Ce10[Si10O9N17]Br, Nd10[Si10O9N17]Br and Nd10[Si10O9N17]Cl oxonitridosilicate halides with a new layered structure type

The isotypic oxonitridosilicate halides Ce₁₀[Si₁₀O₉N₁₇]Br, Nd₁₀[Si₁₀O₉N₁₇]Br and Nd₁₀[Si₁₀O₉N₁₇]Cl were obtained by the reaction of the respective lanthanide metals, their oxides and halides with “Si(NH)₂” in a radiofrequency furnace at temperatures around 1800 °C, using CsBr, resp. CsCl, as a flux. The crystal structures were determined by single-crystal X-ray diffraction (Pbam, no. 55, Z=2; Ce/Br: a=10.6117(9) Å, b=11.2319(10) Å, c=11.688(8) Å, R1=0.0356; Nd/Br: a=10.523(2) Å, b=11.101(2) Å, c=11.546(2) Å, R1=0.0239; Nd/Cl: a=10.534(2) Å, b=11.109(2) Å, c=11.543(2) Å, R1=0.0253) and represent a new layered structure type. The structure refinements were performed utilizing an O/N-distribution model according to Paulings rules, i.e. nitrogen was positioned on all bridging sites and mixed O/N-occupation was assumed on the terminal sites resulting in charge neutrality of the compounds. The layers consist of condensed [SiN₂(O/N)₂] and [SiN₃(O/N)] tetrahedra of Q² and Q³ type. The chemical composition of the compounds was derived from chemical analyses for Nd₁₀[Si₁₀O₉N₁₇]Br and electron probe micro analyses (EPMA) for all three compounds. The results of IR spectroscopic investigations are reported.     

Molecular beam chemiluminescence. VIII: Pressure dependence and kinetics of Sm + (N2O,O3, F2, Cl2) and Yb + (O3, F2, Cl2) reaction. Dissociation energies of the diatomic reaction products

The CL spectra of the title reactions and their pressure dependences have been studied over the 5 × 10^?6 ? 5 × 10^?3 torr range in a beam-gas experiment. In the Sm + N₂O, O₃ and Yb + O₃ reactions simple bimolecular formation of the short lived (radiative lifetime τ_R < 3 × 10^?6 s) MO* emitters dominates the entire pressure range. In the other systems Sm + (F₂, Cl₂), Yb + (F₂, Cl₂) the CL spectra are strongly pressure dependent, indicating extensive energy transfer from long-lived intermediates. Reaction mechanisms are suggested. The quantum yields Φ, obtained by calibrating relative quantum yields with Dickson and Zare's absolute value for Sm + N₂O [Chem. Phys. 7 (1975) 367], range from Φ = 2.3% (for Sm + F₂, the most efficient reaction) down to Φ = 0.005% for Yb + Cl₂. The following lower limit estimates were obtained for the product dissociation energies from the short wavelength CL cutoffs: D⁰₀(SmF) ? 121.3 ± 2.4 kcal/mole, D⁰₀(SmCl) ? ? 100 ± 3 kcal/mole, D⁰₀(YbO) ? 94.2 ± 1.5 kcal/moie, D⁰₀(YbF) ? 123.7 ± 2.3 kcal/mole.     

Enhancing and inhibiting effects of aromatic compounds on luminol-dimethylsulfoxide-OH(-) chemiluminescence and determination of intermediates in oxidative hair dyes by HPLC with chemiluminescence detection

The effect of 36 aromatic compounds on the luminol-dimethylsulfoxide-OH⁻ chemiluminescence (CL) was systematically studied. It was found that dihydroxybenzenes, and ortho- and para-substituted aminophenols and phenylenediamines inhibited the CL and phenols with three or more than three hydroxyls except phloroglucin tended to enhance the CL. The CL inhibition and enhancement was proposed to be dependent on whether superoxide anion radical (O₂⁻) was competitively consumed by compounds in the CL system. Trihydroxybenzenes were capable of generating superoxide anion radical, leading to the CL enhancement, whereas dihydroxybenzenes were superoxide anion radical scavenger, causing the CL inhibition. Based on the inhibited CL, a novel method for the simultaneous determination of p-phenylenediamine, o-phenylenediamine, p-aminophenol, o-aminophenol, resorcinol and hydroquinone by high-performance liquid chromatography coupled with chemiluminescence detection was developed. The method has been successfully applied to determine intermediates in oxidative hair dyes and wastewater of shampooing after hair dyed.     

Synthesis,Biological Evaluation,and Molecular Modeling of Aza-Crown Ethers

Synthetic and natural ionophores have been developed to catalyze ion transport and have been shown to exhibit a variety of biological effects. We synthesized 24 aza- and diaza-crown ethers containing adamantyl, adamantylalkyl, aminomethylbenzoyl, and ε-aminocaproyl substituents and analyzed their biological effects in vitro. Ten of the compounds (8, 10–17, and 21) increased intracellular calcium ([Ca²⁺]_i) in human neutrophils, with the most potent being compound 15 (N,N’-bis[2-(1-adamantyl)acetyl]-4,10-diaza-15-crown-5), suggesting that these compounds could alter normal neutrophil [Ca²⁺]_i flux. Indeed, a number of these compounds (i.e., 8, 10–17, and 21) inhibited [Ca²⁺]_i flux in human neutrophils activated by N-formyl peptide (fMLF). Some of these compounds also inhibited chemotactic peptide-induced [Ca²⁺]_i flux in HL60 cells transfected with N-formyl peptide receptor 1 or 2 (FPR1 or FPR2). In addition, several of the active compounds inhibited neutrophil reactive oxygen species production induced by phorbol 12-myristate 13-acetate (PMA) and neutrophil chemotaxis toward fMLF, as both of these processes are highly dependent on regulated [Ca²⁺]_i flux. Quantum chemical calculations were performed on five structure-related diaza-crown ethers and their complexes with Ca²⁺, Na⁺, and K⁺ to obtain a set of molecular electronic properties and to correlate these properties with biological activity. According to density-functional theory (DFT) modeling, Ca²⁺ ions were more effectively bound by these compounds versus Na⁺ and K⁺. The DFT-optimized structures of the ligand-Ca²⁺ complexes and quantitative structure-activity relationship (QSAR) analysis showed that the carbonyl oxygen atoms of the N,N’-diacylated diaza-crown ethers participated in cation binding and could play an important role in Ca²⁺ transfer. Thus, our modeling experiments provide a molecular basis to explain at least part of the ionophore mechanism of biological action of aza-crown ethers.     

N,N-Bis(halomethyldimethylsilyl)acetamides and their reactions

N,N-Bis(halomethyldimethydimethylsilyl)acetamides, MeCON(SiMe₂CH₂X)₂, (X = Cl, Br) were prepared by transsilylation of N,O-bis(trimethylsilyl)acetamide with halomethyldimethylchlorosilane. With water and methanol, instead of the expected SiN cleavage, nucleophilic substitution of halogen took place and the products were 1-acetyl-2,2,6,6-tetramethyldisilamorpholine and N,N-bismethoxymethyldimethylsilyl)acetamide respectively. These compounds were shown by IR and ¹H NMR spectra to have the N,N-disilylacetamide structure. Thermodynamic, kinetic constants of hindered rotation around the CN bond in these compounds were determined from their temperature-variable ¹H NMR spectra. The main products of thermolysis of the silylamides are α,ω-dichloropolydimethylsiloxanes and polydimethylcyclosiloxanes.     

The single-crystal electron spin resonance spectra of bis chloro bis(N,N′-substituted urea)oxovanadium(IV) compounds diluted in the corresponding tris-chloro bis(N,N′-substituted)urea indium(III) compounds

Single crystal ESR spectra of VOCl₂L₂ (where L = N, N, N′, N′-tetramethyl urea (tmu), N, N′-dimethylethyleneurea, N, N′-dimethylpropyleneurea, tris(dimethylamino)phosphincoxide) diluted in the corresponding Inøcl₃L₂, at Q-band frequencies are reported. The ESR data are consitent with C₂ point symmetry for VOCl₂(tmu)₂ whilst the other compounds approximate very closely to this point symmetry. A rotation of the g and A tensor axes in the plane perpendicular to the terminal VO vector fall in the range 8–15° for the four compounds studied. The spin Hamiltonian parameters for VOCl₂(tmu)₂, in conjunction with the published polarized electronic absorption spectra, have been analysed via angular overlap calculations. For VOCl₂(tmu)₂ unusual ligand hyperfine splittings were observed. These were analysed by spectrum simulation in terms of two equivalent chlorine atoms where the chlorine hyperfine and nuclear quadrupole tensors are of comparable magnitude.     

Stopped-flow study of the enhanced chemiluminescence for the oxidation of luminol with hydrogen peroxide catalyzed by microperoxidase 8

The presence of carbonate or Tris causes a dramatic enhancement in the cheminluminescence (CL) for the oxidation of luminol with hydrogen peroxide catalyzed by microperoxidase 8 (MP8). A nearly constant enhancement in CL was observed over a wide range of H₂O₂ and luminol concentrations. The enhancement in CL is strongly pH-dependent, varying from 1.3 to 22.2 for carbonate and 1.6 to 10.2 for Tris. The CL enhancement is much more prominent at pH 9-10 than at high pH (>10.5) because of the extremely weak CL emission at pH below 10 when no enhancer is present. The CL enhancement is attributed to an accelerated CL cycle and the existence of alternative routes for luminol CL, possibly involving the carbonate, or Tris radicals. The dramatic enhancement in CL of the MP8-luminol-H₂O₂ system by the readily available reagents, sodium carbonate or Tris, will have general applications for sensitive CL assays. As an example, the presence of antioxidant results in a diminished and delayed CL emission, allowing the determination of its concentration at sub-micromolar level.     

Synthesis of polyfunctionalized methylphosphine oxides

N,N-Dialkylamino(diphenylphosphoryl)chloromethanes, a new type of organophosphorus compounds, were synthesized. On dissolving in polar and low polar solvents, N,N-dialkylamino(diphenylphosphoryl)chloromethanes dissociate spontaneously with the P??C bond cleavage to form the diphenylphosphinite anion Ph₂PO^?. This was confirmed by the reaction of N,N-dimethylamino(diphenylphosphoryl)chloromethane with electrophilic substrates to form the corresponding addition or substitution products of Ph₂PO^?. The capability of spontaneous generating the diphenylphosphinite anion considers accessible N,N-dimethylamino(diphenylphosphoryl)chloromethane as a synthetic equivalent of the diphenylphosphinite anion.     

Two-photon induced fluorescence of novel dyes

Three novel compounds, trans-2-[p-(N-ethyl-N-(hydroxyethyl)amino)styryl]-N-methylbenzothiazolium iodide (1), trans-2-[p-(N-ethyl-N-(hydroxyethyl)amino)styryl]-1′,3′,3′-trimethylindolium iodide (2), and trans-2-[p-(N,N-dimethylamino)styryl]-1′,3′,3′-trimethylindolium iodide (3), were synthesized and their two-photon induced fluorescence behavior was studied. Under excitation by 1064 nm laser irradiation, the solutions of these compounds exhibit two-photon induced fluorescence with λ_max at 639, 666 and 665 nm for 1, 2 and 3 respectively.     

Synthesis and antimicrobial screening of 1,3,4-oxadiazole and clubbed thiophene derivatives

In the present study, a novel series of 2-{5-[4-(1-aza-2-(2-thienyl)vinyl)phenyl](1,3,4-oxadiazol-2-ylthio)}-N-arylacetamides (IV)_1–12 were synthesized and tested for their antimicrobial activity. Newly synthesized compounds were screened for their antibacterial and antifungal activities on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus pyogenes, Candida albicans, Aspergillus niger and Aspergillus clavatus. The chemical structures of newly synthesized compounds were elicited by IR, ¹H NMR, ¹³C NMR and mass spectral data. The synthesized bio-active compounds exhibited excellent to moderate antimicrobial activity. Compounds (IV)₅, (IV)₆ and (IV)₇ possess excellent antibacterial activity whereas compounds (IV)₆, (IV)₉ and (IV)₁₁ possess excellent antifungal activity.     

A simple accurate model for prediction of deflagration temperature of energetic compounds

A novel general method is introduced to predict deflagration temperature of organic energetic compounds containing at least –NNO₂, –ONO₂, or –CNO₂ groups. Deflagration temperature is an important safety parameter in working with dangerous energetic compounds and their environmental problems. It is shown that the contribution of some molecular structure parameters can be used to interpret thermal decomposition of an energetic compound. For 86 energetic materials (corresponding to 102 measured values) with different molecular structures, the new correlation has the root mean square (rms) and the average deviations of 23.8 and 19.0 K, respectively. The new method is also tested for some energetic compounds with complex molecular structures, e.g., two new organic energetic molecules N,N′-bis(1,2,4-triazol-3yl)-4,4′-diamino-2,2′,3,3′,5,5′,6,6′-octanitroazobenzene (BTDAONAB) and 2,4,6-trinitrophloroglucinol.     

Relaxivity studies and X-ray structure of Gd(III)-diethylenetriamine-N,N′,N″-triacetic acid-N,N″-bis(2-methoxyphenethylamide) as a potential contrast agent for magnetic resonance imaging

A new bis(amide) derivative of diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid (H₅dtpa), diethylenetriamine-N,N′,N″-triacetic-N,N″-bis(2-methoxyphenethylamide) (H₃L), has been synthesized. The crystal structure of gadolinium(III) complex of H₃L ([GdL]) has been determined by X-ray crystallography. The coordination sphere of Gd(III) comprises three amine nitrogens, two amide oxygens, three carboxylic acid oxygens, and one water molecule. ¹⁷O NMR shifts showed that the [DyL] complex had one inner-sphere water molecule. Relaxivity studies with the gadolinium(III) complex showed that they associate strongly with proteins leading to a significant relaxivity enhancement.     

Micellar electrokinetic chromatography-chemiluminescent detection of biogenic amines using N-(4-aminobutyl)-N-ethylisoluminol as derivatization reagent and trivalent copper chelate as chemiluminescence enhancer

A facile, sensitive and universal method was established for analysis of biogenic amines using micellar electrokinetic chromatography coupled with chemiluminescent (CL) detection. It was found that diperiodatocuprate (III) (K₅[Cu(HIO₆)₂], DPC), a transition metal chelate at unstable high oxidation state, could effectively enhance the reaction between luminol-type compound and hydrogen peroxide, to produce very strong CL signal. In addition, triethylamine was found to be able to effectively improve the yield of the derivatization reaction between biogenic amines and a luminol-type derivatization reagent, N-(4-aminobutyl)-N-ethylisoluminol (ABEI). Based on these facts, three biogenic amines were pre-column derivatized with ABEI, and post-column detected using high sensitive luminol-hydrogen peroxide-DPC CL system. Since the background was quite low, and the signal was quite strong, a considerable improved sensitivity was obtained. The presented method had been successfully applied to simultaneously analyze glycine, proline and phenylalanine with the detection limits (S/N = 3) of 0.030 μmol L⁻¹, 0.23 μmol L⁻¹ and 0.21 μmol L⁻¹, respectively. To evaluate its potential application value, glycine in saliva and urine samples was detected using this method, and satisfied results were obtained. This approach can be further extended to detection of many other compounds such as peptides and drugs by using luminol-type derivatization reagent.     

Complexes of organometallic compounds : XXXVII. Mössbauer and other studies on adducts of organotin(IV) chlorides with N,N′-ethylenebis(salicylideneiminato)-nickel(II)

Novel 1/1 adducts have been obtained from the complex N,N′-ethylenebis(salicylideneiminato)nickel(II) (NiSalen) with di- and mono-organotin(IV) chlorides, and their solid state configuration investigated by Mössbauer , IR and electronic spectroscopy and magnetic measurements. In coordinated NiSalen the square planar structure is maintained around Ni^II, and the coordination to tin involves three-coordinate phenolic oxygens. The environment of Sn^IV is judged to be octahedral in both types of compounds. A trans-R₂, cis-Cl₂ configuration is advanced for R₂SnCl₂NiSalen.     

Synthesis, characterization and thermal properties of new aromatic quaternary ammonium bromides: precursors for ionic liquids and complexation studies

Series of new aromatic R₂R′₂N⁺Br⁻ (R=benzyl, 4-methylbenzyl, 2-phenylethyl, 3-phenylpropyl; R′=ethyl, methyl, isopropyl) or RR′₂NH⁺Br⁻-type (R=benzyl, R′=isopropyl) quaternary ammonium bromides were prepared by using novel synthetic route in which a formamide (N,N-diethylformamide, N,N-dimethylformamide, N,N-diisopropylformamide) is treated with aralkyl halide in presence of a weak base. The compounds were characterized by ¹H-NMR and ¹³C-NMR spectroscopy and mass spectrometry. Structures of the crystalline compounds were determined by X-ray single crystal diffraction, and in addition the powder diffraction method was used to study the structural similarities between the single crystal and microcrystalline bulk material. Three of the compounds crystallized in monoclinic, two in orthorhombic and one in triclinic crystal system, showing ion pairs, which are interconnected by weak hydrogen bonds and weak π-π interactions between the phenyl rings. Three of the compounds appeared as viscous oil or waxes. Finally, TG/DTA and DSC methods were used to analyze thermal properties of the prepared compounds. The lowest melting points were obtained for diethyldi-(2-phenylethyl)ammonium bromide (122.2 °C) and for diethyldi-(3-phenylpropyl)-ammonium bromide (109.1 °C). In general, decomposition of the compounds started at 170-190 °C without identifiable cleavages, thus liquid ranges of 30-70 °C were observed for some of the compounds.     

Chemiluminescence in O2 oxidation of organosodium compounds of polycyclic aromatic hydrocarbons and benzophenone

Chemiluminescence (CL) in oxidation of organosodium compounds by O₂ in THF was studied. Emitters of CL are excited complexes of polycyclic aromatic hydrocarbons, excimers¹(R·R)^*. The mechanism of their formation was proposed. The Na⁺, R^.−+O₂ CL system is a unique source for the selective generation of excimers of aromatic hydrocarbons. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 284–288, February, 1997.     

Structure and C-C cross-coupling reactivity of iron(III) complexes of halogenated amine-bis(phenolate) ligands

The preparation of tetradentate amine-bis(phenol) proligands with dichloro and difluoro substituted phenol groups and their reaction with FeX₃ (X = Cl or Br) is described. The compounds, 2-pyridylamino-N,N-bis(2-methylene-4,6-dichlorophenol), H₂[L₁]; 2-pyridylamino-N,N-bis(2-methylene-4,6-difluorophenol), H₂[L₂]; dimethylaminoethylamino-N,N-bis(2-methylene-4,6-dichlorophenol), H₂[L₃]; 2-tetrahydrofurfuryl-N,N-bis(2-methylene-4,6-dichlorophenol), H₂[L₄]; and methoxyethylamino-N,N-bis(2-methylene-4,6-dichlorophenol), H₂[L₅] were prepared in aqueous medium and obtained as white powders in good to excellent yield. Ten new iron(III) halide complexes supported by these tetradentate ligands are reported. Representative single crystal X-ray diffraction structures were obtained for H₂[L₁] and a water adduct of the iron(III) complex, aquachloro{2-pyridylamino-N,N-bis(2-methylene-4,6-dichlorophenolato)}iron(III), 2·H₂O. The structure of the proligand H₂[L₁] shows intramolecular hydrogen bonding. In the solid-state structure, the iron complex exhibits intermolecular hydrogen bonding between the water ligand and the phenolate oxygen of a neighbouring complex. The anhydrous complexes were studied for catalytic activity towards C-C cross-coupling of Grignard reagent nucleophiles with alkyl halide electrophiles.     

Photosynthesis-Inhibiting Activity of N-(Disubstituted-phenyl)-3-hydroxynaphthalene-2-carboxamides

A set of twenty-four 3-hydroxynaphthalene-2-carboxanilides, disubstituted on the anilide ring by combinations of methoxy/methyl/fluoro/chloro/bromo and ditrifluoromethyl groups at different positions, was prepared. The compounds were tested for their ability to inhibit photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. N-(3,5-Difluorophenyl)-, N-(3,5-dimethylphenyl)-, N-(2,5-difluorophenyl)- and N-(2,5-dimethylphenyl)-3-hydroxynaphthalene-2-carboxamides showed the highest PET-inhibiting activity (IC₅₀ ~ 10 µM) within the series. These compounds were able to inhibit PET in photosystem II. It has been found that PET-inhibiting activity strongly depends on the position of the individual substituents on the anilide ring and on the lipophilicity of the compounds. The electron-withdrawing properties of the substituents contribute towards the PET activity of these compounds.     

Heats of formation and thermal stability of substituted 1,1′-Azobis(tetrazole) compounds with an extended nitrogen chain

The molecular structures of 1,1′-Azobis(tetrazole) (N₁₀) and monosubstituted compounds involving  F,  CH₃,  CN,  NH₂,  OH,  OCH₃,  N₃,  NF₂,  NO₂, and  CH₂NO₂ groups are investigated using density functional theory. The heats of formation of these compounds are investigated using ab initio composite methods. Intrinsic reaction coordinate calculations are performed to determine the energies along the decomposition pathways. The optimized geometries of the N₁₀ compounds indicate planar configurations consisting of aromatic nitrogen–nitrogen and carbon–nitrogen bonds. The stability and energy content of the substituted compounds are highly correlated with the nature of the substituents. Electron-donating groups reduce the heats of formation but increase the exothermicity of the decomposition. The decomposition of the N₁₀ compounds is classified into two general pathways: (1) a scheme involving straight-up decomposition and (2) a scheme involving functional rearrangement. Compounds undergoing decomposition pathway (1) are more exothermic with lower rate-determining activation barriers than those undergoing the latter pathway (2).     

Synthesis, characterization, and spectrophotometric studies of novel fluorescent arachno decaborane and nonaborane clusters containing aza-distyrylbenzene derivatives

Two aza-analogues of distyrylbenzene namely: 1,4-bis[β-(4-quinolyl)vinyl]benzene (PhQ) and 1,4-bis[β-(4-pyridyl)vinyl]benzene (PhPy) containing arachno-decaborane or arachno-nonaborane clusters have been isolated: 6,9-(PhQ)₂-arachno-B₁₀H₁₂ (1), N,N′-bis[9-Me₂S-arachno-B₁₀H₁₂-6-yl]PhQ (2), 6,9-(PhPy)₂-arachno-B₁₀H₁₂ (3), N,N′-bis[(9-Me₂S)-arachno-B₁₀H₁₂-6-yl]PhPy (4), N,N′-bis[arachno-B₉H₁₃-4-yl]PhQ (5), 4-PhQ-arachno-B₉H₁₃ (6), N,N′-bis[arachno-B₉H₁₃-4-yl]PhPy (7), and 4-PhPy-arachno-B₉H₁₃ (8). These boronated compounds were easily prepared from the displacement reactions of weaker ligand (SMe₂) of bis (dimethyl sulfide) arachno-decaborane(14) {6,9-(Me)₂SB₁₀H₁₂}or dimethyl sulfide-arachno-nonaborane {4-(Me)₂SB₉H₁₃} by the stronger bidentate ligands of PhQ or PhPy in ratio (1:2). The electronic interaction between decaborane or nonaborane arachno-type unit and the bonded pyridine units has been investigated by UV-Vis spectroscopy and by AM1 molecular orbital calculations. The resulting compounds undergo trans-cis photoisomerization upon excitation. The connection of boron clusters to PhQ and PhPy led to enhancing of the photoreactivity and decreasing of the fluorescence quantum yield of the products.