NOUVELLE SYNTHÈSE DE [1,2-A]BENZIMIDAZOLO-1,3,5,2-TRIAZAPHOSPHORINES ET DE [1,2-A]BENZIMIDAZOLO-1,3,5,2- TRIAZAPHOSPHORINE-2-THIONES

The condensation of N₁-benzimidazolyl amidines 1 with tris(dimethy- lamino)phosphine leads to the corresponding [1,2a]Benzimidazolo-1,3,5,2-triazaphosphorines 3 . The N₂-phosphoroamidine intermediates 2′ are isolated and yielded the corresponding cyclic compounds 4 upon heating. The oxidation by sulfur of the compounds 3 gives the thiooxide derivatives 4 .

The structure of these compounds is unambiguously confirmed by IR, ¹H, ³¹P, and ¹³C NMR spectroscopy and by MS for some products.     

Analysis of the local structure of phosphorus-substituted LAMOX oxide ion conductors

The effect of partial substitution of molybdenum by phosphorus on the global and local structural arrangement of the fast oxide-ion conductor La(2)Mo(2)O(9) (LAMOX) has been studied by X-ray powder diffraction as well as (139)La and (31)P solid state NMR. The diffraction patterns show that La(2)Mo(2-y)P(y)O(9-y/2) forms a solid solution at low phosphorus concentrations, and that there is a structural phase transition upon increasing phosphorus concentration. This phase transition is also reflected in (139)La and (31)P NMR spectra. The possibility to excite (31)P multiple-quantum coherences of one of the (31)P NMR signals gives evidence of an accumulation of phosphorus atoms on neighbouring Mo-type sites already before formation of three-dimensional precipitates. On the basis of our X-ray and NMR results we propose a possible structural arrangement of the compound La(2)Mo(2-y)P(y)O(9-y/2) that explains the experimental observations by crystal twinning.     

Theoretical infrared line shapes of H‐bonds within the strong anharmonic coupling theory and Fermi resonances effects

In this article, we extend a previous work toward presenting a theoretical study of the effects of Fermi resonances and the fundamental anharmonic coupling parameter α between the high‐frequency mode and the H‐bond bridge. The model incorporates (i) both intrinsic anharmonicities of the fast mode (double well potential) and the H‐bond Bridge (Morse potential), (ii) strong anharmonic coupling theory, (iii) Fermi resonances by the aid of an anharmonic coupling between the fast mode and one or several harmonic bending modes, (iv) quadratic modulation of both the angular frequency and the equilibrium position of the X? …Y stretching mode on the intermonomer ? H… motions, and (v) the quantum direct (fast and bending modes) and indirect dampings (slow mode). The IR spectral density is obtained by Fourier transform of the autocorrelation function of the transition dipole moment operator of the X? H bond. The numerical calculation shows that Fermi resonances generate very complicated profiles with multisubstructure and also provide a direct evidence of Fermi resonances which were predicted to be a major feature of H‐bonds. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Fourier transform infrared spectroscopic approach to the study of the secondary cell wall development in cotton fiber

Cotton fiber maturity is a major yield component and an important fiber quality trait that is directly linked to the quantity of cellulose deposited during the secondary cell wall (SCW) biogenesis. Cotton fiber development consists of five major overlapping stages: differentiation, initiation, polar elongation, secondary cell wall development, and maturation. The transition period between 16 and 21 dpa (days post anthesis) is regarded to represent a major developmental stage between the primary cell wall and the SCW. Fourier Transform Infrared spectroscopy was used to investigate the structural changes that occur during the different developmental stages. The IR spectra of fibers harvested at different stages of development (10, 14, 17, 18, 19, 20, 21, 24, 27, 30, 36, 46, and 56 dpa) show the presence of vibrations located at 1,733 cm⁻¹ (C=O stretching originating from esters or amides) and 1,534 cm⁻¹ (NH₂ deformation corresponding to proteins or amino acids). The results converge towards the conclusion that the transition phase between the primary cell wall and the secondary cell wall occurs between 17 and 18 dpa in fibers from TX19 cultivar, while this transition occurs between 21 and 24 dpa in fibers from TX55 cultivar.     

Photocatalytic degradation of an azo reactive dye,Reactive Yellow 84, in water using an industrial titanium dioxide coated media

The photocatalytic degradation of an azo reactive dye, Reactive Yellow 84 (RY84), in aqueous solutions using industrial titanium dioxide coated non-woven paper was studied. The experiments were carried out to investigate the factors that influence the dye photocatalytic degradation, such as adsorption, initial concentration of dye, temperature, and solution pH. The experimental results show that adsorption is an important parameter controlling the apparent kinetics constant of degradation. The photocatalytic degradation rate was favored by a high concentration of solution in respect to Langmuir–Hinshelwood model. The degradation was enhanced by the temperature and was favored in acidic pH range.     

Bis‐clickable Mesoporous Silica Nanoparticles: Straightforward Preparation of Light‐Actuated Nanomachines for Controlled Drug Delivery with Active Targeting

Bis(clickable) mesoporous silica nanospheres (ca. 100 nm) were obtained by the co‐condensation of TEOS with variable amounts (2–5 % each) of two clickable organosilanes in the presence of CTAB. Such nanoparticles could be easily functionalized with two independent functions using the copper‐catalyzed alkyne‐azide cycloaddition (CuAAC) reaction to transform them into nanomachines bearing cancer cell targeting ligands with the ability to deliver drugs on‐demand. The active targeting was made possible after anchoring folic acid by CuAAC click reaction, whereas the controlled delivery was performed by clicked azobenzene fragments. Indeed, the azobenzene groups are able to obstruct the pores of the nanoparticles in the dark whereas upon irradiation in the UV or in the blue range, their trans‐to‐cis photoisomerization provokes disorder in the pores, enabling the delivery of the cargo molecules. The on‐command delivery was proven in solution by dye release experiments, and in vitro by doxorubicin delivery. The added value of the folic acid ligand was clearly evidenced by the difference of cell killing induced by doxorubicin‐loaded nanoparticles under blue irradiation, depending on whether the particles featured the clicked folic acid ligand or not.     

Molecular Characteristics and Antioxidant Activity of Spruce (Picea abies) Hemicelluloses Isolated by Catalytic Oxidative Delignification

Spruce (Picea abies) wood hemicelluloses have been obtained by the noncatalytic and catalytic oxidative delignification in the acetic acid-water-hydrogen peroxide medium in a processing time of 3–4 h and temperatures of 90–100 °C. In the catalytic process, the H₂SO₄, MnSO₄, TiO₂, and (NH₄)₆Mo₇O₂₄ catalysts have been used. A polysaccharide yield of up to 11.7 wt% has been found. The hemicellulose composition and structure have been studied by a complex of physicochemical methods, including gas and gel permeation chromatography, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The galactose:mannose:glucose:arabinose:xylose monomeric units in a ratio of 5:3:2:1:1 have been identified in the hemicelluloses by gas chromatography. Using gel permeation chromatography, the weight average molar mass M_w of hemicelluloses has been found to attain 47,654 g/mol in noncatalytic delignification and up to 42,793 g/mol in catalytic delignification. Based on the same technique, a method for determining the α and k parameters of the Mark–Kuhn–Houwink equation for hemicelluloses has been developed; it has been established that these parameters change between 0.33–1.01 and 1.57–472.17, respectively, depending on the catalyst concentration and process temperature and time. Moreover, the FTIR spectra of the hemicellulose samples contain all the bands characteristic of heteropolysaccharides, specifically, 1069 cm⁻¹ (C–O–C and C–O–H), 1738 cm⁻¹ (ester C=O), 1375 cm⁻¹ (–C–CH₃), 1243 cm⁻¹ (–C–O–), etc. It has been determined by the thermogravimetric analysis that the hemicelluloses isolated from spruce wood are resistant to heating to temperatures of up to ~100 °C and, upon further heating, start destructing at an increasing rate. The antioxidant activity of the hemicelluloses has been examined using the compounds simulating the 2,2-diphenyl-2-picrylhydrazyl free radicals.     

Synthesis,characterization and antioxidant,antibacterial activity Zn2+, Cu2+, Ni2+ and Co2+, complexes of ligand [2-(thiophen-2-yl)-1-(thiophen-2-ylmethyl)-1H-benzo[d]imidazole]

New metal complexes of (Zn(II), Co(II), Ni(II) and Cu(II)) based on the ligand 2-(thiophen-2-yl)-1-(thiophen-2-ylmethyl)-1H-benzo[d]imidazole] were synthesized, whose structures were determined with the different spectroscopic techniques ¹H NMR,¹³C NMR, FT-IR, UV–Visible and by mass spectrometry. The thermal analysis was performed by TG-DTA. The antioxidant activity of the ligand and its complexes was evaluated by DPPH (2,2-diphenyl-1-picrylhydrazyl) method, in comparison with the synthetic antioxidant, ascorbic acid. The results obtained showed that the antioxidant activity of the ligand and its complexes is moderate and that the copper complex has a high activity that exceeds that of ascorbic acid. Antimicrobial activity of the ligand and its metal complexes was studied against two Gram-positive bacteria: Bacillus subtilis ILP1428B, Staphylococcus aureus CIP543154 and two Gram-negative bacteria: Pseudomonas aeruginosa ATCC27653, Escherichia coli CIP5412 (American Type Culture Collection)the activity data show that the metal complexes are more potent than the free ligand.     

Synthesis,design of experiments and optimization of heterogeneous Fenton-like degradation of tartrazine by MgFe2O4 nano-catalyst

In this work, magnesium ferrites nanoparticles (MgFe₂O₄ NPs) were successfully fabricated by sol-gel auto-combustion (SGAC) method and were used in heterogeneous Fenton-like degradation of tartrazine. The obtained products were characterized using XRD, FTIR, SEM and EDX. XRD studies confirmed that the synthesized MgFe₂O₄ NPs had a cubic spinel structure. The average crystallite size was evaluated using the Debyee Scherrer formula and found to be in the range 16.18–28.55 nm. In FTIR spectra, two primary absorption bands at 571 cm^?1 and 415 cm^?1 were observed. The spinel ferrites are characterized by these bands and the EDX confirms the presence of the desired elements Mg, Fe, and O. The influences of operating parameters were examined using the Box Behnken statistical design (BD), including magnesium ferrite dosage (0.04–0.12 g/L), tartrazine concentration (30–50 mg/L) and H₂O₂ concentration (3.53–7.06 mM). Using analysis of variance, a significant quadratic model was created. Optimum conditions were magnesium ferrite dosage of 0.092 g/L, tartrazine concentration of 30.21 mg/L and H₂O₂ concentration of 6.66 mM, respectively. The predicted degradation efficiency within the optimum conditions as established by the suggested model was 98.4%. Confirmatory tests were carried out and the degradation efficiency of 98.9% was observed, which was in good agreement with the model's prediction. After five recuperation and reapplications, the catalyst's degradation efficiency remains stable. These findings indicate that a heterogeneous Fenton-like process utilizing MgFe₂O₄ is effective in advanced wastewater treatment.