Synthesis, structural characterization, antimicrobial and cytotoxic effects of aziridine, 2-aminoethylaziridine and azirine complexes of copper(II) and palladium(II)

The synthesis, spectroscopic and X-ray structural characterization of copper(II) and palladium(II) complexes with aziridine ligands as 2-dimethylaziridine HNCH(2)CMe(2) (a), the bidentate N-(2-aminoethyl)aziridines C(2)H(4)NC(2)H(4)NH(2) (b) or CH(2)CMe(2)NCH(2)CMe(2)NH(2) (c) as well as the unsaturated azirine NCH(2)CPh (d) are reported. Cleavage of the cyclometallated Pd(II) dimer [μ-Cl(C(6)H(4)CHMeNMe(2)-C,N)Pd](2) with ligand a yielded compound [Cl(NHCH(2)CMe(2))(C(6)H(4)CHMe(2)NMe(2)-C,N)Pd] (1a). The reaction of the aziridine complex trans-[Cl(2)Pd(HNC(2)H(4))(2)] with an excess of aziridine in the presence of AgOTf gave the ionic chelate complex trans-[(C(2)H(4)NC(2)H(4)NH(2)-N,N')(2)Pd](OTf)(2) (2b) which contains the new ligand b formed by an unexpected insertion and ring opening reaction of two aziridines ("aziridine dimerization"). CuCl(2) reacted in pure HNC(2)H(4) or HNCH(2)CMe(2) (b) again by "dimerization" to give the tris-chelated ionic complex [Cu(C(2)H(4)NC(2)H(4)NH(2)-N,N')(3)]Cl(2) (3b) or the bis-chelated complex [CuCl(C(2)H(2)Me(2)NC(2)H(2)Me(2)NH(2)-N,N')(2)]Cl (4c). By addition of 2H-3-phenylazirine (d) to PdCl(2), trans-[Cl(2)Pd(NCH(2)CPh)(2)] (5d) was formed. All new compounds were characterized by NMR, IR and mass spectra and also by X-ray structure analyses (except 3b). Additionally the cytotoxic effects of these complexes were examined on HL-60 and NALM-6 human leukemia cells and melanoma WM-115 cells. The antimicrobial activity was also determined. The growth of Gram-positive bacterial strains (S. aureus, S. epidermidis, E. faecalis) was inhibited by almost all tested complexes at the concentrations of 37.5-300.0 μg mL(-1). However, MIC values of complexes obtained for Gram-negative E. coli and P. aeruginosa, as well as for C. albicans yeast, mostly exceeded 300 μg mL(-1). The highest antibacterial activity was achieved by complexes 1a and 2b. Complex 2b also inhibited the growth of Gram-negative bacteria.     

Induction of the Prenylated Stilbenoids Arachidin-1 and Arachidin-3 and Their Semi-Preparative Separation and Purification from Hairy Root Cultures of Peanut (Arachis hypogaea L.)

Prenylated stilbenoids such as arachidin-1 and arachidin-3 are stilbene derivatives that exhibit multiple pharmacological activities. We report an elicitation strategy using different combinations of cyclodextrin, hydrogen peroxide, methyl jasmonate and magnesium chloride to increase arachidin-1 and arachidin-3 production in peanut hairy root cultures. The treatment of hairy root cultures with cyclodextrin with hydrogen peroxide selectively enhanced arachidin-1 yield (132.6 ± 20.4 mg/L), which was 1.8-fold higher than arachidin-3. Similarly, cyclodextrin combined with methyl jasmonate selectively enhanced arachidin-3 yield (178.2 ± 6.8 mg/L), which was 5.5-fold higher than arachidin-1. Re-elicitation of the hairy root cultures further increased the levels of arachidin-1 and arachidin-3 by 24% and 42%, respectively. The ethyl acetate extract of the culture medium was consecutively fractionated by normal- and reversed-phase column chromatography, followed by semi-preparative HPLC purification on a C18 column to yield arachidin-1 with a recovery rate of 32% and arachidin-3 with a recovery rate of 39%, both at higher than 95% purity. This study provided a sustainable strategy to produce high-purity arachidin-1 and arachidin-3 using hairy root cultures of peanuts combined with column chromatography and semi-preparative HPLC.     

Pseudo-steady-state solutions for solidification in a wedge

Polubarinova-Kochina's analytical differential equation methodis used to determine the pseudo-steady-state solution to problemsinvolving the freezing (solidification) of wedges of liquidwhich are initially at their fusion temperature. In particular,we consider four distinct problems for wedges which are: freezingwith the same constant boundary temperature, freezing with thesame constant boundary heat fluxes, freezing with distinct constantboundary temperatures and freezing with distinct constant fluxesat the boundaries. For the last two problems, a Heun's differentialequation with an unknown singularity is derived, which in bothcases admits a particularly elegant simple solution for thespecial case when the wedge angle is . The moving boundariesobtained are shown pictorially.     

Synthesis,Characterization and Structure of Bis‐ and Tetrakis‐Aziridine‐Nickel(II) and Copper(II) Complexes

The synthesis and characterization of mononuclear tetrakis‐aziridine nickel(II ) and copper(II ) complexes as well as of a dinuclear bis‐aziridine copper(II ) complex are described. The reactions of anhydrous MCl₂ (M = Ni^II, Cu^II) with aziridine (= az = C₂H₄NH, C₂H₃MeNH, CH₂CMe₂NH) in CH₂Cl₂ at room temperature in a 1:5 and 1:2 molar ratio, respectively, afforded the tetrakis‐aziridine complexes [M(az)₄Cl₂] (M = Ni, Cu) or the dimeric bis‐aziridine complex [Cu(az)₂Cl₂]₂. After purification, all of the complexes were fully characterized. The single crystal structure analysis revealed two different coordination modes. Whereas both nickel(II ) complexes can be classified as showing an elongated octahedral structure, copper(II ) complexes show either an elongated octahedral or a square pyramidal arrangement forming dimers with chlorido bridges in axial positions. Furthermore, the results of magnetic measurements of the nickel(II ) and copper(II ) compounds are presented.     

On the local sensitivity of different IR techniques: Ba species relevant in NO(x) storage-reduction

IR spectroscopy is widely used to elucidate reaction mechanisms in NO(x) storage and reduction (NSR). Observed band positions and assignments of vibrational modes, however, differ remarkably among the various investigations. We report an IR study of barium species relevant in NSR, aiming to clarify the source of the reported discrepancies and different surface and bulk sensitivity of various IR measurement configurations. Four IR techniques, namely, transmission IR spectroscopy (TIRS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), attenuated total reflection infrared spectroscopy (ATR-IRS), polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS), all suitable for in situ studies of the reaction system, were used. Depending on the IR technique certain bands undergo a clear band shift or disappearance, evidently showing different surface and bulk sensitivity. In spectra of barium nitrate recorded by the more bulk sensitive IR techniques, i.e. TIRS, ATR-IRS, and PM-IRRAS, fewer bands appeared than in the more surface sensitive DRIFTS spectra. This work constitutes a collection of IR spectra of reference barium compounds for the clarification of species present in the NSR catalyst system. The band position or the presence of certain bands assigned to the same chemical species may deviate if the spectra were measured by different IR techniques, especially if the compared IR techniques differ in surface/bulk sensitivity. This implies that the band assignment valid for spectra measured by DRIFTS can be transferred to TIRS, ATR-IRS, and PM-IRRAS only with precautions.     

Organocopper thin-film structures exhibiting threshold switching with short term memory

An amorphous thin film device exhibiting reproducible bistable threshold switching from a high impedance ($\text{≈10}{}^5\text{Ω}$) state to a low impedance ($\text{≈ 10Ω}$) state is described. Short term zero-bias memory behavior is also observed. The device configuration is a sandwich structure, typically, Al-film-Cu. Films are grown on Cu substrates by immersion in acetonitrile solutions of 2,5-di-N-chlorothioimino-3,4-dicyanothiophene at room temperature. Physical and electronic properties of this novel system are presented as well as evidence that the switching mechanism is electronic in nature.