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Journal of Physical Chemistry. A

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https://www.readbyqxmd.com/read/28650637/a-dft-tddft-study-on-the-sensing-mechanism-of-a-fluorescent-probe-for-hydrogen-sulfide-excited-state-intramolecular-proton-transfer-coupled-twisted-intramolecular-charge-transfer
#1
Yang Li, Tian-Shu Chu
By using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, the sensing mechanism of a fluorescent probe 2-(2-hydroxyphenyl) benzothiazole (HBT) derivative HBTPP-S for hydrogen sulfide has been thoroughly studied. The thiolysis reaction has a moderate reaction barrier of 18.40 kcal mol-1, which indicates that the hydrogen sulfide sensing process has a favorable response speed. Due to the non-radiative donor-excited photoinduced electron transfer (d-PET, fluorophore as the electron donor) from the excited HBTPP group to the electron-withdrawing 2,4-dinitrophenyl group, as well as the inhibition of the proton transfer (PT) and the excited state intramolecular proton transfer (ESIPT) process by 2,4-dinitrophenyl group, the probe HBTPP-S is essentially non-fluorescent...
June 26, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28650633/two-photon-spectroscopy-of-a-series-of-platinum-acetylides-conformation-induced-ground-state-symmetry-breaking
#2
Thomas M Cooper, Joy E Haley, Douglas M Krein, Aaron R Burke, Jonathan E Slagle, Aleksandr Mikhailov, Aleksander Rebane
With the goal of elucidating electronic and conformational effects on structure-spectroscopic property relationships in platinum acetylides, we synthesized a series of nominally centrosymmetric chromophores trans-Pt(PBu3)2(CC-Phenyl-X)2, where X = diphenylamino(DPA), NH2, OCH3, t-Bu, CH3, H, F, benzothiazole(BTH), CF3, CN and NO2. We collected one- and two-photon absorption spectra and also performed DFT and TDDFT calculations on the ground and excited state properties of these compounds. The DFT calculations revealed facile rotation between the two ligands, suggesting that the compounds exhibit nonplanar ground state conformations in solution...
June 26, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28650172/the-quantum-molecular-trajectory-and-its-statistical-properties
#3
Francesco Avanzini, Giorgio J J Moro
Despite the quantum nature of molecules, Classical Mechanics is often employed to describe molecular motions that play a fundamental role in a wide range of phenomena including chemical reactions. This is due to the need of assigning well defined positions to the atomic nuclei during the time evolution of the system in order to describe unambiguously the molecular motions, whereas Quantum Mechanics provides information of probabilistic nature only. One would like to employ a quantum molecular trajectory that defines rigorously the instantaneous nuclear positions and, simultaneously, guarantees the conservation of all Quantum Mechanics predictions unlike the classical trajectory...
June 26, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28650164/effect-of-ancillary-ligands-a-on-oxidative-addition-of-ch4-to-re-iii-complexes-a-b-al-ch-sih-n-p-using-mp2-ccsd-t-and-mcscf-methods
#4
Riffat Parveen, Thomas R Cundari
A computational study of oxidative addition (OA) of methane to Re(OC2H4)3A (A = ancillary ligand, which thus may interact with the metal) was carried out. The choice of ancillary ligands has been made based on their electronic properties: A = B or Al (Lewis acid), CH or SiH (electron precise), N (σ-donor) and P (σ-donor/π-acid). The main objective of this study was to understand how variation in A affects the structural and electronic properties of the reactant d(4)-Re(III) complex, which can ultimately tune the kinetics and thermodynamics of OA...
June 26, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28650163/enhanced-hydrogen-production-with-chiral-conductive-polymer-based-electrodes
#5
Francesco Tassinari, Koyel Banerjee-Ghosh, Francesca Parenti, Kiran Vankayala, Adele Mucci, Ron Naaman
Efficient photoelectrochemical production of hydrogen from water is the aim of many studies in recent decades. Typically, one observes that the electric potential required to initiate the process significantly exceeds the thermodynamic limit. It was suggested that by controlling the spins of the electrons that are transferred from the solution to the anode, and ensuring that they are co-aligned, the threshold voltage for the process can be decreased to that of the thermodynamic voltage. In the present study, by using anodes coated with chiral conductive polymer, the hydrogen production from water is enhanced and the threshold voltage is reduced, as compared with anodes coated with achiral polymer...
June 26, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28609622/combined-electron-diffraction-and-spectroscopic-determination-of-the-structure-of-spiropentane-c5h8
#6
Jason W Sandwisch, Blake A Erickson, Kenneth Hedberg, Joseph W Nibler
Gas-phase electron-diffraction (GED) data have been combined with recent spectroscopic rotational constants to determine the rα(0) structural parameters for spiropentane, C5H8. The structure has D2d symmetry, and the results yield values of 1.105(2) Å for the CH bond length, 1.557(3) Å for the distal CC bond length, and a smaller value of 1.482(1) Å for the four lateral CC bonds that connect to the central carbon atom. The HCH angle is 113.7(13)°, and the HCH flap angle, defined as the angle of the HCH bisector and the distal CC bond, is 150...
June 26, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28598172/feasibility-of-photosensitized-reactions-with-secondary-organic-aerosol-particles-in-the-presence-of-volatile-organic-compounds
#7
Kurtis T Malecha, Sergey A Nizkorodov
The ability of a complex mixture of organic compounds found in secondary organic aerosol (SOA) to act as a photosensitizer in the oxidation of volatile organic compounds (VOCs) was investigated. Different types of SOAs were produced in a smog chamber by oxidation of various biogenic and anthropogenic VOCs. The SOA particles were collected from the chamber onto an inert substrate, and the resulting material was exposed to 365 nm radiation in an air flow containing ∼200 ppbv of limonene vapor. The mixing ratio of limonene and other VOCs in the flow was observed with a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS)...
June 26, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28581295/mqct-i-inelastic-scattering-of-two-asymmetric-top-rotors-with-application-to-h2o-h2o
#8
Alexander Semenov, Dmitri Babikov
A mixed quantum/classical theory (MQCT) for the inelastic collision of two asymmetric-top rotor molecules is developed. In this method, the quantum state-to-state transitions between the rotational states of molecules (internal) are treated quantum mechanically using the time-dependent Schrodinger equation, whereas their relative translational motion (responsible for scattering) is treated classically, using the average trajectory approach. Two versions of the formula for transition matrix elements are presented: a straightforward approach that uses numerical multidimensional quadrature over all the internal degrees of freedom and a more standard analytic approach that uses the expansion of the PES over the basis set of spherical harmonics...
June 26, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28644629/environmental-polymer-degradation-using-the-distonic-radical-ion-approach-to-study-the-gas-phase-reactions-of-model-polyester-radicals
#9
Bethany I Taggert, Richard A J O'Hair, Uta Wille
A novel precursor to the distonic O- and C-centred radical cations Oxo+O• and Oxo+C• was designed and synthesized, which represent model systems for radicals produced during polyester degradation. The precursor is equipped with a nitrate functional group, which serves as a masked site for these alkoxyl and carbon radicals that are unleashed through collision-induced dissociation (CID). Oxo+O• and Oxo+C• feature a cyclic carboxonium ion as permanent charge tag to enable monitoring their ion-molecule reactions on the millisecond to second timescale in the ion trap of the mass spectrometer...
June 23, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28644628/stereoelectronics-of-the-hydrogen-bond-induced-fluorescence-quenching-of-3-aminofluorenones-with-alcohols
#10
Isaac G Alty, Christopher John Abelt
Two derivatives of 3-amino-9-fluorenone (1) bearing one (2) and two methyl (3) groups flanking carbonyl group are prepared. Comparison of their photophysical properties show that all suffer efficient radiationless deactivation in the presence of alcohols. Preferential solvation studies with mono alcohols reveal that a single H-bonding interaction quenches the excited states of 1 and 2, but not that of 3. In contrast, a single molecule of ethylene glycol quenches all three. These results are interpreted in a quenching mechanism similar to one proposed by Inoue and coworkers, but where an out-of-plane H-bond with the carbonyl group gives rise to an emissive species, while an in-plane H-bond results in quenching...
June 23, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28644619/long-bonding-in-hngcn-nc-ng-noble-gas-molecules-an-nbo-nrt-investigation
#11
Guiqiu Zhang, Shengnan Zhang, De-Zhan Chen
Recently, Weinhold et al. put forward one new concept of σ̂-type long-bonding and applied it to the comprehension of halogen noble-gas hydrides HNgY (Ng = noble gas; Y = halogen) bonding. The present study extends this new concept into HNgX (X = CN, NC) pseudo-halogen molecules. At the B3LYP and CCSD(T) levels of theory, we perform Natural Bond Orbital (NBO) and Natural Resonance Theory (NRT) studies on the HNgX molecules and compare it with the previous results of HNgY molecules. The NBO/NRT results clearly reveal that each of the HNgX, but not the HHeCN, HNeCN and HNeNC molecules, is composed of three leading resonance structures: two ω-bonding structures H-Ng(+) :X(-), H:(-) Ng(+)-X and one long-bonded structure H^X...
June 23, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28613897/radical-ions-of-a-%C3%AF-bowl-sumanene-effects-of-strained-structure-on-the-electronic-transitions
#12
Mamoru Fujitsuka, Sachiko Tojo, Toru Amaya, Toshikazu Hirao, Tetsuro Majima
Strained polyaromatic carbon molecules exhibit interesting properties owing to enhanced interactions between p orbitals of sp(2) carbons; sumanene (SUM) is one of these bowl-shaped π-conjugated molecules (π-bowls). In the present study, the radical cation and radical anion of SUM were characterized by radiation chemical methods, that is, pulse radiolysis and γ-ray radiolysis. Absorption spectra of the SUM radical cation and radical anion in a wide spectral region ranging from the visible to near-IR were successfully obtained...
June 23, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28598617/role-of-n-heterocyclic-carbenes-as-ligands-in-iridium-carbonyl-clusters
#13
Shengjie Zhang, Sawyer D Foyle, Alexander Okrut, Andrew Solovyov, Alexander Katz, Bruce C Gates, David A Dixon
The low-energy isomers of Irx(CO)y(NHC)z (x = 1, 2, 4) are investigated with density functional theory (DFT) and correlated molecular orbital theory at the coupled cluster CCSD(T) level. The structures, relative energies, ligand dissociation energies, and natural charges are calculated. The energies of tetrairidium cluster are predicted at the CAM-B3LYP level that best fit the CCSD(T) results compared with the other four functionals in the benchmark calculations. The NHC's behave as stronger σ donors compared with CO's and have higher ligand dissociation energies (LDEs)...
June 23, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28558212/thermal-decomposition-mechanism-for-ethanethiol
#14
AnGayle K Vasiliou, Daniel E Anderson, Thomas W Cowell, Jessica Kong, William F Melhado, Margaret D Phillips, Jared C Whitman
The thermal decomposition of ethanethiol was studied using a 1 mm × 2 cm pulsed silicon carbide microtubular reactor, CH3CH2SH + Δ → Products. Unlike previous studies these experiments were able to identify the initial ethanethiol decomposition products. Ethanethiol was entrained in either an Ar or a He carrier gas, passed through a heated (300-1700 K) SiC microtubular reactor (roughly ≤100 μs residence time) and exited into a vacuum chamber. Within one reactor diameter the gas cools to less than 50 K rotationally, and all reactions cease...
June 23, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28640617/5-methylhydantoin-from-isolated-molecules-in-a-low-temperature-argon-matrix-to-solid-state-polymorphs-characterization
#15
Bernardo A Nogueira, Gulce O Ildiz, João Canotilho, M Ermelinda S Eusébio, Marta Sofia C Henriques, José A Paixão, Rui Fausto
The molecular structure, vibrational spectra and photochemistry of 5-methylhydantoin (C4H6N2O2; 5-MH) were studied by matrix isolation infrared spectroscopy and theoretical calculations at the DFT(B3LYP)/6-311++G(d,p) theory level. The Natural Bond Orbital (NBO) analysis approach was used to study in detail the electronic structure of the minimum energy structure of 5-MH, namely the specific characteristics of the σ and π electronic systems of the molecule, and the stabilizing orbital interactions. UV irradiation of 5-MH isolated in argon matrix resulted in its photofragmentation through a single photochemical pathway, yielding isocyanic acid, ethanimine and carbon monoxide, thus following a pattern already observed before for the parent hydantoin and 1-methylhydantoin molecules...
June 22, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28613903/effects-of-water-molecule-on-co-oxidation-by-oh-reaction-pathways-kinetic-barriers-and-rate-constants
#16
Linyao Zhang, Li Yang, Yijun Zhao, Jiaxu Zhang, Dongdong Feng, Shaozeng Sun
The water dilute oxy-fuel combustion is a clean combustion technology for near-zero emission power; and the presence of water molecule could have both kinetic and dynamic effects on combustion reactions. The reaction OH + CO → CO2 + H, one of the most important elementary reactions, has been investigated by extensive electronic structure calculations. And the effects of a single water molecule on CO oxidation have been studied by considering the preformed OH(H2O) complex reacts with CO. The results show little change in the reaction pathways, but the additional water molecule actually increases the vibrationally adiabatic energy barriers (Va(G))...
June 22, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28610422/tracking-intramolecular-vibrational-redistribution-in-polyatomic-small-molecule-liquids-by-ultrafast-time-frequency-resolved-cars
#17
Xiaosong Liu, Wei Zhang, Yunfei Song, Guoyang Yu, Zhaoyang Zheng, Yangyang Zeng, Zhe Lv, Huajie Song, Yanqiang Yang
Selective excitation of C-H stretching vibrational modes, detection of intramolecular vibrational energy redistribution (IVR), and vibrational modes coupling in the electronic ground state of benzene are performed by using femtosecond time- and frequency-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy. Both of the parent modes in the Raman-active bands are coherently excited by an ultrafast stimulated Raman pump, giving initial excitations of 3056 cm(-1) (A1g) and 3074 cm(-1) (E2g) and subsequent IVR from the parent modes to daughter modes of 1181 and 992 cm(-1), and the coherent vibrational coupling of the relevant modes is tracked...
June 22, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28636381/density-functional-study-of-trimetallic-auxpdyptz-x-y-z-7-clusters-and-their-interactions-with-the-o2-molecule
#18
Shuang Zhao, Bo Zhao, XinZhe Tian, Yun-Lai Ren, Kaisheng Yao, JianJi Wang, JunNa Liu, Yunli Ren
Density functional theory calculations were performed to investigate the structural and energetic properties of trimetallic AuxPdyPtz clusters with x+y+z=7. The possible stable geometrical configurations with their electronic states are determined. We analyze the chemical order, binding energies, vertical ionization potential, electron affinity and HOMO-LUMO gaps as a function of the whole concentration range. The affinity of AuxPdyPtz clusters towards one O2 molecule is also evaluated in terms of the changes in geometry, adsorption energy and charge transfer...
June 21, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28636377/enthalpies-of-formation-of-hydrazine-and-its-derivatives
#19
Olga V Dorofeeva, Oxana N Ryzhova, Taisiya A Suchkova
Enthalpies of formation, ∆_f H_298^°, both in the gas and condensed phase, and enthalpies of sublimation or vaporization have been estimated for hydrazine, NH2NH2, and its 36 various derivatives using quantum chemical calculations. The composite G4 method has been used along with isodesmic reaction schemes to derive a set of self-consistent high accuracy gas-phase enthalpies of formation. To estimate the enthalpies of sublimation and vaporization with reasonable accuracy (5-20 kJ/mol), the method of molecular electrostatic potential (MEP) has been used...
June 21, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28636374/correction-to-rate-coefficients-of-the-hcl-oh-%C3%A2-cl-h2o-reaction-from-ring-polymer-molecular-dynamics
#20
Junxiang Zuo, Yongle Li, Hua Guo, Daiqian Xie
No abstract text is available yet for this article.
June 21, 2017: Journal of Physical Chemistry. A
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