Synthesis, characterization, and UV-vis linear absorption of centrosymmetric pi-systems incorporating closo-dodecaborate clusters

Single- and multibranched centrosymmetric derivatives incorporating B12 clusters [B12H11-N(H)=C(H)-C6H4-C6H4-C(H)=(H)N-B12H11]2- (3) and [1,3,5-(4-(B12H11-N(H)=C(H))-C6H4)-C6H3]3- (5) have been synthesized. Both derivatives were characterized by multinuclear NMR and ESI-MS analyses. To the best of our knowledge, compound 5 is the first example of a multicage derivative bearing three B12 units. Compounds 3 and 5 are only slightly yellowish colored. The UV-vis absorption curves of 3 and 5 show intense absorption bands at 360 and 314 nm, respectively. This result permits us to confirm the strong donor effect of the B12 cluster. The hypsochrome effect observed for compound 5 compared to that of compound 3 confirms the interest in multibranched derivatives for the preparation of two-photon absorption materials active in the visible range.     

Magnetic investigations of titanium-doped gamma iron oxides dispersed in polymers

The preparation and characterization of titanium-doped iron oxides–styrene isoprene styrene block copolymer composites is reported. The precursor, as-synthesized nanoparticles, contains akaganeite, maghemite, and titanium-doped maghemite. Hysteresis loops obtained by SQUID measurements revealed an exchange biased field assigned to the presence of akaganeite nanoparticles. It was found that the coercive field and the exchange bias field decreases as the temperature of the sample is increased. The temperature dependence of the magnetization revealed a blocking temperature of about 220 K. The ESR spectra in the temperature range 150 K to about 300 K are single broad resonance lines. It was observed that the resonance line position is strongly temperature dependent due to the combined action of the external and molecular magnetic fields. The decrease of the resonance line width as the temperature is increased is governed by the reorientation of the magnetization. Thermally activated movements of magnetic nanoparticles within the soft phase (polyisoprene) of the matrix may also contribute to resonance line narrowing. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3432–3437, 2005     

Thermal stability of some new complexes bearing ligands with polymerizable groups

A series of new complexes with mixed ligands of the type M(4,4’-dipy)(C₃H₃O₂)₂(H₂O)_y ((1) M=Mn, y=2; (2) M=Ni, y=2; 4,4’-dipy: 4,4’-dipyridyl and C₃H₃O₂ is acrylate anion) and respectively M₂(4,4’-dipy)(C₃H₃O₂)₄(H₂O)_y ((3) M=Cu, y=0; (4) M=Zn, y=1). The modification evidenced in IR spectra was correlated with the presence of acrylate ion as unidentate in the case of complex (1) and as bidentate for others complexes. The electronic reflectance spectra showed the d–d transition for complex (1) and (2) characteristic for the octahedral surrounding while the spectrum for complex (3) have the characteristic pattern for square-pyramidal stereochemistry. The thermal behaviour steps were investigated. The thermal transformations are complex processes according to TG and DTG curves including dehydration, acrylate ion oxidative degradation and thermolysis process of aromatic amine. The final products of decomposition are the most stable metal oxides.     

The perturbation method applied to tube drawing with floating plug

The determination of the load on the machine tool is crucial in the mechanics of metal forming processes as it has a critical influence over the deformation of the material into a new shape and the optimal conditions for the process. The problems of strip, wire, tube drawing without plug, tube drawing with floating plug [1-4] viscoplastic deformation has no exact solutions, but this paper addresses them using an approximate method. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Insight on thermal,spectral, magnetic and biological behaviour of new Ni(II), Cu(II) and Zn(II) complexes with a pentaazamacrocyclic ligand derived from nicotinamide

New species of type [MLCl₂]·nH₂O (M:Ni, n = 0; M:Cu, n = 1 and M:Zn, n = 0; L: 1,3,5,8,11-pentaazacyclotridecane-3-yl-(pyrid-3-yl)-methanone resulted by N,N’-bis(2-aminoethyl)ethane-1,2-diamine, nicotinamide and formaldehyde) were synthesised by one-pot condensation. Chemical analysis, ESI–MS, IR, ¹H NMR, ¹³C NMR, UV–Vis–NIR, EPR spectroscopy as well as magnetic data at room temperature were used in order to characterise the compounds. The data provided by IR, ESI–MS and NMR spectra are consistent with the macrocycle formation. Electronic spectra indicate that both Ni(II) and Cu(II) adopt an octahedral stereochemistry data furthermore confirmed by magnetic moments and EPR spectrum at room temperature. The electrochemical behaviour of the compounds was investigated by cyclic voltammetry. Processes as water and chloride elimination as well as oxidative degradation of the macrocyclic ligand were observed by simultaneously TG–DTA measurements. The final residue as the most stable metallic oxide was identified by X-ray powder diffraction. The compound [CuLCl₂]·H₂O (2) exhibits fungicidal and anti-biofilm activity on Candida albicans strains. The complexes exhibit a low cytotoxicity on HEp 2 cells, except for Cu(II) species that induce the cellular cycle arrest in the G2/M phase.     

Thermal behaviour and characterisation of new biologically active Cu(II) complexes with benzimidazole as main ligand

Four coordination compounds of copper(II) were synthesised and characterised in solid state by elemental analysis, infrared, electronic and EPR spectroscopy, as well as by thermal analysis (TG/DTA). The complexes were formulated on the basis of experimental data as: [Cu(BzIm)₂(H₂O)]·H₂O (1), [Cu₂(Acr)₄(HBzIm)₂] (2), [Cu(Acr)₂(HBzIm)₂] (3) and [Cu(Acr)₂(HBzIm)₂(H₂O)]·H₂O (4). IR data are in accordance with the unidentate nature of benzimidazole, in complexes (2), (3) and (4), and bridge bidentate nature of benzimidazole, in complex (1), while acrylato acts as uni- or bridge/chelate ligand. The electronic spectra display the characteristic pattern of square planar, square pyramidal, or octahedral stereochemistry, also confirmed by EPR spectra. Thermal decomposition evidenced several well-defined steps as dehydration of complexes (1) and (4), benzimidazole molecule releases for all complexes and acrylate decomposition in carbonate for complexes (3) and (4). In all four cases, the final residue after thermal treatment in air flow is copper(II) oxide, formed during the decomposition steps for complexes (3) and (4), and, respectively, after the oxidation of the metallic copper for complexes (1) and (2). Antimicrobial activities of the complexes have been determined by in vitro assays, against various Gram-negative and Gram-positive bacterial and fungal strains. Copper(II) complexes were also evaluated for their cytotoxicity on eukaryotic cells.     

An Approximate Kinetic Treatment of Slow‐Initiated Living Polymerization. I. First‐Order Initiation and Propagation

A new method for deriving the initiation rate constant for a slowinitiated living polymerization process in which all reactions are first order with respect to all participants is presented. The method is based upon an approximate analytical solution of the set of differential equations modeling this class of processes. The solution is found by asymptotic expansion of the unknown functions, using a dimensionless parameter which characterizes the process.     

Thermal and spectral studies of palladium(II) and platinum(IV) complexes with dithiocarbamate derivatives

Four new coordination complexes of palladium(II) and platinum(IV) starting from bis(dimethylthiocarbamoyl)sulphide (L¹) and bis(diethylthiocarbamoyl)disulphide (L²) were synthesized and characterized in solid state by elemental analysis, infrared and electronic spectroscopy as well as thermal analysis (TG/DTA). The complexes were formulated on the basis of experimental data as [Pd(Me₂NCS₂)₂] (1), [Pt(Me₂NCS)₂SCl₄]·3H₂O (2), [Pd(Et₂NCS₂)₂] (3) and [Pt(Et₂NCS)₂S₂Cl₄]·4H₂O (4), respectively. TG experiments revealed the nature of complex species as hydrated (2 and 4) or anhydrous (1 and 3). Thermal decomposition of coordinated organic ligands occurs in one or two exothermic stages, the final residue being in all cases the free metal (Pd or Pt).     

Lipophilicity of oils and fats estimated by TLC

A representative series of natural toxins belonging to alkaloids and mycotoxins classes was investigated by TLC on classical chemically bonded plates and also on oils‐ and fats‐impregnated plates. Their lipophilicity indices are employed in the characterization and comparison of oils and fats. The retention results allowed an accurate indirect estimation of oils and fats lipophilicity. The investigated fats and oils near classical chemically bonded phases are classified and compared by means of multivariate exploratory techniques, such as cluster analysis, principal component analysis, or fuzzy‐principal component analysis. Additionally, a concrete hierarchy of oils and fats derived from the observed lipophilic character is suggested. Human fat seems to be very similar to animal fats, but also possess RP‐18, RP‐18W, and RP‐8.     

Rose Hips,a Valuable Source of Antioxidants to Improve Gingerbread Characteristics

The present study analyzes the complex of bioactive compounds from rose hips pulp powder (RHP) obtained after separating the seeds from Rosa canina L. in order to obtain the oil. The extract prepared from RHP was characterized in terms of the total content of polyphenols, flavonoids, cinnamic acids, flavonols, carotenoids, but also the content of individual polyphenols and carotenoids, antioxidant activity, and CIELab color parameters. The effects of some salts, potentially present in foods, and pH variations were examined to predict possible interactions that could occur when adding rosehip pulp as a food component. The results turned out to be a high content of polyphenols, carotenoids and antioxidant activity. The main phenolic components are procyanidin B1, chlorogenic acid, epicatechin, procyanidin B2, gallic acid, salicylic acid, and catechin. The carotenoid complex includes all-trans-β-carotene, all-trans-lycopene, zeaxanthin, α-cryptoxanthin, β-cryptoxanthin, rubixanthin, cis-β-carotene, cis-γ-carotene and cis-lycopene. The addition of CaCl₂ and NaCl to the RHP extract reduced the antioxidant activity and the strong acidic environment (pH to 2.5) decreased the antioxidant activity by 29%. The addition of rose hip powder to gingerbread has improved its general characteristics, and increased its antioxidant activity and microbiological stability, the effects of 4% RHP being the most important.