45 research outputs found

    Streamlining collection of training samples for object detection and classification in video

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    Synthesis, structural analysis, electrochemical and magnetic properties of tetrachloroferrate ionic liquids

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    Eight ionic liquids have been synthesized with the tetrachloroferrate anion and varying cations with the general formula of [RA]+[FeCl4]− (R = –CH3, –CH2C6H5; A = pyridine, benzimidazole, trimethylamine, triphenylphosphine). They were characterized using spectroscopic techniques such as FT-IR, ESI-MS, Raman, and AAS along with single-crystal XRD to validate their structural motifs. The ionic conductivity, electrochemical and magnetic properties were determined to assess their possible uses in synthesis, separation, magnetic and transportation technologies, and high-energy capacitors. The diffusion coefficient value for these compounds was calculated to be around 7.55 × 10−8 cm2 s−1 and the heterogeneous rate constant value is about 3.60 × 10−3 cm s−1, which quantitatively complemented not only quasi reversibility but also moderately fast electron transfer processes. The effective magnetic moment values for the ionic liquids were determined to be similar to that expected from the spin-only approximation

    Mechanochemical reactivity inhibited, prohibited and reversed by liquid additives: examples from crystal-form screens

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    We demonstrate that liquid additives can exert inhibitive or prohibitive effects on the mechanochemical formation of multi-component molecular crystals, and report that certain additives unexpectedly prompt the dismantling of such solids into physical mixtures of their constituents. Computational methods were employed in an attempt to identify possible reasons for these previously unrecognised effects of liquid additives on mechanochemical transformations

    Doubly Encapsulated Perylene Diimides: Effect of Molecular Encapsulation on Photophysical Properties

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    Intermolecular interactions play a fundamental role on the performance of conjugated materials in organic electronic devices, as they heavily influence their optoelectronic properties. Synthetic control over the solid state properties of organic optoelectronic materials is crucial to access real life applications. Perylene diimides (PDIs) are one of the most highly studied classes of organic fluorescent dyes. In the solid state, π–π stacking suppresses their emission, limiting their use in a variety of applications. Here, we report the synthesis of a novel PDI dye that is encapsulated by four alkylene straps. X-ray crystallography indicates that intermolecular π–π stacking is completely suppressed in the crystalline state. This is further validated by the photophysical properties of the dye in both solution and solid state and supported by theoretical calculations. However, we find that the introduction of the encapsulating “arms” results in the creation of charge-transfer states which modify the excited state properties. This article demonstrates that molecular encapsulation can be used as a powerful tool to tune intermolecular interactions and thereby gain an extra level of control over the solid state properties of organic optoelectronic materials

    Silver-Free Palladium-Catalyzed C(sp3)-H Arylation of Saturated Bicyclic Amine Scaffolds

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    Herein, we report a silver-free Pd(II)-catalyzed C(sp3)-H arylation of saturated bicyclic and tricyclic amine scaffolds. The reaction provides good yields using a range of aryl iodides and aryl bromides including functionalized examples bearing aldehydes, ketones, esters, free phenols, and heterocycles. The methodology has been applied to medicinally relevant scaffolds. Two of the intermediate palladium complexes in the catalytic cycle have been prepared and characterized, and a mechanism is proposed. Removal of the directing group proceeded with good yield under relatively mild conditions

    4d-inner-shell ionization of Xe+ ions and subsequent Auger decay

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    We have studied Xe+4d inner-shell photoionization in a direct experiment on Xe+ ions, merging an ion and a photon beam and detecting the ejected electrons with a cylindrical mirror analyzer. The measured 4d photoelectron spectrum is compared to the 4d core valence double ionization spectrum of the neutral Xe atom, obtained with a magnetic bottle spectrometer. This multicoincidence experiment gives access to the spectroscopy of the individual Xe2+4d−15p−1 states and to their respective Auger decays, which are found to present a strong selectivity. The experimental results are interpreted with the help of ab initio calculations.1\. Auflag

    Two-to-one Auger decay of a double L vacancy in argon

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    We have observed L223−M3 Auger decay in argon where a double vacancy is filled by two valence electrons and a single electron is ejected from the atom. A well-resolved spectrum of these two-to-one electron transitions is compared to the result of the second-order perturbation theory and its decay branching ratio is determined

    Auger shake-up assisted electron recapture

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    The presence of doubly excited states (DESs) above the core-hole ionization threshold nontrivially modulates the x-ray absorption because the participator Auger decay couples DESs to the underlying low-energy core-hole continuum. We show that coupling also affects the high-energy continuum populated by the spectator Auger decay of DESs. For the K−L223 Auger decay of the 1s−13p−14s21P state in argon, the competing nonresonant path is assigned to the recapture of the 1s photoelectron caused by emission of the fast electron from the shake-up K−L223 decay of the 1s−1 ion

    Potential Energy Surface Reconstruction and Lifetime Determination of Molecular Double-Core-Hole States in the Hard X-Ray Regime

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    A combination of resonant inelastic x-ray scattering and resonant Auger spectroscopy provides complementary information on the dynamic response of resonantly excited molecules. This is exemplified for CH3I, for which we reconstruct the potential energy surface of the dissociative I 3d−2 double- core-hole state and determine its lifetime. The proposed method holds a strong potential for monitoring the hard x-ray induced electron and nuclear dynamic response of core-excited molecules containing heavy elements, where ab initio calculations of potential energy surfaces and lifetimes remain challenging

    Highly Luminescent Encapsulated Narrow Bandgap Polymers Based on Diketopyrrolopyrrole

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    We present the synthesis and characterisation of a series of encap-sulated diketopyrrolopyrrole red-emitting conjugated polymers. The novel materials display extremely high fluorescence quantum yields in both solution (>70%) and thin film (>20%). Both the absorption and emission spectra show clearer, more defined features compared to their naked counterparts demonstrating the suppression of inter and intra-molecular aggregation. We find that the encapsulation results in decreased energetic disorder and a dramatic increase in backbone co-linearity as evidenced by STM. This study paves the way for DPP to be used in emissive solid state applications and demonstrates a novel method to reduce structural disorder in conju-gated polymers
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