meso-Aryl substituted rubyrin and its higher homologues: structural characterization and chemical properties

meso-Aryl substituted rubyrin ([26]hexaphyrin(1.1.0.1.1.0)) 2 and a series of rubyrin-type large expanded porphyrins were obtained from a facile one-pot oxidative coupling reaction of meso-pentafluorophenyl substituted tripyrrane 1. The structures of two of the resulting products were determined by single-crystal X-ray diffraction analysis. Whereas [52]dodecaphyrin(1.1.0.1.1.0.1.1.0.1.1.0) 4 takes a symmetric helical conformation, the larger species, [62]pentadecaphyrin(1.1.0.1.1.0.1.1.0.1.1.0.1.1.0) 5, adopts a nonsymmetric distorted conformation in the solid state that contains an intramolecular helical structure. The ability of rubyrin 2 to act as an anion receptor in its diprotonated form (2(.)2H(+)) was demonstrated in methanolic solutions. Oxidation of 2 with MnO(2) gave [24]rubyrin 6, a species that displays antiaromatic characteristics. [26]Rubyrin 2 and [24]rubyrin 6 both underwent metallation when reacted with Zn(OAc)(2) to give the corresponding bis-zinc(II) complexes 7 and 8 quantitatively without engendering a change in the oxidation state of the ligands. As a result, complexes 7 and 8 exhibit aromatic and antiaromatic character, respectively. NICS calculation on these compounds also supported aromaticity of 2 and 7, and antiaromaticity of 6 and 8.     

Zirconium(IV) fluorosulphates : Preparation and characterization

Zr(SO₃F)₄, (A); ZrO(SO₃F)₂, (B); Zr(O₂CCH₃)₂, (SO₃F)₂, (C); and Zr(O₂CCH₃)₃SO₃F, (D) have been prepared and characterized (elemental analysis,i.r. Spectra and thermal analysis). The SO₃F groups are bidentate in (A) – (C) but have C_3V symmetry in D where all the three oxygen atoms of SO₃F group are coordinated in an equivalent manner. (A) – (D) are good Lewis acids and form coordination complexes with pyridine, triphenylphosphine oxide and 2,2′-bipyridyl. The thermal decomposition of the fluorosulphates is complex.     

LaNiO2: Synthesis and structural characterization

The preparation of a single phase LaNiO₂ by controlled H₂ reduction of the perovskite LaNiO₃ is reported. The different steps of the synthesis are detailed. The structural characterization is made by X-ray diffraction (XRD) and neutron powder diffraction (NPD) and discussed; the derived crystal structure is the infinite-layer CaCuO₂. Both XRD and NPD patterns are characterized by anisotropic shape broadening originating from size effect linked to the reduction process. From NPD, the LaNiO₂ powder is composed of platelet-like crystallites having an average thickness equal to 20 nm along the [001] direction. A modulation of the neutron diffraction background is observed and discussed in connection to the reduction process.     

Mechanism of photoisomerization of 1-naphthyl-2-phenylethylenes in organic glasses

Photoisomerization reactions of cis isomers of 1-beta-naphthyl-2-phenylethylene, an o-methylated homolog and 1-alpha-naphthyl-2-phenylethylene in organic glasses at liquid nitrogen temperature were studied. Reactions were followed by changes in UV-absorption spectra of the irradiated samples. Formation of an unstable trans-photoproduct was detected only with the o-methylated homolog. The results are consistent with high regioselective Hula-twist photoisomerization at the benzylic sites of the three compounds examined. Calculated data on relative energies of the conformers of both the cis and the trans isomers are in agreement with the suspected conformational population of the starting materials and the photoproducts.     

Design and characterization of thermosetting polyimide structural adhesive and composite matrix systems

Fully cyclized, organo soluble, phenylethynyl-terminated, ether-imide oligomers of 2–10,000 g/mol (M_n) were prepared by the reaction of 2,2′-bis[4-(3,4-dicarboxyphenoxy)phenyl]-propane dianhydride (bisphenol-A dianhydride, BPADA) with a stoichiometric excess of either para, meta, or isomeric mixtures of phenylene diamine and phenylethynylphthalic anhydride (4-PEPA) endcapper. High para-containing oligomers produced semicrystalline powders, but the all meta isomer was completely amorphous. The lower molecular weight oligomers displayed an attractive low viscosity melt and were cured to very high gel content networks at 350–380°C for 30–90 min. The cured 3000 g/mol oligomers showed a (DSC) glass transition temperature (T_g) of 267°C and produced tough, solvent-resistant films. Excellent adhesion to surface-treated titanium alloys was achieved, as judged by single-lap shear measurements. Resin infusion molding was conducted, which permitted low-void, graphite-fabric composite panels to be prepared. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2943–2954, 1997     

Radiological,structural and chemical characterization of raw materials and ceramic tiles in Serbia

Journal of Radioanalytical and Nuclear Chemistry - This paper presents the results of the gamma spectrometric analysis of 27 raw materials used for the production of ceramic tiles in Serbia and 9...     

Optical waveguide techniques for structural and chemical analysis in thin film and interfacial systems

This review considers some of the problems with which analytical chemists interested in thin-film and interfacial structures must deal. It is advocated that the types of classical spectroscopies which have served so well for so long in the solution regime are not particularly well suited to attacking these problems and that entirely new approaches are required. One such approach uses the generation of resonant optical waveguide modes in thin-film structures as the basis for spectroscopic excitation. The details of the waveguiding process are discussed and the properties important for spectroscopic experiments emphasized. The power of the technique for generating qualitative spectroscopic information is demonstrated by considering some specific Raman and resonance Raman experiments, and the implementation of an optical depth profiling capability is discussed. Finally, some recent four-wave mixing experiments are detailed to demonstrate both the breadth of capabilities and the vitality of research in the area. It should be noted that several fairly extensive efforts have not been covered. Notable among these is the use of resonant optical modes for thin-film absorption spectroscopy in which active research is ongoing (D. A. Stephens and P. W. Bohn, unpublished results).     

1,5-二苯基-3-萘基-2-吡唑啉化合物光物理行为的研究

本工作对1,5-二苯基-3-萘基-2-吡唑啉化合物(TPP)的稳态,瞬态光物理行为进行了研究,结果表明:化合物TPP具有强的荧光发射特性和溶致变色效应;其荧光可以被电子给体或受体猝灭剂所猝灭;TPP/CCI~4体系以及TPP/N,N-二甲基-p- 甲基苯胺体系均是良好的光敏引发聚合体系.     

Vanadium-doped hafnia: elaboration and structural characterization

Powders of HfO₂ doped with various amounts of vanadium were prepared by pyrolysis of oxalic precursors at relatively low temperature (700 °C). This pyrolysis was carried out under different atmospheres in order to insert vanadium under different oxidation states into hafnia. The various amounts of inserted vanadium into HfO₂ were determined by energy dispersive spectroscopy. The powders were structurally characterized by X-ray diffraction, and electron diffraction. Nano particles of monoclinic HfO₂ were obtained when incorporating V⁵⁺. The solubility limit in that case was found to be less than 10 at %. The insertion of vanadium with a lower oxidation state than 5+ led to the stabilization of the cubic phase, with a solubility limit higher than 30 % at.     

N-2-hydroxy-4-methoxyacetophenone-N'-4-nitrobenzoyl hydrazine: synthesis and structural characterization

A new aroyl hydrazone, N-2-hydroxy-4-methoxyacetophenone-N'-4-nitrobenzoyl hydrazine was prepared by the condensation reaction of 2-hydroxy-4-methoxyacetophenone and 4-nitrobenzoyl hydrazine. Characterization of the compound was done by elemental analysis and electronic, infrared and NMR spectral analyses. The complete structural assignment of the compound was done by NMR studies by using COSY homonuclear and HSQC heteronuclear techniques. The crystal and molecular structure was determined by single crystal X-ray diffraction studies: crystallized in the monoclinic system, space group P2(1)/n, Z=4, a=7.3343(9)A, b=20.3517(9)A, c=10.1375(5)A, alpha=90.00 degrees, beta=95.735(7) degrees and gamma=90.00 degrees. From the crystal structure, it is concluded that the compound exists as the keto isomer in the solid state. There is a completely extended conformation in the central part of the molecule C5C8N1N2C10O2 with an E configuration at the double bond of the hydrazinic bridge.     

Diazo compounds of the heterocyclic series. 6. Amination of methoxy-substituted 2-naphthyl- and 2-arylazobenzimidazoles

The amination of azo compounds inactivated by quaternization was carried out for the first time using 4-methoxyphenyl-, 2- and 4-methoxynaphthylazobenzimidazoles as examples. In contrast to the quaternary salts of 2-arylazobenzimidazoles, during the amination of the above bases of azo compounds, the substitution of the methoxy group rather than of the hydrogen atom was observed. The anomalous ease of substitution of the methoxy group, located in the naphthalene ring in a position adjacent to the azo bridge was attributed to the manifestation of an ortho-effect, discovered in the series of azo compounds for the first time.For Communication 5, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1209–1214, September, 1991.     

Synthesis and structural characterization of endohedral pyrrolidinodimetallofullerene: La2@C80(CH2)2NTrt

The endohedral pyrrolidinodimetallofullerene, La2@C80(CH2)2NTrt (Trt = triphenylmethyl), was successfully synthesized and characterized. X-ray crystallographic and NMR spectroscopic analyses reveal that two La atoms in the 6,6-adduct are localized at the stable site on the mirror plane. Theoretical calculation also suggests the localization of two La atoms in the 6,6-adduct.     

Electronic structural characterization of cycloheptadienequinone and cyclopentenequinone systems having an electron donating diaminocyclopropenylidene moitey

7, 8-Bis(di-isopropylamino)heptatriafulvalene-1, 6-quinone and 5, 6-bis(di-isopropylamino)calicene-1, 4-quinone have been synthesized and an essential electronic structural difference between them originated from the contribution of pseudo 6π and pseudo 4π electron delocalizations to the 7- and 5-membered rings, respectively, has been clarified.     

Synthesis and structural characterization of novel 2-benzimidazolylthioureas: adducts of natural isothiocyanates and 2-amino-1-methylbenzimidazole

Adducts of natural allyl, phenethyl, and benzyl isothiocyanates and 2-amino-1-methylbenzimidazole were synthesized. After optimization of the reaction conditions, the target 2-benzimidazolylthioureas were obtained in reasonable yields. The detailed molecular and crystal structures of these compounds were characterized by spectroscopic and X-ray methods. Spectral analysis demonstrated that N-(1-methylbenzimidazolyl)-N′-allylthiourea, N-(1-methylbenzimidazolyl)-N′-benzylthiourea, and N-(1-methylbenzimidazolyl)-N′-phenethylthiourea exist in solution in an unprecedented three tautomeric forms, whose structures were corroborated unambiguously.