Thermal and long period stability of series of V(V), V(IV) and V(III) complex with Schiff base ligands in solid state

The synthesis and physicochemical properties of three new complexes of vanadium at +5, +4 and +3 oxidation state are described and discussed. The octahedral surrounding of vanadium for V(III) complexes of [V(L1)(HL1)] general formula is filled with two ONO tridentate ligand L, for V(IV) one ONO ligand L, oxido ligand and 1,10-phenanthroline (phen) as a co-ligand are presented in complexes of [VO(L2)(phen)]. For V(V) the complexes of [VO2(L1)(solv)] type were formed. As ligands, the H2L Schiff bases were formed in reaction between 5-hydroxysalcylaldehyde and phenylacetic hydrazide (H2L1) and 3,5- dichlorosalicyaldehyde and 4-hydroxybenzhydrazide (L2). The magnetic moment measurements, in 8 year period, show, that V(III) complexes slowly oxidise to V(IV) with preservation of the nonoxido character of the complexes, while V(IV) complexes were found to be stable. The TG and SDTA measurements indicate, that thermal stability depends mainly on the oxidation state of vanadium. The less thermally stable are the V(V) complexes, while V(IV) and V(III) are stable up to ca. 200oC. In solution, at pH 2 (similar to that in human digestion system), again the V(IV) are the most stable, only at pH 7.0 V(III) complexes had higher stability. The most stable, thus best for pharmaceutical use, are V(IV) complexes

Synthesis, structure and properties of V(V) monooxido complex with ONO tridentate Schiff base

The oxidovanadium(V) Schiff base complex of formula [VO(L)(EtO)(EtOH)] (where H2L = Schiff base ligand derived from 5-methoxysalicylaldehyde and phenylacetic hydrazide) was synthesized and described. Complex crystalizes in triclinic P-1 space group. Octahedral geometry of the vanadium(V) centre is filed with oxido, ONO L2- ligand and two solvent molecules both in ethoxo and as neutral ethanol form. The complex is neutral, with 5- and 6-memebered ring formed by ONO ligand coordinated in octahedral plane with oxido and EtOH ligands in vertical positions. Two isomers are present in the unit cell, with different position of 5-membered ring versus vertical plane. The elemental analysis, magnetic susceptibility, thermogravimetry and spectroscopy (IR, UV-Vis) measurements were measured and are discussed. The cyclic voltammetry measurements show irreversible processes for vanadium(IV/V) redox system. Thermal stability both in a solid state (TG and SDTA measurements) as well as in solutions (at pH 7.0 and 2.0, studied by UV-Vis spectroscopy) is discussed

Spectroscopic properties of halite from Kłodawa salt mine, central Poland

The dynamics of colour centre transformation was investigated in blue halite single crystals from Kłodawa Salt Mine, Central Poland, using UV-vis spectroscopy. The following colour centres were considered: F, R_{1}, R_{2}, as well as plasmons and M centres. The R_{2} centres predominated in navy blue (A) and pale blue (B) halites. Other relatively large populations were plasmons found in all examined samples. In purple (C) halite samples the plasmon population is the highest one among others and R_{1} centres appeared to be equally significant, whereas M centres were almost absent. For A and C samples unidentified bands were observed at 26,500 to 26,200 cm^{-1}, respectively. The bleaching process of the blue halites was investigated using temperature dependent UV-vis and micro-Raman spectroscopies. In micro-Raman 300-100 cm^{-1} region three very intense sharp bands were attributed to the colour centres and colloidal Na precipitation in A and B halites. The one broad band in the range 3,500 to 500 cm^{-1}, which was characteristic even for the colourless sample D but absent in the spectra of colourless NaCl obtained after recrystallization of sample A, requires further study

Critical factors besides treatment dose and duration need to be controlled in Pb toxicity tests in plant cell suspension cultures

The study was designed to determine the proper conditions for suspension culture of Viola tricolor cells in toxicity studies of Pb at different concentrations (0, 200, 500, 1000, 2000 \mu M) and exposure times (24, 48, 72 h). By forming insoluble salts with ions from the medium, lead (II) nitrate added to the medium decreased the initial 5.7-5.8 pH of the medium, depending on the Pb salt concentration and light intensity. In alamarBlue assays, we found no dose- or time-dependent effect of Pb on cell viability when we did not adjust pH and did not standardize the illumination conditions to correct the effect of lead-salt-induced turbidity. When effective illumination was adjusted to correct for turbidity at the highest lead concentration and pH was adjusted to 5.7-5.8, cell viability decreased with the increase of Pb(NO_{3})_{2} concentration and with treatment time. These experiments demonstrate that the toxic action of lead on cells in suspension depends strongly on culture conditions, and not only on the metal concentration and duration of treatment

Ionic dioxidovanadium(V) complexes with Schiff-base ligands as potential insulin-mimetic agents : substituent effect on structure and stability

Four dioxidovanadium(V) complexes with Schiff-base ligands based on 2-hydroxybenzhydrazide with four different substituted salicylaldehydes (5-chlorosalicylaldehyde, 3,5-dichlorosalicylaldehyde, 5-nitrosalicylaldehyde, 3-bromo-5-chlorosalicylaldehyde) were synthesized and described, by using V(2)O(5) and triethylamine. The single crystal X-ray structure measurements as well as elemental analyses and IR spectra confirmed the formulas of the ionic complexes with a protonated triethylamine acting as counterion, HTEA[VO(2)(L)] (HL = Schiff-base ligand). The kinetic stability of the complexes at pH = 2 and 7 was discussed with respect to the neutral vanadium(V) complexes previously studied as potential insulin-mimetic agents. A correlation between the substituents in an aromatic ring of the Schiff-base ligands with crystal packing, and also with the stability of the compounds, was presented

Synthesis, structure and properties of V(III,IV and V) complexes with ONO Schiff bases

The synthesis and physicochemical properties of vanadium(III,IV,V) complexes with Schiff base ligands based on 3,5-dibromo-4-methoxy-salicylaldehyde and phenylacetic hydrazide (H2L1), 5-chlorosalicylaldehyde and 4-hydroxybenzhydrazide (H2L2) and 5- chlorosalicylaldehyde and 2-hydroxybenzhydrazide (H2L3) were presented. The formulas of the complexes {[V(L1)(HL2)]·EtOH (1), [VO(L2)(phen)]·2H2O (2) and [VO(L3)(EtO)] (3)} were proposed based on the elemental analysis, IR and UV-Vis spectra. Additionally, the IR and UV-Vis spectra (in solvents as well as in a solid state) have been discussed from the vanadium oxidation state point of view. The single crystal structure of 3 shows triclinic, P-1 space group, structure is stabilized by hydrogen bonds and strong π-π stacking interactions. The oxidation state of the metal centre was also confirmed by the magnetic susceptibility measurements. The stability of the complexes was measured in pH = 7.00 and in pH = 2.00 which allows to evaluate the use of these compounds as insulin mimetic compounds

Structure and Reactivity of (PPh4)3[W(CN)5O] ⋅ 7H2O. Kinetics and Mechanism of the Reaction with Molecular Oxygen

The (PPh4)3[W(CN)5O] ⋅ 7H2O has been synthesised and structurally characterised by X-ray diffraction. In the solid state and in ethanol-acetone mixture, the salt reacts with molecular oxygen giving (PPh4)2[W(CN)4O(O2)]. The progress of the solid state reaction was followed by measuring infrared spectra. The integrated intensities of the W=O, O−O and C≡N bands changed with time according to the pseudo first-order kinetics. In solution, the kinetic measurements indicate that the rate law is of the form -d[complex]/dt = k[complex][O2]. The k value is equal to 5.78 (±0.26) mol-1 dm3 s-1 at 298 K. The activation parameters, ΔH‡(k) and ΔS‡(k), are 55 (±3) kJ mol-1 and -46 (±8) J K-1 mol-1, respectively. A reaction mechanism is proposed