Elektronenstoss-induzierter zerfall von benzol-tricarbonyl-chrom- und -wolfram-derivaten; ein vergleich

The Electron impact mass spectra of (CO)₃ MC₆H₅—X complexes (M = Cr, W; X = OCH₃, OC₄H₉, CO₂CH₃, CO₂C₄H₉) were recorded. From metastable transitions and by high-resolution measurements complete fragmentation diagrams were obtained; in some cases comparative structure determinations of fragment ions were carried out by collisional activation. The fragmentation of the tungsten complexes considerably differs from that of the chromium compounds. The differences may be attributed to the stronger-electrophilic character as well as to the more pronounced tendency of tungsten to attain higher oxidation states.     

o-Nitrobenzylidene compounds. I—Competitive ortho interactions in the mass spectra of n-o-nitrobenzylidene-o-substituted anilines

The intense [M – 17]⁺ ion, which is a characteristic feature of the mass spectra of N-o-nitrobenzylideneaniline and its simple derivatives, may be substantially reduced in intensity when the aniline-derived ring is also ortho substituted: the intensity is lowest when this ortho substituent has a nucleophilic character and can itself interact with the CH?N group. The ortho substituents examined are Br, CH₃, OH, NH₂, SH, SC₆H₄CH₃(p), CO₂CH₃ and CO₂C₂H₅.     

Synthesis,characterization and in vitro antitumor activity of some arylantimony ferrocenecarboxylates and crystal structures of C5H5FeC5H4CO2SbPh4 and (C5H5FeC5H4CO2)2Sb(4‐CH3C6H4)3

A series of arylantimony ferrocenecarboxylates with the formula (C₅H₅FeC₅H₄CO₂)_nSbAr_(5?n) (n = 1, 2; Ar = C₆H₅, 4‐CH₃C₆H₄, 3‐CH₃C₆H₄, 2‐CH₃C₆H₄, 4‐ClC₆H₄, 4‐FC₆H₄) were synthesized and characterized by elemental analysis, IR, ¹H NMR and mass spectra. The crystal structures of (C₅H₅FeC₅H₄CO₂)₂Sb(4‐CH₃C₆H₄)₃ and C₅H₅FeC₅H₄CO₂SbPh₄ were determined by X‐ray diffraction. Four human neoplastic cell lines (HL‐60, Bel‐7402, KB and Hela) were used to screen these compounds. The results indicate that these compounds at 10 µM show certain in vitro antitumor activities. Copyright © 2003 John Wiley & Sons, Ltd.     

Conformational preferences of some substituted methyl groups in cyclohexanes as studied by carbon-13 nuclear magnetic resonance

Low temperature ¹³C NMR spectra of 80:20 mixtures of cis and trans-4? CH₃? CH₃? C₆H₁₀CH₂X, where ? C₆H₁₀-is 1, 4-disubtituted cyclohexyl and X=Br, CN, OH, OCH₃, Si(CH₃)₃, Sn(CH₃)₃, Pb(CH₃)₃ and HgOCOCH₃ have been recorded. The signals of the trans (e, e) components were assigned from the ambient temperature spectra of C₆H₁₁CH₂X and the established substituent effects of an equatorial methyl group in cyclohexane. Conformational equilibria of the cis (e, a?a, e) components were then computed from the intensities of the (remaining) signals (～180 K) of the two conformational isomers. From these equilibria A values of CH₂X were calculated, assuming additivity of conformational energies of CH₃ and CH₂X (the counter-poise approach). In general, these values are very similar to the value of the CH₃, although some trends do emerge. This study provides α, β, γ, and δ effects for a wide range of axial and equatorial ? CH₂X groups.     

Fast atom bombardment mass spectrometry of some alkoxv- and chloro-silanes

The positive and negative FAB mass spectra of a series of alkoxy- and chloro-silanes X_m(CH₃)₃-_mSi(CH₂)_nR [m = 1 or 3, n = 3, 10 or 17, X = Cl or OMe or OEt, R = Me, NH₂, glycidoxy, COOMe, NHCO(CH₂)₇COOMe or NHCO(CH₂)₁₀CH₂OAc] were recorded in NBA and NPOE matrices. The chlorosilanes underwent rapid hydrolysis into silanols which condense to form siloxanes, the process being complete in NBA and partial in NPOE, yielding siloxane-based fragment ions in the positive spectra and silyloxyanions in the negative spectra. The alkoxysilanes were more resistant to hydrolysis, affording abundant [MH – HX]⁺ ions (X = OMe or OEt) in their positive FAB spectra and moderate to high intensity [M – H]^? ions in the negative mode, the latter undergoing characteristic sequential loss of C₂H₄, EtOH and C₂H₄. Significant variations were observed in the positive spectra of all the silanes with change of matrix.     

Mono‐ and heterodi‐nuclear complexes of aluminium: synthesis,characterization and antifungal activity

Some new types of mononuclear derivatives, AlL(1–4)L(1–4)H ( 1a–1d ) of aluminium were synthesized by the reaction of Al(OPrⁱ)₃ and LH₂ [XC(NYOH)CHC(R)OH], X = CH₃, Y = (CH₂)₂, R = CH₃(L1H₂); X = C₆H₅, Y = (CH₂)₂, R = CH₃(L2H₂); X = CH₃, Y = (CH₂)₃, R = CH₃(L3H₂); X = C₆H₅, Y = (CH₂)₃, R = CH₃(L4H₂) in 1:2 molar ratio in refluxing benzene. Reactions of AlL(1–4)L(1–4)H with hexamethyldisilazane in 2:1 molar ratio yielded some new ligand bridged heterodinuclear derivatives AlL(1–4)L(1–4)SiMe₃ ( 2a – 2d ). All these newly synthesized derivatives were characterized by elemental analysis and molecular weight measurements. Tentative structures were proposed on the basis of IR and NMR spectra (¹H, ¹³C, 27 Al and ²⁹Si) and FAB‐mass studies. Schiff base ligands and their mono‐ and heterodi‐nuclear derivatives with aluminium have been screened for fungicidal activities. These compounds showed significant antifungal activity against Aspergillus niger and A. flavus. Copyright © 2007 John Wiley & Sons, Ltd.     

Gas‐Phase Preparation of Carbonic Acid and Its Monomethyl Ester

Carbonic acid (H₂CO₃), an essential molecule of life (e.g., as bicarbonate buffer), has been well characterized in solution and in the solid state, but for a long time, it has eluded its spectral characterization in the gas phase owing to a lack of convenient preparation methods; microwave spectra were recorded only recently. Here we present a novel and general method for the preparation of H₂CO₃ and its monomethyl ester (CH₃OCO₂H) through the gas‐phase pyrolysis of di‐tert‐butyl and tert‐butyl methyl carbonate, respectively. H₂CO₃ and CH₃OCO₂H were trapped in noble‐gas matrices at 8 K, and their infrared spectra match those computed at high levels of theory [focal point analysis beyond CCSD(T)/cc‐pVQZ] very well. Whereas the spectra also perfectly agree with those of the vapor phase above the β‐polymorph of H₂CO₃, this is not true for the previously reported α‐polymorph. Instead, the vapor phase above α‐H₂CO₃ corresponds to CH₃OCO₂H, which sheds new light on the research that has been conducted on molecular H₂CO₃ over the last decades.     

STUDIES ON THE BACTERIAL ACTIVITY OF COBALT(III) COMPLEXES. PART III. COBALT(III) CARBOXYLATE COMPLEXES

Abstract

Cobalt(III) complexes of the type [Co(en)₂(chel)]X.nH₂O where en = ethylenediamine, chel = phthalato = C₆H₄CO₂)^2? ₂, maleato = (O₂CCH = CHCO₂)^2?, succinato = (O₂CCH₂CH₂CO₂)^2?, homophthalato = (O₂CC₆H₄(CH₂)CO₂)^2?, citraconato = (O₂CC(CH₃) = CHCO₂)^2?, itaconato = (CH₂ = C(CO₂)CH₂CO₂)^2?, X = NO^? ₃, Br^?, (O₂CC₆H₄CO₂H)^?, (O₂CHC = CHCO₂H)^?, (O₂C(CH₂)₂CO₂H)^?, (O₂CC₆H₄(CH₂)CO₂H)^?, (O₂CHC = C(CH₂)-CO₂H)^?, and (O₂C-CH₂?C(= CH₂)-CO₂H)^?, [Co(en)₂(malonato)]X.2H₂O (where malonato = (O₂CCH₂CO₂)^2?, X = Cl^?, Br^?, and NO^? ₃) and [Co(en)₂CO₃]Cl.2H₂O have been investigated for their bacterial activity against Escherichia coli B growing on EMB agar and in minimal glucose media both in lag and log phases. Among the most active are where chel = phthalato and homophthalato. The effects are distinct from those known for compounds of Pt, e.g., cis?[Pt(NH₃)₂Cl₂] and rhodium, e.g., trans?[Rh(C₅H₅N)₄,Cl₂].6H₂O. Antagonisms are reported.     

Dihydroxytrimethylstiboran – einige Eigenschaften und Struktur

Dihydroxytrimethylstiborane – Properties and Structure (CH₃)₃Sb(OH)₂ · H₂O ( 1 ) is prepared by reaction of (CH₃)₃SbCl₂ and NaOH. 1 reacts with CO₂ to yield [(CH₃)₃SbOH]₂CO₃ · 2 H₂O ( 2 ). Thermogravimetric investigations and mass spectra show that 1 and 2 decompose at low temperature and low pressure to H₂O, CO₂ and (CH₃)₃SbO. The crystal and molecular structures of 1 and 2 are determined. 1 crystallizes orthorhombic (Pbca) with a = 1185.2, b = 1069.6, c = 1207.6 pm and Z = 8. 2 crystallizes in the acentric monoclinic space group Cc with a = 657.3, b = 1168.5, c = 2048.2 pm, β = 95,33° and Z = 4. The infrared spectra are discussed with regard to the hydrogen bonding.     

Synthesis,characterization and cytotoxicity of some triarylbismuth(V) di(N‐p‐toluenesulfonyl) aminoacetates and the crystal structure of (4‐CH3C6H4SO2NHCH2CO2)2Bi(C6H4Cl‐4)3

A series of triarylbismuth(V) di(N‐p‐toluenesulfonyl)aminoacetates with the formula (4‐CH₃C₆H₄SO₂NHCH₂CO₂)₂BiAr₃ (Ar?C₆H₅, 4‐CH₃C₆H₄, 4‐ClC₆H₄, 4‐BrC₆H₄) were synthesized and characterized by elemental analysis, IR, ¹H NMR and mass spectra. The crystal structure of (4‐CH₃C₆H₄SO₂NHCH₂CO₂)₂Bi(C₆H₄Cl‐4)₃ was determined and shows the bismuth to exist in a distorted trigonal bipyramidal geometry. Four human neoplastic cell lines (HL‐60, PC‐3MIE8, BGC‐823 and MDA‐MB‐435) were used to screen these compounds. The results indicate that these compounds at 10 μM show cytotoxicity. Copyright © 2004 John Wiley & Sons, Ltd.     

A Microporous Metal‐Organic Framework Supramolecularly Assembled from a CuII Dodecaborate Cluster Complex for Selective Gas Separation

A novel 3D metal‐organic framework BSF‐1 based on the closo‐dodecaborate cluster [B₁₂H₁₂]^2? was readily prepared at room temperature by supramolecular assembly of CuB₁₂H₁₂ and 1,2‐bis(4‐pyridyl)acetylene. The permanent microporous structure was studied by X‐ray crystallography, powder X‐ray diffraction, IR spectroscopy, thermogravimetric analysis, and gas sorption. The experimental and theoretical study of the gas sorption behavior of BSF‐1 for N₂, C₂H₂, C₂H₄, CO₂, C₃H₈, C₂H₆, and CH₄ indicated excellent separation selectivities for C₃H₈/CH₄, C₂H₆/CH₄, and C₂H₂/CH₄ as well as moderately high separation selectivities for C₂H₂/C₂H₄, C₂H₂/CO₂, and CO₂/CH₄. Moreover, the practical separation performance of C₃H₈/CH₄ and C₂H₆/CH₄ was confirmed by dynamic breakthrough experiments. The good cyclability and high water/thermal stability render it suitable for real industrial applications.     

Theoretical influence of third molecule on reaction channels of weakly bound complex CO2… HF systems

In this investigation, reaction channels of weakly bound complexes CO₂…HF, CO₂…HF…NH₃, CO₂…HF…H₂O and CO₂…HF…CH₃OH systems were established at the B3LYP/6‐311++G(3df,2pd) level, using the Gaussian 98 program. The conformers of syn‐fluoroformic acid or syn‐fluoroformic acid plus a third molecule (NH₃, H₂O, or CH₃OH) were found to be more stable than the conformers of the related anti‐fluoroformic acid or anti‐fluoroformic acid plus a third molecule (NH₃, H₂O, or CH₃OH). However, the weakly bound complexes were found to be more stable than either the related syn‐ and anti‐type fluoroformic acid or the acid plus third molecule (NH₃, H₂O, or CH₃OH) conformers. They decomposed into CO₂ + HF, CO₂ + NH₄F, CO₂ + H₃OF or CO₂ + (CH₃)OH₂F combined molecular systems. The weakly bound complexes have four reaction channels, each of which includes weakly bound complexes and related systems. Moreover, each reaction channel includes two transition state structures. The transition state between the weakly bound complex and anti‐fluoroformic acid type structure (T₁₃) is significantly larger than that of internal rotation (T₂₃) between the syn‐ and anti‐FCO₂H (or FCO₂H…NH₃, FCO₂H…H₂O, or FCO₂H…CH₃OH) structures. However, adding the third molecule NH₃, H₂O, or CH₃OH can significantly reduce the activation energy of T₁₃. The catalytic strengths of the third molecules are predicted to follow the order H₂O < NH₃ < CH₃OH. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Early synthetic dyes – a challenge for tandem mass spectrometry

The present study concerns identification of early yellow synthetic dyes from silk fibers taken from the 1930 spring color palette of the Lyon Dyers’ Guild (La Chambre Syndicale des Teinturiers). The identification was based mainly on the electrospray ionization tandem mass spectrometry spectra obtained in the positive and negative ion modes. This technique was combined with high‐performance liquid chromatography, which enabled separation of the analyzed compounds. Spectra registered for each of the examined synthetic dye allowed identification of their lost fragments. Moreover, isotopic profiles and exact measurements of m/z by using time of flight analyzer made possible to evaluate their elemental composition. In consequence, all obtained data, including UV–vis spectra, allowed to reconstruct molecular structures of examined colorants. Due to the lack of standards, the identification of the dyes was based only on the registration of fragment and quasi‐molecular ions, what is rather uncommon in such analysis and means groping for the correct structure rather than proving signal identity by comparison with standards. Depending on substituents present in dye molecules, the lost fragments of the examined compounds involved SO₂, NO^?, NO₂^?, CH₄, C₂H₄, C₂H₅^?, C₂H₆, CH₂ = N–CH₃, (CH₃)₂NH, CH₂ = NH, CH₃–NH₂, as well as CO and CO₂. The performed study led to identification of various colorants: rhodamine 6 G, rhodamine B, malachite green, quinoline yellow, picric acid and acetoquinone yellow 5JZ. Copyright © 2013 John Wiley & Sons, Ltd.     

Site of protonation in the chemical ionization mass spectra of olefinic methyl esters

The H₂ and CH₄ chemical ionization mass spectra of the olefinic esters methyl acrylate, methyl methacrylate, methyl crotonate, methyl 3-butenoate, methyl 2-methyl-2-butenoate, methyl 3-methyl-2-butenoate and methyl cinnamate have been determined. In addition to the expected loss of CH₃OH from [MH]⁺, in many cases the protonated molecules also show loss of CO or CH₂CO with methoxy group migration to the positive ion centre, indicative of protonation at the double bond. These rearrangement reactions, which have analogies in electron impact mass spectra, result in chemical ionization mass spectra of isomeric molecules which show more substantial differences than the electron impact mass spectra. In the case of methyl cinnamate, isotopic labelling experiments show considerable interchange of the added proton with the ortho and meta phenyl hydrogens prior to CH₃OH or CH₂CO loss, although the extent of interchange is not the same for both cases.     

Gas-chromatographic determination of impurities of organic and chlorinated organic compounds and carbon monoxide and dioxide in high-purity hydrogen chloride

A gas-chromatographic procedure was developed for determining impurities (CH₄, C₂H₆, C₃H₈, C₄H₁₀, iso-C₄H₁₀, C₅H₁₂, iso-C₅H₁₂, neo-C₅H₁₂, CH₃Cl, C₂H₅Cl, CH₂Cl₂, CHCl₃, CO, and CO₂) in hydrogen chloride using two columns and a column switching technique in an isothermal mode with a flame ionization detector; the detection limits were 0.01–0.1 ppm. The matrix was separated in a precolumn packed with urea. CO and CO₂ were determined by reaction gas chromatography with their conversion into methane.     

Schwingungsspektroskopische Untersuchungen an den Organohydrogensilanen (XCH2)(CH3)2SiH (X = Cl,Br, J), X(YO)2SiH (X = CH3, C2H5/Y = CH3, C2H5 … tert.-C4H9), (C6H5)2SiH2 und C6H5SiH3

Infrared and Raman Spectroscopic Investigations on the Organosubstituted Silicon Hydrides (XCH₂)(CH₃)₂SiH (X = Cl, Br, J), X(YO)₂SiH (X = CH₂, C₂H₅/Y = CH₃, C₂H₅ … tert.-C₄H₉), (C₆H₅)₂SiH₂ and C₆H₅SiH₃ Typical band splittings, specially for the SiH stretching vibration, are shown in the infrared and Raman spectra of the silicon hydrides (XCH₂)(CH₃)₂SiH (X = Cl, Br, J), and X(YO)₂SiH (X = CH₃, C₂H₅/Y = CH₃, C₂H₅ … tert.-C₄H₉). The cause of this behavior is in all probability the existence of rotational isomers. Raman polarization measurements at organosubstituted silicon di- and trihydrides demonstrate the accidental degeneracy of the SiH valence vibrations.     

基于密度泛函理论对等离子体中H/CO2相互作用的第一性原理研究

深入理解辐照条件下氢同位素与CO₂反应的微观机制,可为聚变堆氘氚燃料循环工艺的优化设计提供数据支撑。基于此,采用第一性原理计算研究了等离子体放电条件下H₂和CO₂的微观反应机制,研究了不同温度和氢同位素效应对反应过程的影响。通过内禀反应坐标（IRC）算法结合反应过渡态获得4条初始反应路径,并对比研究了生成产物CH₄及CH₃OH的2条路径在热力学上的容易程度,以及不同氢同位素对各个反应的影响。研究发现,氚的自发衰变或等离子体中的高能电子都会诱导氢同位素与CO₂发生反应,形成CO、H₂O、CH₄及CH₃OH等产物;在高能电子诱导CO₂的离解后,由4条初始反应路径组成的复杂反应可以自持发生,且该复杂反应中存在2种倾向;升高反应温度对CO₂转化为有机物（CH₄和CH₃OH）具有一定的促进作用。     

Hammett Correlation in the Accelerated Formation of 2,3-Diphenylquinoxalines in Nebulizer Microdroplets

The accelerated formation of 2,3-diphenylquinoxalines in microdroplets generated in a nebulizer has been investigated by competition experiments in which equimolar quantities of 1,2-phenylenediamine, C₆H₄(NH₂)₂, and a 4-substituted homologue, XC₆H₃(NH₂)₂ [X = F, Cl, Br, CH₃, CH₃O, CO₂CH₃, CF₃, CN or NO₂], or a 4,5-disubstituted homologue, X₂C₆H₂(NH₂)₂ [X = F, Cl, Br, or CH₃], compete to condense with benzil, (C₆H₅CO)₂. Electron-donating substituents (X = CH₃ and CH₃O) accelerate the reaction; in contrast, electron-attracting substituents (X = F, Cl, Br and particularly CO₂CH₃, CN, CF₃ and NO₂) retard it. A structure–reactivity relationship in the form of a Hammett correlation has been found by analyzing the ratio of 2,3-diphenylquinoxaline and the corresponding substituted-2,3-diphenylquinoxaline, giving a ρ value of −0.96, thus confirming that the electron density in the aromatic ring of the phenylenediamine component is reduced in the rate-limiting step in this accelerated condensation. This correlation shows that the phenylenediamine acts as a nucleophile in the reaction.     

Synthesis and in vitro antitumor activity of some tetraphenylantimony derivatives of exo‐7‐oxa‐bicyclo[2,2,1] heptane (ene)‐3‐arylamide‐2‐acid

A series of novel tetraphenylantimony derivatives of exo‐7‐oxa‐bicyclo[2,2,1] heptane (ene)‐3‐arylamide‐2‐acid of the general formula Ph₄SbO₂CCHCHCH₂CH₂CH(O)HCONHAr (Ar = Ph,4‐ClC₆H₄, 4‐BrC₆H₄, 3‐BrC₆H₄, 4‐F‐3‐ClC₆H₃ and 4‐MeC₆H₄) have been synthesized and characterized by elemental analysis, IR, ¹H NMR and mass spectra. The crystal structure of Ph₄SbO₂CCHCHCH₂CH₂CH(O)HCONHC₆­H₄CH₃·CHCl₃ was determined by X‐ray diffraction. Five human neoplastic cell lines (HL‐60, KB, Bel‐7402, BGC‐823 and HCT‐8) were used to screen these compounds. The results indicate that these compounds at 10 µM show certain in vitro antitumor activities. Copyright © 2001 John Wiley & Sons, Ltd.     

CH4, CO2和H2O在非金属原子修饰石墨烯表面的吸附

煤层气(矿井瓦斯)是一种有望替代传统化石燃料，如煤、石油和天然气的非常规气体. 作为可得的清洁能源，它的利用被认为是节能和经济的选择. 在本工作中，非金属原子X(X=H，O，N，S，P，Si，F，Cl)修饰的石墨烯(Gr)被用来代表具有结构异性的煤表面模型. 通过密度泛函理论系统地研究了煤层气组分Y(Y=CH₄，CO₂，H₂O)在非金属原子修饰石墨烯上的吸附作用. 结果表明Y在非金属原子修饰石墨烯上的吸附均为物理吸附. 态密度和差分电荷密度共同表明了这种弱的相互作用.其中，H和Cl对CH₄的作用较大； N、O、F、Cl对CO₂的作用较强； N，Cl对H₂O的影响不容忽视. 总的来说，吸附能大小依次为：H₂O>CO₂>CH₄. 因此，在CH₄富集的煤层里注入H₂O或CO₂可以与CH₄形成竞争吸附，进而提高煤层气采收率. 本工作提供了在分子水平下煤层气与非金属原子修饰石墨烯之间的相互作用的详情，并为煤层瓦斯的开采与分离提供了有用的信息.