Dinuclear Fluoride Single-Bridged Lanthanoid Complexes as Molecule Magnets: Unprecedented Coupling Constant in a Fluoride- Bridged Gadolinium Compound

The authors thank the Spanish Ministerio de Ciencia e Innovacion projects (PGC2018-102052-B-C21, PGC2018093863-B-C21, MCIN/AEI/10.13039/501100011033/FEDER "Una manera de hacer Europa") for financial support. E.C. acknowledges Junta de Andalucia for the FEDER Andalucia project A-FQM-172-UGR18. J.C.-V. also thanks Xunta de Galicia for his Ph.D. fellowship (ED481A-2018/136). The authors acknowledge computer resources, technical expertise, and assistance provided by the CSUC.The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.2c00773. Figures S1−S9 and Tables S1−S9 (PDF) https://pubs.acs.org/doi/suppl/10.1021/acs.inorgchem.2c00773/suppl_file/ic2c00773_si_001.pdfA new synthetic method allows isolating fluoride-bridged complexes Bu4N{[M(3NO(2),5Br-H3L1,1,4)](2)(mu-F)} (M = Dy, 1; M = Ho, 2; M = Gd, 3) and Bu4N{[Dy(3Br,5Cl-H3L1,2,4)](2)(mu-F)}center dot 2H(2)O, 4 center dot 2H(2)O. The crystal structures of 1 center dot 5CH(3)C(6)H(5),center dot 2 center dot 2H(2)O center dot 0.75THF, 3, and 4 center dot 2H(2)O center dot 2THF show that all of them are dinuclear compounds with linear single fluoride bridges and octacoordinated metal centers. Magnetic susceptibility measurements in the temperature range of 2-300 K reveal that the Gd-III ions in 3 are weakly antiferromagnetically coupled, and this constitutes the first crystallographically and magnetically analyzed gadolinium complex with a fluoride bridge. Variabletemperature magnetization demonstrates a poor magnetocaloric effect for 3. Alternating current magnetic measurements for 1, 2, and 4 center dot 2H(2)O bring to light that 4 center dot 2H(2)O is an SMM, 1 shows an SMM-like behavior under a magnetic field of 600 Oe, while 2 does not show relaxation of the magnetization even under an applied magnetic field. In spite of this, 2 is the first fluoride-bridged holmium complex magnetically analyzed. DFT and ab initio calculations support the experimental magnetic results and show that apparently small structural differences between 1 and 4 center dot 2H(2)O introduce important changes in the dipolar interactions, from antiferromagnetic in 1 to ferromagnetic in 4 center dot 2H(2)O.Spanish Ministerio de Ciencia e Innovacion projects PGC2018-102052-B-C21, PGC2018093863-B-C21Junta de Andalucia A-FQM-172-UGR18Xunta de Galicia ED481A-2018/13

Decanuclear Ln10 wheels and vertex-shared spirocyclic Ln5 cores: synthesis, structure, SMM behavior, and MCE properties

et al.The reaction of a Schiff base ligand (LH3) with lanthanide salts, pivalic acid and triethylamine in 1:1:1:3 and 4:5:8:20 stoichiometric ratios results in the formation of decanuclear Ln10 (Ln=Dy(1), Tb(2), and Gd (3)) and pentanuclear Ln5 complexes (Ln=Gd (4), Tb (5), and Dy (6)), respectively. The formation of Ln10 and Ln5 complexes are fully governed by the stoichiometry of the reagents used. Detailed magnetic studies on these complexes (1–6) have been carried out. Complex 1 shows a SMM behavior with an effective energy barrier for the reversal of the magnetization (Ueff)=16.12(8) K and relaxation time (τo)=3.3×10−5 s under 4000 Oe direct current (dc) field. Complex 6 shows the frequency dependent maxima in the out-of-phase signal under zero dc field, without achieving maxima above 2 K. Complexes 3 and 4 show a large magnetocaloric effect with the following characteristic values: −ΔSm=26.6 J kg−1 K−1 at T=2.2 K for 3 and −ΔSm=27.1 J kg−1 K−1 at T=2.4 K for 4, both for an applied field change of 7 T.We are thankful to the Department of Science and Technology, New Delhi, for financial support. S.D., A.D., S.K., and S.B. thank CSIR, India for Senior Research Fellowship. V.C. is thankful to the Department of Science and Technology for a J.C. Bose National Fellowship. EC is thankful for financial support to Ministerio de Economía y Competitividad (MINECO) for Projects CTQ-2011-24478, CTQ2014-56312-P, the Junta de Andalucía (FQM-195 and the Project of excellence P11-FQM-7756), the University of Granada financial support. M.E. acknowledges financial support from MINECO through grant MAT2012-38318-C03-01. ST thanks the Junta de Andalucía for a postdoctoral contract.Peer Reviewe

Single-Molecule Magnets: From Mn12-ac to dysprosium metallocenes, a travel in time

The discovery of the first Single-Molecule Magnet, Mn12-ac, in 1993 changed the perspective of how information can be stored. The current bit, occupying few hundreds of nanometers in present devices, would be minimized to tens of angstroms at molecular level. However, until a couple of years these materials could only operate at temperatures near to the absolute zero. From 1993 to date, the field of Single-Molecule Magnets (SMMs) has continuously evolved thanks to the close collaboration of chemists and physicists obtaining materials already operating above the liquid nitrogen temperature. This long journey, however, has involved the study of many different routes towards high performance SMMs, being each of them essential in order to deeply understand the quantum dynamics behind these molecules. An era of high spin 3d metal clusters was the beginning of everything, but it went through highly anisotropic low coordinate 3d compounds, lanthanide based magnets, radical bridged compounds and 3d-4f mixed systems, among others, to end up in the current state of the art dysprosium metallocenes. Furthermore, after the magnetic studies in bulk, SMM based hybrid systems are emerging for future application devices, which also involve very interesting multifunctionalities. All in all, this work aims to explain how these materials work and show the trajectory and some of the major advances that have been made during recent years in this fieldThis work was supported by the Spanish Ministerio de Innovación, Ciencia y Universidades (PGC2018 102052-B-C21) and by the University of the Basque Country (GIU 17/13). E.C. is gratefully acknowledged to the Junta de Andalucía (FQM-195 and the Project financed by FEDER funds A-FQM-172-UGR18). A.Z.-L. is grateful for his predoctoral fellowship from GV/EJ

Poly[diaqua-μ2-oxalato-di-μ2-pyrimidine-2-carboxyl­ato-dimanganese(II)]

In the title compound, [Mn2(C2O4)(C5H3N2O2)2(H2O)2]n, the MnII atom exhibits a distorted octa­hedral coordination geometry, with the centrosymmetric oxalate anion and the monoanionic pyrimidine-2-carboxyl­ate ligands generating a two-dimensional honeycomb network with a (6,3)-topology

A ferromagnetically coupled diphenoxo-bridged Gd3+-Mn2+ dinuclear complex with a large magneto-caloric effect

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.A novel diphenoxo-bridged Gd3+-Mn2+ dimer is proposed as a good candidate for cryogenic magnetic refrigeration. The large MCE is enhanced by the ferromagnetic interaction between the two metal ions. © 2013 The Royal Society of Chemistry.We are grateful to MINECO (contracts MAT2012-38318-C03 and CTQ2011-24478), EC for a Marie Curie-IEF (PIEF-GA-2011-299356 to GL). EKB thanks the EPSRC and Leverhulme Trust.The authors also thank the Unit of Information Resources for Research (URICI-CSIC) for the co-financing of this publication in Open Access.Peer Reviewe

Heterometallic Octanuclear Ni(4)(II)Ln(4)(III) (Ln = Y, Gd, Tb, Dy, Ho, Er) Complexes Containing Ni(2)(II)Ln(2)(III)O(4) Distorted Cubane Motifs: Synthesis, Structure, and Magnetic Properties

The reaction of 2-methoxy-6-[{2-(2-hydroxyethylamino)ethylimino}methyl] phenol (LH3) with lanthanide metal salts followed by the addition of nickel acetate allowed isolation of a family of octanuclear complexes, [Ni4Ln4(μ2-OH)2(μ3- OH)4(μ-OOCCH3)8(LH2)4]·(OH)2·xH2O. Single crystal X-ray diffraction studies of these complexes reveal that their central metallic core consists of two tetranuclear [Ni2Ln2O4] cubane subunits fused together by acetate and hydroxide bridges. The magnetic study of these complexes reveals a ferromagnetic interaction between the LnIII and the NiII center. The magnitude of exchange coupling between the NiII and LnIII center, parametrized from the magnetic data of the Gd analogue, gives J = +0.86 cm−1. The magneto caloric effect, studied for the NiII 4GdIII 4 complex, shows a maximum of magnetic entropy change, −ΔSm = 22.58 J kg−1 K−1 at 3 K for an applied external field of 5 T.Ministerio de Economía y Competitividad (MINECO) and EU Feder Funds (Project CTQ2014-56312-P), the Junta de Andalucía (FQM-195 and the Project of Excellence P11-FQM- 7756), and the University of Granada for financial support

Aurophilicity as a cofactor in crystal engineering. Dicyanoaurate(I) anion as a building block in a novel Co(II)–Au(I) bimetallic assembly

A 2D grid-shaped cyanide-bridged Co(II)–Au(I) bimetallic coordination polymer, [Co(DMF)2{Au(CN)2}2], has been prepared from the [Au(CN)2]2 building block; sheets associate pair-wise by aurophilic interactions and the compound exhibits zeolite-like properties.Lloret Pastor, Francisco, [email protected]

Large easy-axis magnetic anisotropy in a series of trigonal prismatic mononuclear cobalt(II) complexes with zero-field hidden single-molecule magnet behaviour: the important role of the distortion of the coordination sphere and intermolecular interactions in the slow relaxation

Financial support from the Spanish Ministerio de Ciencia e Innovacion project (PGC2018 102052-B-C21) MCIN/AEI/10.13039/501100011033/FEDER "Una manera de hacer Europa", to Junta de Andalucia (FQM-195) and the project I +D+i (P20_00692) and the University of Granada. Part of this work was performed at the NHMFL, which is funded by the National Science Foundation (Cooperative Agreement DMR 1644779) and the State of Florida. HN and IFDO acknowledge GIMRT and ICC-IMR. M. M. Q. M. thanks Junta de Andalucia for a postdoctoral fellowship (DOC_01282) and Ministerio de Ciencia, Innovacion y Universidades for a Juan de la Cierva formacion contract (grant FJC2018-035709-I supported by MCIN/AEI/10.13039/501100011033). We acknowledge Gloria Pelayo for her help in the synthesis of compound 2 and Silvia Gomez Coca for insightful discussions and help with the quantum-chemical calculations.The complexes [Co(L))X center dot S (X = CoCl42-, S = CH3CN (1); X = ZnCl42- 2, S = CH3OH (2)), [Co(L))X-2 center dot S (X = ClO4-, S = 2CH(3)OH (3) and X = BF4- (4)) and [Co(L(NCS)(2)] (5), where L = the N-6-tripodal ligand tris(pyridylhydrazonyl)phosphorylsulfide, were prepared and studied by X-ray crystallography, ac and dc magnetic data, FIRMS and HFEPR spectra, and theoretical calculations. On passing from 1 to 4, the change of the counteranion decreases slightly the distortion of the CoN6 coordination polyhedron from trigonal prismatic to octahedral, with a parallel increase of the easy-axis magnetic anisotropy. Compound 1 does not show slow magnetic relaxation, even in the presence of a dc magnetic field, due to fast QTM triggered by dipolar interactions. Although the complexes 2-4 show a weak frequency and temperature dependence of the ac susceptibility below 10 K at zero field, they exhibit slow relaxation and single-molecule magnet (SMM) behaviour under the corresponding optimal field. The relaxation of the magnetization takes place mainly through a Raman relaxation process above 4 K, whereas below this temperature QTM and/or direct processes dominate. The relaxation time increases with the parallel increase of the uniaxial anisotropy on passing from 1. to 4. The width of the hysteresis for the trigonal prismatic complexes at 0.4 K decreases in the order 3 > 2 > 4 > 1, which is due to combined effects of QTM relaxation and axial anisotropy. Magnetic dilution of complexes 3 and 4 with Zn-II triggers the slow relaxation of the magnetization at zero-field, so that these complexes can be considered as "hidden mononuclear SMMs". Compound 5, with a compressed octahedral geometry, exhibits easy-plane magnetic anisotropy (D = +34.7 cm(-1)), and it is a field-induced mononuclear SMM with magnetization relaxation faster than compounds 2-4 and a smaller hysteresis loop.Spanish Ministerio de Ciencia e Innovacion MCIN/AEI PGC2018 102052-B-C21 FQM-195project I +D+i P20_00692University of GranadaNational Science Foundation (NSF) DMR 1644779State of FloridaJunta de Andalucia DOC_01282Ministerio de Ciencia, Innovacion y Universidades (MCIN/AEI) FJC2018-035709-

Pushing up the easy-axis magnetic anisotropy and relaxation times in trigonal prismatic CoII mononuclear SMMs by molecular structure design

The replacement of pyridine by 1-methyl-imidazol in the arms of a N6-tripodal ligand allows preparing two new CoII complexes with quasi-ideal triangular prismatic geometry, which behave as SIMs (Single Ion Magnets) at zero dc field with enhanced axial magnetic anisotropy, magnetic relaxation times and magnetic hysteresis.Junta de Andalucia FQM-195 DMR 1644779project I + D + i DOC_01282University of GranadaNational Science Foundation (NSF) P20_00692State of FloridaMCIN (MCIN/AEI) FJC2018-035709-

Eight coordinated mononuclear dysprosium complexes of heptadentate aminophenol ligands: the influence of the phenol substituents and the ancillary donors on the magnetic relaxation

The mononuclear complexes [Dy(3Br,5Cl-H3L1,1,4)(D)]·solvate (D = H2O, solvate = 0.25MeOH, 1W·0.25MeOH; D = Py without solvate, 1Py), and [Dy(3NO2,5Br-H3L1,1,4)(H2O)] (2W) were isolated. The crystal structures of 1W·0.25MeOH, 1Py and 2W·2CH3C6H5 show that the DyIII ion is octacoordinated, in N4O4 or N5O3 environments, with distorted geometries, between square antiprism, biaugmented trigonal prism and triangular dodecahedral. A similar environment for the metal ion is shown in the chiral crystals of the diamagnetic yttrium analogue [Y(3Br,5Cl-H3L1,1,4)(MeOH)] (3M), which were spontaneously resolved. Magnetic analyses of the three dysprosium complexes, and their diluted analogous 1W@Y, 1Py@Y and 2W@Y, reveal that none of them seem to relax through an Orbach mechanism at Hdc = 0. However, the three complexes show Orbach relaxation under Hdc = 1000 Oe, and 1Py is the in-field SIM with the highest energy barrier among these complexes, with a Ueff value of 358 K. Analysis of ac magnetic data shows that the electron-withdrawing substituents on the phenol rings of the aminophenol ligands, as well as the auxiliary oxygen donors from water ligands, reduce the energy barriers of the complexes, which is attributed to a charge reduction in the coordinating atoms of the aminophenol donor. Ab initio calculations support the experimental results.Authors thank the Spanish Ministerio de Innovación, Ciencia y Universidades (PGC2018 102052-B-C21) and Xunta de Galicia for financial support. J. C. V also thanks Xunta de Galicia for his Ph.D. fellowship. The authors acknowledge computer resources, technical expertise and assistance provided by the CESGA.S