Synthesis of new phosphorus ylides: Spectroscopic and X‐ray structural studies

Stable phosphoranes, Ar₃P = CHCOR (R = C₆H₅, C₆H₄NO₂, C₆H₄OCH₃, CH₃, OCH₂C₆H₅; Ar = p‐tolyl or phenyl), have been C‐acylated by acetic anhydride to obtain new types of phosphorus ylides. Synthesis and characterization of six phosphorus ylides of the type Ar₃PC(COCH₃)(COR) are reported. The reaction of {(p‐tolyl)₃PCHCOC₆H₅} ( I ), {(p‐ tolyl)₃PCHCOC₆H₄NO₂} ( II ), {Ph₃PCHCOC₆H₄NO₂} ( III ), {Ph₃PCHCOC₆H₄OCH₃} ( IV ), {(p‐tolyl)₃PCHCOCH₃} ( V ), and {Ph₃PCHCOOCH₂C₆H₅} ( VI ) with acetic anhydride in dry chloroform as solvent gives (p‐tolyl)₃PC(COMe)(COC₆H₅), α‐acetyl‐α‐benzoylmethy‐lenetriphenylphosphorane ( 1 ), {(p‐tolyl)₃PC(COMe) (COC₆H₄NO₂)} ( 2 ), {Ph₃PC(COMe)(COC₆H₄NO₂)} ( 3 ), {Ph₃PC(COMe)(COC₆H₄OCH₃)} ( 4 ), {(p‐tolyl)₃ PC(COCH₃)₂} ( 5 ), and {Ph₃PC(COMe)(COOCH₂ C₆H₅)} ( 6 ). Single crystal X‐ray analyses for ylides 2 , 5 , and 6 reveal the monoclinic ( 2, 5 ) and triclinic ( 6 ) crystal systems. Characterization of the obtained compounds was also performed by elemental analysis, IR, ¹H, ³¹P, and ¹³C NMR. The geometries of these compounds have been investigated using density functional theory (DFT). In addition, electronic parameters of these compounds such as HOMO and LUMO energy, Mulliken partial charge, and dipole moment were obtained. In this paper, the reactivity of these ylides is discussed in regard to the aforementioned data. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:475–485, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20633     

X‐ray structural analysis and theoretical studies of new phosphite‐derived ylides

The reaction between dialkyl acetylenedicarboxylates and NH heterocyclic compounds in the presence of triethyl phosphite leads to stable phosphorus ylide derivatives in good yields. The X‐ray crystallographic data and theoretical study show that there is a resonance between two bonds of C₁₉P₁ and C₁₉₁O₁₉₁ in phosphorus ylide 4d . This compound crystallizes in the orthorhombic system, space group (Pca2₁), with unit cell parameters a = 17.3699(3) Å, b = 13.5500(2) Å, c = 18.4627(3) Å, α = 90°, β = 90°, γ = 90°, Z = 8, and V = 4345.4(12) ų. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:715–722, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20739     

NMR and X‐ray crystallographic studies of linear and cyclic aminomethanephosphinates

We report the preparation of four diastereoisomeric pairs of ethyl {[(3‐hydroxypropyl)‐ amino](aryl)methyl}phenylphosphinates. In two cases, the phosphinates were transformed to 1,4,2‐oxazaphosphepane heterocycles through one‐pot intramolecular esterification. The analogous reaction with formaldehyde gave the six‐membered ethyl (1,3‐oxazinan‐3‐ylmethyl)phenylphosphinate, which could be transformed in a posterior reaction to the corresponding aminomethanephosphinic acid. The new compounds were characterized by IR, ¹H, ¹³C, and ³¹P NMR. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:81–87, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20179     

Spectroscopic and X‐ray structural characterization of new polymeric organotin(IV) carboxylates and their in vitro antifungal activities: Part II

The reactions of R₃SnCl (R = Me, Bu or Ph) with sodium 4‐phenylbutyrate, Na(OPh^b), in EtOH yielded three polymeric triorganotin carboxylates, namely [R₃Sn(OPh^b)]_n (R = Me ( 1 ), Bu ( 2 ) or Ph ( 3 )). All complexes were spectroscopically characterized using Fourier transform infrared, ¹¹⁹Sn Mössbauer, ¹H NMR, ¹³C{¹H} NMR and ¹¹⁹Sn{¹H} NMR spectral techniques. In addition, the crystal structures of 1 and 3 were determined using single‐crystal X‐ray diffraction. Their polymeric structures are sustained by bridging carboxylates which connect two five‐coordinate Sn(IV) centres. Each metallic cation displays a distorted trigonal bipyramidal coordination geometry (Addison's parameters ranging from 0.84 in 1 to 0.77–0.91 in 3 ), with the oxygen atoms occupying the apical positions and the organic groups at the equatorial corners. The one‐dimensional zigzag chains of 1 propagate along the b ‐axis, whereas 3 displays wave‐like double polymeric chains along the b ‐axis. For both 1 and 3 , parallel one‐dimensional polymeric chains are interconnected by C─H⋅⋅⋅π interactions. The antifungal activity of 1 – 3 was screened against Candida albicans (ATCC 18804), C. tropicalis (ATCC 750), C. glabrata (ATCC 90030), C. parapsilosis (ATCC 22019), C. lusitaniae (CBS 6936) and C. dubliniensis (clinical isolate 28). The antifungal activity of 3 was noteworthy since it was not only more active than 1 and 2 , but also more active than the control drugs (nystatin and fluconazole nitrate) in some cases.     

Crystal‐Field and Covalency Effects in Uranates: An X‐ray Spectroscopic Study

The electronic structure of U^V‐ and U^VI‐containing uranates NaUO₃ and Pb₃UO₆ was studied by using an advanced technique, namely X‐ray absorption spectroscopy (XAS) in high‐energy‐resolution fluorescence‐detection (HERFD) mode. Due to a significant reduction in core–hole lifetime broadening, the crystal‐field splittings of the 5f shell were probed directly in HERFD‐XAS spectra collected at the U 3d edge, which is not possible by using conventional XAS. In addition, the charge‐transfer satellites that result from U 5f–O 2p hybridization were clearly resolved. The crystal‐field parameters, 5f occupancy, and degree of covalency of the chemical bonding in these uranates were estimated by using the Anderson impurity model by calculating the U 3d HERFD‐XAS, conventional XAS, core‐to‐core (U 4f–3d transitions) resonant inelastic X‐ray scattering (RIXS), and U 4f X‐ray photoelectron spectra. The crystal field was found to be strong in these systems and the 5f occupancy was determined to be 1.32 and 0.84 electrons in the ground state for NaUO₃ and Pb₃UO₆, respectively, which indicates a significant covalent character for these compounds.     

Uncertainty quantification in theoretical spectroscopy: The structural sensitivity of X‐ray emission spectra

We present a methodology for analyzing the dependence of molecular spectra calculated with quantum‐chemical methods on the underlying molecular structure. This analysis is applied to investigate the structural sensitivity of calculated valence‐to‐core X‐ray emission (VtC‐XES) spectra for the test case of three iron carbonyl complexes, Fe(CO)₅, [FeCp(CO)₂(THF)]⁺ (Cp = cyclopentadienyl, THF = tetrahydrofuran), and Fe(CO)₃(cod) (cod = cyclooctadienyl). Based on this analysis, we discuss how the VtC‐XES spectra depend on changes of metal–ligand bond distances and bond angles as well as on the structure of the ligands. The benefits of such an analysis of the structural sensitivity are discussed. Our methodology can serve as a first step toward quantifying and accounting for uncertainties due to the underlying model structure in theoretical spectroscopy.     

Synthesis,NMR spectroscopic and X‐ray crystallographic studies of functionalized 2‐aminopyrrolin‐4‐ones

An efficient method for the preparation of novel cyano derivatives of 4‐amino‐3‐hydroxybutenoic acids 4–8 and N‐substituted‐2‐aminopyrrolin‐4‐ones 9–18 is described; the structure of compound 13 has been elucidated with X‐ray analysis.     

X‐ray action on polymeric membrane surfaces: a chemical and morphological characterization

The surfaces of six polymeric membranes—two polysulphone membranes, two composite reverse‐osmosis polyamide/polysulphone membranes having polyamide as the active layer and two activated membranes containing di‐2‐ethylhexylphosphoric acid and di‐2‐ethylhexyldithiophosphoric acid as carriers, respectively—have been characterized before and after irradiation with an x‐ray source, both chemically and topographically by XPS and atomic force microscopy (AFM), respectively. Changes in atomic concentrations of the characteristic elements of the membranes and in the shape of XPS spectra as a function of irradiation time can be related to chemical modifications on the membrane surface. The most significant changes have been observed for polysulphone, which is reduced by x‐ray action; this fact also shows the inhomogeneity of the surface of the di‐2‐ethylhexyldithiophosphoric‐activated membrane. In contrast, polyamide top layers of composite membranes have been shown to be the most stable. Chemical modifications are not related directly to changes in membrane roughness because for all membranes only small changes have been observed for AFM images recorded before and after membrane irradiation. Moreover, the roughness of both polysulphone membranes decreases slightly due to x‐ray radiation but increases slightly for all polyamide‐containing membranes (composite and activated membranes). Copyright © 2003 John Wiley & Sons, Ltd.     

NMR and X‐ray structural studies on 3‐benzyl‐8‐bromoadenine

8‐Bromoadenine was benzylated in the presence of base to give a mixture of two regioisomers. One was easily recognized as 9‐benzyl‐8‐bromoadenine, but the other structure could not be determined with absolute certainty by NMR. Therefore, X‐ray crystallography was used to prove that the benzyl group was attached to N‐3. Furthermore, it is shown that the 3‐benzyl adenine derivative exists as the amine tautomer both in the crystalline state as well as in solution (DMSO‐d₆), with restricted rotation around the N⁶? C6 bond. J. Heterocyclic Chem., (2011).     

Powder X‐ray studies of meso‐hexamethyl propylene amine oxime (meso‐HMPAO) in two different phases

Two different forms of meso‐3,3′‐[2,2‐dimethylpropane‐1,3‐diylbis(azanediyl)]dibutan‐2‐one dioxime, commonly called meso‐hexamethyl propylene amine oxime (HMPAO), C₁₃H₂₈N₄O₂, designated α and β, were isolated by fractional crystallization and their crystal structures were determined by powder X‐ray diffraction using the direct‐space method with the parallel tempering algorithm. The α form was first crystallized from acetonitrile solution, while the β form was obtained by recrystallization of the α phase from diethyl ether. The α form crystallizes in the triclinic system (space group P), with one molecule in the asymmetric unit, while the crystal of the β form is monoclinic (space group P2₁/n), with one molecule in the asymmetric unit. In both phases, the molecules have similar conformations and RS/EE geometric isomerism. The crystal packing of the two phases is dominated by intermolecular hydrogen‐bonding interactions between the two O—H oxime groups of an individual molecule and the amine N atoms of two different adjacent molecules, which lead to segregation of extended poly(meso‐HMPAO) one‐dimensional chains along the c direction. The structures of the two phases are primarily different due to the different orientations of the molecules in the chains.     

X‐ray crystallographic analysis and differential scanning calorimetry of two polymorphic forms of 2,6‐diphenyl‐1,4‐dithiin

2,6‐Diphenyl‐1,4‐dithiin 2 exists in the two polymorphic forms. The dithiin 2L , mp 62–63°C, was assigned as the metastable form, while the dithiin 2H , mp 79–80°C, was assigned as the stable form, mainly on the basis of differential scanning calorimetry (DSC) analysis. X‐Ray crystallographic analysis showed that the largest difference in the molecular structure between 2L and 2H is found in the coplanarity between the benzene ring and the double bond part of the dithiin ring; the benzene ring and the double bond are nearly coplanar for 2L , whereas these are far from being coplanar for 2H . © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:424–427, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20035     

Solid‐state 11B and 13C NMR,IR, and X‐ray crystallographic characterization of selected arylboronic acids and their catechol cyclic esters

Nine arylboronic acids, seven arylboronic catechol cyclic esters, and two trimeric arylboronic anhydrides (boroxines) are investigated using ¹¹B solid‐state NMR spectroscopy at three different magnetic field strengths (9.4, 11.7, and 21.1 T). Through the analysis of spectra of static and magic‐angle spinning samples, the ¹¹B electric field gradient and chemical shift tensors are determined. The effects of relaxation anisotropy and nutation field strength on the ¹¹B NMR line shapes are investigated. Infrared spectroscopy was also used to help identify peaks in the NMR spectra as being due to the anhydride form in some of the arylboronic acid samples. Seven new X‐ray crystallographic structures are reported. Calculations of the ¹¹B NMR parameters are performed using cluster model and periodic gauge‐including projector‐augmented wave (GIPAW) density functional theory (DFT) approaches, and the results are compared with the experimental values. Carbon‐13 solid‐state NMR experiments and spectral simulations are applied to determine the chemical shifts of the ipso carbons of the samples. One bond indirect ¹³C‐¹¹B spin‐spin (J) coupling constants are also measured experimentally and compared with calculated values. The ¹¹B/¹⁰B isotope effect on the ¹³C chemical shift of the ipso carbons of arylboronic acids and their catechol esters, as well as residual dipolar coupling, is discussed. Overall, this combined X‐ray, NMR, IR, and computational study provides valuable new insights into the relationship between NMR parameters and the structure of boronic acids and esters. Copyright © 2012 John Wiley & Sons, Ltd.     

Metal‐based isatin‐bearing sulfonamides: their synthesis,characterization and biological properties

A new series of antibacterial and antifungal isatin bearing sulfonamides and their cobalt (II), copper (II), nickel (II) and zinc (II) metal complexes have been synthesized, characterized and screened for their in vitro antibacterial activity against Bacillus cereus, Corynebacterium diphtheriae, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi, Shigilla dysentriae and Staphylococcus aureus and for in vitro antifungal activity against Trichophyton schoenleinii, Candid glabrata, Pseudallescheria boydii, Candida albicans, Aspergillus niger, Microsporum canis and Trichophyton mentagrophytes. The results of these studies revealed that all compounds showed moderate to significant antibacterial activity. The brine shrimp bioassay was also carried out to study their in vitro cytotoxic properties. Only three compounds, 2, 11 and 22 displayed potent cytotoxic activity as LD₅₀ = 1.56 × 10^?7, 1.59 × 10^?7 and 1.67 × 10^?7 M /ml respectively, against Artemia salina. Copyright © 2006 John Wiley & Sons, Ltd.     

A new synthetic route to cyclophosphadithiatriazenes: synthesis and X‐ray structural characterization of the first spirocycle containing thiadiazaphosphetidine and phosphadithiatriazene heterocycles

The phosphetidine 2,4‐Di‐tert‐butyl‐3‐chloro‐1λ⁶‐thia‐2,4‐diaza‐3‐phosphetidine‐1,1‐dioxide, O₂S (^tBuN)₂PCl, reacts with tetrasulfur tetranitride, S₄N₄, in benzene under reflux to afford the novel 4,6‐spirocycle in moderate yield. The deep‐blue crystals of the spirocycle are airstable and high melting in nature. The spiro phosphorus atom subtends a four‐membered P^VS^VIN₂ ring which is saturated, and a six‐membered P^VS N₃ ring which is unsaturated. The single‐crystal X‐ray structure of this first example of the spirocycle reveals a planar PSN₂ ring and a puckered PS₂N₃ ring and the molecule is symmetric in nature. Copyright © 2006 John Wiley & Sons, Ltd.     

X‐ray characterization and magnetic properties of dioxygen‐bridged CuII and MnIII Schiff base complexes

The coordination chemistry of multinuclear metal compounds is important because of their relevance to the multi‐metal active sites of various metalloproteins and metalloenzymes. Multinuclear Cu^II and Mn^III compounds are of interest due to their various properties in the fields of coordination chemistry, inorganic biochemistry, catalysis, and optical and magnetic materials. Oxygen‐bridged binuclear Mn^III complexes generally exhibit antiferromagnetic interactions and a few examples of ferromagnetic interactions have also been reported. Binuclear Cu^II complexes are important due to the fact that they provide examples of the simplest case of magnetic interaction involving only two unpaired electrons. Two novel dioxygen‐bridged copper(II) and manganese(III) Schiff base complexes, namely bis(μ‐4‐bromo‐2‐{[(3‐oxidopropyl)imino]methyl}phenolato)dicopper(II), [Cu₂(C₁₀H₁₀BrNO₂)₂], (1), and bis(diaqua{4,4′‐dichloro‐2,2′‐[(1,1‐dimethylethane‐1,2‐diyl)bis(nitrilomethanylylidene)]diphenolato}manganese(III)) bis{μ‐4,4′‐dichloro‐2,2′‐[(1,1‐dimethylethane‐1,2‐diyl)bis(nitrilomethanylylidene)]diphenolato}bis[aquamanganese(III)] tetrakis(perchlorate) ethanol disolvate, [Mn(C₁₈H₁₆Cl₂N₂O₂)(H₂O)₂]₂[Mn₂(C₁₈H₁₆Cl₂N₂O₂)₂(H₂O)₂](ClO₄)₄·2C₂H₅OH, (2), have been synthesized and single‐crystal X‐ray diffraction has been used to analyze their crystal structures. The structure analyses of (1) and (2) show that each Cu^II atom is four‐coordinated, with long weak Cu…O interactions of 2.8631 (13) Å linking the dinuclear halves of the centrosymmetric tetranucelar molecules, while each Mn^III atom is six‐coordinated. The shortest intra‐ and intermolecular nonbonding Mn…Mn separations are 3.3277 (16) and 5.1763 (19) Å for (2), while the Cu…Cu separations are 3.0237 (3) and 3.4846 (3) Å for (1). The magnetic susceptibilities of (1) and (2) in the solid state were measured in the temperature range 2–300 K and reveal the presence of antiferromagnetic spin‐exchange interactions between the transition metal ions.     

Synthesis,characterization and X‐ray shielding properties of polypyrrole/lead nanocomposites

Novel radiation shielding nanocomposites based on a conducting polymer were fabricated and investigated to determine their abilities in attenuation of X‐rays. Polypyrrole/Pb nanocomposites were prepared through chemical reduction of lead salt by a facile solution‐phase method using t‐BuOLi‐activated LiH and in situ chemical polymerization of pyrrole in the presence of dodecyl benzene sulfonic acid as dopant and surfactant and iron chloride as the oxidant. The morphology, composition, and electrical conductivity of resulting products were characterized by scanning electron microscopy, transmission electron microscopy, X‐ray diffraction analysis, energy‐dispersive X‐ray spectroscopy, fourier transform infrared spectroscopy, and standard four‐wire technique, respectively. In order to evaluate capability of nanocomposites in radiation shielding, X‐ray photon interaction parameters such as linear attenuation coefficient, attenuation percentage, and half‐value thickness were determined for the samples with different Pb loadings and thicknesses, at photon energies of 13.95, 17.74, 20.08, 26.34, and 59.50 keV. The investigation was carried out to explore the potential of polypyrrole/Pb nanocomposites as thin and light‐weight radiation shielding materials. Copyright © 2015 John Wiley & Sons, Ltd.     

Interface characterization of a metal‐oxide‐semiconductor structure by biased X‐ray photoelectron spectroscopy

X‐ray photoelectron spectroscopy (XPS) measurements of a Pt/HfO₂(SiO₂)/Si metal‐oxide‐semiconductor (MOS) structure under a bias voltage applied between the gate metal and the silicon substrate were studied. The binding energy shifts of Pt 4f, Hf 4f, O 1s and Si 2p according to the applied voltage were investigated using the MOS structure. After the influence of measurements on the results was carefully examined under various conditions, the amount of the shifts was analyzed from a viewpoint of band alignment. Based on the experimental results, a new way of interpreting the deviation of the electric properties from the ideal ones in a band diagram was proposed. It was demonstrated that the biased XPS is a very powerful method to understand the origin of the electric properties of MOS. Copyright © 2010 John Wiley & Sons, Ltd.     

anti‐2‐Hydr­oxy‐2‐methyl‐1‐tetra­lone oxime: X‐ray and density functional theory study

Crystals of the title racemic compound, C₁₁H₁₃NO₂, consist of two types of mol­ecules (conformers); one mol­ecule has an exocyclic OH group in an equatorial position and the other has this group in an axial position. Consequently, the hydrogen‐bond schemes for the two mol­ecules are different. The mol­ecules with equatorial OH groups create infinite parallel chains (formed by the same enantio­mer), connected by centrosymmetric dimers of mol­ecules (of mixed enantio­mers), both with axial OH groups. Possible inter­conversion of the conformers and the flexibility of the mol­ecule were studied by means of different MP2 and density functional theory (DFT) methods. The optimization of the structure by the DFT method confirmed the types of the hydrogen bonds.