Characterization and analysis of mycobacteria and Gram-negative bacteria and co-culture mixtures by Raman microspectroscopy, FTIR, and atomic force microscopy

The molecular composition of mycobacteria and Gram-negative bacteria cell walls is structurally different. In this work, Raman microspectroscopy was applied to discriminate mycobacteria and Gram-negative bacteria by assessing specific characteristic spectral features. Analysis of Raman spectra indicated that mycobacteria and Gram-negative bacteria exhibit different spectral patterns under our experimental conditions due to their different biochemical components. Fourier transform infrared (FTIR) spectroscopy, as a supplementary vibrational spectroscopy, was also applied to analyze the biochemical composition of the representative bacterial strains. As for co-cultured bacterial mixtures, the distribution of individual cell types was obtained by quantitative analysis of Raman and FTIR spectral images and the spectral contribution from each cell type was distinguished by direct classical least squares analysis. Coupled atomic force microscopy (AFM) and Raman microspectroscopy realized simultaneous measurements of topography and spectral images for the same sampled surface. This work demonstrated the feasibility of utilizing a combined Raman microspectroscopy, FTIR, and AFM techniques to effectively characterize spectroscopic fingerprints from bacterial Gram types and mixtures.

Synchrotron FTIR microspectroscopy of Escherichia coli at single-cell scale under silver-induced stress conditions

The present work was focused on elucidating biochemical changes in the model bacterium Escherichia coli exposed to ionic silver mediated stress, at a single-cell scale. In order to achieve this, in situ synchrotron Fourier-transform infrared (sFTIR) microspectroscopy was performed, for the first time, on individual cells by attenuated total reflectance (ATR) combined with the use of zinc-selenide hemisphere for high spatial resolution. In a first part, the potential of the method was evaluated on bacteria subjected to a lethal 100 μM AgNO₃ concentration for 2 h compared to untreated 100 % viable cells. Differences in cell composition were assessed for the C–H stretching and protein spectral regions, indicating that the inhibitory action was targeted against both fatty acids and proteins. Transmission electron microscopy (TEM) confirmed morphological damages of the cell ultrastructure. The relevance of ATR-sFTIR microspectroscopy for highlighting the heterogeneity in Ag⁺-mediated effects within a given bacterial population was also pointed out. In a second part, cells were exposed to sub-lethal Ag⁺ concentrations (<10 μM AgNO₃) tested under “dynamic” growth mode: early addition vs. pulse in the mid-exponential phase, and compared to simultaneously batch-grown untreated bacteria or cells sampled just before the pulse, respectively. sFTIR microspectroscopy and TEM imaging were performed in close relation with growth kinetics characterization. No significant effect of the Ag⁺ pulses was detected, in accordance with macrokinetics data. For early-treated cells, effects on fatty acid composition were shown, although no major alteration of protein secondary structure was noticed. These partial effects were consistent with TEM observations and growth kinetics.

Raman spectroscopic identification of single bacterial cells under antibiotic influence

The identification of pathogenic bacteria is a frequently required task. Current identification procedures are usually either time-consuming due to necessary cultivation steps or expensive and demanding in their application. Furthermore, previous treatment of a patient with antibiotics often renders routine analysis by culturing difficult. Since Raman microspectroscopy allows for the identification of single bacterial cells, it can be used to identify such difficult to culture bacteria. Yet until now, there have been no investigations whether antibiotic treatment of the bacteria influences the Raman spectroscopic identification. This study aims to rapidly identify bacteria that have been subjected to antibiotic treatment on single cell level with Raman microspectroscopy. Two strains of Escherichia coli and two species of Pseudomonas have been treated with four antibiotics, all targeting different sites of the bacteria. With Raman spectra from untreated bacteria, a linear discriminant analysis (LDA) model is built, which successfully identifies the species of independent untreated bacteria. Upon treatment of the bacteria with subinhibitory concentrations of ampicillin, ciprofloxacin, gentamicin, and sulfamethoxazole, the LDA model achieves species identification accuracies of 85.4, 95.3, 89.9, and 97.3 %, respectively. Increasing the antibiotic concentrations has no effect on the identification performance. An ampicillin-resistant strain of E. coli and a sample of P. aeruginosa are successfully identified as well. General representation of antibiotic stress in the training data improves species identification performance, while representation of a specific antibiotic improves strain distinction capability. In conclusion, the identification of antibiotically treated bacteria is possible with Raman microspectroscopy for diverse antibiotics on single cell level.

Isolating stem cells in the inter-follicular epidermis employing synchrotron radiation-based Fourier-transform infrared microspectroscopy and focal plane array imaging

Normal function and physiology of the epidermis is maintained by the regenerative capacity of this tissue via adult stem cells (SCs). However, definitive identifying markers for SCs remain elusive. Infrared (IR) spectroscopy exploits the ability of cellular biomolecules to absorb in the mid-IR region (λ?=?2.5–25?μm), detecting vibrational transitions of chemical bonds. In this study, we exploited the cell’s inherent biochemical composition to discriminate SCs of the inter-follicular skin epidermis based on IR-derived markers. Paraffin-embedded samples of human scalp skin (n?=?4) were obtained, and 10-μm thick sections were mounted for IR spectroscopy. Samples were interrogated in transmission mode using synchrotron radiation-based Fourier-transform IR (FTIR) microspectroscopy (15?×?15?μm) and also imaged employing globar-source FTIR focal plane array (FPA) imaging (5.4?×?5.4?μm). Dependent on the location of derived spectra, wavenumber–absorbance/intensity relationships were examined using unsupervised principal component analysis. This approach showed clear separation and spectral differences dependent on cell type. Spectral biomarkers concurrently associated with segregation of SCs, transit-amplifying cells and terminally-differentiated cells of epidermis were primarily PO ₂ ^? vibrational modes (1,225 and 1,080?cm^?1), related to DNA conformational alterations. FPA imaging coupled with hierarchical cluster analysis also indicated the presence of specific basal layer cells potentially originating from the follicular bulge, suggested by co-clustering of spectra. This study highlights PO ₂ ^? vibrational modes as potential putative SC markers.

Reactivity and characterisation of various rank turkish bituminous coal chars

A set of seven bituminous coal chars has been characterised by IR spectroscopy (FTIR), thermogravimetry (TG) and elemental analysis. FTIR study provided suitable information to establish differences between coal samples according to their chemical compositions. The reactivity of these samples was also studied and correlated with the coal parameters of mean vitrinite reflectance, fuel ratio and H/C ratio. The data suggest that reactivity as determined can be correlated with the mean vitrinite reflectance, fuel ratio and H/C ratio (0.90). The order of reactivity of samples were; Amasra (S1) (R _m= 0.65)>Azdavay (S4) (R _m=0.99)»Armutcuk (S2) (R _m=0.81)»Acenta (S3) (R _m=0.92)>Ac2l2k (S6) (R _m=1.11) Cay (S5) (R _m=1.03)>Sogutozu (S7) (R _m=2.14).     

Ammonium carbamate type self-derivative salts of (R-)- and racemic α-methylbenzylamine

Two different compounds have formed from liquid enantiomeric (R-) and racemic α-methylbenzylamine (α-MBA, named also as 1-phenylethylamine, 1-FEA) with supercritical fluid CO₂. The crystalline solids have been characterized by elemental CHN analysis, X-ray diffraction (XRD), FTIR, ¹H, and ¹³C NMR spectroscopy, and found to be α-methylbenzylammonium α-methylbenzylcarbamate self-derivative ionic salts 1 (R/R) and 2 (rac RS), respectively, of the corresponding amines. Compound 2 (rac RS) has shown different XRD pattern from that of enantiomerically pure 1 (R/R), indicating a preferential formation of a 1:1 mixture of (R/S-) and (S/R-) or rather a racemate compound of (RS/SR-) ammonium carbamate salt (2 (rac RS)) from racemate. For thermal stability, the compounds have been checked by differential scanning calorimetry (DSC), simultaneous thermogravimetry and differential thermal analysis (TG/DTA), and in situ coupled evolved gas analysis by mass spectroscopy (TG/DTA?EGA?MS) and FTIR-gas cell (TG?FTIR). No melting point is observed because of the low thermal stability of the compounds. Decomposition stages are tried to be separated with using semi-closed (sealed with a pinhole on the top) crucibles, thus different evolution courses of CO₂ and organic vapors could be followed by MS and FTIR spectroscopy. The α-MBA vapors themselves, evolved from open crucibles could be identified by FTIR-gas cell, while vapors up to m/z = 164 have been detected by MS from semi-closed Al crucible.     

The Anticancer Activity and HSA Binding Properties of the Structurally Related Platinum (II) Complexes

The development of resistance and unwanted harmful interaction with other biomolecules instead of DNA are the major drawbacks for application of platinum (Pt) complexes in cancer chemotherapy. To conquer these problems, much works have been done so far to discover innovative Pt complexes. The objective of the current study was to evaluate the anti cancer activities of a series of four and five-coordinated Pt(II) complexes, having deprotonated 2-phenyl pyridine (abbreviated as C^N), biphosphine moieties, i.e., dppm?=?bis(diphenylphosphino) methane (Ph₂PCH₂PPh₂) and dppa?=?bis(diphenylphosphino)amine (Ph₂PNHPPh₂), as the non-leaving carrier groups. The growth inhibitory effect of the Pt complexes [Pt(C^N)(dppm)]PF₆: C ₁ , [Pt(C^N)(dppa)]PF₆: C ₂ , and [Pt(C^N)I(dppa)]: C ₃ , toward the cancer cell lines was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. In addition, the florescence quenching experiments of the interaction between human serum albumin (HSA) and the Pt complexes were performed in order to obtain the binding parameters and to evaluate the denaturing properties of these complexes upon binding to the general carrier protein of blood stream. The structure?Cactivity relationship studies reveal that four-coordinated Pt complexes C ₁ and C ₂ with both significant hydrophobic and charge characteristics, not only exhibit strong antiproliferation activity toward the cancer cell lines, but also they display lower denaturing effect against carrier protein HSA. On the other hand, five-coordinated C ₃ complex with the unusual intermolecular NH??Pt hydrogen binding and the intrinsic ability for oligomerization, exhibits poor anticancer activity and strong denaturing property. The current study reveals that the balance between charge and hydrophobicity of the Pt complexes, also their hydrogen binding abilities and coordination mode are important for their anticancer activities. Moreover, this study may suggest C ₁ and C ₂ as the potential template structures for synthesis of new generation of four-coordinated Pt complexes with strong anticancer activities and weak denaturing effects against proteins.     

Phosphorus–nitrogen compounds: part 16. Synthesis, stereogenism, anisochronism and the relationship between 31P NMR spectral and crystallographic data of monotopic spiro-crypta phosphazene derivatives

The condensation reactions of N₂O₃-donor type coronands (1–3) with hexachlorocyclotriphosphazatriene, N₃P₃Cl₆, resulted in the formation of spiro-crypta phosphazene derivatives (4–6). These compounds with excess morpholine and 1,4-dioxa-8-azaspiro[4,5]decane (DASD) afford fully substituted morpholino (7 and 10) and 1,4-dioxa-8-azaspiro[4,5]deca (8)-substituted phosphazene derivatives, respectively. Whilst, in the same conditions, the reactions of 4, 5 and 6 with pyrrolidine, morpholine and DASD also produce partially pyrrolidino-substituted geminal (9 and 11), mono-substituted pyrrolidino (12), morpholino (13) and 1,4-dioxa-8-azaspiro[4,5]deca (14) phosphazenes. It has been clearly observed that the chloride replacement reactions of 4, 5 and 6 with pyrrolidine lead to the geminal products. Compounds 7, 8 and 10 are the first examples of anisochronic tetrakis (amino) phosphazenes according to ³¹P NMR data. The structures of 7, 8 and 10–14 have been determined by FTIR, MS, ¹H, ¹³C and ³¹P NMR, DEPT, and HETCOR spectral data. The solid-state structures of 9, 13 and 14 have been examined by X-ray diffraction techniques. The sums of the bond angles around the spiro cyclic nitrogen atoms [344.8(4)° and 347.6(4)°] of 9, indicate that the nitrogen atoms have pyramidal geometries. Thus, the N atoms seem to have stereogenic configurations. Compounds 12–14 also have two stereogenic P-atoms, and they are expected to be in the mixture of enantiomers. The relationships between NPN (α and α′) bond angles and δP_spiro values and the correlation of Δ(P–N) with δP_spiro and Δ(δP) values are presented.     

Novel 2H-pyrazolo[4,3-c]hexahydropyridine derivatives: Synthesis, crystal structure, fluorescence properties and cytotoxicity evaluation against human breast cancer cells

A series of novel 2H-pyrazolo[4,3-c]hexahydropyridine derivatives (II) have been designed and synthesized. The target compounds have been identified by elemental analysis and spectral (¹H NMR, IR, and MS) data and the absolute configuration of compound (II ₁ ) was confirmed by single crystal X-ray diffraction. The cytotoxicity of the target compounds have been evaluated in vitro against two human breast cancer cell lines MCF-7 and MDA-MB-231 by MTT assay. Most compounds exhibited good inhibition, and compounds II ₂₁ (IC₅₀ = 4.7 μM for MCF-7 and IC₅₀ = 9.3 μM for MDA-MB-231), II ₃₃ (IC₅₀ = 2.4 μM for MCF-7 and IC₅₀ = 4.2 μM for MDA-MB-231) and II ₄₀ (IC₅₀ = 3.3 μM for MCF-7 and IC₅₀ =8.6 μM for MDA-MB-231) displayed better inhibitory activity than 5-fluorouracil (IC₅₀ = 4.8 μM for MCF-7 and IC₅₀ = 9.6 μM for MDA-MB-231, respectively). Flow cytometric analysis and DNA fragmentation suggest that II ₃₃ is cytotoxic and able to induce the apoptosis of MCF-7 cells. The fluorescence properties of compounds II ₁ , II ₆ , II ₁₁ , II ₁₆ , II ₂₃ , II ₂₈ , and II ₃₅ were also studied and compound II ₂₈ afforded the highest photoluminescence quantum yield (38%).     

Effect of chemical composition and heat treatment condition on microstructure and magnetic properties of nanocrystalline BaDyxFe12−xO19 (x = 0.1, 0.2, 0.3, 0.4) microfibres

A series of BaDy_xFe_12?xO₁₉ ferrite microfibres have been synthesized from metal nitrates and citric acid by the sol–gel method. TG-DSC, XRD, FTIR, FESEM, TEM and VSM were employed to characterize the thermal decomposition process, crystallite sizes, structure and magnetic properties of ferrite microfibres. The effect of calcined temperature, holding time, ion substitution on structure, magnetic properties of barium ferrite microfibres was investigated. The nanoparticle growth mechanism of ferrite microfibres was discussed. The results indicated that the hexaferrite phase was formed at 750 °C and Dy³⁺ ions entered the magnetoplumbite lattice. However, the reflections shift to a lower angle and the characteristic peaks of ferrite microfibres in FTIR shift to the lower wavenumber with the Dy content increasing. The VSM results shown that saturation magnetization (M _s ) gradually increased with calcined temperature increasing and holding time prolonging, while coercive force (H _c ) revealed an increase at first and then decreases. With the Dy content increasing, the M _s achieved values of M _s  = 50 emu?g^?1 (297 K) and 70 emu?g^?1 (77 K) and the H _c value shown a continuous reduction from 515 kA??m^?1 (297 K) and 435 kA?m^?1 (77 K) (x = 0.0) to 242 and 215 kA?m^?1 (x = 0.4).     

Synthesis and spectroscopic studies of some new oxazepine derivatives throughout [2+5] cycloaddition reactions (III)

The present work included condensation reactions of o-tolidine with different aromatic aldehydes in absolute ethanol to give Schiff bases (w ₉ –w ₁₂ ) in high yield which, on reaction with maleic and phthalic anhydride by [2+5] cycloaddition reactions in the presence of suitable solvents, give the corresponding [1,3]oxazepine-4,7-dione (w ₉ m–w ₁₂ m) and [1,3]oxazepine-1,5-dione (w ₉ ph–w ₁₂ ph), respectively. The structure of the newly synthesized compounds were monitored by TLC and established on the basis of elemental analysis, FT-IR, and ¹H NMR.     

Tri- and tetraphenylantimony propiolates: Syntheses and structures

The reaction of triphenylantimony with propiolic acid in the presence of hydrogen peroxide (molar ratios 1 : 2 : 1 and 1 : 1 : 1) in diethyl ether affords triphenylantimony dipropiolate Ph₃Sb[OC(O)C≡CH]₂ (I) and μ₂-oxobis[(propiolato)triphenylantimony] [Ph₃SbOC(O)C≡CH]₂O (II). Tetraphenylantimony propiolate Ph₄SbOC(O)C≡CH (III) is synthesized from pentaphenylantimony and propiolic or acetylenedicarboxylic acid in toluene. According to the X-ray diffraction data, the crystals of compounds I and III include two types of crystallographically independent molecules (a and b). The antimony atoms in molecules Ia, Ib, II, IIIa, and IIIb have the trigonal-bipyramidal coordination mode with different degrees of distortion. The OSbO and OSbC axial angles are 176.8(2)° (Ia, Ib), 170.17(15)°, 178.78(14)° (II), and 173.2(5)°, 174.4(5)° (IIIa, IIIb). The CSbC equatorial angles lie in the ranges 108.2(3)°–143.1(3)° (I), 109.0(2)°–131.0(2)° (II), and 113.1(4)°–125.4(4)° (III). The SbOSb angle in II is 141.55(19)°. The Sb-C bond lengths are 2.103(8)–2.141(5) (I), 2.105(5)–2.119(5) (II), and 2.076(12)–2.166(13) Å (III). The Sb-O distances increase in a series of I, II, and III: 2.139(6)–2.156(7) (Ia, Ib); 2.206(4), 2.218(3) (II); and 2.338(10), 2.340(10) Å (III).     

Synthesis and characterization of glycol-modified vanadium(V) oxoisopropoxide and their oximato derivatives: sol–gel transformations of [VO(OPr i )3], [VO{OCH2CH2OCH2CH2O}{OPr i }] and [VO{OCH2CH2OCH2CH2O}{ON=C(CH3)(C4H3S-2)}] to vanadia

Reaction of [VO(OPr ⁱ )₃] (1) with [O(CH₂CH₂OH)₂] in 1:1 molar ratio in anhydrous benzene yield glycol-modified precursor, [VO{OCH₂CH₂OCH₂CH₂O}{OPr ⁱ }] (2). Further reactions of (2) with internally functionalized oximes in anhydrous benzene yield heteroleptic complexes of the type [VO{OCH₂CH₂OCH₂CH₂O}{ON=C(R)(Ar)}] (3–8) {where R=CH₃, Ar=C₄H₃O-2 (3), C₄H₃S-2 (4), C₅H₄N-2 (5); and when R=H, Ar=C₄H₃O-2 (6), C₄H₃S-2 (7), C₅H₄N-2 (8)}. All these derivatives have been characterized by elemental analyses, molecular weight measurements and spectroscopic techniques. The crysoscopic molecular weight measurement as well as FAB mass study suggests dimeric nature of (2). However, FAB mass spectrum of (4), and the crysoscopic molecular weight measurements of (3), (4), (5) and (6) indicate the monomeric behavior of the oximato derivatives (3–8). Hexa-coordination around vanadium(V) has been proposed for both monomeric and dimeric derivatives. Sol–gel transformations of (1), (2) or (4) to vanadia [(a), (b) or (c), respectively] have been carried out at low sintering temperature (600 °C). The XRD patterns of (a), (b) or (c) indicate formation of a single orthorhombic phase in all the three cases. The SEM images suggest grain like [for (a) and (b)] and rod like [for (c)] morphology of the crystallites. IR, Raman spectra as well as EDX analyses indicate formation of pure vanadia. Absorption spectra of the vanadia (b) and (c) suggest energy band gaps of 2.53 and 2.65 eV, respectively.     

Copper complexes of two isomeric NS2-macrocycles

Two isomeric NS₂-macrocycles incorporating a xylyl group at ortho (o -L) and meta (m -L) positions were employed and their copper complexes (1?C5) were prepared and structurally characterized. The copper(II) nitrate complexes [Cu(L)(NO₃)₂] (1: L = o -L, 2: L = m -L) for both ligands were isolated. In each case, the copper center is five-coordinated with a distorted square pyramidal geometry. Despite the overall geometrical similarity, 1 and 2 show the different ligand conformation due to the discriminated packing pattern. Reaction of o -L with copper(II) perchlorate afforded complex 3 containing two independent complex cations [Cu(o -L)(H₂O)(DMF)(ClO₄)]⁺ and [Cu(o -L)(H₂O)(DMF)]²⁺; the coordination geometry of the former is a distorted octahedron while the latter shows a distorted square pyramidal arrangement. In the reactions of copper(I) halides (I or Br), o -L gave a mononuclear complex [Cu(o-L)I] (4) with a distorted tetrahedral geometry, while m -L afforded a unique exodentate 2:1 (ligand-to-metal) complex [trans-Br₂Cu(m-L)₂] (5) adopting a trans-type square-planar arrangement.     

Conformational space of tetrakis(2-naphthalenyl)ethene: a naphthologous AIE luminogen

The AIE luminogen tetrakis(2-naphthalenyl)ethene (2-NA ₄ E) was synthesized by Barton’s double extrusion diazo-thione coupling method from 2,2′-dinaphthyl thioketone and 2,2′-(diazomethylene)bisnaphthylene in 77 % yield. The structure of 2-NA ₄ E was confirmed by its ¹H NMR and ¹³C NMR spectra with full assignments. 2-NA ₄ E and its parent tetraphenylethene (Ph ₄ E) have been subjected to a comprehensive computational DFT study, in search of their conformational spaces. Seven conformers and two transition states of 2-NA ₄ E have been located. Four conformers and one transition state of Ph ₄ E have been located. The conformers of 2-NA ₄ E and Ph ₄ E are not overcrowded, as indicated by the contact distances in the fjord and cove regions. The relative free energies (ΔG ₂₉₈) of the six most stable conformers of 2-NA ₄ E are in the narrow range of 2.3 kJ/mol; they make comparable contributions (12–29 %) to the equilibrium mixture. The energy barriers for the diastereomerization D ₂-Z,Z,Z,Z $ \rightleftharpoons $ ? D ₂-E,E,E,E via the transition state C ₁-Z,E,E,Z and for the enantiomerization C ₂-Z,Z,E,E $ \rightleftharpoons $ ? C ₂-E,E,Z,Z via the transition state C _i -Z,E,Z,E are only 29.8 and 29.0 kJ/mol, respectively, indicating very rapid rates of diastereomerization and enantiomerization at room temperature. The values of naphthalenyl torsion angles and ethenic twist angles in 2-NA ₄ E are almost identical to those in the parent Ph ₄ E. The previously proposed “bulkiness” of the naphthalenyl substituents and the validity of the restriction of naphthalenyl rotation are challenged. The analysis of the AIE effect in 2-NA ₄ E should take into account the intermolecular homochiral and heterochiral interactions between the conformers.     

Derivatives of Bis(diphenylphosphino)maleic Anhydride as Ligands in Polynuclear Gold(I) Complexes

Based on the new binuclear gold(I) complex [(AuCl)₂(L1)] (1) (L1?=?2,3-bis(diphenylphosphino)maleic anhydride) four new polynuclear compounds were synthesized by reactions of 1 with E(SiMe₃)₂ (E?=?S, Se). During the formation of these new compounds the initial ligand L1 undergoes various transformations (e.g. substitution, hydration or hydrogenation) leading to the new ligands: trans-2,3-bis(diphenylphosphino)succinic anhydride (L2), 2-diphenylphosphino-3-mercapto-maleic anhydride anion (L3), 2-diphenylphosphino-3-selenolato-maleic anhydride anion (L4) and 2,3-bis(diphenylphosphino)succinic acid (L5). In case of using the sulfur species S(SiMe₃)₂ a pentanuclear cluster, [Au₅(PPh₂)₃(L3)₂] (2), and a 24-nuclear cluster, [Au₂₄S₆(PPh₂)₄(L3)₈] (3), could be obtained. With Se(SiMe₃)₂ the binuclear complex, [(AuCl)₂(L2)] (4), and the dodecanuclear cluster, [Au₁₂Se₄(L4)₄(L5)₂] (5), were yielded.     

Studies on heterocyclization of acetoacetanilide

Base-induced cyclocondensation of acetoacetanilide (1) and benzoyl isothiocyanate (2) afforded mercaptopyridine (4). Compound 4 reacted with NaOCl in presence of NH₄OH/NaOH to produce isothiazolopyridine (6). Heterocyclization of 4 by ethyl bromoacetate and/or phenacyl bromide afforded pyridothiazapene and pyridine derivatives 7, 8, respectively. The synthesis of pyrazolopyridine (9) was achieved by reaction of 4 with hydrazine hydrate. Oxidative cyclization of 4 by Br₂ produced isothiazolopyridine (10). Chlorination of compound 4 yielded isothiazolopyridine dioxide (11). Compound 1 transformed into pyrane derivatives 12 and 13 by reaction with benzylidenemalononitrile and benzylideneacetophenone, respectively. Heterocyclization of compound 1 by ethylcyanoacetate and diethyloxalate afforded pyridine and cyclopentane derivatives 14 and 15, respectively. Compound 1 heterocyclized to indenopyrane (16) or indenopyrrole (17) upon reacted with ninhydrin on cold and hot condition, respectively. Heterocyclization of compound 1 and benzilmonohydrazone afforded pyridazine derivative 18. Coupling of 1 with diazonium salt afforded hydrazone 19 which cyclized using CS₂/KOH gave pyridazine derivative 20.     

Heat stable and organosoluble benzoxazole or benzothiazole-containing poly(imide-ester)s and poly(etherimide-ester)s: synthesis and characterization

Two series of poly(imide-ester)s (PIEs) and poly(ether-imide-ester)s (PEIEs), having benzoxazole or benzothiazole pendent groups, were conveniently prepared by the diphenylchlorophosphate-activated direct polyesterification of two bis(imide-carboxylic acid)s (1), such as 2-[3,5-bis(N-trimellitimidoyl)phenyl]benzoxazole (1 _O ) and 2-[3,5-bis(Ntrimellitimidoyl) phenyl]benzothiazole (1 _S ) and two bis(imide-ether-carboxylic acid)s (2), such as 2-[3,5-bis(4-trimellitimidophenoxy)-phenyl]benzoxazole (2 _O ), and 2-[3,5-bis(4-trimellitimidophenoxy)-phenyl]benzothiazole (2 _S ) with various aromatic dihydroxy compounds in the presence of pyridine and lithium chloride. The structures, solubilities and thermal properties of obtained polymers were investigated in detail. All of the resulting polymers were characterized by FTIR and ¹H-NMR spectroscopy and elemental analysis. All of the resulting polymers exhibited excellent solubility in common organic solvents, such as pyridine, tetrahydrofuran and m-cresol, as well as in polar organic solvents, such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and dimethyl sulfoxide. The modified polymers were obtained in quantitative yields with inherent viscosities between 0.47 and 0.67 dl·g^?1. Experimental results indicated that all the polymers had glass transition temperature between 198 °C and 262 °C, the decomposition temperature at 10% weight loss between 398 °C and 531 °C under nitrogen.     

Theoretical study on the singlet and triplet potential energy surfaces of NH (X3Σ−) + HCNO reaction

Both the singlet and triplet potential energy surfaces (PESs) of the NH (X³Σ^?) + HCNO reaction have been investigated at the BMC-CCSD level based on the UB3LYP/6-311++G(d, p) structures. The results show that the title reaction is more favorable through the singlet potential energy surface than the triplet one. For the singlet potential energy surface of the NH (X³Σ^?) + HCNO reaction, the most feasible association of NH (X³Σ^?) with HCNO is found to be a non-barrier nitrogen-to-carbon attack forming the adduct a (trans-HNCHNO), which can isomerize to the adduct b (cis-HNCHNO). The most feasible channel is that the 1, 3-H shift with N2–H2 and C–N1 bonds cleavage associated with the N1–H2 bond formation of adduct a leads to the product P ₁ (HCN + HNO). Moreover, P ₂ (HNC + HNO) should be the competitive product. The other products, including P ₃ (NH₂ + NCO) and P ₄ (N₂H₂ + CO), are minor products. The product P ₁ can be obtained through two competitive channels Path 1: R → a → P ₁ and Path 3: R → b → d → P ₁ , whereas the product P ₂ can be formed through Path 2: R → b → d → P ₂ . At high temperatures, the nitrogen-to-nitrogen approach may become feasible. For the triplet potential energy surface of the NH (X³Σ^?) + HCNO reaction, the Path 10: R → ³ a → ³ a ₁ → P ₁ should be the most feasible pathway due to the less reaction steps and lower barriers. These conclusions will have impacts on further experimental investigations.     

Syntheses and characterization of a new class of vanadia precursors of oxime-modified oxovanadium(V) isopropoxide,crystal and molecular structure of [VO{ONC10H16}3]

Modification of [VO(OPrⁱ)₃] with oximes in different molar ratios, yielded new class of vanadia precursors, [VO{OPrⁱ}_3?n{L}_n] {where, n = 1–3 and LH = C₉H₁₆C=NOH (1–3) and (CH₃)₂C=NOH (4–6)}.All the products are yellow in colour. (1) and (2) are liquid/viscous liquid, while others are solids. Molecular weight measurements of all these derivatives and the ESI-mass spectral studies of (1), (2), (3) and (5) indicate their monomeric nature. ¹H and ¹³C{¹H} NMR spectra suggest that the oximato moieties are monodentate in solution which was further confirmed by the ⁵¹V NMR signals, appeared in the region expected for tetra-coordinated oxo-vanadium atoms. On ageing, a disproportionation reaction occurs in (1) and some crystals appeared. Single crystal X-ray diffraction analyses of the crystals obtained from (1) as well as from (3) were found to be the same and indicate the presence of side-on {dihapto η ²-(N, O)} binding modes of the oximato ligands, leading to the formation of seven coordination environment around the vanadium atom. Thermogravimetric curve of (1) exhibits multi-step decomposition with the formation of V₂O₅ as the final product at ~850 °C. Sol–gel transformation of (3) yielded (a) VO₂ sintered at 300 °C and (b) V₂O₅ at 600 °C. Similarly, sol–gel transformations of (1) and (2) yielded V₂O₅ (c) and (d) at 600 °C, respectively. Formation of monoclinic phase in (a) and orthorhombic phase in (b), (c) and (d) were confirmed by powder XRD patterns.