Search results for "HALO"
showing 10 items of 2623 documents
Halogen Bonds in Square Planar 2,5-Dihalopyridine-Copper(II) Bromide Complexes
2018
Halogen bonding in self-complementary 1:2 metal–ligand complexes obtained from copper(II) bromide (CuBr2) and seven 2,5-dihalopyridines were analyzed using single-crystal X-ray diffraction. All presented discrete complexes form 1D polymeric chains connected with C–X···Br–Cu halogen bonds (XB). In (2-chloro-5-X-pyridine)2·CuBr2 (X = Cl, Br, and I) only the C5-halogen and in (2-bromo-5-X-pyridine)2·CuBr2 (X = Cl, Br, and I) both C2- and C5-halogens form C–X···Br–Cu halogen bonds with the X acting as the XB donor and copper-coordinated bromide as the XB acceptor. The electron-withdrawing C2-chloride in (2-chloro-5-X-pyridine)2·CuBr2 complexes has only a minor effect on the C5–X5···Br–Cu XBs, a…
One Dimensional Convolutional Neural Networks for Seizure Onset Detection Using Long-term Scalp and Intracranial EEG
2021
Epileptic seizure detection using scalp electroencephalogram (sEEG) and intracranial electroencephalogram (iEEG) has attracted widespread attention in recent two decades. The accurate and rapid detection of seizures not only reflects the efficiency of the algorithm, but also greatly reduces the burden of manual detection during long-term electroencephalogram (EEG) recording. In this work, a stacked one-dimensional convolutional neural network (1D-CNN) model combined with a random selection and data augmentation (RS-DA) strategy is proposed for seizure onset detection. Firstly, we segmented the long-term EEG signals using 2-sec sliding windows. Then, the 2-sec interictal and ictal segments w…
Thiourea Based Tritopic Halogen Bonding Acceptors
2023
Series of thiourea based tritopic receptor molecules were synthesized to be used as building blocks for halogen-bonded assemblies. Here 16 new receptor molecules were synthesized from two different 2,4,6-trialkyl-1,3,5-tris(bromomethyl)benzene starting materials via tris(isothiocyanatomethyl)benzene intermediates. The alkyl substituents in the benzene ring showed to be important for isothiocyanate group formation instead of competing thiocyanate group. The synthesis route allowed us to synthesize the isothiocyanate intermediates and further the receptor molecules without typically used and highly toxic thiophosgene. Synthesized receptor molecules were used to study their halogen bond accept…
Solid‐state NMR Spectroscopy of Iodine(I) Complexes
2023
Solid-state NMR has been applied to a series of Barluenga-type iodine(I) [L-I-L]PF6 (L=pyridine, 4-ethylpyridine, 4-dimethylaminopyridine, isoquinoline) complexes as their hexafluorophosphate salts, as well as their respective non-liquid ligands (L), their precursor silver(I) complexes, and the respective N-methylated pyridinium and quinolinium hexafluorophoshate salts. These results are compared and contrasted to the corresponding solution studies and single-crystal X-ray structures. As the first study of its kind on the solid-state NMR behavior of halogen(I) complexes, practical considerations are also discussed to encourage wider utilization of this technique in the future. peerReviewed
Carbonyl hypoiodites from pivalic and trimesic acid and their silver(I) intermediates
2022
The first tris(O–I–N) carbonyl hypoiodites have been synthesised based on trimesic acid and pyridine or 4-methylpyridine, with their structures definitively confirmed by single crystal X-ray diffraction (SCXRD). The more soluble carbonyl hypoiodites based on pivalic acid have also been studied via NMR, SCXRD, and computational analyses, enabling the study of the direct silver(I) precursor and intermediates of the resulting carbonyl hypoiodites generated using a range of substituted pyridines. peerReviewed
Halogen-Bonded [N–I–N]− Complexes with Symmetric or Asymmetric Three-Center–Four-Electron Bonds
2023
A series of LH[Z–I–Z] halogen(I) complexes, where Z = saccharinato or phthalimido anions and LH = pyridinium, pyrazinium, tetrabutyl (TBA)- or tetramethylammonium (TMA) cations, were prepared, structurally characterized, and discussed as complexes consisting of a [N–I–N]− anion with a three-center–four-electron (3c-4e) halogen bond, and a hydrogen-bonding (pyridinium or pyrazinium) or inert (TBA or TMA) cation. The symmetric [N–I–N]− anion, reminiscent of the triiodide [I–I–I]− anion, is found to be structurally equivalent to its cationic analogue [N–I–N]+ with N–I bond lengths of 2.26 Å. In contrast to the homoleptic [N–I–N]+ complexes, asymmetry of the N–I bond lengths (2.21 and 2.28 Å) w…
Macrocyclic complexes based on [N⋯I⋯N]+ halogen bonds
2021
New 1–2 nm macrocyclic iodine(I) complexes prepared VIA a simple ligand exchange reaction manifest rigid 0.5–1 nm cavities that bind the hexafluorophosphate anion in the gas phase. The size of the cavities and the electrostatic interactions with the iodine(I) cations influence the anion binding properties of these macrocyclic complexes. peerReviewed
Ligand exchange among iodine(I) complexes
2022
A detailed investigation of ligand exchange between iodine(I) ions in [N⋯I⋯N]+ halogen-bonded complexes is presented. Ligand exchange reactions were conducted to successfully confirm whether iodine(I) complex formation, via the classical [N⋯Ag⋯N]+ to [N⋯I⋯N]+ cation exchange reaction from their analogous Ag+ complexes, could be determined solely by using 1H NMR spectroscopy. In instances where the formation of the iodine(I) complex was unclear or in low yield by the traditional cation exchange reaction, a ligand exchange reaction was used to form the desired iodine(I) complexes in a quantitative manner. Mixing two homoleptic [N⋯I⋯N]+ iodine(I) complexes in 1 : 1 ratio was found to undergo a…
Halogen-Bonded Mono-, Di-, and Tritopic N-Alkyl-3-iodopyridinium Salts
2023
Halogen bonding interactions of 15 crystalline 3-iodopyridinium systems were investigated. These systems were derived from four N-alkylated 3-iodopyridinium salts prepared in this study. The experimental results in the solid state show that halogen bonding acts as a secondary intermolecular force in these charged systems but sustains the high directionality of interaction in the presence of other intermolecular forces. Halogen bonds donated by polytopic 3-iodopyridinium cations are also sufficient to enclose guest molecules inside the formed supramolecular cavities. The experimental data were supplemented by computational gas-phase and solid-state studies for selected halogen-bonded systems…
Iodine Clathrated : A Solid-State Analog of the Iodine-Starch Complex
2019
Co-crystallizing iodine with a simple dicationic salt (1,8- diammoniumoctane chloride) results in the clathration of the iodine (I2) molecules inside trigonal and hexagonal helical channels of the crystal lattice with 72 wt% overall I2 loading. The I2 inside the bigger trigonal channel forms a I-I•••I-I•••I-I halogen-bonded infinite helical chain, while the I2 in the smaller hexagonal channel is disordered. In both channels the I2 interaction with the channel wall happens through I-I•••Cl- halogen bonds. The helical channels in the crystal lattice are constructed via the strong charge-assisted H2N+ -H•••Cl- hydrogen bonds between the dications and the chloride anions. The structure shows a …