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Journal of Physical Chemistry. A

Tana Tandaric, Robert Vianello
DFT B3LYP calculations convincingly showed that aromatic pnictogen-oxides offer scaffolds suitable for tailoring powerful organic superbases exhibiting exceptional oxygen basicity in both gas-phase and polar aprotic acetonitrile solution. With their protonation enthalpies and pKa values, they surpass the basicity of classical proton sponges and related nitrogen bases. The most potent system is provided with two arsenic-oxide moieties on the phenanthrene framework assisted with the two phosphazeno groups in the para-position to both basic centers...
January 19, 2018: Journal of Physical Chemistry. A
Francesca Ingrosso, Manuel F Ruiz-Lopez
Iminophosphoranes or phosphazenes are an important class of compounds with increasing use in synthetic organic chemistry as neutral organic superbases exhibiting low nucleophilicity. Their electronic structure and therefore their properties strongly depend on substitution but there have been very few theoretical studies devoted to this topic, and more specifically to the formation of electron donor-acceptor complexes of iminophosphoranes with electrophiles. In this work, we have investigated the interaction with carbon dioxide at different ab initio levels...
January 18, 2018: Journal of Physical Chemistry. A
Tsung-Yen Lee, Chia-Chun Chou
The moving boundary truncated grid method is developed to significantly reduce the number of grid points required for wave packet propagation. The time-dependent Schrodinger equation (TDSE) and the imaginary time Schrodinger equation (ITSE) are integrated using an adaptive algorithm which economizes on the number of grid points. This method employs a variable number of grid points in the Eulerian frame (grid points fixed in space) and adaptively defines the boundaries of the truncated grid. The truncated grid method is first applied to the time integration of the TDSE for the photodissociation dynamics of NOCl and a three-dimensional quantum barrier scattering problem...
January 17, 2018: Journal of Physical Chemistry. A
Égil da Brito Sá, Albert Rimola, Luis Rodríguez-Santiago, Mariona Sodupe, Xavier Solans-Monfort
Present work addresses the reactivity of several phenyl-substituted metal-carbene complexes with 4-methylstyrene by means of DFT(OPBE) simulations. Different paths that lead to cyclopropanation have been explored and compared to the olefin metathesis mechanism. For this purpose, we have chosen different catalysts: i) the Grubbs 2nd generation olefin metathesis catalyst, ii) a Grubs 2nd generation-like complex, in which ruthenium is replaced by an iron atom, and iii) two iron carbene complexes that experimentally catalyze alkene cyclopropanation...
January 17, 2018: Journal of Physical Chemistry. A
David Wilian Oliveira de Sousa, Marco Antonio Chaer Nascimento
The Interference Energy Partitioning Analysis method developed by our group and used to study the nature of the chemical bond was extended to partition of the electric dipole moment in quasi-classical and interference contributions. Our results show that interference participates in charge displacement in polar molecules, providing a relevant contribution for the total dipole moment. A linear correlation was found between the interference contribution of the dipole moment from the bond electron group, μINT(bond), and the difference of electronegativity of the atoms which form the bond, ΔXAB...
January 16, 2018: Journal of Physical Chemistry. A
David Danovich, Cina Foroutan-Nejad, Philippe Charles Hiberty, Sason Shaik
We analyze the properties of fifteen 3-electron bonds, which include σ-3-electron-bonds, such as dihalide radical anions and di-Noble gas radical cations, π-3-electron-bonds as in hydrazine-radical cation, and doubly-π-(3e)-bonded species such as O2, FeO+, S2, etc. The primary analytical tool is the breathing-orbital valence-bond (BOVB) method, which enables us to quantify the charge-shift resonance energy (RECS) of the 3-electrons, and the bond dissociation energies (De). BOVB is tested reliable against MRCI calculations...
January 16, 2018: Journal of Physical Chemistry. A
Ulises Orozco-Valencia, José L Gázquez, Alberto Vela
The local and global charge transfer approach based on the two parabolas model is applied to several problems aiming to show the importance of incorporating the reaction conditions to evaluate the global and local chemical descriptors. It is shown that by preparing the reactants the chemical potentials of the reacting species determined by the two parabolas model satisfy the condition for the transfer of electrons in the direction dictated by the chemical potential difference. The model is applied to the hydration of alkenes, showing that it recovers Markovnikov's rule, to aromatic nitration, and to the interaction of nitrobenzenes with 1,3-diethylurea, an electrochemically controlled hydrogen-bonding problem...
January 16, 2018: Journal of Physical Chemistry. A
Rocío Sánchez-de-Armas, Carmen J Calzado
The interaction between itinerant π- and localized d- electrons in metal-phthalocyanines, namely Jπd interaction, is considered as responsible for the giant negative magnetoresistance observed in several phthalocyanine-based conductors, among many other important physical properties. Despite the fundamental and technological importance of this on-site intramolecular interaction, its giant ferromagnetic nature has been only recently demonstrated by the experiments conducted by Murakawa et al. in the neutral radical [Fe(Pc)(CN)2]2CHCl3 (Phys...
January 16, 2018: Journal of Physical Chemistry. A
Johan F Triana, Daniel Pelaez Ruiz, Jose Luis Sanz-Vicario
The quantum photodynamics of a simple diatomic molecule with a permanent dipole immersed within an optical cavity containing a quantized radiation field is studied in detail. The chosen molecule under study, lithium fluoride (LiF), is characterized by the presence of an avoided crossing between the two lowest 11Σ potential energy curves (covalent-ionic diabatic crossing). Without field, after prompt excitation from the ground state 11Σ, the excited nuclear wave packet moves back and forth in the upper 21Σ state, but in the proximity of the avoided crossing, the non-adiabatic coupling transfers part of the nuclear wave packet to the lower 11Σ state, which eventually leads to dissociation...
January 16, 2018: Journal of Physical Chemistry. A
Gao-Lei Hou, Niranjan Govind, Sotiris S Xantheas, Xue-Bin Wang
Four new Zeise's family ions with mixed halide ligands, i.e., PtClnX3-n(C2H4)‒ (X = Br, I; n = 1, 2), were synthesized via ligand-exchange reactions of KX salts with KPtCl3(C2H4) in aqueous solutions, and were detected in vacuum via electrospray ionization mass spectrometry. Their photoelectron spectra reveal a series of well-resolved spectral peaks with their electron binding energies (EBEs) decreasing with increasing halide size, with I having a much stronger effect than Br, i.e., 4.57 (-Cl3) > 4.56 (-Cl2Br) > 4...
January 16, 2018: Journal of Physical Chemistry. A
Philippe B Wilson, Ian H Williams
DFT calculations for CH3+ within a constrained cage of water molecules permit the controlled manipulation of distances rax and req to "axial" and "equatorial" waters. Equatorial CH…O interactions catalyze methyl transfer (MT) between axial waters. Variation in rax has a greater effect on CH bond lengths and stretching force constants in the symmetric SN2-like transition structures than variation in req. In-plane bending frequencies are insensitive to these variations in cage dimensions, but axial interactions loosen the out-of-plane bending mode (OP) whereas equatorial interactions stiffen it...
January 16, 2018: Journal of Physical Chemistry. A
Guy M Bernard, Roderick E Wasylishen, Christopher I Ratcliffe, Victor V Terskikh, Qichao Wu, Jillian M Buriak, Tate C Hauger
In light of the intense recent interest in the methylammonium lead halides, CH3NH3PbX3 (X = Cl, Br and I) as sensitizers for photovoltaic cells, the dynamics of the methylammonium (MA) cation in these perovskite salts has been reinvestigated as a function of temperature via 2H, 14N and 207Pb NMR spectroscopy. In the cubic phase of all three salts, the MA cation undergoes pseudo-isotropic tumbling (ps time scale). For example, the correlation time, τ2, for the C-N axis of the iodide salt is 0.85 ± 0.30 ps at 330 K...
January 16, 2018: Journal of Physical Chemistry. A
Hyun Sik You, Junggil Kim, Songhee Han, Doo-Sik Ahn, Jean Sun Lim, Sang Kyu Kim
Conformational isomers of hydroquinone and their 1:1 clusters with water have been spatially separated using the Stark deflector in the supersonic jet. Trans-hydroquinone (HyQ) conformer with zero dipole moment is little influenced by inhomogeneous electric fields whereas cis-conformer with nonzero dipole moment (2.38 D) is significantly deflected from the molecular beam axis into the direction along which the strong field gradient is applied. Resonant two photon ionization carried out by shifting the laser position perpendicular to the molecular beam axis after the Stark deflector then gives an exclusive S1-S0 excitation spectrum of the cis-conformer only, making possible immaculate conformer-specific spectroscopy and dynamics...
January 16, 2018: Journal of Physical Chemistry. A
Dmitri G Fedorov, Kazuo Kitaura
Pair interaction energy decomposition analysis in the fragment molecular orbital (FMO) method is extended to treat density functional theory (DFT) and density-functional tight-binding (DFTB). Fluctuations of energy contributions are obtained from molecular dynamics simulations. Interactions at the DFT and DFTB levels are compared to the values obtained with Hartree-Fock, second order Møller-Plesset (MP2) and coupled cluster methods. Hydrogen bonding in water clusters is analyzed. 200 ps NVT molecular dynamics simulations are performed with FMO for two ligands bound to the Trp-cage miniprotein (PDB: 1L2Y); the fluctuations of fragment energies and interactions are analyzed...
January 16, 2018: Journal of Physical Chemistry. A
Meiheng Lu, Panwang Zhou, Yinhua Ma, Zhe Tang, Yanqiang Yang, Keli Han
Rapid detection of chemical explosives is crucial for national security and public safety, and investigation of sensing mechanisms is important to design highly efficient chemosensors. This study theoretically investigates the detection and fluorescence mechanism of a newly synthesized pyrene based chemosensor for detection of trinitrotoluene (TNT) through density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, suggesting a different interaction product of the probe and TNT from previously reported ones (Mosca, L...
January 16, 2018: Journal of Physical Chemistry. A
Eshani Hettiarachchi, Omar Hurab, Gayan Rubasinghege
Over the last several decades, iron has been identified as a limiting nutrient in about half of the world's oceans. Its most significant source is identified as deposited iron-containing mineral dust that has been processed during atmospheric transportation. The current work focuses on chemical and photochemical processing of iron-containing mineral dust particles in the presence of nitric acid, and an organic pollutant dimethyl sulfide under atmospherically relevant conditions. More importantly, ilmenite (FeTiO3) is evaluated as a proxy for the iron-containing mineral dust...
January 16, 2018: Journal of Physical Chemistry. A
Kirill S Ershov, Sergei A Kochubei, Vitaly G Kiselev, Alexey V Baklanov
UV-photodissociation at 266 nm of a widely used TiO2 precursor, titanium tetraisopropoxide (Ti(OiPr)4, TTIP), was studied under molecular beam conditions. Using the MS-TOF technique, atomic titanium and titanium(II) oxide (TiO) were detected among the most abundant photofragments. Experimental results were rationalized with the aid of quantum chemical calculations (DLPNO-CCSD(T) and DFT). Contrary to existing literature data, the new four-centered reaction of acetone elimination was found to be the primary decomposition process of TTIP...
January 15, 2018: Journal of Physical Chemistry. A
John C Walton
Radical centers close to protons are known to enhance their dissociation. Investigation of the generality of this Radical Enhanced Deprotonation (RED-shift) phenomenon and the kinds of structures in which it operates are reported. The pKas for sulfinic, sulfonic, pentan-2,4-dione and Meldrum's acid species, with adjacent radicals centered on C-, N- and O-atoms, were computed by a DFT method from free energies of deprotonation. All series showed significant RED-shifts that increased with the electronegativity of the radical center...
January 15, 2018: Journal of Physical Chemistry. A
Neil James Reilly, Gabriel da Silva, Callan M Wilcox, Zijun Ge, Damian L Kokkin, Tyler P Troy, Klaas Nauta, Scott H Kable, Michael C McCarthy, Timothy W Schmidt
The products of an electrical discharge containing toluene are interrogated using resonance-enhanced multiphoton ionization and laser-induced fluorescence spectroscopies. A previously unreported electronic spectrum recorded at m/z = 105, with a putative origin band at 26053 cm-1, is assigned to methyltropyl radical, which appears to be a major product of the toluene discharge, plausibly arising from CH insertion. All three o-, m- and p-xylyl isomers are also identified. These isomers are detected in electrical discharges containing various xylenes, where it is also found that interconversion occurs: A discharge of o-xylene produces some m-xylyl; a discharge of m-xylene produces some o-xylyl; and a discharge of p-xylene produces all three isomers...
January 15, 2018: Journal of Physical Chemistry. A
Bright U Emenike, Ronald A Spinelle, Ambar Rosario, David W Shinn, Barney Yoo
CH-π aromatic interactions are ubiquitous in nature and are capable of regulating important chemical and biochemical processes. Solvation and aromatic substituent effects are known to perturb the CH-π aromatic interactions. However, the nature by which the two factors influence one another is relatively unexplored. Here we demonstrate experimentally that there is a quantitative correlation between substituent effects in CH-π interactions and the hydrogen-bond acceptor constant of the solvating molecule. The CH-π interaction energies were measured by the conformational study of a series of aryl-substituted molecular balances in which the conformational preferences depended on the relative strengths of the methyl and aryl CH-π interactions in the folded and unfolded states, respectively...
January 15, 2018: Journal of Physical Chemistry. A
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