ln = Gd, x = 30 (1), Ln = Dy, x = 32 (2), Ln = Sm, x = 31 (3), Ln = Eu, x = 29 (4), Ln = Tb, x = 30 (5)]. The octametallic skeleton of the cage describes a heavily distorted [GdIII6] octahedron capped on two faces by ZnII ions. The metal core is stabilised by a series of μ3- and μ4-CO32− ions, originating from the serendipitous fixation of atmospheric CO2. The magnetic properties of all family members were examined via SQUID magnetometry, with the χMT product and VTVB data of the Gd analogue (1) being independently fitted by numerical diagonalisation to afford the same best-fit parameter JGd–Gd = −0.004 cm−1. The MCE of complex 1 was elucidated from specific heat data, with the magnetic entropy change reaching a value of 22.6 J kg−1 K−1 at T = 1.7 K, close to the maximum entropy value per mole expected from six GdIII spins (SGd = 7/2), 23.7 J kg−1 K−1., S.P. thanks the Danish Ministry of Science, Innovation and Higher Education for a Sapere Aude Fellowship (10-081659), M.E. acknowledges financial support from MINECO through grant MAT2012-38318-C03-01. EKB thanks the EPSRC.

ortho-Vanillin in the presence of nickel and lanthanide ions yields three types of heteronuclear Ni

The synthesis, characterization, crystal structures and magnetic properties of isoskeletal heptanuclear disk‐like MII3LnIII4 coordination clusters with the general formula [CoII3LnIII4(µ3‐OH)6L6(CF3SO3)][(CF3SO3)5] where Ln = Gd (2), Y (3) and [NiII3LnIII4(µ3‐OH)6L6(CF3SO3)][(CF3SO3)5] where Ln = Dy (4), Gd (5), Y (6) are presented. All the compounds are stable in solution as confirmed by ESI‐MS. Magnetic studies were performed for compounds 2, 4, 5 and 6 and indicate ferromagnetic coupling while the magnetocaloric properties of 5 are characterized by ΔSm = –15.4 J kg–1 K–1 at T = 5.0 K and ΔTad = 5.9 K at T = 2.3 K, for µ0ΔH = 7 T., We thank the Engineering and Physical Sciences Research Council (EPSRC) UK National Crystallography Service at the University of Southampton for the collection of the crystallographic data for compounds 3, 4 and 4′, the Research Development Fund (RDF) (V. N. D.) and Junior Research Associate (JRA) summer fellowship (C. H.) from the University of Sussex. A. E., G. L. and M. E. thank the Ministerio de Economía, Industria y Competitividad for financial support (Projects CTQ2015-63614-P and MAT2015-68204-R) and for a postdoctoral contract (to G. L.).

The syntheses, structures, magnetic and thermodynamic properties of three related triethanolamine-based Gd

The syntheses, structures, magnetic and thermodynamic properties of three related triethanolamine-based GdIII complexes are described. The smallest, a dimer ([Gd2]), can be viewed as the subunit from which the two larger complexes, a linear tetramer ([Gd2]2) and a cyclic hexamer ([Gd2]3), are composed by further deprotonation of the triethanolamine ligand. In all cases, nearest neighbour magnetic ions are weakly correlated by antiferromagnetic isotropic exchange, whose strength does not change significantly from one complex to another; J ranging from -0.10 to -0.13 cm-1. Therefore, rather than the strength of the coupling, it is the spin topology that is the dominant factor in determining the differences between the physical properties - specifically, the nuclearity and the transition from open (dimer and tetramer) to cyclic (hexamer) boundary conditions. Indeed the hexanuclear wheel reaches the continuum limit of classical Heisenberg spin chains. In terms of the magnetocaloric properties, the smaller the nuclearity, the larger the magnetic entropy and adiabatic temperature changes., EKB thanks the EPSRC for funding. SGC, GL, ER and ME thank the Spanish Ministry of Economy, Industry and Competitiveness (MAT2015-68204-R and CTQ2015-64579-C3-1-P) and for a postdoctoral grant (to GL). ER acknowledges the Generalitat de Catalunya for an ICREA Academia grant and the BSC (Barcelona Supercomputer Center) for computational resources. KSM thanks the Australian Research Council for a Discovery grant.

The adiabatic temperature change of the star-shaped {CoGd} magnetocaloric ring is enhanced via topological control over the assembly process, by using a pre-formed {Co

The employment of 2-amino-isobutyric acid, Haib, and 2-hydroxy-1-naphthaldehyde, Hnaphth, in Ni

The syntheses, structures, and magnetic properties of two heterometallic CuII-LnIII (LnIII = Gd, Tb, and Dy) families, utilizing triethanolamine and carboxylate ligands, are reported. The first structural motif displays a nonanuclear {CuII 2LnIII 7} metallic core, while the second reveals a hexadecanuclear {CuII 4LnIII 12} core. The differing nuclearities of the two families stem from the choice of carboxylic acid used in the synthesis. Magnetic studies show that the most impressive features are displayed by the {CuII 2GdIII 7} and {CuII 4GdIII 12} complexes, which display a large magnetocaloric effect, with entropy changes -ΔSm = 34.6 and 33.0 J kg-1 K-1 at T = 2.7 and 2.9 K, respectively, for a 9 T applied field change. It is also found that the {CuII 4DyIII 12} complex displays single-molecule magnet behavior, with an anisotropy barrier to magnetization reversal of 10.1 K., K.S.M. thanks the Australian Research Council (ARC) and the Australia-India Strategic Research Fund (AISRF) for support of this work. M.E. acknowledges financial support from MINECO through grant MAT2012-38318-C03-01.

Two series of isostructural C3-symmetric Ln3 complexes Ln3·[BPh4] and Ln3·0. 33[Ln(NO3)6] (in which LnIII=Gd and Dy) have been prepared from an amino-bis(phenol) ligand. X-ray studies reveal that LnIII ions are connected by one μ2-phenoxo and two μ3-methoxo bridges, thus leading to a hexagonal bipyramidal Ln3O5 bridging core in which LnIII ions exhibit a biaugmented trigonal-prismatic geometry. Magnetic susceptibility studies and ab initio complete active space self-consistent field (CASSCF) calculations indicate that the magnetic coupling between the DyIII ions, which possess a high axial anisotropy in the ground state, is very weakly antiferromagnetic and mainly dipolar in nature. To reduce the electronic repulsion from the coordinating oxygen atom with the shortest Dy-O distance, the local magnetic moments are oriented almost perpendicular to the Dy3 plane, thus leading to a paramagnetic ground state. CASSCF plus restricted active space state interaction (RASSI) calculations also show that the ground and first excited state of the DyIII ions are separated by approximately 150 and 177 cm-1, for Dy3·[BPh 4] and Dy3·0.33[Dy(NO3)6], respectively. As expected for these large energy gaps, Dy3· [BPh4] and Dy3·0.33[Dy(NO3)6] exhibit, under zero direct-current (dc) field, thermally activated slow relaxation of the magnetization, which overlap with a quantum tunneling relaxation process. Under an applied Hdc field of 1000 Oe, Dy 3·[BPh4] exhibits two thermally activated processes with Ueff values of 34.7 and 19.5 cm-1, whereas Dy 3·0.33[Dy(NO3)6] shows only one activated process with Ueff=19.5 cm-1. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., Financial support from the Spanish Ministerio de Ciencia e Innovación (MICINN) (projects CTQ-2011-24478, CTQ2011-23862-C02-01 and MAT2012-38318-C03), the Junta de Andalucía (FQM-195, Project of Excellence P11-FQM-7756), and the Generalitat de Catalunya (grant no. 2009SGR-1459). D.A. thanks Conicyt- Chile for a predoctoral fellowship.

In this work we study the assisted translocation of a polymer across a membrane nanopore, inside which a molecular motor exerts a force fuelled by the hydrolysis of ATP molecules. In our model the motor switches to its active state for a fixed amount of time, while it waits for an ATP molecule which triggers the motor, during an exponentially distributed time lapse. The polymer is modelled as a beads-springs chain with both excluded volume and bending contributions, and moves in a stochastic three dimensional environment modelled with a Langevin dynamics at a fixed temperature. The resulting dynamics shows a Michaelis-Menten translocation velocity that depends on the chain flexibility. The scaling behavior of the mean translocation time with the polymer length for different bending values is also investigated., The authors acknowledge funding from the Spanish MINECO and EU FEDER through projects MAT2013-44063-R (E. P.), MAT2014-53961-R (O. R., E. N., G. L.), MAT2015-70868-ERC (O. R.) and MAT2015-68204-R (M. E., G. L.), as well as for a postdoctoral contract (to G. L.).

The employment of 2-amino-isobutyric acid, Haib, and 2-hydroxy-1-naphthaldehyde, Hnaphth, in NiII/LnIII chemistry has led to the isolation and characterization of two new isostructural 3d–4f tetradecanuclear [NiII6LnIII8] clusters (Ln = GdIII, DyIII), with the Dy analogue displaying temperature and frequency dependent out-of-phase signals, and the Gd analogue showing interesting magnetocaloric properties., CJM: This work was supported by the ARISTEIA Action (Project code 84, acronym MAGCLOPT) of the Operational Programme Education and Lifelong Learning”, co-funded by ESF and National Resources. GL and ME thank Spanish MINECO (MAT2015-68204-R). MS and TL: “Project partially supported by Wroclaw Centre of Biotechnology, programme The Leading National Research Centre (KNOW) for years 2014–2018”. RI thanks the Royal Society of Edinburgh for funding.