Quantum-chemical analysis

A detailed experimental investigation and quantum-chemical analysis of 2PA spectra for quadrupolar D-ti-A-ji-D structures in cyanine-like molecules are... 

The ESA spectra of asymmetrical dyes in toluene are shown in Fig. 25. They show broad structureless bands in the NIR region (750-1,100 nm for G19, 850-1,100 nm for G40, and 950-1,100 nm for G188) and more intense transitions in the visible range (400-550 nm for G19, 400-600 nm for G40, and 450-650 nm for G188). Similarly to symmetrical anionic polymethine dyes (Fig. 20), the increase of conjugation length leads to a small red shift of ESA spectra, and to an enhancement of ESA cross sections and the ratio between the ESA and linear absorption oscillator strengths by approximately a factor of two. More detailed experimental description and quantum-chemical analysis can be found in [86]. 

In the CP-O2 complex, the CP surface is an electron density donor. For example, in the case of PANI, the bond orders in adsorbed 02 molecules decrease by about 30%, and the bond lengths L increase by about 24%. Thus, the adsorbed 02 molecules have a fairly high degree of activation and can readily interact with the protons. Hence, quantum-chemical analysis confirms the mechanism of O2 electroreduction and gives possibility to understand the reasons of PANI catalytic activity. 

Therefore, quantum-chemical analysis confirms the mechanism of 02 electroreduction and gives possibility to understand the reasons of PANI catalytic activity. 

The recent quantum-chemical analysis of the reaction of dioxygen with ethyl radical in the gas phase provided evidence for two pathways of interaction [83] ... 

For the first time, the primary nitrone (formaldonitrone) generation and the comparative quantum chemical analysis of its relative stability by comparison with isomers (formaldoxime, nitrosomethane and oxaziridine) has been described (357). Both, experimental and theoretical data clearly show that the formal-donitrones, formed in the course of collision by electronic transfer, can hardly be molecularly isomerized into other [C,H3,N,0] molecules. Methods of quantum chemistry and molecular dynamics have made it possible to study the reactions of nitrone rearrangement into amides through the formation of oxaziridines (358). 

Green, J. P., Johnson, C. L., Weinstein, H., Kang, S., and Chou, D. (1978) Molecular determinants for interaction with the LSD receptor Biochemical studies and quantum chemical analysis. In The Psychopharmacology of Hallucinogens, edited by R. C. Stillman and R. E. Willette, pp. 28-60. Pergamon Press, New York. 

The reversal of the thermal decomposition of 6 to ethylene and vinylacetylene cannot be utilized to generate 6, since, according to a quantum-chemical analysis, the reaction is slightly endergonic and requires a large free activation enthalpy (0.9 and 42 kcal mol-1, respectively) [59]. The intramolecular variant of this process as well as the addition of typical dienophiles of the normal Diels-Alder reaction to divinylace-tylenes will be discussed at the end of Section 6.3.3. 

Sakurai M, Tamagawa H, Inoue Y, Ariga K, Kunitake T (1997) Theoretical study of intermolecular interaction at the lipid-water interface. 1. Quantum chemical analysis using a reaction field theory. J Phys Chem B 101 4810-4816... 

However, a quantum-chemical analysis indicates the stability of the ZnsSnsBig cluster core. It can be described as a Zn-centered monocapped pentagonal antiprism, which is equivalent to an icosahedron with one missing apex atom, and consists of a planar Zns unit which is coplanar with an (Sn/Bi)s five-membered ring. As in [Zn ... 

For the description of a solution of alanine in water two models were compared and combined with one another (79), namely the continuum model approach and the cluster ansatz approach (148,149). In the cluster approach snapshots along a trajectory are harvested and subsequent quantum chemical analysis is carried out. In order to learn more about the structure and the effects of the solvent shell, the molecular dipole moments were computed. To harvest a trajectory and for comparison AIMD (here CPMD) simulations were carried out (79). The calculations contained one alanine molecule dissolved in 60 water molecules. The average dipole moments for alanine and water were derived by means of maximally localized Wannier functions (MLWF) (67-72). For the water molecules different solvent shells were selected according to the three radial pair distributions between water and the functional groups. An overview about the findings is given in Tables II and III. 

Ultraviolet spectra,291292 dipole moments,291 quantum chemical analysis,293,294 and photochromism295 have been reported. 

An example of the inherent complexities in assigning homoaromaticity in neutral hydrocarbons, even when accompanied by thermochemical, molecular mechanical and/or quantum chemical analysis, is shown by the competing studies of the energetics of triquinacene ... 

Jensen carried out a structural determination of l,3-dichloro-l,3-diazetidine-2,4-dione 45 <2004SAA2719>. Due to its symmetry and unusual bonding, l,3-dichloro-l,3-diazetidine-2,4-dione is an interesting case for quantum chemical analysis. The vibrational frequencies of 45 were calculated using 6-311G" basis set. The calculation utilized the Cy, symmetry of 1, 3-dichloro-l, 3-diazetidine-2, 4-dione molecule (Tables 6 and 7). 

Quantum-chemical analysis provides a wide array of powerful tools that have been underutilized in deciphering the complex reactions affecting warfare agents. The computational approach secures development of extensive knowledge of such processes without exposing researchers to their deadly outcome. Therefore, this review is mainly devoted to summarize the results of the theoretical studies of organophosphates interacting with catalytic surfaces (clay minerals and metal oxides). 

Schuurmann, G., Quantum chemical analysis of the energy of proton transfer from phenol and chlorophenols to H20 in the gas phase and in aqueous solution, J. Chem. Phys., 109, 9523-9528, 1998b. 

Molecular structure is theoretically intimately related to electron-density distribution functions. In quantum-chemical analysis this density is synthesized as a molecular orbital, by a linear combination of real atomic orbitals, and minimized as a function of total energy. Crystallographically the unit cell density is represented by a Fourier sum over periodic electron wave functions... 

Szefczyk B, Mulholland AJ, Ranaghan KE, Sokalski WA (2004) Differential transition-state stabilization in enzyme catalysis Quantum chemical analysis of interactions in the chorismate mutase reaction and prediction of the optimal catalytic field. J Am Chem Soc 126 16148—16159... 

Grembecka J, Sokalski WA, Kedzierski P (2001) Quantum chemical analysis of the interactions of transition state analogs with leucine aminopeptidase. Int J Quantum Chem 84 302-310... 

Kroon J, Ranters JA, Van-Duijneveldt-Van der Rijdt JGCM, Van-Duijneveldt FB, Vliegenthart JA (1975) O-H—O Hydrogen bonds in molecular crystals. Statistical and quantum-chemical analysis. J Molec Struct 24 109-129... 

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