Search results for "Computational Chemistry"
showing 10 items of 1209 documents
On the role of the triplet state in the cis/trans isomerization of rhodopsin: A CASPT2//CASSCF study of a model chromophore
2011
The possibility of population of the lowest-lying triplet state (T1) in the early events of the photochemical isomerization process of a model chromophore of Rhodopsin (Rh) has been analyzed using multireference perturbation theory (CASPT2//CASSCF) methods. It is shown that the characteristics of the isomerization process namely small S1−T1 gap, presence of hydrogen out of plane active vibrational modes, and existence of a dense manifold of vibrational states, render possible the fulfilment of the conditions needed for the population of T1. The possible consequences for the photochemistry and photophysics of Rh are also discussed. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem 111:3431–3…
Gas phase behavior of radical cations of perfluoroalkyl-1,2,4-triazines: an experimental and theoretical study
2009
Electron ionization mass spectrometry and low-energy collision-induced decomposition reactions occurring in a tridimensional ion trap, together with density functional theory (DFT) calculations on neutrals, even- and odd-electron cations, have been used to study the gas-phase ion chemistry of a series of perfluoroalkyl-1,2,4-triazines. Loss of oxygen, due to thermal degradation occurring before ionization, likely involving the hydroxylamino group, has been observed. Compounds having a carbonyl group at position 6 of the triazine ring fragment in the source by elimination of NO followed by HF or CO. The decomposition pathways occurring due to CID experiments have shown interesting features d…
On the potential carcinogenic and mutagenic character of benzobiphenylenes
1979
Abstract PMO estimations suggest certain partially saturated benzobiphenylene carbonium ions might exhibit carcinogenic and/or mutagenic activity.
Rotational spectrum of silyl chloride: hyperfine structure and equilibrium geometry
2012
The Lamb-dip technique was employed to record the rotational spectra of two isotopic species of silyl chloride, namely (28)SiH3Cl and (29)SiH3Cl, in order to investigate their hyperfine structure. High-accuracy quantum-chemical computations were employed to predict the hyperfine parameters involved and to support the experimental investigation. Analysis of the experimental spectra led to an improvement in the accuracy of the known spectroscopic constants as well as allowed us to determine additional spectroscopic parameters for the first time. Furthermore, the equilibrium structure of silyl chloride was reinvestigated using both theoretical and experimental data. The best theoretical and se…
Characterizing Cavities in Model Inclusion Fullerenes: A Comparative Study
2001
Abstract: The fullerene-82 cavity is selected as a model system in order to test several methods for characterizing inclusion molecules. The methods are based on different technical foundations such as a square and triangular tessellation of the molecular surface, spherical tessellation of the molecular surface, numerical integration of the atomic volumes and surfaces, triangular tessellation of the molecular surface, and cubic lattice approach to the molecular volume. Accurate measures of the molecular volume and surface area have been performed with the pseudorandom Monte Carlo (MCVS) and uniform Monte Carlo (UMCVS) methods. These calculations serve as a reference for the rest of the meth…
Persistence of oxidation state III of gold in thione coordination
2017
Ligands N,N'-tetramethylthiourea and 2-mercapto-1-methyl-imidazole form stable Au(III) complexes [AuCl3(N,N'-tetramethylthiourea)] (1) and [AuCl3(2-mercapto-1-methyl-imidazole)] (2) instead of reducing the Au(III) metal center into Au(I), which would be typical for the attachment of sulfur donors. Compounds 1 and 2 were characterized by spectroscopic methods and by X-ray crystallography. The spectroscopic details were explained by simulation of the UV-Vis spectra via the TD-DFT method. Additionally, computational DFT studies were performed in order to find the reason for the unusual oxidation state in the crystalline materials. The preference for Au(III) can be explained via various weak in…
Rearrangements of 1,2,4-Oxadiazole: “One Ring to Rule Them All”
2017
[Figure not available: see fulltext.] 1,2,4-Oxadiazoles are heterocycles characterized by low aromaticity and the presence of a weak OâN bond and are widely studied due to their tendency to rearrange into more stable heterocyclic compounds. This review covers literature from the last fifteen years, highlighting the general features of 1,2,4-oxadiazoles and their applications. Regarding the reactivity, the development of classical reactions (thermal and photochemical rearrangements) is presented in terms of synthetic utility and mechanistic insight. Among the relevant rearrangement reactions, the BoultonâKatritzky Rearrangement (BKR), Migration â Nucleophilic Attack â Cyclization (MN…
A Computational Study of Adsorption of CO2, SO2, and H2CO on Free-Standing and Molybdenum-Supported CaO Films
2018
Oxide films play a significant role in a wide range of fields from catalysis to solar cell materials. CaO films are promising sorbents for many environmentally harmful molecules. Here, we report a systematic investigation of adsorption of CO2, SO2, and H2CO on bulk and Mo-supported CaO(100) films using density functional theory. Significant effects on adsorption energy, charge transfer to the molecules, and degree of the C–O bond activation were demonstrated on Mo-supported CaO films by changing the film thickness, composition, and the strength and direction of an applied external electric field. These findings are relevant for interpreting results from scanning tunneling microscopy of smal…
Comment on “Crystallographic Snapshot of an Arrested Intermediate in the Biomimetic Activation of CO2”
2015
Out of focus: A recent Communication published in this journal describes the synthesis of [nBu4 N]HCO3 . The authors performed a single-crystal X-ray study that revealed a putative species described as an incipient hydroxide ion engaging in a long, and presumably weak, interaction with CO2 . Our recent exploration of the coordination chemistry of CO2 with small ions leads us to believe that such an exceptional bonding situation is unlikely. Instead, we argue that the crystal structure is that of [nBu4 N]O2 CCH3 and therefore not representative of the bulk powder from the synthesis.
A Computational Study of Adsorption of CO2, SO2, and H2CO on Free-Standing and Molybdenum-Supported CaO Films
2019
Oxide films play a significant role in a wide range of fields from catalysis to solar cell materials. CaO films are promising sorbents for many environmentally harmful molecules. Here, we report a systematic investigation of adsorption of CO2, SO2, and H2CO on bulk and Mo-supported CaO(100) films using density functional theory. Significant effects on adsorption energy, charge transfer to the molecules, and degree of the C−O bond activation were demonstrated on Mo-supported CaO films by changing the film thickness, composition, and the strength and direction of an applied external electric field. These findings are relevant for interpreting results from scanning tunneling microscopy of smal…