Investigation of fungicidal activity of 3‐piperazine‐bis(benzoxaborole) and its boronic acid analogue

3‐Piperazine‐bis(benzoxaborole) and its bis(phenylboronic acid) analogue were investigated in terms of their fungicidal activity. The study was carried out against five filamentous fungi: Aspergillus terreus, Fusarium dimerum, Fusarium solani, Penicillium ochrochloron and Aspergillus niger. 3‐Piperazine‐bis(benzoxaborole) revealed higher inhibitory activity towards the examined strains than standard antibiotic (amphotericin B), whereas bis(phenylboronic acid) proved to be inactive. The study unequivocally showed that the presence of the heterocyclic benzoxaborole system is essential for antifungal action of the examined compounds. Copyright © 2014 John Wiley & Sons, Ltd.     

Chromatographic Study of Novel Heteronuclear Complexes with Schiff Base as Main Ligand

The properties of 12 new heterodi- and heterotrinuclear complexes having general formulae [Cu₂Ln(L)₂(NO₃)(H₂O)₂](NO₃)₂·3H₂O [where Ln = Pr (1), Nd (2), Sm (3) and Eu (4)], and [CuLn(L)(NO₃)₂(H₂O)₃MeOH]NO₃·MeOH [where Ln = Gd (5), Tb (6), Dy (7), Ho (8), Ef (9), Tm (10), Yb (11) and Lu (12)], and their main ligand [L = C₁₉H₁₈N₂O₄Br₂ = N,N’-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine] have been characterized by chromatographic analyses. The parameter of relative lipophilicity (R _M0) of the tested compounds was determined experimentally by reversed-phase high-performance thin layer chromatography method with mixtures of methanol and water as a mobile phase. We also described interactions between chromatographed substances and various surfaces (silica—SiO₂ and modified by hydrocarbon chains—RP-2, RP-8, RP-18 phases). This study also investigates the effect of pH of the mobile phase on the retention on the polar stationary phase. Thin layer chromatography combined with magnetic and electric field has been proposed as a complementary method for the determination of physicochemical properties of the investigated compounds. The chromatograms in the field and outside of it were developed simultaneously in three identical chromatographic chambers. One of them was placed in external magnetic field of 0.4 T inductivity, and the second in external electrical field. In magnetic and electric fields, retention of some complexes changed, which indicated that the presence of these fields influenced physicochemical properties of the compounds and their interactions with the stationary phase.     

Formation of dilithiated bis-(1H-pyrazol-1-yl)alkanes and their application in the synthesis of diboronic acids

Bis-(1H-pyrazol-1-yl)alkanes were deprotonated at the pyrazole 5-positions on treatment with LDA in THF at low temperature. These dianions reacted with tert-butylisocyanate as the electrophile to install a tert-butylamide group at the pyrazole 5-position. The obtained amides were next converted into the respective diboronic acids by Br–Li exchange with t-BuLi in THF at low temperature, followed by the use of triethyl borate as the electrophile. The X-ray analysis of the obtained diboronic acids revealed the presence of a variety of structural motifs, which stabilize the structure by hydrogen bond formation. The stabilization pattern differs greatly with a minor modification of the linker connecting the pyrazole rings.     

Concerning the Basicity of 4-Dimethylaminoquinazoline Derivatives

 Two series of selected 4-N,N-dimethylamino-2-phenylquinazoline and 2-N,N-diethylamino-4-N,N-dimethylamino-quinazoline derivatives obtained in the reaction of substituted N-phenylbenzimidoyl chlorides or N¹,N¹-diethyl-N²-phenylchlorocarboxyamidines with N,N-dimethylcyanamide in the presence of TiCl₄ were examined in order to detect the protonation centre. The untypical correlations between pK _a and σ were supported by MNDO calculations and single crystal X-ray diffraction data and point to a protonation of the ring-N-atoms with delocalization of the positive charge into the N,N-dimethylamino group.     

O‐Phenyl (triphenylphosphoniomethyl)phosphonate phenol solvate: supramolecular structure generated by O—H...O,C—H...O and C—H...π(arene) hydrogen bonds

The title compound, C₂₅H₂₂O₃P₂·C₆H₆O, has a zwitterionic betaine‐like structure and crystallizes as a phenol solvate. The two molecular components are held together by an almost linear intermolecular O—H...O hydrogen bond. The structure also contains three weak C—H...O and two C—H...π(arene) interactions.     

Structural, spectroscopic, and magnetic study of bis(9,10-dihydro-9-oxo-10-acridineacetate)bis(imidazole)bis(methanol) nickel(II)

The mixed ligand complex [Ni(CMA)2(im)2(MeOH)2] (where CMA = 9,10-dihydro-9-oxo-10-acridineacetate ion, im = imidazole) was prepared, and its crystal and molecular structure were determined. The nickel ions are hexa-coordinated by four oxygen atoms of the carboxylate and hydroxyl groups and by two imidazole nitrogen atoms, to form a distorted octahedral arrangement. The structure consists of a one-dimensional network of the complex molecules connected by strong intermolecular hydrogen bonds. The weak intermolecular C-H...X hydrogen bonds and stacking interactions make up the 2-D structure. Very strong intramolecular hydrogen bonds significantly affect the geometry and vibrational characteristics of the carboxylate group. The UV-vis-NIR electronic spectrum was deconvoluted into Gaussian components. Electronic bands of the Ni(II) ion were assigned to suitable spin-allowed transitions in the D4h symmetry environment. The single ion zero-field splitting (ZFS) parameters for the S = 1 state of Ni(II), as well as the g components, have been determined by high-field and high-frequency EPR (HF-HFEPR) spectroscopy over the frequency range of 52-432 GHz and with the magnetic fields up to 14.5 T: D = 5.77(1) cm-1, E = 1.636(2) cm-1, gx = 2.29(1), gy = 2.18(1), and gz = 2.13(1). These values allowed us to simulate the powder magnetic susceptibility and field-dependent magnetization of the complex.     

An atomistic simulation scheme for modeling crystal formation from solution

We present an atomistic simulation scheme for investigating crystal growth from solution. Molecular-dynamics simulation studies of such processes typically suffer from considerable limitations concerning both system size and simulation times. In our method this time-length scale problem is circumvented by an iterative scheme which combines a Monte Carlo-type approach for the identification of ion adsorption sites and, after each growth step, structural optimization of the ion cluster and the solvent by means of molecular-dynamics simulation runs. An important approximation of our method is based on assuming full structural relaxation of the aggregates between each of the growth steps. This concept only holds for compounds of low solubility. To illustrate our method we studied CaF2 aggregate growth from aqueous solution, which may be taken as prototypes for compounds of very low solubility. The limitations of our simulation scheme are illustrated by the example of NaCl aggregation from aqueous solution, which corresponds to a solute/solvent combination of very high salt solubility.     

Trianglamines--readily prepared, conformationally flexible inclusion-forming chiral hexamines

Trianglamines, macrocyclic heteraphanes, were readily synthesised through a [3+3] cyclocondensation of (R,R)-1,2-diaminocyclohexane with terephthalaldehyde, followed by NaBH4 reduction and N-alkylation. The macrocyclic ring shows a remarkable ability to change its conformation, as a consequence of rotation about the C-N bonds or nitrogen inversion due to protonation or N-alkylation, as revealed by circular dichroism spectra, computational modelling and X-ray diffraction analysis. The flexible natures of the trianglamine macrocycles allow ready accommodation of a variety of guest molecules to form crystalline inclusion complexes of highly diversified interpenetrating structures.     

Diffusion and viscosity in a crowded environment: from nano- to macroscale

Although water is the chief component of living cells, food, and personal care products, the supramolecular components make their viscosity larger than that of water by several orders of magnitude. Using fluorescence correlation spectroscopy (FCS), photon correlation spectroscopy (PCS), NMR, and rheology data, we show how the viscosity changes from the value for water at the molecular scale to the large macroviscosity. We determined the viscosity experienced by nanoprobes (of sizes from 0.28 to 190 nm) in aqueous micellar solution of hexaethylene-glycol-monododecyl-ether (in a range of concentration from 0.1% w/w to 35% w/w) and identified a clear crossover at the length scale of 17 +/- 2 nm (slightly larger than persistence length of micelles) at which viscosity acquires its macroscopic value. The sharp dependence of the viscosity coefficients on the size of the probe in the nanoregime has important consequences for diffusion-limited reactions in crowded environments (e.g., living cells).     

Spectroscopic properties and photodynamic effects of new lipophilic porphyrin derivatives: efficacy, localisation and cell death pathways

Photodynamic therapy (PDT) and photodynamic diagnostics (PDD) of cancer are based on the use of non-toxic dyes (photosensitisers) in combination with harmless visible light. This paper reports physicochemical properties, cell uptake, localisation as well as photodynamic efficiency of two novel lipophilic porphyrin derivatives, suitable for use as PDT sensitisers. Both compounds are characterised by high quantum yield of singlet oxygen generation which was measured by time-resolved phosphorescence. Photodynamic in vitro studies were conducted on three cancer cell lines. Results of cell survival tests showed negligible dark cytotoxicity but high phototoxicity. The results also indicate that cell death is dependent on energy dose and time following light exposure. Using confocal laser scanning microscopy both compounds were found to localise in the cytoplasm around the nucleus of the tumour cells. The mode of cell death was evaluated based on the morphological changes after differential staining. In summary, good photostability, high quantum yield of singlet oxygen and biological effectiveness indicate that the examined lipophilic porphyrin derivatives offer quite interesting prospects of photodynamic therapy application.