80 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
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
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
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
4d-inner-shell ionization of Xe+ ions and subsequent Auger decay
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
Silver-Free Palladium-Catalyzed C(sp3)-H Arylation of Saturated Bicyclic Amine Scaffolds
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
Two-to-one Auger decay of a double L vacancy in argon
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
Aza-Cibalackrot: Turning on Singlet Fission Through Crystal Engineering
Singlet fission is a photophysical process that provides a pathway for more efficient harvesting of solar energy in photovoltaic devices. The design of singlet fission candidates is non-trivial and requires careful optimization of two key criteria: (1) correct energetic alignment and (2) appropriate intermolecular coupling. Meanwhile, this optimization must not come at the cost of molecular stability or feasibility for device applications. Cibalackrot is a historic and stable organic dye which, although it has been suggested to have ideal energetics, does not undergo singlet fission due to large interchromophore distances, as suggested by single crystal analysis. Thus, while the energetic alignment is satisfactory, the molecule does not have the desired intermolecular coupling. Herein, we improve this characteristic through molecular engineering with the first synthesis of an aza-cibalackrot and show, using ultrafast transient spectroscopy, that singlet fission is successfully "turned on.
Potential Energy Surface Reconstruction and Lifetime Determination of Molecular Double-Core-Hole States in the Hard X-Ray Regime
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
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