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Zero- and one-dimensional metal carboxylates are shown to transform into higher-dimensional structures (see figure), thereby indicating the presence of a progressive building-up process.
XPS studies of the interaction of carbon monoxide with surfaces of Fe, Co and Ni indicate that at 300 K, the disproportionation reaction is prominent up to exposures of 103 L giving rise to high surface concentrations of carbon. At higher exposures and higher temperatures, dissociation of carbon monoxide accompanied by the formation of surface oxide layers becomes more prominent. In the case of copper, disproportionation is prominent up to 104 L even at 500 K followed by dissociation at higher exposures. These results are also supported by Auger spectroscopic studies.
Two open-framework neodymium oxalates, [NH(3)CH(2)CH(NH(3))CH(3)][Nd(C(2)O(4))(2)(HCOO)].H(2)O (I) and [OC(CH(3))NCH(2)CH(CH(3))NH(3)][Nd(C(2)O(4))(2)].H(2)O (II), have been synthesized hydrothermally in the presence of 1,2-diaminopropane (1,2-DAP) and formic (I) and acetic (II) acids. The Nd atoms in both these oxalates have 9-fold coordination with respect to the oxygens, with the Nd atom in a distorted monocapped square antiprism coordination in I and in an idealized D(3)(h) triply capped trigonal prism coordination in II. The three-dimensional framework structures of I and II are built up by in-plane linkages between the Nd and the oxalate moieties, forming layers with 12-membered honeycomb-like apertures, pillared by an out-of-plane oxalate unit. The 12-memberd channel in I contains a dangling formate group in addition to the disordered amine molecule, while in II, the channel has N-(2-aminopropyl acetimide) molecules formed by the in situ reaction of 1,2-DAP and acetic acid. The accessibility of the formate and N-(2-aminopropyl acetimide) functional groups in I and II, respectively, uniformly distributed within the channels enables chemical manipulation. Crystal data: I, monoclinic, space group P2(1)/c (no. 14), M = 459.5, a = 9.0279(4) A, b = 18.1362(8) A, c = 8.5631(4) A, beta = 102.735(10) degrees, V = 1367.56(11) A(3), Z = 4, R(1) = 0.0229, wR(2) = 0.0599 [1782 observed reflections with I > 2sigma(I)]; II, triclinic, space group P(-)1 (no. 2), M = 454.5, a = 8.6222(9) A, b = 9.5683(10) A, c = 9.5712(10) A, alpha = 109.388(2) degrees, beta = 98.508(10) degrees, gamma = 102.361(12) degrees, V = 706.73(13) A(3), Z = 2, R(1) = 0.0446, wR(2) = 0.115 [1730 observed reflections with I > 2sigma(I)].
An organically templated iron(II) sulfate of the composition [H3N(CH2)2NH2(CH2)2(NH3]4[Fe(II)9F18(SO4)6].9H2O with a distorted Kagome structure has been synthesized under solvothermal conditions in the presence of diethylenetriamine. The distortion of the hexagonal bronze structure comes from the presence of two different types of connectivity between the FeF4O2 octahedra and the sulfate tetrahedra. This compound exhibits magnetic properties different from those of an Fe(II) compound with a perfect Kagome structure and is a canted antiferromagnet at low temperatures.
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Abstract Infrared spectra of La2−xSrxCuO4 and YBa2Cu3O7−δ are discussed, specially with respect to the disappearance of the high-frequency (∼650 cm) band of the superconducting compositions at 300K. Some of the bands persist at 300K eventhough the materials are fairly conducting. YBa2Cu3O7−δ does not show evidence in the far IR spectrum for the presence of an optical gap.
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Although it is customary to substitute cations in metal oxides, sulfides, and other materials to modify their structure and properties, effects of anion substitution have not been investigated sufficiently. This is particularly true of materials cosubstituted by two anions (such as N3– and F– in place of O2– or P3– and Cl– in place of S2–). Substitution of a trivalent anion along with a monovalent anion helps to eliminate defects, the three anions being isoelectronic and of nearly the same size. Furthermore, such aliovalent anion substitution gives rise to marked changes in the electronic structure and properties. Isovalent anion substitution (e.g., S2– in place of O2– or Se2– in place of S2–) does not bring about such changes. In this Perspective, we examine the electronic structures and properties of several oxides involving cosubstitution of N and F for oxygen. The oxides discussed are TiO2, ZnO, Cr2O3, and BaTiO3. Aliovalent anion substitution decreases the band gaps of the oxides and affect the magnetic and ferroelectric transitions. Sulfides such as CdS and ZnS where sulfur is substituted by P and Cl also show a large decrease in band gaps. Unlike in cation substitution where the conduction band is mainly affected, in the aliovalent anion-substituted materials the p-states of the trivalent anions (N3– and P3–) dominate the top of the valence band, with the metal-trivalent anion (N, P) bond being shorter and the metal–halogen bond longer. Such materials with high visible absorption extending to long wavelengths may indeed find uses.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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Formation of fibril-type nanostructures of the Alzheimer's β-amyloid diphenylalanine (l-Phe-l-Phe, FF) at the organic−aqueous interface and the factors affecting their structures have been investigated. Such nanostructures are also formed by bovine serum albumin and bovine pancreas insulin. The concentration of the precursor taken in the aqueous layer plays an important role in determining the morphology of the nanostructures. The addition of curcumin to the organic layer changes the structure of the self-assembled one-dimensional aggregates of diphenylalanine. By coating the diphenylalanine dipeptide fibrils with appropriate precursors followed by calcination in air, it has been possible to obtain one-dimensional nanostructures of inorganic materials.
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The temperature dependence of the N(1s) spectrum of N2 adsorbed on a polycrystalline Ni surface suggests the presence of two species. N2 adsorbed on Ba- or Al-promoted Ni is more strongly bound to the surface as evidenced by the decrease in the intensity of the N(1s) signal due to the unscreened final state relative to the screened final state as well as an increased separation between the 5σ and 4σ levels; intra-molecular bonding on promoted surfaces is weaker as also found by EELS studies. Electron-withdrawing modifiers, on the other hand, decrease the strength of the metal-nitrogen bonding.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTImproved Method for the Synthesis of Alkyl Azides1EUGENE LIEBER, TAI SIANG CHAO, and C. N. RAMACHANDRA RAOCite this: J. Org. Chem. 1957, 22, 3, 238–240Publication Date (Print):March 1, 1957Publication History Published online1 May 2002Published inissue 1 March 1957https://pubs.acs.org/doi/10.1021/jo01354a003https://doi.org/10.1021/jo01354a003research-articleACS PublicationsRequest reuse permissionsArticle Views1073Altmetric-Citations41LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Semiconductor-Metal transitions in Ti2O3, VO2, V2O3 and Ti3O5 have been investigated employing X-ray and UV Photoelectron spectroscopy. The transitions are accompanied by significant changes in the 3d band of the transition metals as well as some of the core levels.
