Double Helix of Icosahedra Structure and Spin Glass Magnetism of the δ-Co2.5Zn17.5-xMnx (x = 0.4-3.5) Pseudo-Binary Alloys.

We have synthesized δ-Co2.5Zn17.5-xMnx (x = 0.4-3.5) pseudo-binary alloys of 10 different compositions by a high-temperature solid-state synthetic route, determined their crystal structures and the Mn substitution pattern, and estimated the existence range of the δ-phase. The alloys crystallize in two chiral enantiomorphic space groups P62 and P64, where the basic atomic polyhedron of the chiral structure is an icosahedron and the neighboring icosahedra share vertices to form an infinitely long double helix along the hexagonal axis (like in the δ-Co2.5Zn17.5 parent binary phase). The alloys are pure δ-phase up to the Mn content x ≈ 3.5. The Mn atoms partially substitute Zn atoms at particular crystallographic sites located on the icosahedra. The study of magnetism was performed on the Co2.5Zn17.1Mn0.4 alloy with the lowest Mn content. Contrary to the expectation that structural chirality may induce the formation of a nontrivial magnetic state, a spin glass state with no relation to the structural chirality was found. The magnetic sublattice contains all of the necessary ingredients (randomness and frustration) for the formation of a spin glass state. Typical out-of-equilibrium dynamic phenomena of a spin system with broken ergodicity were detected below the spin freezing temperature Tf ≈ 8 K.

Carbonyl-Supported Coordination in Imidazolates: A Platform for Designing Porous Nickel-Based ZIFs as Heterogeneous Catalysts.

Zeolitic imidazolate frameworks (ZIFs) are a subclass of metal-organic framework that have attracted considerable attention as potential functional materials due to their high chemical stability and ease of synthesis. ZIFs are usually composed of zinc ions coordinated with imidazole linkers, with some other transition metals, such as Cu(II) and Co(II), also showing potential as ZIF-forming cations. Despite the importance of nickel in catalysis, no Ni-based ZIF with permanent porosity is yet reported. It is found that the presence and arrangement of the carbonyl functional groups on the imidazole linker play a crucial role in completing the preferred octahedral coordination of nickel, revealing a promising platform for the rational design of Ni-based ZIFs for a wide range of catalytic applications. Herein, the synthesis of the first Ni-based ZIFs is reported and their high potential as heterogeneous catalysts for Suzuki-Miyaura cross-coupling C─C bond forming reactions is demonstrated.

The Kondo Effect in CexLaLuScY (x = 0.05-1.0) High-Entropy Alloys.

In the search for electronic phenomena in high-entropy alloys (HEAs) that go beyond the independent-electron description, we have synthesized a series of hexagonal rare earth (RE)-based HEAs: CexLaLuScY (x = 0.05-1.0). The measurements of electrical resistivity, magnetic susceptibility and specific heat have shown that the CexLaLuScY HEAs exhibit the Kondo effect, which is of a single impurity type in the entire range of employed Ce concentrations despite the alloys being classified as dense (concentrated) Kondo systems. A comparison to other known dense Kondo systems has revealed that the Kondo effect in the CexLaLuScY HEAs behaves quite differently from the chemically ordered Kondo lattices but quite similar to the RE-containing magnetic metallic glasses and randomly chemically disordered Kondo lattices of the chemical formula RE1xRE21-xM (with RE1 being magnetic and RE2 being nonmagnetic). The main reason for the similarity between HEAs and the metallic glasses and chemically disordered Kondo lattices appears to be the absence of a periodic 4f sublattice in these systems, which prevents the formation of a coherent state between the 4f-scattering sites in the T→ 0 limit. The crystal-glass duality of HEAs does not bring conceptually new features to the Kondo effect that would not be already present in other disordered dense Kondo systems. This study broadens the classification of HEAs to correlated electron systems.

Hydrothermal topotactic epitaxy of SrTiO3 on Bi4Ti3O12 nanoplatelets: understanding the interplay of lattice mismatch and supersaturation.

The engineering of epitaxial, two-dimensional (2D) nano-heterostructures has stimulated great interest owing to an expectation of better functional properties (e.g., photocatalytic, piezoelectric). Hydrothermal topotactic epitaxy is one of the promising synthetic approaches for their preparation, particularly the formation of a highly ordered, epitaxial interface and possibilities for the preparation of anisotropic nanostructures of symmetrical materials. The present study highlights the key parameters when steering the alkaline, hydrothermal, topochemical conversion process from Bi4Ti3O12 nanoplatelets to the intermediate, epitaxial, SrTiO3/Bi4Ti3O12 nano-heterostructures and the final SrTiO3 nanoplatelets by balancing the lattice mismatch and the supersaturation. An atomic-scale examination revealed the formation of an ordered epitaxial SrTiO3/Bi4Ti3O12 interface with the presence of dislocations. The SrTiO3 grows in islands for a stoichiometric amount of Sr (Sr/Ti = 1) and the growth resembles a layer-by-layer mode for surplus Sr content (Sr/Ti ≥ 12). The latter enables SrTiO3 overgrowth of the Bi4Ti3O12 basal surface planes, protecting them against dissolution from the top and consequently ensuring the preservation of the platelet morphology during the entire transformation process, the kinetics of which is controlled by the base concentration. A developed understanding of this particular transformation provides the guiding principles and ideas for designing other defined or complex epitaxial heterostructures and structures under low-temperature hydrothermal conditions.

Complex magnetism of single-crystalline AlCoCrFeNi nanostructured high-entropy alloy.

We have investigated magnetism of the Al28Co20Cr11Fe15Ni26 single-crystalline high-entropy alloy. The material is nanostructured, composed of a B2 matrix with dispersed spherical-like A2 nanoparticles of average diameter 64 nm. The magnetism was studied from 2 to 400 K via direct-current magnetization, hysteresis curves, alternating-current magnetic susceptibility, and thermoremanent magnetization time decay, to determine the magnetic state that develops in this highly structurally and chemically inhomogeneous material. The results reveal that the Cr-free B2 matrix of composition Al28Co25Fe15Ni32 forms a disordered ferromagnetic (FM) state that undergoes an FM transition at TC≈ 390 K. The Al- and Ni-free A2 nanoparticles of average composition Co19Cr56Fe25 adopt a core-shell structure, where the shells of about 2 nm thickness are CoFe enriched. While the shells are FM, the nanoparticle cores are asperomagnetic, classifying into the broad class of spin glasses. Asperomagnetism develops below 15 K and exhibits broken-ergodicity phenomena, typical of magnetically frustrated systems.

Trinuclear Magnesium Imidazolate Borohydride Complex.

A new type of hybrid compound, combining properties of MOFs and borohydrides, was synthesized solvothermally using Mg(BH4)2 and imidazole as precursors. Material in the form of acetonitrile solvate with formula [Mg3{(Im)BH2(Im)}6(ImH)6]·CH3CN crystallizes in the space group R3̅, having the unit cell parameters a = 15.1942(2) Å and c = 28.3157(3) Å as determined by single crystal X-ray diffraction. The structure was further investigated by solid-state NMR and DFT quantum chemical calculations. The main feature of the structure, reported here for the first time, is a linear trinuclear complex, where octahedrally nitrogen-coordinated Mg2+ ions are bridged with {(Im)BH2(Im)}- units, forming inside voids of 4.6 Å in diameter between the magnesium ions. Polar intermolecular interactions hold the molecules in a dense rhombohedral stacking, where a disordered acetonitrile molecule plays a cohesive role. The compound is stable in air and upon heating to about 160 °C. Using an alternative synthesis method from an imidazole melt, an imidazole solvate with the formula [Mg3{(Im)BH2(Im)}6(ImH)6]·ImH and a very similar crystal structure to acetonitrile solvate was prepared. It is stable up to 220 °C. Upon further heating, it transformed into a layered structure with the formula Mg(Im3BH)2, space group P3̅1c, and unit cell parameters a = 8.7338(9) Å and c = 17.621(2) Å determined by synchrotron powder diffraction. Besides its structural novelty, two types of potentially reactive hydrogens, bonded to boron and nitrogen in the same molecule, make the material highly interesting for future investigations in the fields of energy storage applications.

Electronic transport properties of the Al0.5TiZrPdCuNi alloy in the high-entropy alloy and metallic glass forms.

High-entropy alloys (HEAs) are characterized by a simultaneous presence of a crystal lattice and an amorphous-type chemical (substitutional) disorder. In order to unravel the effect of crystal-glass duality on the electronic transport properties of HEAs, we performed a comparative study of the electronic transport coefficients of a 6-component alloy Al0.5TiZrPdCuNi that can be prepared either as a HEA or as a metallic glass (MG) at the same chemical composition. The HEA and the MG states of the Al0.5TiZrPdCuNi alloy both show large, negative-temperature-coefficient resistivity, positive thermopower, positive Hall coefficient and small thermal conductivity. The transport coefficients were reproduced analytically by the spectral conductivity model, using the Kubo-Greenwood formalism. For both modifications of the material (HEA and MG), contribution of phonons to the transport coefficients was found small, so that their temperature dependence originates predominantly from the temperature dependence of the Fermi-Dirac function and the variation of the spectral conductivity and the related electronic density of states with energy within the Fermi-level region. The very similar electronic transport coefficients of the HEA and the MG states point towards essential role of the immense chemical disorder.

Ferroelectric bismuth-titanate nanoplatelets and nanowires with a new crystal structure.

Two different morphologies of ferroelectric bismuth titanate (Bi4Ti3O12) nanoparticles, i.e., nanoplatelets and nanowires, were synthesized by changing the concentration of NaOH during a hydrothermal treatment of precipitated Ti4+ and Bi3+ ions. The nanoparticles' crystal structures were characterized using atomic-resolution imaging with a CS-probe-corrected scanning-transmission electron microscope in combination with X-ray diffractometry and Raman spectroscopy. The nanoplatelets (10 nm thick and from 50 nm to 200 nm wide) exhibit the Aurivillius-type layered-perovskite crystal structure that is characteristic of Bi4Ti3O12, whereas the nanowires (from 15 nm to 35 nm wide and from several hundreds of nm to several µm long) exhibit an entirely new structure with an orthorhombic unit cell (a = 3.804(1) Å, b = 11.816(3) Å, and c = 9.704(1) Å). The nanowire structure is composed of two structural layers alternating along the orthorhombic c-direction: a structural layer composed of two parallel layers of Bi atoms that resembles the (Bi2O2)2+ layer of the Aurivillius structure, and a structural layer composed of two parallel layers of Ti atoms, where every sixth Ti is replaced with Bi. Observations of the ferroelectric domains with transmission electron and piezo-response force microscopy indicated the ferroelectric nature of both nanostructures. The nanowire structure is a metastable polymorph of the bismuth titanate stabilized at the nanoscale. With annealing at temperatures above 500 °C the nanowire structure topotactically transforms into the Aurivillius structure.

The Effect of Scandium on the Structure, Microstructure and Superconductivity of Equimolar Sc-Hf-Nb-Ta-Ti-Zr Refractory High-Entropy Alloys.

In this study, we investigate the scandium-containing Sc-Hf-Nb-Ta-Ti-Zr system of refractory high-entropy alloys (HEAs). Using the arc-melting method, we synthesized nine equimolar alloys (five 4-, three 5- and one 6-component), with all of them containing Sc. The alloys were characterized by XRD, electron microscopy and EDS, while superconductivity was investigated via electrical resistivity, specific heat and the Meissner effect. The results were compared to the parent Hf-Nb-Ta-Ti-Zr refractory HEAs, forming a single-phase body-centered cubic (bcc) structure and quite homogeneous microstructure. The addition of Sc produces a two-phase structure in the Sc-Hf-Nb-Ta-Ti-Zr alloys, with one phase being bcc and the other hexagonal close-packed (hcp). The hcp phase absorbs practically all Sc, whereas the Sc-poor bcc phase is identical to the bcc phase in the Hf-Nb-Ta-Ti-Zr parent system. Upon the Sc addition, the microstructure becomes very inhomogeneous. Large bcc dendrites (10-100 µm) are homogeneous in the central parts, but become a fine dispersion of sub-micron precipitates of the bcc and hcp phases close to the edges. The interdendritic regions are also a fine dispersion of the two phases. Superconductivity of the Sc-Hf-Nb-Ta-Ti-Zr alloys originates from the bcc phase fraction, which demonstrates identical superconducting parameters as the bcc Hf-Nb-Ta-Ti-Zr parent alloys, while the Sc-containing hcp phase fraction is non-superconducting.

Structure and Superconductivity of Tin-Containing HfTiZrSnM (M = Cu, Fe, Nb, Ni) Medium-Entropy and High-Entropy Alloys.

In an attempt to incorporate tin (Sn) into high-entropy alloys composed of refractory metals Hf, Nb, Ti and Zr with the addition of 3d transition metals Cu, Fe, and Ni, we synthesized a series of alloys in the system HfTiZrSnM (M = Cu, Fe, Nb, Ni). The alloys were characterized crystallographically, microstructurally, and compositionally, and their physical properties were determined, with the emphasis on superconductivity. All Sn-containing alloys are multi-phase mixtures of intermetallic compounds (in most cases four). A common feature of the alloys is a microstructure of large crystalline grains of a hexagonal (Hf, Ti, Zr)5Sn3 partially ordered phase embedded in a matrix that also contains many small inclusions. In the HfTiZrSnCu alloy, some Cu is also incorporated into the grains. Based on the electrical resistivity, specific heat, and magnetization measurements, a superconducting (SC) state was observed in the HfTiZr, HfTiZrSn, HfTiZrSnNi, and HfTiZrSnNb alloys. The HfTiZrSnFe alloy shows a partial SC transition, whereas the HfTiZrSnCu alloy is non-superconducting. All SC alloys are type II superconductors and belong to the Anderson class of "dirty" superconductors.

Assessment of critical material attributes of polyethylene oxide for formulation of prolonged-release tablets.

Physicochemical evaluation of polyethylene oxide (PEO) polymers with various molecular weights was performed at molecular (polymeric dispersion) and bulk level (powders, polymeric films, and tablets) with the aim of specifying polymer critical material attributes with the main contribution to drug release from prolonged-release tablets (PRTs). For this purpose, grades of PEO with low, medium, and high viscosity were used for formulating PRTs with a good soluble drug substance (dose solubility volume 15 ml). The results revealed a good correlation (r2=0.88) between in vivo data (pharmacokinetic parameters: Cmax and AUC) and the elastic property of PEO films determined with the nanoindentation method, demonstrating that film level can also be used for the in vivo prediction of drug dissolution. The study confirmed that polymer molecular weight and its viscosity are the most important critical material attributes affecting drug dissolution (in vitro) and in vivo bioavailability (e.g. Cmax and AUC). Our research revealed that the nanoindentation technique can distinguish well between various types of polymers, classifying PEO as the most ductile and polyvinyl alcohol as the most brittle. Finally, our study provides an approach for the determination of exact physical attributes of PEO as a critical material attribute from clinically relevant data, and it therefore fulfills the basic principles of product development by Quality by Design.

Organoruthenated Nitroxoline Derivatives Impair Tumor Cell Invasion through Inhibition of Cathepsin B Activity.

Lysosomal cysteine peptidase cathepsin B (catB) is an important tumor-promoting factor involved in tumor progression and metastasis representing a relevant target for the development of new antitumor agents. In the present study, we synthesized 11 ruthenium compounds bearing either the clinical agent nitroxoline that was previously identified as potent selective reversible inhibitor of catB activity or its derivatives. We demonstrated that organoruthenation is a viable strategy for obtaining highly effective and specific inhibitors of catB endo- and exopeptidase activity, as shown using enzyme kinetics and microscale thermophoresis. Furthermore, we showed that the novel metallodrugs by catB inhibition significantly impair processes of tumor progression in in vitro cell based functional assays at low noncytotoxic concentrations. Generally, by using metallodrugs we observed an improvement in catB inhibition, a reduction of extracellular matrix degradation and tumor cell invasion in comparison to free ligands, and a correlation with the reactivity of the monodentate halide leaving ligand.

Relation between colour- and phase changes of a leuco dye-based thermochromic composite.

Reversible colour change of leuco dye-based composites is in general closely related to their phase change, thus the two phenomena should occur at around the same temperature and should be influenced similarly. However, spatial confinement of the analysed sample affects the change in colour differently compared to its phase transition and the most pronounced effects can be observed during cooling. The bulk composite is coloured while still liquid and the colour hysteresis does not exhibit a loop. In an open-porous medium the colouration coincides well with the crystallization and the colour hysteresis widens to about 4 °C. Microencapsulated composite exhibits two crystallization processes, one of them taking place at the bulk crystallization temperature and the other one at about 20 °C lower. Under such conditions the composite is coloured just before the onset of the second crystallization, i.e. about 15 °C below crystallization in the bulk, and the corresponding colour hysteresis widens to 18 °C. The two crystallization forms are thermally independent and have the same crystalline structure. These effects should be taken into account when designing future applications where the phase-changing materials are implemented.

Influence of Various Soluble Carbonates on the Hydration of Portland Cement studied by X-ray Diffraction.

The effect of limestone on the hydration of Portland cement has been studied by many researchers. However, a possible influence of adding more soluble carbonates was not explained. Therefore we executed a qualitative and quantitative research on the influence of slightly soluble (CaCO3, MgCO3, dolomite), medium soluble (Li2CO3) and highly soluble (K2CO3 and KHCO3) carbonates on the hydration. Blending of Portland cement with differently soluble carbonates was found to influence the hydrate assemblage of the hydrated cement. With the help of the Rietveld analysis, the study indicated that the amount of reacted carbonate in cement hydration at a 15% addition of slightly or medium soluble carbonates does not exceed 5% and is not affected by their solubility; at a 15% addition of the highly soluble carbonate K2CO3 the amount of reacted carbonate was around 6%. An increase in temperature (25 to 40 °C) gradually affects the rate of hydration and the quantity of stable phase assemblage.

Synthesis and Structural Evaluation of Organo-Ruthenium Complexes with ß-Diketonates.

Four novel ruthenium organometallic complexes: [(η6-p-cymene)Ru(4,4,4-trifluoro-1-(4-bromophenyl)-1,3-butanedione)Cl] (1), [(η6-p-cymene)Ru(4,4,4-trifluoro-1-(4-bromophenyl)-1,3-butanedione)pta]PF6 (2), [(η6-p-cymene)Ru(4,4,4-trifluoro-1-(4-iodophenyl)-1,3-butanedione)Cl] (3) and [(η6-p-cymene)Ru(4,4,4-trifluoro-1-(4-iodophenyl)-1,3-butanedione)pta]PF6 (4) were synthesized and characterized by elemental analysis, infrared (IR), UV-Vis, NMR and mass spectroscopy and single-crystal X-ray diffraction. The crystal structures and spectroscopic data were compared to the previously published complexes [(η6-p-cymene)Ru(4,4,4-trifluoro-1-(4-chloro-phenyl)-1,3-butanedione)Cl] (5) and [(η6-p-cymene)Ru(4,4,4-trifluoro-1-(4-chlorophenyl)-1,3-butanedione)pta]PF6 (6). The pairs of complexes 1 and 3 as well as 2 and 4 are isostructural, with the former crystallizing in triclinic P-1 and the latter in monoclinic P21/c. The ruthenium(II) ion is found in a pseudo-octahedral "piano-stool" geometry in all compounds. Bond lengths and angles are consistent with other complexes of this type. Complexes 2 and 4 exhibit some moderate dynamic disorder. The lack of hydrogen bonding and major π-π interactions means that most of intramolecular interactions are fairly weak and involve halogen atoms present. This was further confirmed by ¹H-NMR spectra, where a significant difference is observed only on the ligand near the halogen atom, following an expected trend. The combined data show that the difference in any activity depends substantially on the type of the ligand's substituted halogen atom.

Influence of Crystal Habit on the Dissolution of Simvastatin Single Crystals.

In order to achieve better in-vivo performance of the final dosage form comprising a poorly soluble drug the physicochemical properties of the active pharmaceutical ingredient can be altered not only by changing the solid state form but also through the conversion of their crystal habits. To elucidate this approach in the case of simvastatin, the dissolution behaviour of large crystals with the same internal structure but expressing different crystal habits was studied using atomic force microscope. The obtained differences in the dissolution were explained through the determination of crystal morphology its orientation and assignation of the molecular functional groups that were emerging on the surface of the dissolving crystal face. The dissolution rates of the particular crystal faces were found to be distinctly higher than others. The dissolution rate of single crystals differed as a consequence of higher incidence of more polar faces in case of rod shaped crystals isolated from more hydrophilic solvent mixture which we have established through a thorough research of the single crystal morphology, orientation and the assignation of specific functional groups for each of evolved crystal faces.

Supramolecular Potential of Vanadium ß-Diketonate and Picolinate Compounds and The First One-dimensional Oxidovanadium(IV) Complex with ß-Diketonate Ligand.

Three vanadium compounds with ß-diketonato or picolinato ligands were prepared and structurally characterized. In compounds [VO(tfpb)2]∞ (1) (tfpb = 4,4,4-trifluoro-1-phenylbutane-1,3-dionate) and [VO(acac)2(2-pyridone)] (2) the coordination of vanadium atom is octahedral and in the compound Hpy[VO2(pic)Cl] (3) the central atom is pentacoordinated. X-Ray crystallographic studies reveal infinite chain formation due to V=O···V=O interactions in 1, while 2 and 3 are mononuclear compounds. Centrosymmetric hydrogen-bonded dimers are formed in 2 via N-H···O interactions due to the 2-pyridone ligand. In 3 the Hpy+ cation is hydrogen bonded to the complex anion and crystal structure is further stabilized by π···π and C-H···O interactions.

Recycling of ladle slag in cement composites: Environmental impacts.

In the present work compact and ground cement composites in which 30% of cement by mass was replaced by ladle slag were investigated for their chemical and physico-mechanical properties. To evaluate long-term environmental impacts, leachability test based on diffusion, which combined both, diffusion and dissolution of contaminants, was performed in water and saline water. Total element concentrations and Cr(VI) were determined in leachates over a time period of 180days. At the end of the experiment, the mineralogical composition and the physico-mechanical stability of cement composites was also assessed. The results revealed that Cr(III) and Cr(VI) were immobilized by the hydration products formed in the cement composites with the addition of ladle slag. Cr(VI) content originating from the cement was also appreciably reduced by Fe(II) from minerals present in the added ladle slag, which thus had significant positive environmental effects. Among metals, only Mo and Ba were leached in elevated concentrations, but solely in ground cement composites with the addition of ladle slag. Lower V concentrations were observed in leachates of ground than compact composite. It was demonstrated that the presence of ladle slag in cement composites can even contribute to improved mortar resistance. The investigated ladle slag can be successfully implemented in cement composites as supplementary cementitious material.

The novel crystal structure with Zr6O4(OH)4 core and hydrazine carboxylate ligands, and its thermal properties.

The title compound, [Zr(6)(OH)(4)O(4)(N(2)H(3)COO)(12)] · 14H(2)O, was prepared with a novel multi-step synthetic pathway. The structure contains a Zr(6)(µ(3)-OH)(4)(µ(3)-O(4))(12+) core on which twelve hydrazine carboxylate anions are bound to form neutral coordination molecules. The coordination mode of carboxylate ligand is exclusively N,O-bidentate chelating, which is observed for the first time in this class of compounds. The title compound is also the first example of isolated Zr(IV) oxo clusters with cubic symmetry. The structure is stabilized with an extensive hydrogen bond network between coordination and water molecules, and amongst the solvent water molecules themselves. Thermogravimetric studies have shown that the prepared [Zr(6)(OH)(4)O(4)(N(2)H(3)COO)(12)] · (14)H(2)O decomposed in several consecutive steps characterized by evolution of H(2)O, CO, CO(2), N(2) and H(2), finally yielding ZrO(2). The decomposition mechanism is rather complex and includes the formation of a series of amorphous intermediates.

Synthesis and characterization of V(IV)O complexes of picolinate and pyrazine derivatives. Behavior in the solid state and aqueous solution and biotransformation in the presence of blood plasma proteins.

Oxidovanadium(IV) complexes with 5-cyanopyridine-2-carboxylic acid (HpicCN), 3,5-difluoropyridine-2-carboxylic acid (HpicFF), 3-hydroxypyridine-2-carboxylic acid (H2hypic), and pyrazine-2-carboxylic acid (Hprz) have been synthesized and characterized in the solid state and aqueous solution through elemental analysis, IR and EPR spectroscopy, potentiometric titrations, and DFT simulations. The crystal structures of the complexes (OC-6-23)-[VO(picCN)2(H2O)]·2H2O (1·2H2O), (OC-6-24)-[VO(picCN)2(H2O)]·4H2O (2·4H2O), (OC-6-24)-Na[VO(Hhypic)3]·H2O (4), and two enantiomers of (OC-6-24)-[VO(prz)2(H2O)] (Λ-5 and Δ-5) have been determined also by X-ray crystallography. 1 presents the first crystallographic evidence for the formation of a OC-6-23 isomer for bis(picolinato) V(IV)O complexes, whereas 2, 4, and 5 possess the more common OC-6-24 arrangement. The strength order of the ligands is H2hypic ≫ HpicCN > Hprz > HpicFF, and this results in a different behavior at pH 7.40. In organic and aqueous solution the three isomers OC-6-23, OC-6-24, and OC-6-42 are formed, and this is confirmed by DFT simulations. In all the systems with apo-transferrin (VO)2(apo-hTf) is the main species in solution, with the hydrolytic V(IV)O species becoming more important with lowering the strength of the ligand. In the systems with albumin, (VO)(x)HSA (x = 5, 6) coexists with VOL2(HSA) and VOL(HSA)(H2O) when L = picCN, prz, with [VO(Hhypic)(hypic)](-), [VO(hypic)2](2-), and [(VO)4(µ-hypic)4(H2O)4] when H2hypic is studied, and with the hydrolytic V(IV)O species when HpicFF is examined. Finally, the consequence of the hydrolysis on the binding of V(IV)O(2+) to the blood proteins, the possible uptake of V species by the cells, and the possible relationship with the insulin-enhancing activity are discussed.