Complexes of heteroscorpionate trispyrazolylborate ligands. Part VI. Carboxylate induced conversion of mono-ligand Tp′M(L) into bis-ligand Tp′2M complexes (M=Co(II) and Cu(II))

A series of homoleptic complexes of hexacoordinate cobalt(II) and copper(II) complexes with 3,5-disubstituted homo- and heteroscorpionate tris(pyrazolyl)borate anionic ligands (Tp′) were synthesized, i.e. bis[hydrotris(3-phenyl,5-methylpyrazol-1-yl)borato]cobalt(II), bis[hydrobis(3-phenyl,5-methylpyrazol-1-yl)(3-methyl,5-phenylpyrazol-1-yl)borato]cobalt(II) and bis[hydrobis(3-phenyl,5-methylpyrazol-1-yl)(3-methyl,5-phenylpyrazol-1-yl)borato]copper(II) and their structures were elucidated crystallographically. The complexes were also formed spontaneously during attempted metathesis of the corresponding Tp′M(NCS) complexes into Tp′M(OOCCH(OH)CH₃) complexes. In the case of the analogous conversion applied for the thiocyanato [hydrobis(3-phenyl,5-methylpyrazol-1-yl)(3,5-dimethylpyrazol-1-yl)boratocobalt(II) complex with sodium carboxylates (lactate, pyruvate and 2-hydroxybutyrate), the cross-transfer of pyrazolyl residues between starting anionic ligands was observed resulting in formation of bis-ligand homo- and heteroleptic Tp′CoTp″ complexes, where Tp′, Tp″ were tris(pyrazolyl)borates composed of n 3(5)-phenyl,5(3)-methylpyrazolyl and (3−n) 3,5-dimethylpyrazolyl residues (n=0–3) identified by mass spectrometry. Metathesis of thiocyanate in thiocyanato hydrotris(3-phenyl,5-methylpyrazol-1-yl)boratocobalt(II) into pyruvate led to the isolation of stable the pyruvato hydrotris(3-phenyl,5-methylpyrazol-1-yl)boratocobalt(II) complex, the structure of which was determined crystallographically. The Tp′ ligands are η³ coordinated to metal ions in every case, whereas the pyruvate anion is coordinated through carboxylate and carbonyl oxygen atoms to the cobalt center. Two rotational isomers distinguishable by ¹H NMR spectroscopy for the hexacoordinate bis[hydrobis(3-phenyl,5-methylpyrazol-1-yl)(3-methyl,5-phenylpyrazol-1-yl)borato]cobalt(II) complex were detected in solution.     

Synthesis and evaluation of the catalytic properties of semicarbazides derived from N-triphenylmethyl-aziridine-2-carbohydrazides

A straightforward synthesis of a series of new catalysts derived from N-triphenylmethyl-aziridine-2-carbohydrazides is described. The new compounds have been tested for the enantioselective addition of diethyl- and phenylethynylzinc to aryl and alkyl aldehydes, which afforded the corresponding chiral alcohols in high chemical yields (up to 92%) and with excellent ee’s of approximately 90%.     

Hydroindene-derived chiral synthons from carotol and their cytotoxicity

Ten enantiomerically pure hydroindene-derived compounds obtained by the transformation of (+)-carotol, the main constituent of carrot seed essential oil, were examined for their ability to inhibit the growth of myeloid leukaemia (HL-60) cancer cell lines. All compounds showed significant activity, which was comparable to the most active volatile organic compounds, such as trans–trans-farnesol, citral and nerolidol. Based on the bioactivity and molecular modelling, a 3D QSAR pharmacophore model was generated.     

Mathematical model of aerobic stabilization of old landfills

A short-term aerobic stabilization of digested waste in the final methane phase was studied. The effect of aeration rate on the reduction of leachate parameters and on the rate of CO₂ production and O₂ assimilation was investigated. Experimental simulation of aerobic landfill stabilization was carried out using lysimeters. When testing the effect of aeration rate on the reduction of leachate indices (BOD₅, COD, N-NH₄⁺), it was reported that the most significant reduction was obtained at the highest rate of aeration and the smallest reduction of leachate indices was attained not at the lowest but at medium aeration rates. Both the rate of CO₂ production and the O₂ assimilation reached their highest values in the lysimeters aerated at a high rate of aeration. The proposed mathematical model which consists of a system of five differential equations describing CO₂ production, O₂ assimilation and the changes of organic carbon content in the leachate correspond well with the experimental data.     

Highly enantioselective asymmetric reactions involving zinc ions promoted by chiral aziridine alcohols

Enantiomerically pure, chiral secondary and tertiary aziridine alcohols (including the aziridine analogue of ProPhenol—AziPhenol) have proven to be highly effective catalysts for enantioselective asymmetric reactions in the presence of zinc ions, including arylation of aromatic aldehydes, epoxidation of chalcone and addition of diethylzinc to aldehydes, leading to the desired chiral products in high chemical yields (up to 90%) and with ee’s up to 90%. A higher catalytic activity of Prophenol-type bis(aziridine alcohol) in the aforementioned asymmetric transformations has been demonstrated.     

Solvability and continuous dependence results for second order nonlinear evolution inclusions with a Volterra-type operator

The paper deals with second order nonlinear evolution inclusions and their applications. We study evolution inclusions involving a Volterra-type integral operator, which are considered within the framework of an evolution triple of spaces. First, we deliver a result on the unique solvability of the Cauchy problem for the inclusion by combining a surjectivity result for multivalued pseudomonotone operators and the Banach contraction principle. Next, we provide a theorem on the continuous dependence of the solution to the inclusion with respect to the operators involved in the problem. Finally, we consider a dynamic frictional contact problem of viscoelasticity for materials with long memory and indicate how the result on evolution inclusion is applicable to the model of the contact problem.     

Effective permittivity of liquid crystal nanodispersions and composites with different pore structure

The volume filling fraction dependence of the effective permittivity of the nematic liquid crystal 4-n-pentyl-4’-cyanobiphenyl embedded in different porous membranes and dispersed with aerosil nanoparticles was determined using broadband dielectric spectroscopy in the frequency range from 10⁶ to 10⁹ Hz. The experimental data were analyzed and compared with some existing theories based on the effective medium approximation and their modifications. The obtained effective permittivities as a function of the volume filling fraction lie between the lower limits of the Wiener and Hashin–Shtrikman bounds. The observed shift of the experimental points reflects the changes in the structure of the investigated composites.