171 research outputs found

    Quantum Perturbation Theory in Fluid Mixtures

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    Use of dialkyldithiocarbamato complexes of bismuth(III) for the preparation of nano- and microsized Bi2S3 particles and the X-ray crystal structures of [Bi{S2CN(CH3)(C6H13)}(3)] and [Bi{S2CN(CH3)(C6H13)}(3)(C12H8N2)]

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    A range of bismuth(III) dithiocarbamato complexes were prepared and characterized. The X-ray crystal structures of the compounds [Bi{S2CN(CH3)(C6H13)}3] (1) and [Bi{S2CN(CH3)- (C6H13)}3(C12H8N2)] (2) are reported. The preparation of Bi2S3 particulates using a wet chemical method and involving the thermalysis of Bi(III) dialkyldithiocarbamato complexes is described. The influence of several experimental parameters on the optical and morphological properties of the Bi2S3 powders was investigated. Nanosized Bi2S3 colloids were obtained having long-term stability and showing a blue shift on the optical band edge; the presence of particles exhibiting quantum size effects is discussed. Morphological welldefined Bi2S3 particles were obtained in which the fiber-type morphology is prevalent.FCT - POCTI/1999/CTM/ 3545

    Quenching of Er(III) luminescence by ligand C-H vibrations: Implications for the use of erbium complexes in telecommunications

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    Copyright 2006 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Applied Physics Letters 89, 111115 (2006) and may be found at

    Near IR luminescent rare earth 3,4,5,6-tetrafluoro-2-nitrophenoxide complexes: Synthesis, X-ray crystallography and spectroscopy

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    NOTICE: this is the author’s version of a work that was accepted for publication in Near IR luminescent rare earth 3,4,5,6-tetrafluoro-2-nitrophenoxide complexes: Synthesis, X-ray crystallography and spectroscopy. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Near IR luminescent rare earth 3,4,5,6-tetrafluoro-2-nitrophenoxide complexes: Synthesis, X-ray crystallography and spectroscopy, [VOL27, ISSUE5, (2008)] DOI: 10.1016/j.poly.2008.01.02

    Catalytic and mechanistic studies into the epoxidation of styrenes using manganese complexes of structurally similar polyamine ligands

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    The synthesis and catalytic activity of manganese(ii) complexes of two polyamine ligands is reported which highlights how a small structural change in the ligand affects the overall catalytic behaviour.</p

    (S)-1-Methyl-2-oxoimidazolidine-4-carboxylic Acid

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    first_pagesettingsOrder Article Reprints Open AccessShort Note (S)-1-Methyl-2-oxoimidazolidine-4-carboxylic Acid by Ashley L. Dey,Majid Motevalli,Isaac Abrahams andPeter B. Wyatt *ORCID Department of Chemistry, Joseph Priestley Building, Queen Mary University of London, Mile End Road, London E1 4NS, UK * Author to whom correspondence should be addressed. Molbank 2024, 2024(2), M1835; https://doi.org/10.3390/M1835 Submission received: 25 May 2024 / Accepted: 8 June 2024 / Published: 12 June 2024 Downloadkeyboard_arrow_down Browse Figures Versions Notes Abstract (S)-1-Methyl-2-oxoimidazolidine-4-carboxylic acid 1 is an analog of (S)-pyroglutamic acid, a key component of naturally occurring peptide hormones and synthetic pharmaceutical candidates. The reaction of (S)-2-amino-3-(methylamino)propionic acid with COCl2 and aqueous NaHCO3 followed by ion exchange afforded 1, which was recrystallized from acetonitrile and then characterized by IR, 1H NMR, 13C NMR, polarimetry, elemental microanalysis, high-resolution mass spectrometry and single-crystal X-ray diffraction. The acid 1 crystallized in the orthorhombic chiral space group P212121 with cell constants a = 6.2275(4) Ã…, b = 8.3963(5) Ã…, c = 24.9490(14) Ã…. The X-ray crystal structure revealed that two distinct conformers of 1 occur at alternating positions within helices which are supported by hydrogen bonds. Each molecule of 1 is linked to its two neighbors in the helix by a total of three hydrogen bonds, and four molecules of 1 are contained within each turn of the helix. The pattern of hydrogen bonds illustrates a preference for the carboxylic acid group to act as a hydrogen bond donor and for the urea unit to be a hydrogen bond acceptor

    A Closed Form Solution for Nonlinear Oscillators Frequencies Using Amplitude-Frequency Formulation

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    Many nonlinear systems in industry including oscillators can be simulated as a mass-spring system. In reality, all kinds of oscillators are nonlinear due to the nonlinear nature of springs. Due to this nonlinearity, most of the studies on oscillation systems are numerically carried out while an analytical approach with a closed form expression for system response would be very useful in different applications. Some analytical techniques have been presented in the literature for the solution of strong nonlinear oscillators as well as approximate and numerical solutions. In this paper, Amplitude-Frequency Formulation (AFF) approach is applied to analyze some periodic problems arising in classical dynamics. Results are compared with another approximate analytical technique called Energy Balance Method developed by the authors (EBM) and also numerical solutions. Close agreement of the obtained results reveal the accuracy of the employed method for several practical problems in engineering
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