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Magnetic order in a CuII–DyIII oxamato-based two-dimensional coordination polymer
Abstract and Figures
We report the synthesis, crystal structure, and magnetic characterization of a novel two-dimensional copper(II)–dysprosium(III) coordination polymer of formula [LiI(OH2)4]2[DyIIICuII2(Me2pma)4Cl(H2O)] . 4H2O (1) [Me2pma = N-2,6-dimethylphenyloxamate]. Compound 1 was obtained using the mononuclear anionic complex [CuII(Me2pma)2]2–, as a bis(bidentate) metalloligand toward solvated dysprosium(III) cations, and it shows a square [DyIIICuII2] layered structure of (44.6²) net topology. Interestingly, the combination of two factors, the well-known efficiency of oxamato ligands to transmit strong magnetic couplings between neighboring atoms and such structural topology, is responsible for the observation of a ferromagnetic interaction between copper(II) and dysprosium(III) cations and a magnetic ordering (TC = 7.5 K), paving the way for the obtention of novel future examples of the still very scarce magnetically ordered lanthanide-based coordination polymers.
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... However, basic Hund's rule always may not provide the exact nature of exchange interaction for Cu-Dy (as depicted in Fig. 9) in this type of complex multi-magnetic compounds. The overall magnetic interaction in DyCufr is FM with magnetic hysteresis and appreciable M R. The f-d interaction in Dy 3+ and Cu 2+ states in metallic complexes for layered chain systems is reported to be as FM below 15 K [52][53][54][55][56]. Actually, Dy 3+ and Cu 2+ are bridged by oxygen atoms in a particular structural topology ('oxamato') which is responsible for FM interaction [in contrast to other structural topology ('phenolato') for Ho 3+ / Er 3+ and Cu 2+ states which can't give FM interaction] [52,56]. ...
... However, basic Hund's rule always may not provide the exact nature of exchange interaction for Cu-Dy (as depicted in Fig. 9) in this type of complex multi-magnetic compounds. The overall magnetic interaction in DyCufr is FM with magnetic hysteresis and appreciable M R. The f-d interaction in Dy 3+ and Cu 2+ states in metallic complexes for layered chain systems is reported to be as FM below 15 K [52][53][54][55][56]. Actually, Dy 3+ and Cu 2+ are bridged by oxygen atoms in a particular structural topology ('oxamato') which is responsible for FM interaction [in contrast to other structural topology ('phenolato') for Ho 3+ / Er 3+ and Cu 2+ states which can't give FM interaction] [52,56]. Dy and Cu ions in those complexes are doubly bridged with oxygen atoms [52][53][54][55][56], similar to DyCufr where Dy atom are surrounded by two pairs of oxygen atoms linked to Cu1 atoms as shown in Fig. 2: right panel. ...
... The overall magnetic interaction in DyCufr is FM with magnetic hysteresis and appreciable M R. The f-d interaction in Dy 3+ and Cu 2+ states in metallic complexes for layered chain systems is reported to be as FM below 15 K [52][53][54][55][56]. Actually, Dy 3+ and Cu 2+ are bridged by oxygen atoms in a particular structural topology ('oxamato') which is responsible for FM interaction [in contrast to other structural topology ('phenolato') for Ho 3+ / Er 3+ and Cu 2+ states which can't give FM interaction] [52,56]. Dy and Cu ions in those complexes are doubly bridged with oxygen atoms [52][53][54][55][56], similar to DyCufr where Dy atom are surrounded by two pairs of oxygen atoms linked to Cu1 atoms as shown in Fig. 2: right panel. Further, DyCufr is a layered compound with oxygen being the bridging atom between Cu 2+ and Dy 3+ , so identically DyCufr may be FM. ...
... Ferromagnetic coupling found between lanthanides and copper ions occurs due to overlap of orbitals [39]. This ordering normally occurs at very low temperatures (2 K), with very few 3d-4f polymers having higher Tc values [40]. These interactions are often overshadowed by the magnetic interactions of the lanthanide dimer. ...
... Ferromagnetic coupling found between lanthanides and copper ions occurs due to overlap of orbitals [39]. This ordering normally occurs at very low temperatures (2 K), with very few 3d-4f polymers having higher T c values [40]. These interactions are often overshadowed by the magnetic interactions of the lanthanide dimer. ...
Four new isostructural 3d-4f mixed metal organic frameworks (MOFs) Cu Gd2 (BDC)4, compound 1, Cu Ho2 (BDC)4, compound 2, Cu Eu2 (BDC)4, compound 3, and Cu Dy2 (BDC)4, compound 4 were successfully synthesized. The structure, stability, and magnetic properties were analyzed. Each MOF has two lanthanide ions and one copper ion node with terephthalic acid as the organic linker. The lanthanide ions form a dimer with each having a capped trigonal prismatic geometry while the copper ion has a square planar geometry. Each of these MOFs shows varying degrees of antiferromagnetic interactions.
A new metallosupramolecular compound of formula Na6Ni3(dabtzox)3·10H2O (1) was prepared by the metal-mediated self-assembly of the potentially tris(chelating) N,N’-2,2’-(4,4’-bithiazole)bis(oxamate) (dabtzox) ligand and its structure was determined by single-crystal X-ray diffraction....
The reaction of aqueous solutions of EuIII, TbIII, and GdIII ions with Na2Hpcpa [H3pcpa = N-(4-carboxyphenyl)oxamic acid] afforded three new isostructural oxamate-containing lanthanide(III) coordination polymers of general formula {LnIII2(Hpcpa)3(H2O)5·H2O}
n
[Ln = Eu (1),Tb (2), and Gd(3)]. Their structure is made up of neutral zigzag chains running parallel to the [101] direction where double syn-syn carboxylate(oxamate)-bridged dilanthanide(III) pairs (Ln1 and Ln2) are linked by three Hpcpa2- ligands, one of them with the μ-κ2O,O':κO″ coordination mode and the other two with the μ3-κ2O,O':κO″:κO'''. Additionally, two of those chains are interlinked through hydrogen bonding and π-π type interactions, resulting in a porous structure with channels where water molecules are hosted. The emission properties of 1 and 2 are evaluated as a function of the temperature, exhibiting an emission in red and green, respectively. The external quantum yield for 2 is approximately 7 times that obtained for 1, indicating that the oxamate ligand is a better sensitizer for TbIII ions. The temperature dependence of the dc magnetic properties of 1-3 reveals a different magnetic behavior depending on the nature of the LnIII ion. A continuous decrease of χMT occurs for 1 upon cooling, and finally χMT tends to vanish, as expected for the thermal depopulation of the six magnetic 7F
J
excited states (J = 1-6) of the EuIII ion with a nonmagnetic 7F0 ground state. χMT for 2 decreases sharply with decreasing the temperature due to the depopulation of the splitted m
J
levels of the 7F7 ground state of the magnetically anisotropic TbIII ion. A very weak antiferromagnetic interaction between the magnetically isotropic GdIII ions across the double carboxylate(oxamate) bridge is responsible for the small decrease of χMT at low temperatures for 3. The dynamic (ac) magnetic properties of 2 and 3 reveal a slow magnetic relaxation with very incipient frequency-dependent χM″ signals below 6.0 K (2) and frequency-dependent χM″ peaks below 10.0 K (3) under nonzero applied dc magnetic fields, being thus new examples of field-induced single molecule magnets (SMMs).
Rapidly growing modern information technology demands energy and cost efficient tools that can efficiently store and process large amount of data. However, the miniaturization technology that was being used to boost the performance of the electronic devices, keeping up with the pace as estimated by the Moore’s law, is reaching its limit. To overcome these challenges, several alternative routes that can eventually mimic the modern electronics fabrication using silicon have been proposed. Single molecule magnets (SMMs), being considered as one of the potential alternatives, have gone through significant progress and the focus has shifted from the use of polynuclear cluster to mononuclear complexes in the last few years. The recent frenzy in the field of SMMs is driven by a better understanding of the effects of crystal field (CF) and molecular symmetry on the magnetic properties, especially in case mononuclear paramagnetic complexes, apart from other controlling factors. This has led to the advent of highly anisotropic single-ion magnets (SIMs) with the magnetic blocking temperatures as high as 60 K and anisotropic energy barriers over 1800 K. This article overviews our recent research in the light of the emergence of the importance of CF and symmetry in 4f ions based single-ion magnets (SIMs), especially in the context of SIMs with D5h symmetry, apart from commenting on the synthetic efforts adopted to place these metal ions in unusual coordination geometries.
Toward promising candidates of quantum information processing, the rapid development of lanthanide-based single-molecule magnets (Ln-SMMs) highlights design strategies in consideration of the local symmetry of lanthanide ions. In this review, crystal-field theory is employed to demonstrate the electronic structures according to the semiquantitative electrostatic model. Then, specific symmetry elements are analysed for the elimination of transverse crystal fields and quantum tunnelling of magnetization (QTM). In this way, high-performance Ln-SMMs can be designed to enable extremely slow relaxation of magnetization, namely magnetic blocking; however, their practical magnetic characterization becomes increasingly challenging. Therefore, we will attempt to interpret the experimental behaviours and clarify some issues in detail. Finally, representative Ln-SMMs with specific local symmetries are summarized in combination with the discussion on the symmetry strategies, and some of the underlying questions are put forward.
Abstract Molecular magnetism has travelled a long way from the pioneering studies on electron exchange and double exchange or spin crossover and valence tautomerism in small oligonuclear complexes, from mono- to di- and tetranuclear species, to the current investigations about magnetic anisotropy and spin dynamics or quantum coherence of simple mono- or large polynuclear complexes, behaving as switchable bistable molecular nanomagnets for potential applications in information data storage and processing. In this review, we focus on the origin and development of the research in the field of molecular magnetism from a coordination chemistry viewpoint, which dates back to the establishment of magnetochemistry as a novel discipline among the molecular sciences. This overview is conceived as an attempt to orientate coordination chemists regarding their role in the future direction that molecular magnetism will undergo in its further evolution toward molecular spintronics and quantum computation. A particular emphasis will be given to some selected recent advances in single-molecule spintronic circuitry and quantum computing devices based on the large class of multiresponsive and multifunctional magnetic metal complexes to stimulate the progress in the field of molecular magnetism.
The remarkable Metal-Organic Framework (MOF), {[(Co(NCS)2)3(κ³-TPT)4]·a(H2O)·b(MeOH)}n (1), which is used in the revolutionary crystalline sponge method, displays characteristic Single-Molecule Magnet (SMM) behaviour under applied static fields. We report the subtle effects of changes in the coordination environment of the CoII ions in 1, leading to drastically different magnetic behaviors of two additional related compounds, {[(Co(NCS)2)3(κ⁰⁻³-TPT)4]·c(H2O)}n (2) and {[(Co(NCS)2(H2O)0.65(MeOH)0.35)3(κ³-TPT)2]·2.4(H2O)}n (3). Magnetic measurements reveal unquenched first order orbital angular momentum, leading to significant magnetic anisotropy in all compounds, which was corroborated through CASSCF-type calculations. Notably, the crystalline sponge is the first example of a 3D network built from CoII Single-Ion Magnets (SIMs) as nodes.
Supramolecular interactions are fundamental to host-guest binding in many chemical and biological processes. Based on the direct quantification of such supramolecular interactions within metal-organic frameworks (MOFs), the interactions can be controlled through a flexible structural response to guests. We report a flexible Co-MOF [Co3(OH)2(L)2]·4H2O (1·4H2O, H2L = benzotriazole-5-carboxylic acid), which is liable to undergo structural transformation into [Co3(OH)2(L)2]·EtOH (1·EtOH) by pore breathing. Herein, a new strategy is developed to encapsulate more guest molecules of larger size into the Co-MOF via thermodynamics-directed de novo assembly of metal ions, organic linkers and the expected guest molecules by in situ microcalorimetry. As exemplified by the self-assembly of two N,N-dimethyl formamide (DMF) molecules into a Co-MOF, [Co3(OH)2(L)2]·2DMF (2·2DMF) was solvothermally attained at higher temperature, resulting in the elongation of the crystal unit via the b axis during the reconstruction of the framework and the dramatic change in the Co-O bond length and the Co-O-Co angle. Notably, for 2·2DMF, the calculated Langmuir surface area is nearly 5 times more than those of 1·4H2O and 1·EtOH, in agreement with the result of distorted cavities. Due to the two DMF molecules in the cavity, 2·2DMF displays excellent capability for the capture of Cr(vi) from wastewater by the formation of a new electrostatic interaction between the oxygen of the carbonyl from DMF and Cr(vi). Moreover, the fitting results of magnetic data show that the value of J2 in 2·2DMF is greater than that in 1·4H2O, which implies that ferromagnetic coupling increases. Our observations demonstrate that a detailed understanding of subtle intermolecular interactions between the framework and the guest can be used to induce changes to a different extent in the active (adsorption and magnetism) properties of a supramolecular network.
Hexacyanidochromate(III) anion is here explored as the building block for the construction of bimetallic 3d-4f coordination polymers that combine spin ordering and luminescence. We report the two-dimensional cyanido-bridged {[NdIII(pmmo)2(H2O)3][CrIII(CN)6]} (1) layered framework obtained by the spontaneous crystallization from the aqueous solution of Nd3+, pyrimidine N-oxide (pmmo), and [CrIII(CN)6]3-. 1 crystallizes as light green plates in the orthorhombic Pbca space group, and reveals a topology of a square grid built of nine-coordinated [NdIII(μ-NC)4(H2O)3(pmmo)2]- complexes of a nearly capped square antiprism geometry, and six-coordinated octahedral [CrIII(CN)6]3- moieties. Due to the presence of cyanide-mediated ferromagnetic coupling between paramagnetic NdIII (J = 9/2) and CrIII (S = 3/2) centers, 1 exhibits a long-range ferromagnetic ordering below Curie temperature of 2.8 K, with a tiny magnetization–field hysteresis loop detected at 1.8 K. Under the UV light irradiation, 1 shows the near-infrared fluorescence originated from the 4F3/2 → 4I9/2 (λmax = 895 nm) and 4F3/2 → 4I11/2 (λmax = 1060 nm) electronic transitions of NdIII. The near-infrared emission is realized through the energy transfer from [CrIII(CN)6]3- anions and pmmo ligands to NdIII centers which was possible due to the spectral overlap between the visible-light and near-infrared emission bands of CrIII and pmmo, and the absorption bands of NdIII. Thus, 1 can be considered as a novel type of bifunctional magneto-luminescent layered material taking advantage of the fruitful electronic and magnetic interplay between NdIII(pmmo) and [CrIII(CN)6]3- complexes.
The solid-state incorporation of a mononuclear iron(iii) complex within the pores of a magnetic 3D metal-organic framework (MOF) in a single crystal to single crystal process leads to the formation of a new hybrid material showing both a guest-dependent long-range magnetic ordering and a spin-crossover (SCO) behaviour.
[Sm(hfac)3(boaDTDA)]n is the first coordination compound of a thiazyl-based neutral radical ligand to exhibit ferromagnetic ordering; TC = 3 K. The Sm(III) complex is soluble in common organic solvents and can be sublimed quantitatively. A McConnell I mechanism is implicated in local exchange pathways that contribute to cooperative magnetic properties.
New segmented all-electron relativistically contracted (SARC) basis sets have been developed for the elements Tl-81-Rn-86, thus extending the SARC family of all-electron basis sets to include the 6p block. The SARC basis sets are separately contracted for the second-order Douglas-Kroll-Hess and the zeroth-order regular approximation scalar relativistic Hamiltonians. Their compact size and segmented construction are best suited to the requirements of routine density functional theory (DFT) applications. Evaluation of the basis sets is performed in terms of incompleteness and contraction errors, orbital properties, ionization energies, electron affinities, and atomic polarizabilities. From these atomic metrics and from computed basis set superposition errors for a series of homonuclear dimers, it is shown that the SARC basis sets achieve a good balance between accuracy and size for efficient all-electron scalar relativistic DFT applications.