224 research outputs found
Geminal System O-N-O: XRD Studies of Structure of Cyclic N,N-dialkoxyderivatives of Amines and Ureas
Pyramidal amide nitrogen in N-acyloxy-N-alkoxyureas and N-acyloxy-N-alkoxycarbamates
The XRD studies of N-acyloxy-N-alkoxyamides 1, 2 have revealed a highly pyramidal configuration of amide nitrogen in the O–N–O group
N,N-Dimethoxy-N-tert-alkylamines: new synthesis methods and the crystal structure of the precursor
Under the methanolysis of N-methoxy-N-(1-pyridinium)amines salts 1a–c, nucleophilic substitution occurs at the nitrogen atom to form N,N-dimethoxyamines 2a,b; the crystal structure of precursor 1c has been studied
N,N-Dimethoxy-N-tert-alkylamines: new synthesis methods and the crystal structure of the precursor
Under the methanolysis of N-methoxy-N-(1-pyridinium)amines salts 1a–c, nucleophilic substitution occurs at the nitrogen atom to form N,N-dimethoxyamines 2a,b; the crystal structure of precursor 1c has been studied
N-Chloro-N-alkoxyureas: synthesis, structure and properties
The XRD studies of N-chloro-N-alkoxyureas 1, 2 have revealed the high pyramidality of the amide nitrogen in the O–N–Cl group caused by nO–s*N–Cl anomeric effect, the other sequence of this effect is anionic lability of the chlorine atom; nucleophilic substitution at the nitrogen depends on the N'-substitutent nature: chlorine atoms in ureas 1 and 5 are replaced by outer nucleophile whereas, under the same conditions, ureas 2–4 undergo cyclization into 1-alkoxybenzimidazolin-2-ones 10–12
Controlled dynamic screening of excitonic complexes in 2D semiconductors
We report a combined theoretical/experimental study of dynamic screening of
excitons in media with frequency-dependent dielectric functions. We develop an
analytical model showing that interparticle interactions in an exciton are
screened in the range of frequencies from zero to the characteristic binding
energy depending on the symmetries and transition energies of that exciton. The
problem of the dynamic screening is then reduced to simply solving the
Schrodinger equation with an effectively frequency-independent potential.
Quantitative predictions of the model are experimentally verified using a test
system: neutral, charged and defect-bound excitons in two-dimensional monolayer
WS2, screened by metallic, liquid, and semiconducting environments. The
screening-induced shifts of the excitonic peaks in photoluminescence spectra
are in good agreement with our model
Hardware implementation of quantum stabilizers in superconducting circuits
Stabilizer operations are at the heart of quantum error correction and are
typically implemented in software-controlled entangling gates and measurements
of groups of qubits. Alternatively, qubits can be designed so that the
Hamiltonian corresponds directly to a stabilizer for protecting quantum
information. We demonstrate such a hardware implementation of stabilizers in a
superconducting circuit composed of chains of -periodic Josephson
elements. With local on-chip flux- and charge-biasing, we observe a softening
of the energy band dispersion with respect to flux that is exponential in the
number of frustrated plaquette elements, in close agreement with our numerical
modeling.Comment: 6+30 pages, 4+18 figures, 0+6 tables, published versio
Synthesis and structure of new N-alkoxy-N-(1-pyridinium)urea chlorides
New N-[1-(4-amino)pyridinium]-N-methoxyurea chloride, N-[1-(2-amino)pyridinium]-N-methoxyurea chloride and their analogs were synthesized by N-alkoxy-N-chloroureas reaction with the proper pyridines in acetonitrile or ether solution by improved procedure. XRD study of N-[1-(4-amino)pyridinium]-N-methoxyurea and N-[1-(2 amino)pyridinium]-N-methoxyurea revealed the elongation of N-N+ bonds and some shortening of MeO-N bonds, qunonoid deformation of pyridine rings compare to it unsubstituted analog. The substantial pyramidality of central nitrogen atom in O-N-N+ moiety and N-C carbamoyl bonds difference were established too. The structure summary of N-alkoxy-N-(1-pyridinium)ureas salts and other derivatives of 1-(N-alkoxyamino)pyridinium salts has been done
- …