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https://www.readbyqxmd.com/read/28441539/a-quantum-chemical-insight-into-the-tunable-fluorescence-color-and-distinct-photoisomerization-mechanisms-between-a-novel-esipt-fluorophore-and-its-protonated-form
#1
Huijuan Yuan, Songyan Feng, Keke Wen, Qiuling Zhu, Beibei An, Xugeng Guo, Jinglai Zhang
Enol-keto proton tautomerization and cis-trans isomerization reactions of a novel excited-state intramolecular proton transfer (ESIPT) fluorophore of BTImP and its protonated form (BTImP(+)) were explored using density functional theory/time-dependent density functional theory (DFT/TD-DFT) computational methods with a B3LYP hybrid functional and the 6-31+G(d,p) basis set. In addition, the absorption and fluorescence spectra were calculated at the TD-B3LYP/6-31+G(d,p) level of theory. Our results reveal that both BTImP and BTImP(+) can undergo an ultrafast ESIPT reaction, giving rise to the single fluorescence emission with different fluorescence colors, which are nicely consistent with the experimental findings...
April 19, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28441477/local-electron-correlation-treatment-in-extended-multireference-calculations-effect-of-acceptor-donor-substituents-on-the-biradical-character-of-the-polycyclic-aromatic-hydrocarbon-heptazethrene
#2
Anita Das, Thomas Müller, Felix Plasser, David B Krisiloff, Emily A Carter, Hans Lischka
The implementation of a local correlation (LC) treatment of multireference (MR) configuration interaction approaches within the COLUMBUS program system is reported. The LC treatment is based on the weak pairs approximation of Sæbø and Pulay (Ann. Rev. Phys. Chem.44 (1993) 213) and a geometrical analysis of Walter et al. (Chem. Phys. Lett. 346 (2001) 177). The weak pairs interactions have been eliminated considering just the reference doubly occupied space leading to a straightforward program implementation and a conceptual simplicity in terms of well-defined localized orbitals...
April 25, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28441011/synthesis-characterization-and-dft-analysis-of-bis-terpyridyl-based-molecular-cobalt-complexes
#3
Safwan Aroua, Tanya K Todorova, Paul Hommes, Lise-Marie Chamoreau, Hans-Ulrich Reissig, Victor Mougel, Marc Fontecave
Terpyridine ligands are widely used in chemistry and material sciences owing to their ability to form stable molecular complexes with a large variety of metal ions. In that context, variations of the substituents on the terpyridine ligand allow modulation of the material properties. Applying the Stille cross-coupling reaction, we prepared with good yields a new series of terpyridine ligands possessing quinoline-type moieties in ortho, meta, and para positions and dimethylamino substituents at central or distal positions...
April 25, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28440821/dft-d3-study-of-h2-and-n2-chemisorption-over-cobalt-promoted-ta3n5-100-010-and-001-surfaces
#4
Constantinos D Zeinalipour-Yazdi, Justin S J Hargreaves, Said Laassiri, C Richard A Catlow
The reactants for ammonia synthesis have been studied, employing density functional theory (DFT), with respect to their adsorption on tantalum nitride surfaces. The adsorption of nitrogen was found to be mostly molecular and non-activated with side-on, end-on and tilt configurations. At bridging nitrogen sites (Ta-N-Ta) it results in an azide functional group formation with a formation energy of 205 kJ mol(-1). H2 was found also to chemisorb molecularly with an adsorption energy in the range -81 to -91 kJ mol(-1)...
April 25, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28440645/structural-electronic-and-magnetic-properties-of-iron-disulfide-fens2-0-%C3%A2-n-1-6-clusters
#5
Slimane Tazibt, Aziz Chikhaoui, Said Bouarab, Andres Vega
The structural, electronic and magnetic properties of neutral and charged FenS2(0/±), n=1-6 clusters have been calculated in the framework of the density functional theory in the generalized gradient approximation for the exchange and correlation. The calculated adiabatic electron affinity and the vertical detachment energy are found to be in good agreement with the available experimental data. The impact of disulfide doping of the small iron clusters on the atomic structure, stability, magnetic moment and reactivity is determined through the analysis of the binding energy per atom, electronic charge transfer, spin-polarized electronic density of states and global reactivity indicators like the electronegativity and chemical hardness...
April 25, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28440614/chemical-vapor-deposition-growth-of-degenerate-p-type-mo-doped-res2-films-and-its-homojunction
#6
Jing-Kai Qin, Wen-Zhu Shao, Cheng-Yan Xu, Yang Li, Dan-Dan Ren, Xiao-Guo Song, Liang Zhen
Substitutional doping of transition metal dichalcogenides (TMDs) two-dimensional materials has proven to be effective in tuning their intrinsic properties, such as band gap, transport characteristics and magnetism. In this study, we realized substitutional doping of monolayer rhenium disulfide (ReS2) with Mo via chemical vapor deposition. Scanning transmission electron microscope (STEM) demonstrated that Mo atoms are successfully doped into ReS2 by substitutionally replacing Re atoms in the lattice. Electrical measurements revealed the degenerate p-type semiconductor behavior of Mo-doped ReS2 field effect transistors (FETs), in agreement with density functional theory (DFT) calculations...
April 25, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28440593/single-domain-ferromagnet-of-noncentrosymmetric-uniaxial-magnetic-ions-and-magnetoelectric-interaction
#7
Hyun-Joo Koo, Elijah E Gordon, Myung-Hwan Whangbo
The feasibility of a single-domain ferromagnet based on uniaxial magnetic ions was examined. For a noncentrosymmetric uniaxial magnetic ion of magnetic moment μ at a site of local electric dipole moment p, it is unknown to date whether μ prefers to be parallel or antiparallel to μ. The nature of this magnetoelectric interaction was probed in terms of analogical reasoning based on the Rashba effect and density functional theory (DFT) calculations. We show that μ and p prefer an antiparallel arrangement, predict that Fe-doped CaZnOS is a single-domain ferromagnet like a bar magnet, and find the probable cause for the ferromagnetism and weak magnetization hysteresis in Fe-doped hexagonal ZnO and ZnS at very low dopant concentrations...
April 25, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28440570/mass-spectrometric-characterization-of-the-selective-androgen-receptor-modulator-sarm-yk-11-for-doping-control-purposes
#8
Mario Thevis, Thomas Piper, Josef Dib, Andreas Lagojda, Dirk Kuehne, Lars Packschies, Hans Geyer, Wilhelm Schaenzer
RATIONALE: Selective androgen receptor modulators (SARMs) represent an emerging class of therapeutics targeting inter alia conditions referred to as cachexia and sarcopenia. Due to their anabolic properties, the use of SARMs is prohibited in sports as regulated by the World Anti-Doping Agency (WADA), and doping control laboratories test for these anabolic agents in blood and urine. In order to accomplish and maintain comprehensive test methods, the characterization of new drug candidates is critical for efficient sports drug testing...
April 25, 2017: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/28440269/ruthenium-cobalt-nanoalloys-encapsulated-in-nitrogen-doped-graphene-as-active-electrocatalysts-for-producing-hydrogen-in-alkaline-media
#9
Jianwei Su, Yang Yang, Guoliang Xia, Jitang Chen, Peng Jiang, Qianwang Chen
The scalable production of hydrogen could conveniently be realized by alkaline water electrolysis. Currently, the major challenge confronting hydrogen evolution reaction (HER) is lacking inexpensive alternatives to platinum-based electrocatalysts. Here we report a high-efficient and stable electrocatalyst composed of ruthenium and cobalt bimetallic nanoalloy encapsulated in nitrogen-doped graphene layers. The catalysts display remarkable performance with low overpotentials of only 28 and 218 mV at 10 and 100 mA cm(-2), respectively, and excellent stability of 10,000 cycles...
April 25, 2017: Nature Communications
https://www.readbyqxmd.com/read/28438673/infants-and-adults-have-similar-regional-functional-brain-organization-for-the-perception-of-emotions
#10
N Rotem-Kohavi, T F Oberlander, N Virji-Babul
An infant's ability to perceive emotional facial expressions is critical for developing social skills. Infants are tuned to faces from early in life, however the functional organization of the brain that supports the processing of emotional faces in infants is still not well understood. We recorded electroencephalography (EEG) brain responses in 8-10 month old infants and adults and applied graph theory analysis on the functional connections to compare the network organization at the global and the regional levels underlying the perception of negative and positive dynamic facial expressions (happiness and sadness)...
April 21, 2017: Neuroscience Letters
https://www.readbyqxmd.com/read/28437618/state-of-the-art-calculations-of-sublimation-enthalpies-for-selected-molecular-crystals-and-their-computational-uncertainty
#11
Ctirad Červinka, Michal Fulem
A computational methodology for calculation of sublimation enthalpies of molecular crystals from first principles is developed and validated by comparison to critically evaluated literature experimental data. Temperature dependent sublimation enthalpies for a set of selected 22 molecular crystals in their low-temperature phases are calculated. The computational methodology consists in several building blocks based on high level electronic structure methods of quantum chemistry and statistical thermodynamics...
April 24, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28437256/electron-inelastic-mean-free-path-at-energies-below-100-ev
#12
Hieu T Nguyen-Truong
Knowledge of electron inelastic mean free paths (IMFPs) is important for electron spectroscopy and microscopy studies. Here, we determine the IMFPs at energies below 100 eV for 10 elemental solids (V, Fe, Ni, Mo, Pd, Ag, Ta, W, Pt, and Au) within the dielectric formalism, using the energy-loss function calculated in the adiabatic local-density approximation of time-dependent density-functional theory. The resulting IMFPs at a few eV above the Fermi energy are comparable to those from ab initio calculations in the GW approximation of many-body theory...
April 24, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28437104/redox-active-macrocycles-for-organic-rechargeable-batteries
#13
Dong Jun Kim, Keith R Hermann, Aleksandrs Prokofjevs, Michael T Otley, Cristian Pezzato, Magdalena Owczarek, J Fraser Stoddart
Organic rechargeable batteries, composed of redox-active molecules, are emerging as candidates for the next generation of energy storage materials because of their large specific capacities, cost effectiveness, and the abundance of organic precursors, when compared with conventional lithium-ion batteries. Although redox-active molecules often display multiple redox states, precise control of a molecule's redox potential, leading to a single output voltage in a battery, remains a fundamental challenge in this popular field of research...
April 24, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28437101/ground-state-and-excited-state-tuning-in-ferric-dipyrrin-complexes-promoted-by-ancillary-ligand-exchange
#14
Claudia Kleinlein, Shao-Liang Zheng, Theodore A Betley
Three ferric dipyrromethene complexes featuring different ancillary ligands were synthesized by one electron oxidation of ferrous precursors. Four-coordinate iron complexes of the type ((Ar)L)FeX2 [(Ar)L = 1,9-(2,4,6-Ph3C6H2)2-5-mesityldipyrromethene] with X = Cl or (t)BuO were prepared and found to be high-spin (S = (5)/2), as determined by superconducting quantum interference device magnetometry, electron paramagnetic resonance, and (57)Fe Mössbauer spectroscopy. The ancillary ligand substitution was found to affect both ground state and excited properties of the ferric complexes examined...
April 24, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28437070/large-scale-synthesis-of-carbon-shell-coated-fep-nanoparticles-for-robust-hydrogen-evolution-reaction-electrocatalyst
#15
Dong Young Chung, Samuel Woojoo Jun, Gabin Yoon, Hyunjoong Kim, Ji Mun Yoo, Kug-Seung Lee, Taehyun Kim, Heejong Shin, Arun Kumar Sinha, Soon Gu Kwon, Kisuk Kang, Taeghwan Hyeon, Yung-Eun Sung
Highly active and stable non-Pt electrocatalyst for hydrogen production has been pursed for a long time as alternative of expensive Pt catalyst. Herein we report a simple and effective approach to prepare highly stable iron phosphide (FeP) nanoparticle electrocatalyst using iron oxide nanoparticles as the precursor. A single step heating procedure of polydopamine-coated iron oxide nanoparticles leads to carbonization of dopamine coating to carbon shell and phosphidation of iron oxide to FeP, simultaneously...
April 24, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28437066/electric-field-driven-direct-desulfurization
#16
Bogdana Borca, Tomasz Michnowicz, Rémi Pétuya, Marcel Pristl, Verena Schendel, Ivan Pentegov, Ulrike Kraft, Hagen Klauk, Peter Wahl, Rico Gutzler, Andrés Arnau, Uta Schlickum, Klaus Kern
The ability to elucidate the elementary steps of a chemical reaction at the atomic scale is important for the detailed understanding of the processes involved which is key to uncover avenues for improved reaction paths. Here, we track the chemical pathway of an irreversible direct desulfurization reaction of tetracenothiophene adsorbed on the Cu(111) closed-packed surface at the submolecular level. Using the precise control of the tip position in a Scanning Tunneling Microscope and the electric field applied across the tunnel junction, the two carbon-sulfur bonds of a thiophene unit are successively cleaved...
April 24, 2017: ACS Nano
https://www.readbyqxmd.com/read/28437062/molecular-arrangement-and-charge-transfer-in-c60-graphene-heterostructures
#17
Claudia Ojeda-Aristizabal, Elton J G Santos, Seita Onishi, Aiming Yan, Haider Imad Rasool, Salman Kahn, Yinchuan Lv, Drew Latzke, Jairo Velasco, Michael F Crommie, Matthew Sorensen, Kenneth Gotlieb, Chiu-Yun Lin, Kenji Watanabe, Takashi Taniguchi, Alessandra Lanzara, Alex Zettl
Charge transfer at the interface between dissimilar materials is at the heart of electronics and photovoltaics. Here we study the molecular orientation, electronic structure, and local charge transfer at the interface region of C60 deposited on graphene, with and without supporting substrates such as hexagonal boron nitride. We employ ab initio density functional theory with van der Waals (vdW) interactions, and experimentally characterize interface devices using high-resolution transmission electron microscopy and electronic transport...
April 24, 2017: ACS Nano
https://www.readbyqxmd.com/read/28436662/multiconfiguration-pair-density-functional-theory-predicts-spin-state-ordering-in-iron-complexes-with-the-same-accuracy-as-complete-active-space-second-order-perturbation-theory-at-a-significantly-reduced-computational-cost
#18
Liam Wilbraham, Pragya Verma, Donald G Truhlar, Laura Gagliardi, Ilaria Ciofini
The spin-state orderings in nine Fe(II) and Fe(III) complexes with ligands of diverse ligand-field strength were investigated with multiconfiguration pair-density functional theory (MC-PDFT). The performance of this method was compared to that of complete active space second-order perturbation theory (CASPT2) and Kohn-Sham density functional theory. We also investigated the dependence of CASPT2 and MC-PDFT results on the size of the active-space. MC-PDFT reproduces the CASPT2 spin-state ordering, the dependence on the ligand field strength, and the dependence on active space at a computational cost that is significantly reduced as compared to CASPT2...
April 24, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28436661/performance-of-van-der-waals-corrected-functionals-for-guest-adsorption-in-the-m2-dobdc-metal-organic-frameworks
#19
Bess Vlaisavljevich, Johanna M Huck, Zeric Hulvey, Kyuho Lee, Jarad A Mason, Jeffrey B Neaton, Jeffrey R Long, Craig M Brown, Dario Alfè, Angelos Michaelides, Berend Smit
Small molecule binding in metal-organic frameworks (MOFs) can be accurately studied both experimentally and computationally, provided the proper tools are employed. Herein, we compare and contrast properties associated with guest binding by means of density functional theory (DFT) calculations using nine different functionals for the M2(dobdc) (dobdc4- = 2,5-dioxido,1,4-benzenedicarboxylate) series where M = Mg, Mn, Fe, Co, Ni, Cu, and Zn. Additionally, we perform Quantum Monte Carlo (QMC) calculations for one system to determine if this method can be used to assess the performance of DFT...
April 24, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28436556/theoretical-evidence-for-bond-stretch-isomerism-in-grubbs-olefin-metathesis
#20
Premaja R Remya, Cherumuttathu H Suresh
A comprehensive density functional theory study on the dissociative and associative mechanisms of Grubbs first and second generation olefin metathesis catalysis reveals that ruthenacyclobutane intermediate (RuCB) observed in the Chauvin mechanism is not unique as it can change to a non-metathetic ruthenacyclobutane (RuCB') via the phenomenon of bond stretch isomerism (BSI). RuCB and RuCB' differ mainly in RuCα , RuCβ , and Cα Cβ bond lengths of the metallacycle. RuCB is metathesis active due to the agostic type bonding-assisted simultaneous activation of both Cα Cβ bonds, giving hypercoordinate character to Cβ whereas an absence of such bonding interactions in RuCB' leads to typical CC single bond distances and metathesis inactivity...
April 24, 2017: Journal of Computational Chemistry
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