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Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry

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https://www.readbyqxmd.com/read/28544420/gold-i-hydrides-as-proton-acceptors-in-dihydrogen-bond-formation
#1
Ignacy Cukrowski, Jurgens Hendrik de Lange, Ferdinand Groenewald, Helgard G Raubenheimer
Wavefunction and DFT calculations indicate that anionic dihydride complexes of AuI form strong to moderate directed Au-H···H bonds with one or two HF, H₂O and NH₃ prototype proton donor molecules. The largely electrostatic interaction is influenced by relativistic effects which, however, do not increase the binding energy. Very weak Au···H associations - exhibiting a corresponding bond path - occur between neutral AuH and HF units, although ultimately F becomes the preferred donor atom in the most stable structure...
May 25, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28544253/odd-electron-bonds
#2
Tim Clark
The history and theory of one- and three-electron bonds are presented and discussed. It is shown that the dependence of the odd-electron bond energy on the difference in ionization potentials of the bonding partners must be corrected to include the ion-pairing energy for neutral odd-electron bonded complexes.
May 24, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28544206/prediction-of-t-and-h-phase-two-dimensional-transition-metal-carbides-nitrides-and-their-semiconducting-metallic-phase-transition
#3
Chi Chen, Xiao Ji, Kui Xu, Bao Zhang, Ling Miao, Jianjun Jiang
The discovery of various two-dimensional (2D) nanomaterials with different phases is fundamentally and technologically intriguing, leading to diverse physical and chemical properties for expanded applications. Herein, we performed systematic first-principles calculations to explore a series of single-layer MXenes (M2 X: M=Sc, Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, Ta; X=C, N). The new H-phase MXenes are firstly predicted, which are compared with the usually synthesized MXenes named as T-phase MXenes on their structure and electronic properties...
May 24, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28544199/benzhydryl-ethers-of-tartaric-acid-derivatives-stereochemical-response-of-dynamically-chiral-propeller
#4
Jakub Grajewski, Tomasz Mądry, Marcin Kwit, Beata Beata Warżajtis, Urszula Rychlewska, Jacek K Gawronski
The benzhydryl (diphenylmethyl) group is a molecular propeller that can acts as a chirality reporter when it is introduced nearby the stereogenic center by making the ether bond. Hydrophobic character of the benzhydryl group allows transformation of insoluble in non-polar environment natural tartaric acid derivatives into soluble entities. Electronic circular dichroism spectra, recorded within the short wavelength region of the phenyl 1B transitions (190-200 nm) showed strong bisignate Cotton effects. The signs and magnitudes of these Cotton effects are a function of absolute configuration and conformation of the molecule and primarily are not due to exciton coupling of chiral benzhydryl chromophores...
May 23, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28544113/the-role-of-water-in-catalyst-free-aldol-reaction-of-water-insoluble-n-methyl-2-4-thiazolidinedione-with-n-methyl-isatin-from-qm-mm-monte-carlo-simulation
#5
Jianming Zhao, Fen He, Fan Zhang, Xin Yang, Zhiyue Tian, Ying Xue
The role of water in the uncatalyzed aldol reaction of N-methyl-2,4-thiazolidinedione with N-methyl-isatin has been investigated using Monte Carlo statistical mechanics simulations utilizing the free-energy perturbation theory and the QM/MM model with PDDG/PM3 for the QM method under the "on water" and dimethyl sulfoxide (DMSO) environments. There are several conceivable orientations between thiazolidinedione and isatin in the process of C-C bond formation. However, the formation of C-C bond takes place between the re face of isatin and the si face of E-enol of the thiazolidinedione to form the preferred anti-type product, which results from enhancing hydrogen bonding interaction between water molecules and the oxygen atoms undergoing bond broken and bond formation during the reaction...
May 23, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28544571/reactivity-of-copper-iii-oxo-complexes-in-the-gas-phase
#6
Ghazaleh Yassaghi, Erik Andris, Jana Roithová
We show an efficient way to generate [(L)CuO]+ complexes with a number of monodentate and bidentate ligands L from their [(L)Cu(ClO3)]+ precursors by electrospray ionization. Further, we studied [(L)CuO]+ with L = 9,10-phenanthraquinone, 1,10-phenanthroline and acetonitrile in detail. The signature of these terminal copper-oxo complexes is elimination of the oxygen atom upon collisional activation. We have investigated and compared their reactions with water, ethane, ethylene and 1,4-cyclohexadiene. The [(CH3CN)CuO]+ complex can oxidize water and perform C-H activation and hydroxylation of ethane...
May 22, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28544447/modulation-of-wetting-gradients-by-tuning-the-interplay-between-surface-structuration-and-anisotropic-molecular-layers-with-bipolar-electrochemistry
#7
Laurent Bouffier, Stéphane Reculusa, Valérie Ravaine, Alexander Kuhn
A new simple and versatile method for the preparation of surface wetting gradients is proposed. It is based on the combination of electrode surface structuration introduced by a sacrificial template approach and the formation of a tuneable molecular gradient by bipolar electrochemistry. The gradient involves the formation of a self-assembled monolayer on gold surface by selecting an appropriate thiol molecule and the subsequent reductive desorption by means of bipolar electrochemistry. Under these conditions, the completion of the reductive desorption process evolves along the bipolar surface with a maximum strength localized at the cathodic edge and a decreasing driving force toward the middle of the surface...
May 22, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28524266/single-molecule-and-ensemble-diffusivities-in-individual-nanopores-with-spatially-dependent-mobility
#8
Julia Rybka, Jörg Kärger, Ulrich Tallarek
We investigate single-molecule and ensemble diffusivities in a silica nanopore with chemically modified surface by molecular dynamics simulations. Solutes with graded polarity (nonpolar ethylbenzene and moderately polar benzyl alcohol) are equilibrated with a 40:60 (v/v) water/acetonitrile solvent in a 10 nm pore, whose surface has been rendered hydrophobic by modification with alkyl chains. Simulations enable a detailed sampling of spatially dependent solvent and solute mobilities, which originate in a micro-heterogeneity induced by the surface modification...
May 19, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28521081/thermophysical-and-electrochemical-properties-of-ethereal-functionalised-cyclic-alkylammonium-based-ionic-liquids-as-potential-electrolytes-for-electrochemical-applications
#9
Alex Ryan Neale, Sinead Murphy, Peter Goodrich, Christopher Hardacre, Johan Jacquemin
A series of hydrophobic room temperature ionic liquids (ILs) based on ethereal functionalised pyrrolidinium, piperidinium and azepanium cations bearing the bis{(trifluoromethyl)sulfonyl}imide, [TFSI]-, anion were synthesized and characterized. Their physicochemical properties such as density, viscosity and electrical conductivity and thermal properties including phase transition behaviour and decomposition temperature have been measured. All of the ILs showed low melting point, low viscosity and good conductivity and the latter properties have been discussed in terms of the IL fragility, an important electrolyte feature of the transport properties of glassy-forming ILs...
May 18, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28517362/the-absence-of-quadrupolar-nuclei-facilitates-efficient-13-c-hyperpolarization-via-reversible-exchange-with-parahydrogen
#10
Danila A Barskiy, Roman V Shchepin, Christian P N Tanner, Johannes F P Colell, Boyd M Goodson, Thomas Theis, Warren S Warren, Eduard Y Chekmenev
Nuclear spin hyperpolarization techniques are revolutionizing the field of (13) C molecular MRI. While dissolution dynamic nuclear polarization (d-DNP) is currently the leading technique, it is generally slow (requiring ≈1 h) and costly (≈$USD10(6) ). As a consequence of carbon's central place in biochemistry, tremendous progress using (13) C d-DNP bioimaging has been demonstrated to date including a number of clinical trials. Despite numerous attempts to develop alternatives to d-DNP, the competing methods have faced significant translational challenges...
May 18, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28514503/slicing-diamond-for-more-sp3-group-14-allotropes-reaching-from-direct-band-gap-to-poor-metals
#11
Thomas Friedrich Fässler, Antti J Karttunen, Laura-Alice Jantke
The large interest in novel Si allotropes has led to an intense investigation of tetrahedral framework structures during the last years. Recently, a guide to deriving sp3-Si allotropes from atom slabs of the diamond structure enabled a systematic deduction of several low-density modifications. Some of the Si networks were recognized as experimentally known frameworks - so-called chemi-inspired structures. We herein present nine novel Si by modifying three-atom thick slabs of the cubic diamond structure after their smooth distortion by applying the same construction kit...
May 17, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28513072/self-assembly-and-local-manipulation-of-au-pyridyl-coordination-networks-on-metal-surfaces
#12
Yang Song, Yuxu Wang, Qiao Jin, Kun Zhou, Ziliang Shi, Pei-Nian Liu, Yu-Qiang Ma
Here, using scanning tunneling microscopy (STM), we demonstrate that Au-pyridyl coordination can be used to assemble two-dimensional coordination network structures on metal surfaces, whose polymorphism can be manipulated at both the micro- and nanoscale. Using the same organic ligand, we assembled two distinct polymorphic network structures, which were respectively assisted by threefold Au-pyridyl coordination on Ag(111) with predeposited Au atoms (α-network), and by twofold Au-pyridyl coordination on Au(111) (β-network)...
May 17, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28510283/ca-2-cl-association-in-water-revisited-the-role-of-cation-hydration
#13
Mathieu Salanne, Sami Tazi, Rodolphe Vuilleumier, Benjamin Rotenberg
We investigate the dissociation of a Ca$^{2+}$-Cl$^-$ pair in water using classical molecular dynamics simulations with a polarizable interaction potential, parameterized from ab initio calculations. By computing the potential of mean force as a function not only of the interionic distance but also of the coordination numbers by water molecules, we show it is necessary to use a collective variable describing the cation hydration in order to capture the dissociation mechanism. In the contact ion pair, the Ca$^{2+}$ cation has a first coordination sphere containing 5 or 6 water molecules...
May 16, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28499077/unconventional-behavior-of-friction-at-the-nanoscale-beyond-amontons-law
#14
Jingrun Chen, Wang Gao
Using a many body van der Waals (vdW) corrected density functional theory approach, we study the atomic-scale friction for a prototypical tip-substrate system of a Si tip and a graphene substrate. In a loading-sliding process, the tip-substrate distance is found to be essential for nanofrictional behavior, through determining the competition between vdW contributions and electronic contributions. As the tip approaches the substrate, this competition results in a smooth transition of normal forces from attraction to repulsion, and the friction coefficient in turn undergoes a sign change from negativity to positivity with possible giant magnitudes and strong anisotropy...
May 12, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28497902/size-shape-and-lateral-correlation-of-highly-uniform-mesoscopic-self-assembled-domains-of-fluorocarbon-hydrocarbon-diblocks-at-the-air-water-interface-a-gisaxs-study
#15
Mariam Veschgini, Wasim Abuillan, Shigeto Inoue, AKihisa Yamamoto, Salomé Mielke, Xianhe Liu, Oleg Konovalov, Marie Pierre Krafft, Motomu Tanaka
The shape and size of self-assembled mesoscopic surface domains of fluorocarbon-hydrocarbon (FnHm) diblocks and the lateral correlation between these domains have been quantitatively determined from grazing incidence small-angle X-ray scattering (GISAXS). The full calculation of structure and form factors unraveled the influence of fluorocarbon and hydrocarbon block lengths on the diameter and height of the domains, and provided the inter-domain correlation length. The diameter of the domains, as determined from the form factor analysis, exhibits a monotonic increase in response to the systematic lengthening of each block, which can be attributed to the increase in van der Waals attraction between molecules...
May 12, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28494119/non-convalent-interactions-between-dopamine-and-regular-defected-graphene
#16
Ana Cecilia Rossi Fernández, Norberto Jorge Castellani
The comprehension of the role played by non-covalent interactions in the adsorption of biological molecules on graphene is a subject of fundamental interest regarding the use of graphene as sensor and drug deliver. The adsorption of dopamine (DA) on regular graphene (G) and graphene with monovacancies (GV) was theoretically studied in the framework of density functional theory. Several adsorption modes were considered, noting that those where the DA molecule is parallel or quasi-parallel to the surface are the more stable...
May 11, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28488803/promises-and-challenges-in-continuous-tracking-utilizing-amino-acids-in-skin-secretions-for-active-multi-factor-biometric-authentication-for-cybersecurity
#17
Juliana Agudelo, Vladimir Privman, Jan Halámek
We consider a new concept of biometric-based cybersecurity systems for active authentication by continuous tracking, which utilizes biochemical processing of metabolites present in skin secretions. Skin secretions contain a large number of metabolites and small molecules that can be targeted for analysis. Here we argue that amino acids found in sweat can be exploited for the establishment of an amino acid profile capable of identifying an individual user of a mobile or wearable device. Individual and combinations of amino acids processed by biocatalytic cascades yield physical (optical or electronic) signals, providing a time-series of several outputs that, in their entirety, should suffice to authenticate a specific user based on standard statistical criteria...
May 10, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28488359/electroluminescent-and-optoelectronic-properties-of-oleds-with-bay-extended-distorted-perylene-esters-as-emitter-materials
#18
Heinz Kitzerow, Joachim Vollbrecht, Simon Blazy, Philipp Dierks, Samuel Peurifoy, Harald Bock
Three esters with a perylene, a unilaterally, and a bilaterally extended perylene core, respectively, were used as emitter materials for organic light emitting diodes. The electroluminescent properties of these devices were studied. Different spectral shifts were found, which can be attributed to the formation of excited dimers (excimers) in the nanofilms of the emitter materials. Thermal treatment of the unilaterally extended derivative resulted in a red-shift of the electroluminescence owing to the formation of a denser nanofilm...
May 10, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28485888/full-correlations-across-broad-nmr-spectra-by-two-field-total-correlation-spectroscopy
#19
Pavel Kadeřávek, Léonard Strouk, Samuel François Cousin, Cyril Charlier, Geoffrey Bodenhausen, Thorsten Marquardsen, Jean-Max Tyburn, Pierre-Alain Bovier, Frank Engelke, Werner Maas, Fabien Ferrage
Total correlation spectroscopy (TOCSY) is a key experiment to assign nuclear magnetic resonance (NMR) spectra of complex molecules. Carbon-13 TOCSY experiments are essential to assign signals of protein side chains. However, the performance of carbon-13 TOCSY deteriorates at high magnetic fields since the necessarily limited radiofrequency irradiation fails to cover the broad range of carbon-13 frequencies. Here, we introduce a new concept to overcome the limitations of TOCSY using two-field NMR spectroscopy...
May 9, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28481439/rational-design-of-stable-dianions-by-functionalizing-polycyclic-aromatic-hydrocarbons
#20
Ming Min Zhong, Jian Zhou, Puru Jena
Using density functional theory, we have carried out a systematic study of the stability and electronic properties of neutral and multiply charged molecules BnC10-nX8 (n = 0, 1, 2; X = H, F, CN). Our main objective is to explore if the replacements of core C atoms and/or H atoms in naphthalene (C10H8) can enhance the stability of their dianions. Indeed, we find that the dianions of BnC10-n(CN)8 are more stable than their monoanions with energies of 0.61 eV, 0.57 eV and 1.97 eV for n = 0, 1, 2, respectively...
May 8, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
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