75 research outputs found
Direct observation of the Higgs amplitude mode in a two-dimensional quantum antiferromagnet near the quantum critical point
Spontaneous symmetry-breaking quantum phase transitions play an essential
role in condensed matter physics. The collective excitations in the
broken-symmetry phase near the quantum critical point can be characterized by
fluctuations of phase and amplitude of the order parameter. The phase
oscillations correspond to the massless NambuGoldstone modes whereas the
massive amplitude mode, analogous to the Higgs boson in particle physics, is
prone to decay into a pair of low-energy NambuGoldstone modes in low
dimensions. Especially, observation of a Higgs amplitude mode in two dimensions
is an outstanding experimental challenge. Here, using the inelastic neutron
scattering and applying the bond-operator theory, we directly and unambiguously
identify the Higgs amplitude mode in a two-dimensional S=1/2 quantum
antiferromagnet CHNCuBr near a quantum critical point in two
dimensions. Owing to an anisotropic energy gap, it kinematically prevents such
decay and the Higgs amplitude mode acquires an infinite lifetime.Comment: 12 pages, 4 figures in the main text+3 figures in Supplementary
Informatio
Bis(2,6-diamino-3,5-dibromopyridinium) hexabromidostannate(IV)
The asymmetric unit of the title compound, (C5H6Br2N3)2[SnBr6], contains one cation and one half-anion in which the Sn atom is located on a crystallographic centre of inversion and is in a quasi-octahedral geometry. The crystal structure is assembled via hydrogen-bonding interactions of two kinds, N(pyridine/amine)—H⋯Br—Sn, along with C—Br⋯Br—Sn interactions [3.4925 (19) Å]. The cations are involved in π–π stacking, which adds an extra supramolecularity as it presents a strong case of offset-face-to-face motifs [centroid–centroid distance = 3.577 (3) Å]. The intermolecular hydrogen bonds, short Br⋯Br interactions and π–π stacking result in the formation of a three-dimensional supramolecular architecture
Docking, synthesis, and anticancer assessment of novel quinoline-amidrazone hybrids
A group of new amidrazone compounds that include a quinoline component was produced through the reaction of hydrazonyl chloride, derived from 6-aminoquinoline, with appropriate secondary cyclic amines. The new compounds were confirmed through 1H-NMR, 13C-NMR, FTIR, and HRMS, and further verified by single-crystal X-ray diffraction. The antitumor potential of the synthesized compounds was tested against lung cancer (A549) and breast cancer (MCF-7) cell lines. Among the compounds, the ethyl carboxylate and o-hydroxy phenyl piperazine derivatives (10d and 10g) exhibited the strongest activity against both cell lines, with IC50 values of 43.1 and 59.1 μM for the lung and breast cancer cell lines, respectively. Moreover, the most potent compounds were subsequently docked into the c-Abl kinase binding site (PDB code: 1IEP) as a possible anticancer mechanism. In-silico ADMET study shows acceptable pharmacokinetic properties, and the toxicity profile for the most potent compounds is non-carcinogenic
Bis(2-bromopyridinium) hexachloridostannate(IV)
The asymmetric unit of the title compound, (C5H5BrN)2[SnCl6], contains one cation and one half-anion. The [SnCl6]2− anion is located on an inversion center and forms a quasi-regular octahedral arrangement. Hydrogen-bonding interactions of two kinds, viz. N—H⋯Cl—Sn and C—H⋯Cl—Sn, along with Cl⋯Br interactions [3.4393 (15) Å], connect the ions in the crystal structure into two-dimensional supramolecular arrays. These supramolecular arrays are arranged in layers approximately parallel to (110) built up from anions interacting with six symmetry-related surrounding cations
Metal Hydrides Form Halogen Bonds: Measurement of Energetics of Binding
The formation of halogen bonds from iodopentafluorobenzene and 1-iodoperfluorohexane to a series of bis(η5-cyclopentadienyl)metal hydrides (Cp2TaH3, 1; Cp2MH2, M = Mo, 2, M = W, 3; Cp2ReH, 4; Cp2Ta(H)CO, 5; Cp = η5-cyclopentadienyl) is demonstrated by 1H NMR spectroscopy. Interaction enthalpies and entropies for complex 1 with C6F5I and C6F13I are reported (ΔH° = −10.9 ± 0.4 and −11.8 ± 0.3 kJ/mol; ΔS° = −38 ± 2 and −34 ± 2 J/(mol·K), respectively) and found to be stronger than those for 1 with the hydrogen-bond donor indole (ΔH° = −7.3 ± 0.1 kJ/mol, ΔS° = −24 ± 1 J/(mol·K)). For the more reactive complexes 2–5, measurements are limited to determination of their low-temperature (212 K) association constants with C6F5I as 2.9 ± 0.2, 2.5 ± 0.1, <1.5, and 12.5 ± 0.3 M–1, respectively
trans-Dibromidobis(3-methylpyridine-κN)copper(II)
The asymmetric unit of the title compound, [CuBr2(C6H7N)2], contains one half-molecule, the whole molecule being generated by inversion through a center located at the CuII atom. The geometry around the CuII atom is square planar. Semicoordinate Cu...Br bonds [3.269 (1) Å] and nonclassical C—H...Br hydrogen bonds connect the molecules, forming chains running parallel to the a axis. These chains are further linked via additional C—H...Br hydrogen bonds into a three-dimensional network
4-(9H-Fluoren-9-yl)-4-methylmorpholin-4-ium bromide, C18H20BrNO
C18H20BrNO, orthorhombic, Pbca (No. 61), a = 8.4285(4) Å, b = 19.2055(9) Å, c = 19.7809(12) Å, Z = 8, V = 3202.0(3) Å3, Rgt(F) = 0.0427, wRref(F2) = 0.1025, T = 293(2) K
4-(4-Nitrobenzyl)pyridine
The title compound, C12H10N2O2, has a twisted conformation, with a dihedral angle between the planes of the pyridine and benzene rings of 78.4 (2)°. The nitro group is coplanar with the attached benzene ring within experimental error. The molecules form centrosymmetric dimers via Car—H...O interactions (H...O = 2.49 Å) and the dimers are π-stacked along the b axis [the separation between ring centroids is 3.788 (2) Å]
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