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Quantum ring

Erdeng Du, Jiaqi Li, Siqi Zhou, Lu Zheng, Xinxin Fan
The by-products produced by pharmaceutically active compounds (PhACs) during chlorination are attracting wide concern. Thus, the transformation and toxicity of naproxen (NAP) during the chlorination process were assessed in this study. The transformation of NAP was found to follow pseudo-first-order kinetics, and the first-order rate constant was improved by increasing the NaOCl dose. High-resolution mass spectrometry (HRMS) was successfully applied to identify 14 chlorination products. This study represents the first elucidation and report of the exact structure of the primary chlorine substitution product ((2S)-2-(5-chloro-6-methoxy-2-naphthyl)propionic acid) based on HRMS and 1 H NMR...
August 14, 2018: Chemosphere
Jack B Graneek, William C Bailey, Melanie Schnell
The rotational spectra of 2- and 3-nitrobenzonitrile were recorded via chirped-pulse Fourier transform microwave spectroscopy in the frequency range of 2-8 GHz. These molecules each display large dipole moments, making them viable candidates for deceleration and trapping experiments with AC-electric fields. For both molecules, the main isotopologues and all isotopologues of the respective 13C-, 15N-, 18O-monosubstituted species in their natural abundance were assigned. These assignments allowed for the structural determination of 2- and 3-nitrobenzonitrile via Kraitchman's equations as well as a mass-dependent least-squares fitting approach...
August 17, 2018: Physical Chemistry Chemical Physics: PCCP
J Belfi, N Beverini, G Carelli, A Di Virgilio, U Giacomelli, E Maccioni, A Simonelli, F Stefani, G Terreni
Gyroscopes IN GEneral Relativity (GINGER) is a proposed experiment with the aim of measuring in a ground laboratory the gravitoelectric and gravitomagnetic effects foreseen by general relativity through an array of ring laser gyroscopes. GINGERINO is a square ring-laser prototype that has been built to investigate the level of noise inside the Gran Sasso underground laboratory. GINGERINO has shown the advantage of the underground location. Now it provides suitable data for geophysics and seismology. Since May 2017, it has continuously acquired data...
July 10, 2018: Applied Optics
Lorenzo Luigi Columbo, Paolo Bardella, Mariangela Gioannini
We studied theoretically coherent phenomena in the multimode dynamics of single section semiconductor ring lasers with quantum dots (QDs) active region. In the unidirectional ring configuration our simulations show the occurrence of self-mode-locking in the system leading to ultra-short pulses (sub-picoseconds) with a terahertz repetition rate. As confirmed by the linear stability analysis (LSA) of the traveling wave (TW) solutions this phenomenon is triggered by an analogous of the Risken-Nummedal-Graham-Haken (RNGH) instability affecting the multimode dynamics of two-level lasers...
July 23, 2018: Optics Express
Ephrath Solel, Sebastian Kozuch
Pentafulvalene is a symmetrical unsaturated hydrocarbon built from two five-membered rings connected by an exocyclic double bond, where each ring is one electron short of being a 6π-electron aromatic system. Here we show computationally that by selectively introducing electron withdrawing and donating substituents we can design pentafulvalene derivatives that exhibit tunable aromaticity properties. Pentafulvalene can be shaped into a species with connected aromatic-antiaromatic rings, which can also achieve π-bond shifting by carbon tunneling...
August 16, 2018: Journal of Organic Chemistry
Peng Sun, Zhaojun Zhang, Jun Chen, Shu Liu, Dong H Zhang
Transition state wave packet calculations have been carried out to compute cumulative reaction probabilities for the H2 + OH reaction on the NN1 potential energy surface, as given in the work of Chen et al. , from which well converged thermal rate constants for the reaction up to a temperature of 1000 K were obtained. It was found that both the centrifugal sudden approximation and the " J - K -shifting" approximation slightly underestimated the thermal rate constants, while the ring-polymer molecular dynamics overestimated the rates in the low temperature region...
August 14, 2018: Journal of Chemical Physics
Edward Matthews, Rosaria Cercola, Caroline E H Dessent
Flavin chromophores play key roles in a wide range of photoactive proteins, but key questions exist in relation to their fundamental spectroscopic and photochemical properties. In this work, we report the first gas-phase spectroscopy study of protonated alloxazine (AL∙H⁺), a model flavin chromophore. Laser photodissociation is employed across a wide range (2.34⁻5.64 eV) to obtain the electronic spectrum and characterize the photofragmentation pathways. By comparison to TDDFT quantum chemical calculations, the spectrum is assigned to two AL∙H⁺ protomers; an N5 (dominant) and O4 (minor) form...
August 14, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Lei Wang, Mayu Fujii, Minoru Yamaji, Hideki Okamoto
The absorption and fluorescence spectra of a series of 1,8-naphthalimide derivatives incorporating the amino functionality at the 2-, 3- and 4-positions of the naphthalene ring (2APNI, 3APNI and 4APNI, respectively) were systematically investigated in various solvents and in the solid state. The fluorescence spectra of 2APNI were insensitive to solvent polarity and intermolecular hydrogen-bonding even in a protic medium such as methanol. Thus, 2APNI displayed blue fluorescence with a moderate fluorescence quantum yield (λFmax = 420-445 nm, ΦF 0...
August 15, 2018: Photochemical & Photobiological Sciences
Tingting Yu, Haijiao Wang, Chongzheng Guo, Yanli Zhai, Jianzhou Yang, Jianhui Yuan
The emerging carbon quantum dots (CQDs) have been attracting significant attention for their prominent fluorescence, excellent stability and outstanding biocompatibility. Here, we report a facile one-step synthesis of highly fluorescent CQDs by using phthalic acid and triethylenediamine hexahydrate as precursors through a simple microwave-assisted method. The reaction time needed is only 60 s, which is less time-consuming than most previous reports. The phthalic acid with a benzene ring can improve the photoluminescence properties of CQDs as it can provide foreign sp 2 conjugating units, and then finally result in long-wavelength emission...
July 2018: Royal Society Open Science
Yuri Kozhemyakin, Maximilian Krämer, Frank Rominger, Andreas Dreuw, Uwe Heiko Bunz
We report the synthesis of a doubly bridged tolane. The target is obtained in a five-step synthesis, starting from commercially available 2-amino-meta-xylene by a combination of Sandmeyer reactions, radical bromination and Stille-type coupling, followed by double ring closing. The doubly tethered tolane is crystalline and shows both in solution and in the solid state a highly twisted conformation. Optical spectroscopy and quantum chemical calculations show that doubly bridged 7 is twisted not only in the ground state but also in the excited state, leading to emission from this state in solution and in the solid state, with strong phosphorescence at cryogenic temperatures...
August 13, 2018: Chemistry: a European Journal
Dong Xiang, Weihua Zhu
We performed quantum molecular dynamics simulations to investigate the initiation chemistry of condensed phase δ-HMX at high temperatures by maintaining constant energy and volume to model adiabatic initiation process. The decomposition of HMX began by the C-N bond breaking in one molecule and by the C-H bond cleavage in other HMX molecule at 2400 K. At 2700 K, HMX is triggered by only one path that the C-N bond broke and the ring opened. At 3000 K, the decomposition of HMX is triggered by the C-H bond and N-O bond fission in the branch chains...
August 4, 2018: Journal of Molecular Graphics & Modelling
Wei-De Zhang, Miao Sun, Kui Li, Yu-Xian Yu
In this study, we report a photocatalyst with distorted skeleton, which was synthesized by grafting triamterene onto graphitic carbon nitride (g-C3N4) frameworks. Pteridine ring of triamterene-based nitrogen-enriched organic structure, functions as trapped electron sites due to its inductive effect. Benzene ring in triamterene plays an important role on even dispersion of electrons by conjugative effect. Intramolecular electronic potential redistribution caused by synergistic effect between pteridine ring and benzene ring of triamterene promotes separation and migration of photo-induced charge carriers...
August 11, 2018: Chemistry, An Asian Journal
Cina Foroutan-Nejad, Simon Larsen, Jeanet Conradie, Abhik Ghosh
Density functional theory calculations of magnetically induced current densities have revealed high diatropic ring currents in unsubstituted isocorrole consistent with homoaromatic character. An examination of the Kohn-Sham molecular orbitals showed clear evidence of homoconjugative interactions in four occupied π-type molecular orbitals as well as in the LUMO. Remarkably, substituents at the saturated meso position were found to exert a dramatic influence on the overall current density pattern. Thus, whereas bis(trimethylsilyl)-substitution strongly enhanced the peripheral diatropic current (consistent with enhanced homoaromaticity), difluoro-substitution engendered a strong, net paratropic current (consistent with antihomoaromaticity)...
August 10, 2018: Scientific Reports
Benjamin M Day, Fu-Sheng Guo, Richard A Layfield
The discovery of materials capable of storing magnetic information at the level of single molecules and even single atoms has fueled renewed interest in the slow magnetic relaxation properties of single-molecule magnets (SMMs). The lanthanide elements, especially dysprosium, continue to play a pivotal role in the development of potential nanoscale applications of SMMs, including, for example, in molecular spintronics and quantum computing. Aside from their fundamentally fascinating physics, the realization of functional materials based on SMMs requires significant scientific and technical challenges to be overcome...
August 9, 2018: Accounts of Chemical Research
Shunwei Chen, Naeem Ullah, Rui-Qin Zhang
Recent experiments have suggested that exciton self-trapping plays an important role in governing the optical properties of graphene quantum dots (GQDs) and carbon dots (CDs), while the molecular structures related to this phenomenon remain unclear. This theoretical study reports exciton self-trapping induced by edge-bonded ether (C-O-C) groups in graphene nanosheets. Density functional theory (DFT) and time-dependent DFT calculations show that the initially delocalized electron and hole are trapped in the vicinity of the edge ether groups on graphene nanosheets upon excited-state (S1) relaxation, accompanied by structural planarization of the seven-membered cyclic ether rings in the same region...
August 7, 2018: Journal of Physical Chemistry Letters
Ya-Zhong Dai, Bo-Wei Dong, Yi Kao, Zi-Yuan Wang, Hio-Ieng Un, Zheng Liu, Zhi-Jun Liu, Liang Li, Fang-Bai Xie, Yang Lu, Mei-Xing Xu, Ting Lei, Yu-Jie Sun, Song Gao, Shang-Da Jiang, Jian Pei
Organic semiconductors for spin-based devices require long spin relaxation times. Understanding their spin relaxation mechanisms is critical to organic spintronic devices and applications for quantum information processing (QIP). However, reports on the spin relaxation mechanisms of organic conjugated molecules are rare and the research methods are also limited. Herein, we studied the relationships between the structures and spin relaxation mechanisms by systematically varying the structure of a conjugated radical...
August 7, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Ruijiao Miao, Hailiang Xu, Maxim Skripnik, Longji Cui, Kun Wang, Kim Georg Lind Pedersen, Martin Leijnse, Fabian Pauly, Kenneth Wärnmark, Edgar Meyhofer, Pramod Reddy, Heiner Linke
Molecular junctions offer unique opportunities for controlling charge transport at the atomic scale and for studying energy conversion. For example, quantum interference effects in molecular junctions have been proposed as an avenue for highly efficient thermoelectric power conversion at room temperature. Towards this goal, we investigated the effect of quantum interference on the thermoelectric properties of molecular junctions. Specifically, we employed oligo (phenylene ethynylene) (OPE) derivatives with a para-connected central phenyl ring (para-OPE3) and meta-connected central ring (meta-OPE3), which both covalently bind to gold via sulfur anchoring atoms located at their ends...
August 7, 2018: Nano Letters
Costel Moldoveanu, Ionel Mangalagiu, Dragos Lucian Isac, Anton Airinei, Gheorghita Zbancioc
In this study an efficient and straightforward method for obtaining a new class of blue fluorescent bezofuran derivatives, under microwave irradiation, as well as under conventional thermal heating, is presented. Under conventional TH the reactions occur selectively, and a single type of benzofuran ester derivative was obtained. The synthesis under MW irradiation also led to benzofuran derivatives, but in a time-dependent manner. Irradiation for a short period of time led to a mixture of two types of benzofuran derivatives ( 3a ⁻ c and 4a ⁻ c ), while MW irradiation for a longer period of time led to a single type of benzofuran (3-methylbenzofuran), the reaction becoming highly selective...
August 6, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Xia Zhang, Yuhao Ma, Lulu Xi, Guifen Zhu, Xiang Li, Dongyang Shi, Jing Fan
Highly efficient photocatalytic degradation of refractory organic contaminants in wastewater remains a great challenge due to low quantum efficiency and poor solar energy utilization of the currently employed photocatalysts. Herein, a novel BiVO4 /CH3 COO(BiO) heterojunction photocatalyst is designed and prepared by a simple one-pot solvothermal method, and characterized by various techniques. By using this photocatalyst, degradation efficiency of four kinds of emerging refractory organic pollutants (sulfamethoxazole, bisphenol A, 4‑aminoantipyrine and ibuprofen) in water is investigated under simulated solar irradiation...
July 31, 2018: Science of the Total Environment
Jiaying Hou, Qing Zou, Yijun Wang, Qi Gao, Wenhui Yao, Qizheng Yao, Ji Zhang
Matrix metalloproteinase-9 (MMP-9) has been considered as an attractive target involving cancer therapy. In this study, the 3D QSAR pharmacophore model of MMP-9 inhibitors is built, and its reliability is subsequently validated based on different methods. The built pharmacophore model consists of the four chemical features, including two hydrogen bond acceptors (HBA), one hydrophobic (HY), and one ring aromatic (RA). Among them, both HY and RA are found to be especially important features because they involve the interactions of inhibitors with the S1' pocket of MMP-9, which determines the selectivity of MMP-9 inhibitors...
August 5, 2018: Journal of Biomolecular Structure & Dynamics
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