Search

Using quantum mechanical calculations, we examine magnetic (super)exchange interactions in hypothetical, chemically reasonable molecular coordination clusters containing fluoride-bridged late transition metals or selected lanthanides, as well as Ag(II). By referencing to analogous species comprising closed-shell Cd(II), we provide theoretical evidence that the presence of Ag(II) may modify the magnetic properties of such systems (including metal-metal superexchange) to a surprising degree, specifically both coupling sign and strength may markedly change. Remarkably, this happens in spite of the fact that the fluoride ligand is the least susceptible to spin polarization among all monoatomic ligands known in chemistry. In an extreme case of an oxo-bridged Ni(II)

Fe[C5H5N]2[N(CN)2]2 (1) was synthesized from a reaction of stoichiometric amounts of NaN(CN)2 and FeCl2·4H2O in a methanol/pyridine solution. Single-crystal and powder diffraction show that 1 crystallizes in the monoclinic space group I2/m (no. 12), different from Mn[C5H5N]2[N(CN)2]2 (P21/c, no. 14) due to tilted pyridine rings, with a = 7.453(7) Å, b = 13.167(13) Å, c = 8.522(6) Å, β = 114.98(6)° and Z = 2. ATR-IR, AAS, and CHN measurements confirm the presence of dicyanamide and pyridine. Thermogravimetric analysis shows that π-stacking interactions of the pyridine rings play an important role in structural stabilization. Based on DFT-optimized structures, a chemical bonding analysis was performed using a local-orbital framework by projection from a plane-wave basis. The resulting bond orders and atomic charges are in good agreement with the expectations based on the structure analysis. SQUID magnetic susceptibility measurements show a high-spin state FeII compound with predominantly antiferromagnetic exchange interactions at lower temperatures.

Complementarity of calixarene (H2L) and polyoxometalate ligands results in the first organic-inorganic [MIIIL{Mo5O13(OMe)4(NO)}]2–(M = Y, Gd and Dy) hybrid, directing the formation of a distorted square-antiprismatic MO8 ligand field, producing slow relaxation ofthe magnetisation for the Dy derivative.

Polyanions [{B-α-(OH)Fe2(PW10O37)}2{o-R–C6H4–AsO3)}2]12– (R = NH2 (1) and NO2 (2)) represent the first polyoxotungstates functionalized by both organoarsonates and FeIII. 1 and 2 comprise the rare dilacunary Keggin-type phosphotungstate {B-α-PW10O37}9– isomer that coordinates FeIII ions to form {B-α-FeIII2PW10} complexes linked into dimers via two organoarsonate groups. The title polyanions have been isolated as crystalline materials and fully characterized via single-crystal and powder X-ray diffraction, elemental analysis and IR and UV–vis spectroscopies, including solution stability studies. In addition, their electrochemical and magnetic properties have been characterized.

Chemistry - a European journal 29(13), e202203525 (2023). doi:10.1002/chem.202203525, Published by Wiley-VCH, Weinheim

Two series of charge-neutral coordination clusters featuring quasi-isostructural metal oxide cores, isolated as [Zr6Fe2Ln2O8(ib)14(bda)2(NO3)2]·xMeCN (Ln = La (1), Ce (2), Pr (3), and Nd (4); ib- = isobutyrate; H2bda = N-butyldiethanolamine) and [Zr6Fe2Ln2O8(ib)14(mda)2(NO3)2]·xMeCN (Ln = La (5), Ce (6), Pr (7), and Nd (8); H2mda = N-methyldiethanolamine), were obtained via one-pot reactions of [Fe3O(ib)6(H2O)3]NO3 as a critical precursor, Ln(NO3)3·6H2O (Ln = La, Ce, Pr, and Nd), the respective aminoalcohol, and [Zr6O4(OH)4(ib)12(H2O)]·3Hib in an acetonitrile solution. The coordination clusters in 1-8 feature {Zr6O8} cores that are structurally expanded by two 4f (Ln3+) and two 3d (Fe3+) metal ions, each individually coordinated to one of the eight oxide centers of {Zr6O8}, producing a metal skeleton where the 3d/4f positions cap four of the triangular faces of the central Zr6 octahedron. The coordination clusters differ in the chosen aminoalcohol coligands, N-butyldiethanolamine or N-methyldiethanolamine, which lead to a different isobutyrate coordination pattern in the two series, while the {Fe2Ln2Zr6O8} core structure remains virtually unaffected. All eight coordination clusters are obtained in moderate to good yields of 29-66% after only several days. Complexes 1-8 are stable against air and moisture; they are also surprisingly thermally stable up to 280 °C in air and in nitrogen atmosphere, and they represent the first reported examples of 3d/4f-functionalized zirconium oxide clusters.

Reaction of the polypyridyl ligand 2,4,6-tris(2-pyridyl)

The propensity of the new, phenylphosphonate-stabilized polyoxotungstate [(C6 H5 PV O)2 P4 W24 O92 ]16- to act as a precursor for new 3d metal-functionalized polyanions has been investigated. Reactions with MnII and CuII induce the formation of the previously unknown polyoxotungstate archetype {P4 W27 }, isolated as salts of the polyanions [Na⊂{MnII (H2 O)}{WO(H2 O)}P4 W26 O98 ]13- (1) and [K⊂{CuII (H2 O)}{W(OH)(H2 O)}P4 W27 O99 ]14- (2), which were characterized in the solid state (single-crystal X-ray diffraction, elemental and TG analyses, IR spectroscopy, SQUID magnetometry) and in aqueous solution (UV/Vis spectroscopy, cyclic voltammetry).

{α2,-P2W16O60} polyoxotungstate cluster units featuring phenylphosphonates and CeIII ions embedded into the segregated lacunary sites of the cluster shell organize into the first coordination polymer of a polyoxometalate functionalized by both organophosphonate and lanthanoid. Inter-cluster Ce–OW links result in double-chains, with {CeIII2(α2,-PV2WVI16O60)L2} cluster units oriented alternatingly perpendicular to the chain propagation direction, akin to the protruding teeth of a zipper.

[VIV30SbIII8O78]12−, currently the largest known antimonato-polyoxovanadate (Sb-POV), features three perpendicular, intersecting 12-membered rings of edge-sharing O4VO square pyramids. While in two rings the apices of all O4VO pyramids point outwards, four apices of the third ring are directed into the cavity of the cluster shell, a concave structural motif not previously observed in polyoxovanadate chemistry. SbIII centers cap the eight niches defined by the octands of the {V30O78} cluster shell, resulting in discrete trigonal pyramidal SbO3 units, a second unprecedented feature. Within the resulting spin topology with numerous local geometrically frustrated motifs, the 30 spin-1/2 sites couple antiferromagnetically via a complex set of exchange pathways.

The methylation of p-tert-butylcalix[4]arene in the distal 1,3-phenolic sites provides the ligand H2L = {p-tert-butylcalix[4](OMe)2(OH)2arene} that enables construction of heteroleptic mononuclear lanthanide complexes. The reaction of (N(nBu)4)(acac) (Hacac = acetylacetone), MIIICl3 and H2L under Schlenk conditions results in the formation of a family of (N(nBu)4)[MIIIL(acac)2] complexes where M = Y (1), Gd (2), Tb (3) and Dy (4). The metal ions are eight-coordinate in distorted square-antiprismatic coordination geometries, resulting in slow relaxation of the magnetisation for the Tb derivative.

Charge-neutral [Na2Fe10O6(OH)4(isobutyrate)14(MeO)2(MeCN)2] coordination clusters, comprising a hollow ‘Chinese lantern’-like shell of six condensed planar triangular {FeIII3(μ3-O)} motifs, form upon ultrasonication of trinuclear Fe(III) isobutyrate units in acetonitrile in the presence of sodium azide and 4,4′-bipyridine (bpy), resulting in {[Na2Fe10O6(OH)4(isobutyrate)14(bpy)(MeO)2(MeCN)2]·MeOH}n in which the dodecanuclear cluster units are bpy-bridged into 1D chains.

While zinc μ

Pressure-induced phase transitions of M

We report on the synthesis and structural characterization of two series of lanthanide-containing 22-tungsto-2-germanates. The first series corresponds to a family of polyanions with the formula [Ln(β2-GeW11O39)2]13- (LnIII = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Gd (6), Dy (7)), and the second series corresponds to a family with the formula [Ln(β2-GeW11O39)(α-GeW11O39)]13- (LnIII = Ho (8), Er (9), Tm (10)). All compounds were characterized in the solid state by single-crystal and powder XRD, IR, TGA, and SQUID magnetometry. The polyanions were synthesized in aqueous medium by direct reaction of the monolacunary [β2-GeW11O39]8- POM precursor with the corresponding lanthanide salts. The structure of the polyanions consists of an 8-coordinated lanthanide ion in a square-antiprismatic geometry, which is sandwiched either between two [β2-GeW11O39]8- units for 1-7 or between a [β2-GeW11O39]8- and a [α-GeW11O39]8- unit for 8-10. Furthermore, the effect of the central paramagnetic lanthanide ion on the magnetic behavior of the polyanions was investigated, with the erbium-derivative [Er(β2-GeW11O39)(α-GeW11O39)]13- (9) showing single-molecule magnet (SMM) behavior.

The synthesis, structural characterization, and magnetic behavior of a new family of binuclear CoII–LnIII complexes of formula [LnIIICoIIL2(NO3)3]·H2O (Ln = La, 1; Gd, 2; Tb, 3; Dy, 4; Ho, 5; HL = ...

A series of 12 new metal–organic frameworks based on lanthanide cations (Ln = Nd, Sm–Dy), octahedral cluster anions [Re6S8(CN)6]4− or [Re6Se8(CN)6]4− and adipamide (adp) were synthesized under mild conditions in aqueous ethanol solutions. Compounds of the general composition Cs[Ln(adp)2{Re6Q8(CN)6}]·3H2O (Ln = Nd, Sm–Dy; Q = S or Se) crystallize in the hexagonal space group P6422. Despite the presence of solvate H2O molecules in structure cavities, the crystal structures revealed that the coordination environment of lanthanide cations in these 3D polymers did not contain H2O ligands. This rare feature is attributed to the combination of a bulk cluster anion and flexible adp molecules, which occupy the lanthanide coordination sphere to yield a stable lanthanide-based building block. This assumption was confirmed by synthesis of a second crystalline modification of the compound Cs[Nd(adp)2{Re6S8(CN)6}]·3H2O (orthorhombic space group Cccm). Luminescence studies evidence the presence of the typical red luminescence of hexarhenium cluster complexes and the absence of observable luminescence of lanthanide cations for all the compounds except the Nd derivatives. Magnetic data indicate very weak antiferromagnetic exchange interactions between paramagnetic Ln3+ centers.

Inorganic chemistry 61(5), 2499-2508 (2022). doi:10.1021/acs.inorgchem.1c03344, Published by American Chemical Society, Washington, DC

Crystal growth & design 22(9), 5526-5534 (2022). doi:10.1021/acs.cgd.2c00620 special issue: "Molecular Magnets and Switchable Magnetic Materials", Published by ACS Publ., Washington, DC

Combination of phosphoryl and calix[4]arene moieties in the same organic framework (LPO) directs the formation of homoleptic double-decker complexes [LnIII(LPO)2](O3SCF3)3 for Ln = Tb and Dy, with the latter displaying slow relaxation of the magnetisation.

[VIV30SbIII8O78]12-, currently the largest known antimonato-polyoxovanadate (Sb-POV), features three perpendicular, intersecting 12-membered rings of edge-sharing O4V[double bond, length as m-dash]O square pyramids. While in two rings the apices of all O4V[double bond, length as m-dash]O pyramids point outwards, four apices of the third ring are directed into the cavity of the cluster shell, a concave structural motif not previously observed in polyoxovanadate chemistry. SbIII centers cap the eight niches defined by the octands of the {V30O78} cluster shell, resulting in discrete trigonal pyramidal SbO3 units, a second unprecedented feature. Within the resulting spin topology with numerous local geometrically frustrated motifs, the 30 spin-1/2 sites couple antiferromagnetically via a complex set of exchange pathways.

Four polyoxotungstate solid state structures comprising discrete and polymeric architectures based on CeIII complexes of monolacunary Wells-Dawson-type anions [α2-PV2WVI17O61]10–, isolated as [NMe4...

Crystals of M(NH3)2[N(CN)2]2 with M = Ni and Co were obtained from the reaction of stoichiometric amounts of Na[N(CN)2] with NiCl2·6H2O or CoCl2·6H2O in aqueous, ammoniacal solutions. X-ray single-crystal structure analyses show that M(NH3)2[N(CN)2]2 with M = Ni and Co crystallize isotypically to each other and adopt the monoclinic space group P21/ c (no. 14). The lattice parameters of Ni(NH3)2[N(CN)2]2 are a = 5.8498(9) A, b = 10.6739(12) A, and c = 6.8089(17) A, β = 98.037(3)° and Z = 2, while those of Co(NH3)2[N(CN)2]2 are a = 5.8303(11) A, b = 10.746(2) A, c = 6.7773(13) A, and β = 96.422(3)°. In addition, the crystal structure of the nickel compound was refined from neutron powder diffraction, augmented by DFT calculations as regards atomic displacement parameters. The IR spectra of the title compounds exhibit modes typical for the dicyanamide anion and ammonia. The UV/vis spectrum of Ni(NH3)2[N(CN)2]2 shows that the dicyanamide moiety is a medium-field ligand. Additional superconducting quantum interference device (SQUID) magnetic susceptibility measurements of Ni(NH3)2[N(CN)2]2 and Co(NH3)2[N(CN)2]2 confirm not only significant high-spin moments of χm T = 1.24 cm3·K·mol-1 (μeff = 3.15 μB) and 2.89 cm3·K·mol-1 (μeff = 4.81 μB), respectively, at 290 K and 0.1 T but also an absence of magnetic ordering.

In the presence of dicyanamide and N-butyldiethanolamine (bdeaH2), Fe(III) and Dy(III) precursors self-assemble into the charge-neutral coordination cluster [Fe6Dy3(ib)9(bdea)6(MeO)6]·MeOH (1) (ib:...

The successful synthesis of new pyrimidine based organic ligands with terminal carboxylate and oxime functional groups, followed by their employment in metallogrid self-assembly has yielded three tetranuclear [Ni4(L1)4]∙2CH3CN∙4CH3OH·4H2O (1), [Cu4(HL1′)4]∙8CH3OH·28H2O (2) and [Ni4(H2L2)4](CF3SO3)8∙4CH3NO2·8H2O (3), [2 × 2] metallogrid complexes. The complexes have been well characterized by elemental analyses, IR spectra, UV-vis spectra and X-ray structural analyses. Variable temperature magnetic measurements/studies done on these three complexes followed by magnetic data fitting suggest that all the three complexes are dominated by intramolecular antiferromagnetic exchange coupling.

The charge-neutral bimetallic Zn(ii)/Co(ii) tridecanuclear oxocarboxylate cluster [ZnxCo13-x(μ4-O)4(O2CPh)18] (x≈ 5.6) was synthesized under anaerobic conditions by the controlled hydrolysis of an alkylzinc carboxylate [EtZn(O2CPh)] in the presence of cobalt(ii) benzoate Co(O2CPh)2. The composition and molecular structure of the resulting aggregates were solved by a combination of elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction.

Synthesis towards the preparation of an unsymmetrical binucleating Schiff-base ligand, (H2L) is discussed. It has been synthesized by reacting methyl 6-(hydrazinecarbonyl)picolinate with 2-hydroxy acetophenone. The ligand (H2L) comprises two different asymmetric binding pockets; however, when reacted with Mn(II), Co(II), Cu(II) and Zn(II) salts, very stable self-assembled [2 × 2] grid complexes form regardless of the employed metal-to-ligand ratio. The obtained complexes [Mn4L4]·(CH3CN) (1), [Co4L4]·(CHCl3) (2), [Cu4L4]·(CHCl3) (3) and [Zn4L4] (4) have been fully characterized by physicochemical methods, including ESI mass spectrometry and X-ray crystallographic analyses, and their EPR, magnetic and redox properties are discussed. All discussed complexes self-assembled in a ‘head-to-tail’ fashion leading to [2 × 2] grid architectures. Mn, Co and Cu grid complexes show weak to moderate antiferromagnetic coupling among the four metal centers. The high stability of the grid structures is in line with the lack of any observable dissociation or exchange between metal ions in solution. Complexes 1 and 2 show four quasi-reversible to irreversible oxidative responses in cyclic voltammograms at a glassy carbon working electrode in 1,2-dichlorobenzene and at a platinum working electrode in dichloromethane, respectively.

By using a triaryl-Tren ligated titanium dinitrogen complex, K2[{(Xy-N3N)Ti}2(μ2-N2)] (3), prepared by two-electron reduction of [TiCl(Xy-N3N)] (1-Cl) under N2 atmosphere, catalytic fixation of molecular nitrogen to form tris(trimethylsilyl)amine was achieved under ambient conditions with a turnover number (TON) of up to 16.5 per titanium atom.

A family of solution‐stable polyanions [Na⊂{LnIII(H2O)}{WVIO(H2O)}PV 4WVI 26O98]12− (Ln=Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) represent the first examples of polyoxometalates comprising a single lanthanide(III) or yttrium(III) ion in a rare trigonal prismatic O6 environment. Their synthesis exploits the reactivity of the organophosphonate‐functionalized precursor [P4W24O92(C6H5PVO)2]16− with heterometal ions and yields hydrated potassium or mixed lithium/potassium salts of composition K x Ln y H12–x–y [Na⊂{Ln(H2O)}{WO(H2O)}P4W26O98]⋅nH2O⋅mLiCl (x=8.5–11; y=0–2; n=24–34; m=0–1.5). The Dy, Ho, Er and Yb derivatives are characterized by slow magnetization relaxation., Controlled partial decomposition of the organophosphonate‐functionalized V‐shaped polyoxotungstate [P4W24O92(C6H5PVO)2]16− generates a {Na⊂P4W27} macrocycle with an endo‐oriented pocket that defines an isosceles trigonal‐prismatic coordination environment for yttrium(III) and a wide range of lanthanide(III) ions. The [Na⊂{LnIII(H2O)}{WO(H2O)}P4W26O98]12− series undergoes five consecutive (quasi‐)reversible redox transformations. The Dy, Ho, Er, and Yb derivatives show weak out‐of‐phase components in their ac magnetic susceptibility, where H/D exchange of the aqua ligand in the Dy compound influences the magnetic relaxation.

Bi-functionalizion of Wells–Dawson-type polyoxotungstates with exo-coordinated rare earth metal ions (M = DyIII, YIII) and phenylphosphonate induces the formation of a separate second lacunary site in the pre-functionalized [α2-P2W17O61(PhPO)2]6− precursor. The resulting [{(H2O)xM2(α2,α2′-P2W16O60)(PhPO)2}2]8− dimer clusters are stable in solution, exhibit interesting electrochemical behavior, and, for the DyIII derivative, single ion-magnet characteristics.

The propensity of the new, phenylphosphonate‐stabilized polyoxotungstate [(C6H5PVO)2P4W24O92]16− to act as a precursor for new 3d metal‐functionalized polyanions has been investigated. Reactions with MnII and CuII induce the formation of the previously unknown polyoxotungstate archetype {P4W27}, isolated as salts of the polyanions [Na⊂{MnII(H2O)}{WO(H2O)}P4W26O98]13− (1) and [K⊂{CuII(H2O)}{W(OH)(H2O)}P4W27O99]14− (2), which were characterized in the solid state (single‐crystal X‐ray diffraction, elemental and TG analyses, IR spectroscopy, SQUID magnetometry) and in aqueous solution (UV/Vis spectroscopy, cyclic voltammetry)., {P4W27} represents an extended and stabilized version of the elusive V‐shaped dimer {P2W12}2, derived from the seminal Wells‐Dawson‐type phosphotungstate archetype, and offers a coordination pocket that can induce unusual oxygen coordination polyhedra, such as a trigonal prism for MnII.

Acetate ligand metathesis results in the first hybrid [MIII(Pc)(PW11O39)]6− (M = Y, Dy, Tb) double-decker scaffolds, where a phthalocyanate (Pc2−) and one of the conceptually most simple polyoxotungstates, a monolacunary Keggin cluster, are interlinked via a single rare earth ion. Characterisation includes high-resolution mass spectrometry, synchrotron-based single-crystal X-ray diffraction, various spectroscopic and electrochemical methods, and magnetic studies revealing slow relaxation of the magnetisation for the Dy derivate.

Three new cobalt(ii/iii)-dysprosium(iii) complexes, [DyIII3CoII2CoIII2(L1)2(O2CCMe3)8(OH)4(OMe)2(H2O)4]·Dy(η1-O2CCMe3)2(η2-O2CCMe3)2(MeOH)2·4H2O (1), [DyIII3CoII2CoIII2(L2)2(O2CCMe3)8(OH)4(OMe)2(MeOH)2(H2O)2]·Dy(η1-O2CCMe3)2(η2-O2CCMe3)2(MeOH)2·4MeOH (2) and DyIII2CoII2CoIII2(L2)2(O2CCMe3)10(OH)2 (3) have been reported. In the heptanuclear 3d-4f monocationic aggregates in 1 and 2 the three dysprosium and four cobalt sites are arranged into a vertex shared dicubane structure, induced by two structure-directing ligands. Interestingly, a unique and previously unknown dysprosium(iii)-pivalate based counter anion, Dy(η1-O2CCMe3)2(η2-O2CCMe3)2(MeOH)2-, was trapped by the monocationic cores during crystallization. MeCN induced structural rearrangement of 2 through loss of OMe- bridges and dysprosium(iii) ions at the shared vertex resulted in the hexanuclear 3d-4f neutral aggregate 3, in which two dysprosium and four cobalt sites exhibit a near planar disposition. HRMS(+ve) of solutions of 1 and 2 revealed the pathway for aggregation processes and solvent induced structural transformation along with the importance of bridging OMe- in directing the formation of these compounds. Magnetic studies show a non-zero out-of-phase component in the AC susceptibility measurements of 1 but not in 2 and 3, although 1 and 2 have a very similar {CoIII2CoII2DyIII3} core and another DyIII center. Ab initio single-ion calculations point to the different single-ion anisotropic behavior for DyIII centers (energy in cm-1 and g-tensors) as well as negative and positive D values for CoII sites in 1 and 2 respectively reaffirming the experimental result. However, calculations envision that, zero-field out-of-phase signal and no out-of-phase signal in 1 and 2 respectively do not solely generate from the single-ion Dy/Co anisotropies and the overall relaxation mechanism can be understood by considering the exchange interactions between DyIII-DyIII and DyIII-CoII centres.

We report on the synthesis and structural characterization of two series of lanthanide-containing 22-tungsto-2-germanates. The first series corresponds to a family of polyanions with the formula [Ln(

An unprecedented spin cluster‐based network architecture {[NiII 2(pdaa)(OH)2(H2O)]n (H2pdaa=1,4‐phenylene diacetic acid)}, comprising 1D linear chains of NiII ions crosslinked via Ni4O4 cubanes, forms under hydrothermal conditions; this 3D coordination network exhibits magnetic ordering at 23.9 K as well as a second magnetic ordering process at 2.8 K likely associated with a structural phase transition., All in a spin! An unprecedented spin‐cluster‐based network architecture {[NiII 2(pdaa)(OH)2(H2O)]n (H2pdaa=1,4‐phenylene diacetic acid)}, comprising 1D linear chains of NiII ions crosslinked via Ni4O4 cubanes, forms under hydrothermal conditions (see figure); this 3D coordination network exhibits magnetic ordering at 23.9 K as well as a second magnetic ordering process at 2.8 K likely associated with a structural phase transition.

A series of unprecedented supramolecular associates of phenylarsonate-capped {MII PdII 12 O8 }-type (M=Co, Ni and Zn) polyoxopalladates with α-cyclodextrins (α-CD) was obtained and characterized in the solid state (single-crystal X-ray diffraction (XRD), FT-IR spectroscopy, elemental and thermogravimetric (TGA) analyses), in aqueous solution (1 H and 13 C NMR) and in the gas phase (ESI-MS). The non-covalent host-guest interactions between the organopolyoxoanions and α-CD rings alter the O8 coordination environment of a 3d transition metal ion (MII ) situated at the center of a cuboid polyoxododecapalladate shell. This synthetically controlled "chemical pressure" effectively induces axial distortion of the otherwise cubic polyoxopalladate environment between two trans-positioned α-CD moieties. Its effect on the magnetic properties and the electronic structure of the CoII derivative was assessed in a combined SQUID magnetometry, EPR, X-ray magnetic circular/linear dichroism (XMCD/XMLD), and X-ray absorption near-edge structure (XANES) spectroscopy study.