Surface modification by self-assembled polycation/azo dye multilayers

The formation and stability of some polycation/azo dye multilayers by the alternate adsorption of one polycation of integral type having 95 mol% of N,N-dimethyl-2-hydroxypropyleneammonium chloride repeat units (PCA₅) and four multicharged azo dyes: Crocein Scralet MOO (CSMOO), Ponceau SS (PSS), Direct Blue 1 (DB 1) and Direct Red 80 (DR 80) are discussed in this paper. The dyes were different either by the number of sulfonic groups (PSS, DB 1 and DR 80) or by their position (CSMOO and PSS). The multilayer growth, when PCA₅ was adsorbed from 0.2 M Na₂SO₄ aqueous solution, was followed by UV-Vis spectroscopy and by electrokinetic measurements. Solid state polycation/azo dye complexes were also prepared to get qualitative information on the charge compensation in the multilayers.     

1,3‐Dipolar Cycloadditions to (5Z)‐1‐Acyl‐5‐(cyanomethylidene)‐ imidazolidine‐2,4‐diones: Synthesis and Transformations of Spirohydantoin Derivatives

Cycloadditions of various 1,3‐dipoles to (5Z)‐1‐acyl‐5‐(cyanomethylidene)‐3‐methylimidazolidine‐2,4‐diones 8 or 9 , prepared in 3 steps from hydantoin ( 1 ) (Schemes 1 and 2), were studied. In all cases, reactions proceeded regio‐ and stereoselectively. The type of product depended on the 1,3‐dipole and/or dipolarophile employed as well as on reaction conditions. Thus, with stable dipoles under neutral conditions, spirohydantoin derivatives 12 – 16 were obtained (Scheme 2), while under basic or acidic conditions, pyrazole‐ or isoxazole‐5‐carboxamides 18 and 23 – 26 and carboxylate 27 were formed via aromatization of the newly formed dihydroazole ring, followed by the simultaneous cleavage of the hydantoin ring (Schemes 3 – 5).     

Antimicrobial and Anticancer Application of Silver(I) Dipeptide Complexes

Three silver(I) dipeptide complexes [Ag(GlyGly)]_n(NO₃)_n (AgGlyGly), [Ag₂(GlyAla)(NO₃)₂]_n (AgGlyAla) and [Ag₂(HGlyAsp)(NO₃)]_n (AgGlyAsp) were prepared, investigated and characterized by vibrational spectroscopy (mid-IR), elemental and thermogravimetric analysis and mass spectrometry. For AgGlyGly, X-ray crystallography was also performed. Their stability in biological testing media was verified by time-dependent NMR measurements. Their in vitro antimicrobial activity was evaluated against selected pathogenic microorganisms. Moreover, the influence of silver(I) dipeptide complexes on microbial film formation was described. Further, the cytotoxicity of the complexes against selected cancer cells (BLM, MDA-MB-231, HeLa, HCT116, MCF-7 and Jurkat) and fibroblasts (BJ-5ta) using a colorimetric MTS assay was tested, and the selectivity index (SI) was identified. The mechanism of action of Ag(I) dipeptide complexes was elucidated and discussed by the study in terms of their binding affinity toward the CT DNA, the ability to cleave the DNA and the ability to influence numbers of cells within each cell cycle phase. The new silver(I) dipeptide complexes are able to bind into DNA by noncovalent interaction, and the topoisomerase I inhibition study showed that the studied complexes inhibit its activity at a concentration of 15 μM.     

Molecular Suppression of the Pimerization of Viologens (=4,4′‐Bipyridinium Derivatives) Attached to Nanocrystalline Titanium Dioxide Thin‐Film Electrodes

Twelve viologens, i.e., 4,4′‐bipyridinium derivatives 1 – 12 , were examined for their use as electrochromic material when attached to nanocrystalline titanium dioxide thin‐film electrodes. Eight of these ( 1 – 4 , 7 – 8 , 10 , and 12 ) are new, and their synthesis is included. The modifier compounds consist of one to four bipyridinium subunits with linear or dendritic architecture, equipped with one to three TiO₂‐anchoring phosphonate groups. They are tailored for high electrochromic dynamics (large absorbance change upon reduction) and low extent of pimerization (=charge‐transfer (CT) complexation of viologen cation radicals). A new graphical method is presented for the discrimination of simple dilution phenomena and more complex structural effects on the extent of pimerization in the surface‐attached viologen layer.     

Particle Formation from Single Droplets of Aqueous Solutions of Lead Nitrate

The thermal evolution of droplets of aqueous solution of lead nitrate was studied in a drop-tube furnace, which simulates typical conditions for material synthesis, through spray pyrolysis, and for the thermal destruction of liquid-containing waste. The processes of droplet evaporation, precursor precipitation within the droplet and thermolysis of the precipitated particles were followed by means of the spectral analysis of the ultraviolet light scattered by the aerosol produced during the heating of aqueous droplets (100 μm) of lead nitrate, with different salt concentrations, from ambient temperature up to 1200 K. Dimensions and physico-chemical properties of the droplets/particles were obtained in situ by means of ultraviolet spectra of light scattering (UVSLS) and compared with scanning electron microscopy (SEM) of the sampled material. A plasma generated in the air by an optical breakdown induced by a Nd:YAG laser was employed as the light source in the wavelength range 200–400 nm, thus allowing an exceptionally high photon flux in the ultraviolet region where intense and species-specific interactions with metal species take place. The spray drying process was followed by measuring the light transmitted by the droplets in the backward region. As the drying process progresses, the surface concentration reaches a saturation value and solute is deposited as a solid phase forming a surface crust, which grows steadily. At this point in the process of droplet drying, information was retrieved from the light reflected by the particle interface. Two spectral scattering behaviors were detected at temperatures above the salt precipitation within the droplet. On the basis of Mie calculations and SEM measurements, these behaviors were attributed to lead nitrate particles with typical diameters of the residual droplets (about 50 μm) and to micrometer-sized lead oxide particles. The effect of salt concentration on the drying process and the thermolysis of lead nitrate to oxide was investigated by changing the salt concentration from very dilute conditions up to almost the saturation concentration.     

Insights into the Ligand Binding to Bromodomain-Containing Protein 9 (BRD9): A Guide to the Selection of Potential Binders by Computational Methods

The estimation of the binding of a set of molecules against BRD9 protein was carried out through an in silico molecular dynamics-driven exhaustive analysis to guide the identification of potential novel ligands. Starting from eight crystal structures of this protein co-complexed with known binders and one apo form, we conducted an exhaustive molecular docking/molecular dynamics (MD) investigation. To balance accuracy and an affordable calculation time, the systems were simulated for 100 ns in explicit solvent. Moreover, one complex was simulated for 1 µs to assess the influence of simulation time on the results. A set of MD-derived parameters was computed and compared with molecular docking-derived and experimental data. MM-GBSA and the per-residue interaction energy emerged as the main indicators for the good interaction between the specific binder and the protein counterpart. To assess the performance of the proposed analysis workflow, we tested six molecules featuring different binding affinities for BRD9, obtaining promising outcomes. Further insights were reported to highlight the influence of the starting structure on the molecular dynamics simulations evolution. The data confirmed that a ranking of BRD9 binders using key parameters arising from molecular dynamics is advisable to discard poor ligands before moving on with the synthesis and the biological tests.     

Chirality in the Absence of Rigid Stereogenic Elements: The Absolute Configuration of Residual Enantiomers of C3‐Symmetric Propellers

Two new tris(aryl)phosphane oxides existing as configurationally stable residual enantiomers have been synthesised and their racemates resolved by semipreparative HPLC on a chiral stationary phase (CSP HPLC). One of them, recognised as a conglomerate, could be resolved by fractional crystallisation at a preparative scale level. In this case, the absolute configuration of the propeller‐shaped molecule was determined by anomalous X‐ray scattering. The problem of the correlative assignment of the absolute configuration to all known C₃‐symmetric three‐bladed propeller‐shaped molecules existing as stable residual enantiomers is discussed. The configurational stability of the new chiral phosphane oxides and of the corresponding phosphanes was evaluated by CD signal decay kinetics and dynamic ¹H NMR spectroscopy. The racemisation barriers in phosphanes were found about 10 kcal mol^?1 lower than those found for the corresponding oxides, though geometry and inter‐ring gearing would be very similar in the two series. Configurational stability of residual tris(aryl)phosphanes was found to be influenced by the electronic availability of the phosphorus centre, as evaluated by electrochemical CV experiments.     

HPTLC Quantification of Some Flavonoids in Extracts of Satureja hortensis L. Obtained by Use of Different Techniques

JPC – Journal of Planar Chromatography – Modern TLC - A study of quantitative analysis of some flavonoids in Satureja hortensis L. extracts is presented. The HPTLC analyses were...     

Radical salts of bis(ethylenediseleno)tetrathiafulvalene with paramagnetic tris(oxalato)metalate anions

The synthesis, crystal structure, and physical characterization of five new radical salts formed by the organic donor bis(ethylenediseleno)tetrathiafulvalene (BEST) and the paramagnetic tris(oxalato)metalate anions [M(C2O4)3]3- (M = FeIII and CrIII) are reported. The salts isolated are (BEST)4[M(C2O4)3].PhCOOH.H2O with MIII = Cr (1) or Fe (2) (crystal data: 1, triclinic, space group P(-)1 with a = 14.0999(4) A, b = 15.3464(4) A, c =19.5000(4) A, alpha = 76.711(5) degrees, beta = 71.688(5) degrees, gamma = 88.545(5) degrees, V = 3893.5(2) A3, and Z = 2; 2, triclinic, space group P(-)1 with a = 14.0326(3) A, b =15.1981(4) A, c =19.4106(4) A, alpha = 76.739(5) degrees, beta = 71.938(5) degrees, gamma = 88.845(5) degrees, V = 3824.9(2) A3, and Z = 2), (BEST)4[M(C2O4)3].1.5H2O with MIII = Cr (3) or Fe (4) (crystal data: 3, monoclinic, space group C2/m with a = 33.7480(10) A, b =12.3151(7) A, c = 8.8218(5) A, beta = 99.674(5) degrees, V = 3614.3(3) A3, and Z = 2; 4, monoclinic, space group C2/m with a = 33.659(6) A, b =12.248(2) A, c = 8.759(2) A, beta = 99.74(3) degrees, V = 3558.9(12) A3, and Z = 2), and (BEST)9[Fe(C2O4)3]2.7H2O (5) (crystal data: triclinic, space group P(-)1 with a =12.6993(3) A, b =18.7564(4) A, c = 18.7675(4) A, alpha = 75.649(5) degrees, beta = 107.178(5) degrees, gamma = 79.527(5) degrees, V = 3977.5(3) A3, and Z = 1). The structures of all these salts consist of alternating layers of the organic donors and tris(oxalato)metalate anions. In 1 and 2 the anionic layers contain also benzoic acid molecules H-bonded to the terminal oxygen atoms of the anions. In all salts the organic layers adopt beta-type packings. Along the parallel stacks the donors form dimers in 3 and 4, trimers in 5, and tetramers in 1 and 2. All the compounds are paramagnetic semiconductors with high room-temperature conductivities and magnetic susceptibilities dominated by the Fe- or Cr-containing anions.