Search results for "Sido"
showing 10 items of 522 documents
Chemically Selective Imaging of Individual Bonds through Scanning Electron Energy-Loss Spectroscopy : Disulfide Bridges Linking Gold Nanoclusters
2020
As proof-of-principle of chemically selective, spatially resolved imaging of individual bonds, we carry out electron energy-loss spectroscopy in a scanning transmission electron microscopy instrument on atomically precise, thiolate-coated gold nanoclusters linked with 5,5′-bis(mercaptomethyl)-2,2′-bipyridine dithiol ligands. The images allow the identification of bridging disulfide bonds (R–S–S–R) between clusters, and X-ray photoelectron spectra support the finding. peerReviewed
Cooperative N–H bond activation by amido-Ge(ii) cations
2020
N-heterocyclic carbene (NHC) and tertiary phosphine-stabilized germylium-ylidene cations, [R(L)Ge:]+, featuring tethered amido substituents at R have been synthesized via halide abstraction. Characterization in the solid state by X-ray crystallography shows these systems to be monomeric, featuring a two-coordinate C,N- or P,N-ligated germanium atom. The presence of the strongly Lewis acidic cationic germanium centre and proximal amide function allows for facile cleavage of N–H bonds in 1,2-fashion: the products resulting from reactions with carbazole feature a tethered secondary amine donor bound to a three-coordinate carbazolyl-GeII centre. In each case, addition of the components of the N…
Influence of substituents in aromatic ring on the strength of halogen bonding in iodobenzene derivatives
2020
Halogen bonding properties of 3,4,5-triiodobenzoic acid (1, 2), 1,2,3-triiodobenzene (3), pentaiodobenzoic acid ethanol solvate (4), hexaiodobenzene (5a, 5b, 5c), 2,4-diiodoaniline (6), 4-iodoaniline (7), 2-iodoaniline (8), 2-iodophenol (9), 4-iodophenol (10), 3-iodophenol (11) and 2,4,6-triiodophenol (12) has been studied. The results suggested that substituents other than halogen in aromatic ring affect XB properties of iodine substituents in ortho-, meta- and para-positions. The effect depends on the electron-withdrawing/electron-donating properties of the substituent. Thus, electron-withdrawing substituents with negative mesomeric effect favor m-iodines to act as XB donors and o- and p-…
Tridentate C–I⋯O−–N+ halogen bonds
2017
The X-ray structures of the first co-crystals where the three oxygen lone pairs in N-oxides are fully utilized for tridentate C–I⋯O−–N+ halogen bonding with 1,ω-diiodoperfluoroalkanes are reported, studied computationally, and compared with the corresponding silver(I) N-oxide complexes. peerReviewed
Asymmetric [N–I–N]+ halonium complexes
2020
The first asymmetric halogen-bonded iodonium complexes [I(py)(4-DMAP)]PF6 (2c) and [I(py)(4-Etpy)]PF6 (2e) were prepared via [N-Ag-N]+ → [N-I-N]+ cation exchange of their analogous 2-coordinate silver complexes. The complexes were characterised by 1H and 1H-15N HMBC NMR spectroscopy, and single crystal X-ray crystallography. peerReviewed
A Novel Halogen Bond Acceptor : 1-(4-Pyridyl)-4-Thiopyridine (PTP) Zwitterion
2020
Sulfur is a widely used halogen bond (XB) acceptor, but only a limited number of neutral XB acceptors with bifurcated sp3-S sites have been reported. In this work a new bidentate XB acceptor, 1-(4-pyridyl)-4-thiopyridine (PTP), which combines sp3-S and sp2-N acceptor sites, is introduced. Three halogen bonded cocrystals were obtained by using 1,4-diiodobenzene (DIB), 1,4-diiodotetrafluorobenzene (DIFB), and iodopentafluorobenzene (IPFB) as XB donors and PTP as acceptor. The structures of the cocrystals showed some XB selectivity between the S and N donors in PTP. However, the limited contribution of XB to the overall molecular packing in these three cocrystals and the results from DSC measu…
Strong N−X···O−N Halogen Bonds: Comprehensive Study on N‐Halosaccharin Pyridine N‐oxide Complexes
2019
A detailed study of the strong N−X⋯−O−N+ (X = I, Br) halogen bonding interactions in solution and in the solid‐state reports 2×27 donor×acceptor complexes of N‐halosaccharins and pyridine N‐oxides (PyNO). Density Functional Theory (DFT) calculations were used to investigate the X···O halogen bond (XB) interaction energies in 54 complexes. The XB interaction energies were found to vary from –47.5 to –120.3 kJ mol–1, with the strongest N−I⋯−O−N+ XBs approaching those of 3‐center‐4‐electron [N–I–N]+ halogen‐bonded systems (∼160 kJ mol–1). Using a subset of 32 complexes, stabilized only through N−X···−O−N+ XB interactions, a simplified, computationally fast, electrostatic model to predict the X…
Hydrogen-atom and oxygen-atom transfer reactivities of iron(iv)-oxo complexes of quinoline-substituted pentadentate ligands
2022
A series of iron(II) complexes with the general formula [FeII(L2-Qn)(L)]n+ (n = 1, L = F−, Cl−; n = 2, L = NCMe, H2O) have been isolated and characterized. The X-ray crystallographic data reveals that metal–ligand bond distances vary with varying ligand field strengths of the sixth ligand. While the complexes with fluoride, chloride and water as axial ligand are high spin, the acetonitrile-coordinated complex is in a mixed spin state. The steric bulk of the quinoline moieties forces the axial ligands to deviate from the Fe–Naxial axis. A higher deviation/tilt is noted for the high spin complexes, while the acetonitrile coordinated complex displays least deviation. This deviation from linear…
Reversible O-H bond activation by an intramolecular frustrated Lewis pair
2019
The interactions of the O–H bonds in alcohols, water and phenol with dimethylxanthene-derived frustrated Lewis pairs (FLPs) have been probed. Within the constraints of this backbone framework, the preference for adduct formation or O–H bond cleavage to give the corresponding zwitterion is largely determined by pKa considerations. In the case of the PPh2/B(C6F5)2 system and p-tBuC6H4OH, an equilibrium is established between the two isomeric forms which allows the thermodynamic parameters associated with zwitterion formation via O–H bond cleavage to be probed. peerReviewed
Covalent and non-covalent coupling of a Au102 nanocluster with a fluorophore : energy transfer, quenching and intracellular pH sensing
2021
Interactions between an atomically precise gold nanocluster Au102(p-MBA)44 (p-MBA = para mercaptobenzoic acid) and a fluorescent organic dye molecule (KU, azadioxatriangulenium) are studied. In solution, the constituents form spontaneously a weakly bound complex leading to quenching of fluorescence of the KU dye via energy transfer. The KU can be separated from the complex by lowering pH, leading to recovery of fluorescence, which forms a basis for an optical reversible pH sensor. However, the sensor is not a stable entity, which could be delivered inside cells. For this purpose, a covalently bound hybrid is synthesized by linking the KU dye to the ligand layer of the cluster via an ester b…