A hexanuclear cluster, [Co6(piv)4(Hdea)4(dea)2](piv)2 & sdot;3H2O (1), and one-dimensional coordination polymer, {[Co6(piv)4(Hdea)4(dea)2][Co(piv)2(pys)2]}n (2) (where Hpiv = pivalic acid; H2dea = diethanolamine; Hpys = 3-pyridinesulfonic acid) based on this cluster have been synthesized and characterized by elemental analysis, IR spectroscopy, ESI-MS spectrometry, and single crystal and powder X-ray diffraction measurements. Compound 1 represents a discrete hexanuclear mixed-valent cluster with a {Co(II)4Co(III)2} core, in which the metal atoms are bridged by four pivalates and six partially or fully deprotonated polyalcoholamine ligands. Compound 2 exhibits a one-dimensional chain built from the hexanuclear [Co(II)4Co(III)2(piv)4(Hdea)4(dea)2]2+ clusters, which are interconnected by mononuclear [Co(II)(piv)2(pys)2]2- units. The intermolecular interactions between the hexanuclear clusters and their neighboring units were studied using Hirshfeld surface analysis. Magnetic measurements revealed the predominant antiferromagnetic interactions between high-spin Co(II) centers in the hexanuclear units, with an additional contribution from Co(II) center in mononuclear units in case of 2. The theoretical calculations using the TB2J python package have been performed to estimate both magnetic anisotropy energies and magnetic exchange couplings in the cluster 1 and cluster-based coordination polymer 2.

The crystal structure and magnetic properties of SrNb x Fe 12– x O 19 (0.00 ≤ x ≤ 0.08) nanohexaferrites (NHFs) fabricated using a sol–gel technique is presented in this study. The X-ray powder diffractometry (XRD) and Infrared spectroscopy (FT-IR) confirmed the formation of M-type hexaferrite phase. The analyses of magnetization versus applied magnetic field, M(H), were performed at room (300 K; RT) and low (10 K) temperatures. The Bohr magneton number ( n B ), saturation ( M s ) and remanent ( M r ) magnetization values increase slightly with increasing Nb 3+ content. The room-temperature values of the magnetic parameters M r = 31.41–33.28 emu/g, M s = 57.10–60.14 emu/g and coercivity ( H c ) between 4274 and 4540 Oe, at 10 K, magnetization data were detected that are much higher with respect to RT values: M r = 45.96–51.06 emu/g, M s = 94.42–95.99 emu/g. The magnetic results indicate that the samples are magnetically hard materials at both considered temperatures. The squareness ratio (SQR) is found to be around 0.50, implying single-domain NPs with uniaxial anisotropy for pristine and substituted samples. With exception, the x = 0.0 sample indicated the formation of multi-domain structure with uniaxial anisotropy at 10 K. Field cooling (FC) susceptibility measurements were applied in temperature range of 5–350 K for pristine sample and samples that contained some Nb 3+ ions. The analyses of dc susceptibility data also proved that Nb 3+ ion substitution increases the magnetization and, additionally, allows for an easier alignment of the magnetic domains. The obtained magnetic results were investigated deeply with relation to structural and microstructural properties. The observed remanent magnetization ( M r ) and coercivity ( H c ) render the products are useful for permanent magnets and high-density recording media.

Two polynuclear cobalt(II,III) complexes, [Co5(N3)4(N-n-bda)4(bza·SMe)2] (1) and [Co6(N3)4(N-n-bda)2(bza·SMe)5(MeOH)4]Cl (2), where Hbza·SMe = 4-(methylthio)benzoic acid and N-n-H2bda = N-n-butyldiethanolamine, were synthesized and fully characterized by various techniques. Compound 1 exhibits an unusual, approximately C2-symmetric {CoIICo4III} core of two isosceles Co3 triangles with perpendicularly oriented planes, sharing a central, high-spin CoII ion residing in a distorted tetrahedral coordination environment. This central CoII ion is connected to four outer, octahedrally coordinated low-spin CoIII ions via oxo bridges. Compound 2 comprises a semi-circular {Co4IICo2III} motif of four non-interacting high-spin CoII and two low-spin CoIII centers in octahedral coordination environments. Self-assembled monolayers (SAMs) of 1 and 2 were physisorbed on template-stripped gold surfaces contacted by an eutectic gallium-indium (EGaIn) tip. The acquired current density-voltage (I-V) data revealed that the cobalt-based SAMs are more electrically robust than those of the previously reported dinuclear {CuIILnIII} complexes with Ln = Gd, Tb, Dy, or Y (Schmitz et al., 2018a). In addition, between 170 and 220°C, the neutral, mixed-valence compound 1 undergoes a redox modification, yielding a {Co5}-based coordination cluster (1-A) with five non-interacting, high-spin octahedral CoII centers as indicated by SQUID magnetometry analysis in combination with X-ray photoelectron spectroscopy and infrared spectroscopy. Solvothermal treatment of 1 results in a high-nuclearity coordination cluster, [Co10(N3)2(N-n-bda)6(bza·SMe)6] (3), containing 10 virtually non-interacting high-spin CoII centers.

The crystal structure and magnetic properties of SrNbxFe12–xO19 (0.00 ≤ x ≤ 0.08) nanohexaferrites (NHFs) fabricated using a sol–gel technique is presented in this study. The X-ray powder diffractometry (XRD) and Infrared spectroscopy (FT-IR) confirmed the formation of M-type hexaferrite phase. The analyses of magnetization versus applied magnetic field, M(H), were performed at room (300 K; RT) and low (10 K) temperatures. The Bohr magneton number (nB), saturation (Ms) and remanent (Mr) magnetization values increase slightly with increasing Nb3+ content. The room-temperature values of the magnetic parameters Mr = 31.41–33.28 emu/g, Ms = 57.10–60.14 emu/g and coercivity (Hc) between 4274 and 4540 Oe, at 10 K, magnetization data were detected that are much higher with respect to RT values: Mr = 45.96–51.06 emu/g, Ms = 94.42–95.99 emu/g. The magnetic results indicate that the samples are magnetically hard materials at both considered temperatures. The squareness ratio (SQR) is found to be around 0.50, implying single-domain NPs with uniaxial anisotropy for pristine and substituted samples. With exception, the x = 0.0 sample indicated the formation of multi-domain structure with uniaxial anisotropy at 10 K. Field cooling (FC) susceptibility measurements were applied in temperature range of 5–350 K for pristine sample and samples that contained some Nb3+ ions. The analyses of dc susceptibility data also proved that Nb3+ ion substitution increases the magnetization and, additionally, allows for an easier alignment of the magnetic domains. The obtained magnetic results were investigated deeply with relation to structural and microstructural properties. The observed remanent magnetization (Mr) and coercivity (Hc) render the products are useful for permanent magnets and high-density recording media.

The first mixed antimonato-germanato polyoxovanadates were synthesized using two different strategies, highlighting the critical role of the precursors. Following the traditional route using multiple single sources as precursors the polyanions [V15Sb2Ge4O42(OH)4(H2O)]6- (1) and [V15Sb3Ge3O42(OH)3(H2O)]6- (2) are obtained, which display disorder of their Sb/Ge positions, indicating that clusters of different compositions are in equilibrium in solution. In contrast, if the water-soluble single-source precursor {Ni(en)3}3[V15Sb6O42(H2O)]·ca. 15H2O is reacted with GeO2, {Ni(en)3}3[V15Sb3Ge3O42(OH)3(H2O)]·≈9H2O (3) forms, in which Sb and Ge occupy distinct positions that might have been formed via partial substitution reactions in the {V15Sb6} precursor.

Abstract The first mixed germanato-antimonato derivative of the {V14E8O42} (E=semi-metal) cluster archetype has been synthesized under hydrothermal conditions and isolated as {Ni(phen)3}2[α-VIV14SbIII5GeIV3O42(OH)3(H2O)]· ≈16H2O (phen=1,10-phenanthroline). In the cluster anion, seven of the eight hetero-metal positions are occupied by disordered Ge/Sb atoms, while one position is fully occupied by Sb atoms. The [V14Sb5Ge3O42(OH)3(H2O)]6− anions are arranged in pairs with remarkably short inter-cluster Sb···O contacts. Bond valence sum calculation strongly suggests that the Sb···O contact must be taken into account as a weak bond. The magnetic properties are dominated by strong intra-cluster antiferromagnetic exchange interactions, and the cluster anion is magnetically quasi-isolated from the spins of the Ni2+ complex cations.

The antimonato-polyoxovanadate {NiII(en)3}3[VSbO42(H2O)]·ca.15H2O was utilized as a synthon for the solvothermal in situ generation of the new compound {NiII(phen)3}2[{NiII(en)2}VSbO42(H2O)]·19H2O, a rearrangement induced by ligand metathesis. While in the precursor structure cations and anions are isolated, the solid-state structure of the product is characterized by 1D chains consisting of alternating [V15Sb6O42(H2O)]6- cluster shells and [Ni(en)2]2+ units covalently linked to neighboring clusters via terminal oxygen atoms. Water clusters composed of sixteen hydrogen-bonded H2O molecules are located in void spaces of the structure. The magnetic properties indicate weak antiferromagnetic interactions of the bridging Ni2+ center and adjacent polyoxovanadate anions, as well as small magnetic anisotropy of the individual Ni2+ centers.

Iron loaded zeolites like Fe-ZSM-5 are potent candidates for the catalytic abatement of nitrogen oxides from car exhaust, e.g. from Diesel engines. Recent problems in this field show that there is an urgent need in further improvement of such catalysts, for which a full analysis of Fe species present in them under different conditions is highly desirable. We have studied Fe-ZSM-5 catalysts prepared via solid-state ion exchange by using field dependent Mössbauer spectroscopy at low temperature in order to identify the different iron species present in this type of catalyst in the fresh state and after use in catalysis. Mössbauer spectroscopy proved to be the key technique for a full understanding of species structures, but due to the complexity of structures, guidance by parallel EPR experiments and control by SQUID magnetometry were essential to prove reliability of derived species distributions.

A hierarchical, comparative approach to the complex magnetochemistry of {Fe4M2}-type coordination clusters (M = Y, Eu, Gd, Dy) allows determination of intramolecular exchange energies.

A water molecule encapsulated inside water-soluble {V15Sb6} antimonato polyoxovanadate cages accelerates oxygen-exchange reactions in the cluster periphery.

A water molecule encapsulated inside water-soluble {V15Sb6} antimonato polyoxovanadate cages accelerates oxygen-exchange reactions in the cluster periphery.

Mixed-valence polyoxovanadates(IV/V) have emerged as one of the most intricate class of supramolecular all-inorganic host species, able to encapsulate a wide variety of smaller guest templates during their self-assembly formation process. As showcased herein, the incorporation of guests, though governed solely by ultra-weak electrostatic and van der Waals interactions, can cause drastic effects on the electronic and magnetic characteristics of the shell complex of the polyoxovanadate. We address the question of methodology for the magnetochemical analysis of virtually isostructural {V(IV/V) 22 O54 }-type polyoxoanions of D2d symmetry enclosing diamagnetic VO2 F2 (-) (C2v ), SCN(-) (C∞v ), or ClO4 (-) (Td ) template anions. These induce different polarization effects related to differences in their geometric structures, symmetry, ion radii, and valence shells, eventually resulting in a supramolecular modulation of magnetic exchange between the V(3d) electrons that are partly delocalized over the {V22 O54 } shells. We also include the synthesis and characterization of the novel [V(V) O2 F2 @HV(IV) 8 V(V) 14 O54 ](6-) system that comprises the rarely encountered discrete difluorovanadate anion as a quasi-isolated guest species.

A new structural polyoxometalate motif, [{Ni4 (OH)3 AsO4 }4 (B-α-PW9 O34 )4 ](28-) , which contains the highest nuclearity structurally characterized multi-nickel-containing polyanion to date, has been synthesized and characterized by single-crystal X-ray diffraction, temperature-dependent magnetism and several other techniques. The unique central {Ni16 (OH)12 O4 (AsO4 )4 } core shows dominant ferromagnetic exchange interactions, with maximum χm T of 69.21 cm(3)  K mol(-1) at 3.4 K. Significantly, this structurally unprecedented complex is an efficient, water-compatible, noble-metal-free catalyst for H2 production upon visible light irradiation (photosensitizer=[Ir(ppy)2 (dtbbpy)][PF6 ]; sacrificial electron donor=triethylamine or triethanolamine). The highest turnover number of approximately 580, corresponding to a best quantum yield of approximately 4.07 %, is achieved when using triethylamine as electron donor in the presence of water. The mechanism of this photodriven process has been probed by time-solved luminescence and by static emission quenching.

A new structural polyoxometalate motif, [{Ni4 (OH)3 AsO4 }4 (B-α-PW9 O34 )4 ](28-) , which contains the highest nuclearity structurally characterized multi-nickel-containing polyanion to date, has been synthesized and characterized by single-crystal X-ray diffraction, temperature-dependent magnetism and several other techniques. The unique central {Ni16 (OH)12 O4 (AsO4 )4 } core shows dominant ferromagnetic exchange interactions, with maximum χm T of 69.21 cm(3)  K mol(-1) at 3.4 K. Significantly, this structurally unprecedented complex is an efficient, water-compatible, noble-metal-free catalyst for H2 production upon visible light irradiation (photosensitizer=[Ir(ppy)2 (dtbbpy)][PF6 ]; sacrificial electron donor=triethylamine or triethanolamine). The highest turnover number of approximately 580, corresponding to a best quantum yield of approximately 4.07 %, is achieved when using triethylamine as electron donor in the presence of water. The mechanism of this photodriven process has been probed by time-solved luminescence and by static emission quenching.

Sequential reaction of Mn(II) and lanthanide(III) salts with a new multidentate ligand, 2,2'-(2-hydroxy-3-methoxy-5-methylbenzylazanediyl)diethanol (LH3), containing two flexible ethanolic arms, one phenolic oxygen, and a methoxy group afforded heterometallic tetranuclear complexes [Mn2Dy2(LH)4(μ-OAc)2](NO3)2·2CH3OH·3H2O (1), [Mn2Gd2(LH)4(μ-OAc)2](NO3)2·2CH3OH·3H2O (2), [Mn2Tb2(LH)4(μ-OAc)2](NO3)2·2H2O·2CH3OH·Et2O (3), and [Mn2Ho2(LH)4(μ-OAc)2]Cl2·5CH3OH (4). All of these dicationic complexes possess an arch-like structural topology containing a central Mn(III)-Ln-Ln-Mn(III) core. The two central lanthanide ions are connected via two phenolate oxygen atoms. The remaining ligand manifold assists in linking the central lanthanide ions with the peripheral Mn(III) ions. Four doubly deprotonated LH(2-) chelating ligands are involved in stabilizing the tetranuclear assembly. A magnetochemical analysis reveals that single-ion effects dominate the observed susceptibility data for all compounds, with comparably weak Ln···Ln and very weak Ln···Mn(III) couplings. The axial, approximately square-antiprismatic coordination environment of the Ln(3+) ions in 1-4 causes pronounced zero-field splitting for Tb(3+), Dy(3+), and Ho(3+). For 1 and 3, the onset of a slowing down of the magnetic relaxation was observed at temperatures below approximately 5 K (1) and 13 K (3) in frequency-dependent alternating current (AC) susceptibility measurements, yielding effective relaxation energy barriers of ΔE = 16.8 cm(-1) (1) and 33.8 cm(-1) (3).

Sequential reaction of Mn(II) and lanthanide(III) salts with a new multidentate ligand, 2,2'-(2-hydroxy-3-methoxy-5-methylbenzylazanediyl)diethanol (LH3), containing two flexible ethanolic arms, one phenolic oxygen, and a methoxy group afforded heterometallic tetranuclear complexes [Mn2Dy2(LH)4(μ-OAc)2](NO3)2·2CH3OH·3H2O (1), [Mn2Gd2(LH)4(μ-OAc)2](NO3)2·2CH3OH·3H2O (2), [Mn2Tb2(LH)4(μ-OAc)2](NO3)2·2H2O·2CH3OH·Et2O (3), and [Mn2Ho2(LH)4(μ-OAc)2]Cl2·5CH3OH (4). All of these dicationic complexes possess an arch-like structural topology containing a central Mn(III)-Ln-Ln-Mn(III) core. The two central lanthanide ions are connected via two phenolate oxygen atoms. The remaining ligand manifold assists in linking the central lanthanide ions with the peripheral Mn(III) ions. Four doubly deprotonated LH(2-) chelating ligands are involved in stabilizing the tetranuclear assembly. A magnetochemical analysis reveals that single-ion effects dominate the observed susceptibility data for all compounds, with comparably weak Ln···Ln and very weak Ln···Mn(III) couplings. The axial, approximately square-antiprismatic coordination environment of the Ln(3+) ions in 1-4 causes pronounced zero-field splitting for Tb(3+), Dy(3+), and Ho(3+). For 1 and 3, the onset of a slowing down of the magnetic relaxation was observed at temperatures below approximately 5 K (1) and 13 K (3) in frequency-dependent alternating current (AC) susceptibility measurements, yielding effective relaxation energy barriers of ΔE = 16.8 cm(-1) (1) and 33.8 cm(-1) (3).

Recent measurements of B^0 -> pi pi decays reveal two features that are in conflict with conventional calculations: the channel B^0 (Bbar^0) -> pi^+ pi^- shows a large direct CP-violating asymmetry, and the channel B^0 (B^0) -> pi^0 pi^0 has an unexpectedly high branching ratio. We show that both features can be understood in terms of strong-interaction mixing of pi pi and D Dbar channels in the isospin-zero state, an effect that is important because of the large experimentally observed ratio Gamma(B^0 / Bbar^0 -> D^+ D^-) / Gamma (B^0 / Bbar^0 -> pi^+ pi^-) approx. 50. Our dynamical model correlates the branching ratios and the CP-violating parameters C and S, for the decays B^0 (Bbar^0) -> pi^+ pi^-, B^0 (Bbar^0) -> pi^0 pi^0, B^0 (Bbar^0) -> D^+ D^- and B^0 (Bbar^0) -> D^0 Dbar^0.

We have recently shown that the large direct CP violation observed in the decay B^0 -> pi^+ pi^-, and the enhanced branching ratio for B^0 -> pi^0 pi^0, can be understood by invoking a small mixing of the pi pi system with the dominant D Dbar channel. We examine here the analogous effect of D Dbar <-> K Kbar mixing on the rare decays B^0 -> K^0 K^0bar, B^- -> K^- K^0 and B^0 -> K^+ K^-. We find (a) significant values for the asymmetry parameters C and S in B^0 / B^0bar -> K^0 K^0bar, (b) a possible enhancement of the suppressed mode B^0 -> K^+ K^-, (c) a correlation between the three decay channels following from a triangle relation between amplitudes A_{K^0 K^0bar} - A_{K^+ K^-} = A_{K^- K^0}. The pattern of asymmetries and branching ratios is compared with that derived from the short-distance QCD penguin interaction.