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When attached to Wells–Dawson-type iron polyoxotungstates, Tris ligands adopt an unprecedented chelating mode, accompanied by the formation of a novel {Fe6O24} substructure.

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)

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

Curium is unique in the actinide series because its half-filled 5f 7 shell has lower energy than other 5f n configurations, rendering it both redox-inactive and resistant to forming chemical bonds that engage the 5f shell1–3. This is even more pronounced in gadolinium, curium’s lanthanide analogue, owing to the contraction of the 4f orbitals with respect to the 5f orbitals4. However, at high pressures metallic curium undergoes a transition from localized to itinerant 5f electrons5. This transition is accompanied by a crystal structure dictated by the magnetic interactions between curium atoms5,6. Therefore, the question arises of whether the frontier metal orbitals in curium(iii)–ligand interactions can also be modified by applying pressure, and thus be induced to form metal–ligand bonds with a degree of covalency. Here we report experimental and computational evidence for changes in the relative roles of the 5f/6d orbitals in curium–sulfur bonds in [Cm(pydtc)4]− (pydtc, pyrrolidinedithiocarbamate) at high pressures (up to 11 gigapascals). We compare these results to the spectra of [Nd(pydtc)4]− and of a Cm(iii) mellitate that possesses only curium–oxygen bonds. Compared with the changes observed in the [Cm(pydtc)4]− spectra, we observe smaller changes in the f–f transitions in the [Nd(pydtc)4]− absorption spectrum and in the f–f emission spectrum of the Cm(iii) mellitate upon pressurization, which are related to the smaller perturbation of the nature of their bonds. These results reveal that the metal orbital contributions to the curium–sulfur bonds are considerably enhanced at high pressures and that the 5f orbital involvement doubles between 0 and 11 gigapascal. Our work implies that covalency in actinides is complex even when dealing with the same ion, but it could guide the selection of ligands to study the effect of pressure on actinide compounds. Enhanced covalency is achieved for a curium complex with curium–sulfur bonds by subjecting the compound to high pressures, indicating that pressure can be used to tune covalency in actinide compounds.

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.

Pressure-induced phase transitions of M

Pressure induced phase transitions of MIAgIIF3 perovskites where M = K, Rb, Cs, have been predicted theoretically for the first time for pressures up to 100 GPa. The sequence of phase transitions for M = K and Rb consists of an orthorhombic to monoclinic and back to orthorhombic transition, associated with progressive bending of infinite chains of corner sharing [AgF6]4 minus octahedra and their mutual approaching via secondary Ag...F contacts. In stark contrast, only a single phase transition i.e. tetragonal to triclinic, is predicted for CsAgF3, associated with substantial deformation of the Jahn Teller-distorted first coordination sphere of AgII and association of the infinite [AgF6]4 minus chains into a polymeric sublattice. The phase transitions markedly decrease the coupling strength of intra-chain antiferromagnetic superexchange in MAgF3 hosts lattices., 7 pages, 3 figures, and electronic supplement of 25 pages

Advanced functional materials 2208507 (2022). doi:10.1002/adfm.202208507, Published by Wiley-VCH, Weinheim

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.

Bistable spin crossover complexes such as [Fe{HB(pz)3}2] (pzH = pyrazole) show promise for sensor applications and electrically‐controlled data storage units, but exploiting their potential hinges on their integration into a functional environment. We here present a system enabling such covalent post‐functionalization steps in both symmetric and asymmetric patterns, based on the amine‐functionalized complex [Fe{HB(4‐NH2pz)(pz)2}2], obtained by reduction of the nitro analogue. The building block aspects of [Fe{HB(4‐NH2pz)(pz)2}2] are showcased by its transformation into amide, imine and azo derivatives, which are structurally and magnetically characterized. All tris(pyrazolyl)borate complexes retain the spin crossover properties of their parent compound, with spin crossover temperatures ranging from 350 to 430 K. The transition parameters are correlated with the electronic properties of the functionalizing group, opening the possibility of fine‐tuning the spin crossover properties of the building block as it is integrated in the environment of choice., An amine‐functionalized spin crossover building block based on a FeII tris(pyrazolyl)borate core reacts to form amide, imine, and azo derivatives without loss of magnetic bistability. Controlled pyrazole metathesis allows for symmetric and asymmetric incorporation of nitro groups used as precursor for the amine.John Wiley & Sons, Ltd.

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...

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 new polyoxometalate compound consisting of the 39-tungsto-4-arsenate(III) unit with four incorporated V

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.

A new polyoxometalate compound consisting of the 39-tungsto-4-arsenate(III) unit with four incorporated VIV ions, isolated as (NH4)22[(VIVO)2(VIVO(H2O))(AsIIIWVI9O33)2(AsIIIWVI8.5VIV0.5(OH)O32)2(WVIO2)4]·48H2O (NH4-As4W39(V4)), was synthesized and fully characterized. SQUID magnetometry shows three weakly coupled VIV centers with an antiferromagnetic exchange interaction and one isolated VIV ion as a spin-1/2 Curie paramagnet. UV-vis spectroscopy indicates that the As4W39(V4) structure remains intact in aqueous solution for at least 24 h. To enable the deposition of As4W39(V4) from solution on gold surfaces, its trihexyltetradecylphosphonium salt, THTDP-As4W39(V4), was prepared. The IR spectra of both congeners reveal the structural identity of As4W39(V4) independent of the countercations. The X-ray absorption near-edge structure data confirm the presence of VIV centers in a distorted square-pyramidal coordination geometry in NH4-As4W39(V4) and THTDP-As4W39(V4). X-ray photoelectron spectroscopy of the latter, deposited on Au(111), shows that the 4 V and 35 W centers preserve their IV+ and VI+ oxidation states, while the remaining 4 W ions are reduced to IV+.

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.