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Quantum ring

Robert D Sanner, Victor G Young
The crystal structures of bis-{3,5-di-fluoro-2-[4-(2,4,6-tri-methyl-phen-yl)pyridin-2-yl]phenyl-κ2 N , C 1 }(picolinato-κ2 N , O )iridium(III), [Ir(C20 H16 F2 N)2 (C6 H4 NO2 )], 1 , and bis-[2-(4- tert -butyl-pyridin-2-yl)-3,5-di-fluoro-phenyl-κ2 N , C 1 ](picolinato-κ2 N , O )iridium(III), [Ir(C15 H14 F2 N)2 (C6 H4 NO2 )], 2 , are presented herein. These phospho-rescent cyclo-metallated iridium(III) compounds have been structurally investigated in order to better understand the nature of their blue-shifted emssions while maintaining high quantum yields...
October 1, 2018: Acta Crystallographica. Section E, Crystallographic Communications
Michael R Coates, Martin A B Larsen, Ruaridh Forbes, Simon P Neville, Andrey E Boguslavskiy, Iain Wilkinson, Theis I Sølling, Rune Lausten, Albert Stolow, Michael S Schuurman
The vacuum-ultraviolet photoinduced dynamics of cyclopropane (C3 H6 ) were studied using time-resolved photoelectron spectroscopy (TRPES) in conjunction with ab initio quantum dynamics simulations. Following excitation at 160.8 nm, and subsequent probing via photoionization at 266.45 nm, the initially prepared wave packet is found to exhibit a fast decay (<100 fs) that is attributed to the rapid dissociation of C3 H6 to ethylene (C2 H4 ) and methylene (CH2 ). The photodissociation process proceeds via concerted ring opening and C-C bond cleavage in the excited state...
October 14, 2018: Journal of Chemical Physics
Liangliang Zhang, Yuchen Liu, Yongmei Wang
In the present paper, methyl gallate (MeG), a simple polyphenol and also the monomer of hydrolysable tannins, was selected to study the deprotonation process for the hydroxyls of the galloyl group by the combined use of spectroscopic measurements and quantum chemical calculations. The results of quantum chemical calculations show that the deprotonated form of methyl gallate undergoes the para-quinoid localization in the benzene ring, compared with free methyl gallate. The predicted spectra obtained from the free and deprotonated methyl gallate models are in agreement with the experimental UV-visible (UV-vis) absorption spectra...
October 11, 2018: International Journal of Molecular Sciences
Wenjin Cao, Dilrukshi Hewage, Dong-Sheng Yang
La atom reaction with isoprene is carried out in a laser-vaporization molecular beam source. The reaction yields an adduct as the major product and C-C cleaved and dehydrogenated species as the minor ones. La(C5 H8 ), La(C2 H2 ), and La(C3 H4 ) are characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectra of all three species exhibit a strong origin band and several weak vibronic bands corresponding to La-ligand stretch and ligand-based bend excitations...
May 21, 2018: Journal of Chemical Physics
Kento Suzuki, Takaaki Miyazaki, Toshiyuki Takayanagi, Motoyuki Shiga
The direct photoionization of pure helium clusters, Hen (n = 100, 200 and 300), and its subsequent short-time process have been studied by path integral molecular dynamics (PIMD) and ring-polymer molecular dynamics (RPMD) simulations that can effectively describe the nuclear quantum effects in large systems. The modified diatomics-in-molecule (DIM) model [Calvo et al., J. Chem. Phys., 2011, 135, 124308] has been used to describe the electronic structures of Hen+ clusters. The PIMD simulations were able to reproduce the experimental ionization spectra having a broad and asymmetric nature, which can be ascribed to the inhomogeneity of the energy levels of He atoms in the inner and outer regions of the cluster...
October 11, 2018: Physical Chemistry Chemical Physics: PCCP
Yu-Long Tong, Zhijie Zhu, Gang Peng, Tingting Cui, Su Chen
Gold nanoparticle (Au NP) incorporated photonic crystals (PCs) have been extensively studied due to the intricate interplay between the surface plasmon resonance of Au NPs and the periodic nanostructure of PCs. Herein, we successfully synthesized Au NP decorated poly(styrene-co-(generation 3 carbosilane-thioether vinyl-terminated dendrimer)) (P(st-co-G3Vi)) microspheres via in situ reduction of Au ions based on the strong coordination between the Au ions and the sulfur atom in G3Vi dendrimers. These composite Au-doped microspheres demonstrate a bumpy surface topography, which gives rise to a higher hydrophobicity and could effectively suppress the formation of an ubiquitous coffee-ring during the drying process of a colloidal suspension...
October 10, 2018: Nanoscale
Biao Lian, Xiao-Qi Sun, Abolhassan Vaezi, Xiao-Liang Qi, Shou-Cheng Zhang
The chiral Majorana fermion is a massless self-conjugate fermion which can arise as the edge state of certain 2D topological matters. It has been theoretically predicted and experimentally observed in a hybrid device of a quantum anomalous Hall insulator and a conventional superconductor. Its closely related cousin, the Majorana zero mode in the bulk of the corresponding topological matter, is known to be applicable in topological quantum computations. Here we show that the propagation of chiral Majorana fermions leads to the same unitary transformation as that in the braiding of Majorana zero modes and propose a platform to perform quantum computation with chiral Majorana fermions...
October 8, 2018: Proceedings of the National Academy of Sciences of the United States of America
Shawkat Islam, Aravindhan Ganesan, Rebecca Auchettl, Oksana Plekan, Robert G Acres, Feng Wang, Kevin C Prince
Electronic structures and intramolecular interactions of three methoxyphenol positional isomers and their rotamers have been studied using core X-ray photoelectron spectroscopy and quantum mechanical calculations. The structural calculations are benchmarked against published calculations of enthalpy of formation and rotational constants, and published experimental data. The good agreement obtained confirms the accuracy of the results. A single rotamer of each isomer was then selected and the C 1s photoelectron spectra calculated and compared with experiment...
October 7, 2018: Journal of Chemical Physics
Koichi Ohno, Hiroko Satoh, Takeaki Iwamoto, Hiroaki Tokoyama, Hideo Yamakado
The existence of a new carbon allotrope family with four-membered rings as a key unit has been recently predicted with quantum chemical calculations. This family includes carbon allotropes in prism-, polymerized prism-, sheet-, tube-, and wavy-forms. An atypical bond property has been observed in this series of carbon structures, which differs from the typical sp3 , sp2 , and sp hybridizations. The lowest energy barrier from some of the equilibrium states of the carbon structures has been determined with the SHS-ADDF (scaled-hypersphere-search combined with the anharmonic downward distortion following) method within the GRRM software program package...
October 3, 2018: Journal of Computational Chemistry
Fabio de A Ribeiro, Benedikt Rudek, Henrique B A Cerqueira, Ricardo R Oliveira, Alexandre B Rocha, Maria Luiza M Rocco, Wania Wolff
We report on direct measurement of all major ion-fragments and cluster-ions formed during high-energy electron impact of 2 keV on gaseous and condensed-phase pyridine. The ion-fragments of the parent pyridine cation are discussed in groups according to the number of atoms from the aromatic ring. The ion yield distributions within these groups show significant shifts towards higher masses for condensed pyridine compared to gaseous pyridine due to hydrogen migration. A wide spectrum of desorbed hydrogenated fragment-ions and ionic clusters with masses up to 320 u are observed for pyridine...
October 4, 2018: Physical Chemistry Chemical Physics: PCCP
Den Iacute S Paredes-Roib Aacute S, Muthiah Balaganesh, Toshio Kasai, Jose Gavira Vallejo, King-Chuen Lin
Iodine monochloride (ICl) elimination from one-photon dissociation of CH$_2$ICl at 248 nm is monitored by cavity ring-down absorption spectroscopy (CRDS). The spectrum of ICl is acquired in the transition of $B^3 \Pi_0 \leftarrow X^1 \Sigma^+$ and is confirmed to result from a primary photodissociation; that is, CH$_2$ICl + $h\nu$ $\rightarrow$ CH$_2$ + ICl. The vibrational population ratio is determined with the aid of spectral simulation to be 1:(0.36 $\pm$ 0.10):(0.11 $\pm$ 0.05) for the vibrational levels $v$ = 0, 1 and 2 in the ground electronic state, corresponding to a Boltzmann-like vibrational temperature of 535 $\pm$ 69 K...
October 2, 2018: Journal of Physical Chemistry. A
Xiao-Shuo Wu, Yi-Xiong Wang, Shan-Qing Li, Yin Qian, Lu Zhai, Xiao-Zu Wang, Xiao-Ming Ren
A new 1D phosphorescence coordination polymer (CP) [Pb2O(C6H4NO2)2]n (1; C6H4NO2 = nicotinate) was synthesized by a solvothermal reaction and PbO was used as a Pb(ii) source instead of traditional Pb(ii) salts. This remarkably thermal-stable CP crystallizes in the space group I41/a. In the crystal structure of 1, two different Pb(ii) ions show a five-coordinated and hemidirected coordination geometry, two nonequivalent nicotinate ligands link to Pb(ii) ions in μ2-η1:η1 and μ4-η2:η2 modes, and the hemidirected coordination polyhedra of Pb(ii) form a helical lead-oxide chain via an edge-sharing fashion along the c-axis...
October 2, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
S Rajagopala Reddy, Pedro B Coto, Michael Thoss
We investigate the dynamics of intramolecular singlet fission in a dimer consisting of two pentacene-based chromophores covalently bonded to a phenylene spacer using an approach that combines high-level ab initio multireference perturbation theory methods and quantum dynamical simulations. The results show that the population of the multiexcitonic state, corresponding to the first step of singlet fission, is facilitated by the existence of higher-lying doubly excited and charge transfer states that participate in a superexchange-like way...
October 3, 2018: Journal of Physical Chemistry Letters
Botuo Zheng, Tianwen Bai, Xinfeng Tao, Helmut Schlaad, Jun Ling
Polypeptoids are noticeable biological materials due to their versatile properties and various applications in drug delivery, surface modification, self-assembly, etc. N-Substituted glycine N-thiocarboxyanhydrides (NNTAs) are more stable monomers than the corresponding N-carboxyanhydrides (NNCAs) and enable to prepare polypeptoids via ring-opening polymerization even in the presence of water. However, larger amounts of water (> 10,000 ppm) causes inhibition of the polymerization. Herein, we discover that during polymerization hydrogen sulfide evolves from the hydrolysis of carbonyl sulfide, which is the by-product of ring-opening reaction, and reacts with NNTA to produce cyclic oligopeptoids...
September 26, 2018: Biomacromolecules
Daniel G Congrave, Andrei S Batsanov, Mingxu Du, Yu Liu, Dongxia Zhu, Martin R Bryce
The application of a chiral auxiliary ligand to control the diastereoselectivity in the synthesis of a cyclometalated iridium(III) complex is presented. The diastereomeric iridium(III) complexes 1a and 1b are reported, in which a phenoxyoxazoline auxiliary ligand incorporates a chiral center functionalized with a pendant pentafluorophenyl group. The diastereomers were readily separated, and their structural, electrochemical and photophysical properties are discussed. Solution-state NMR data and X-ray crystal structures establish that the pentafluorophenyl group engages in intramolecular π-π interactions...
September 26, 2018: Inorganic Chemistry
Hong-Bo Xu, Tong-Hua Yang, Pei Xie, Zhi-Shu Tang, Xiao Song, Huai-Li Xu, Yan-Hong Li, Dong-Bo Zhang, Yan-Ru Liu, Yan-Ni Liang, Yu Zhang, Shi-Jun Liu, Si-Min Wei, Chen Sun, Hong-Bo Liu, Chong Deng, Wei Wang
Gracilistones A (1) and B (2), two new eudesmane-type sesquiterpenoids with an unusual tetrahydrofuran-fused 6/6/5 tricyclic ring system, were obtained from Acanthopanax gracilistylus under the guidance of LC-MS investigation. Their structures and absolute configurations were assigned by extensive spectroscopic analyses and quantum calculation methods. Compounds 1 and 2 showed potent inhibitory activity against LPS-induced nitric oxide production in RAW 264.7 macrophages, compared with the positive control L-NMMA...
September 20, 2018: Fitoterapia
Jolanta Brzezinska, Jacek Kujawski, Agnieszka Witkowska, Kornelia Czaja, Marek K Bernard, Marcin K Chmielewski
1D and 2D NMR investigations as well as computational studies, including static quantum-mechanics calculations, density function theory formalism, and classical molecular dynamics, were applied to determine the protonation sites in the thermolabile protecting group (TPG) containing a 2-pyridynyl moiety within its structure. This protecting group has three possible sites for protonation: an azomethine (pyridinic) atom (N1), 2-aminoethanol residue (N2), and 4-amino substituent (N4). Our investigations showed that the protonation mainly occurs on the N1 atom...
2018: PloS One
Andrew Levitz, Fahad Marmarchi, Maged Henary
The unique optical properties of cyanine dyes have prompted their use in numerous applications. Heptamethine cyanines are commonly modified on the methine bridge after synthesis of a meso-chlorine containing cyanine. Herein, a series of heptamethine cyanines containing modified methine bridges were synthesized using substituted dianil linkers. Their optical properties including, molar absorptivity, fluorescence, and quantum yield were measured as well as their hydrophobic effects in polar buffer solution. It was shown that dyes containing cyclopentene in the methine bridge or a phenyl ring in the meso position display increased molar absorptivity while the increased flexibility of the dye containing a cycloheptene in the methine bridge prevented fluorescence...
October 10, 2018: Photochemical & Photobiological Sciences
Krishnan Balasubramanian
We have employed combinatorial techniques based on character cycle indices, Pólya's theory and Euler totem function to enumerate isomers of polysubstituted cycloarenes and coronoid hydrocarbons which have been receiving considerable attention because of their superaromaticity, ring currents, and interesting magnetic properties. Systematic enumeration and construction of tables of polysubstituted isomers such as fluoro-chloro superaromatic hydrocarbons are considered as they are of interest in the study of environmental pollutants and toxicity...
September 20, 2018: Journal of Physical Chemistry. A
J Polo, V Ahufinger, F W J Hekking, A Minguzzi
We study Josephson oscillations of two strongly correlated one-dimensional bosonic clouds separated by a localized barrier. Using a quantum-Langevin approach and the exact Tonks-Girardeau solution in the impenetrable-boson limit, we determine the dynamical evolution of the particle-number imbalance, displaying an effective damping of the Josephson oscillations which depends on barrier height, interaction strength, and temperature. We show that the damping originates from the quantum and thermal fluctuations intrinsically present in the strongly correlated gas...
August 31, 2018: Physical Review Letters
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