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Ab Initio Study (ab + initio_study)
Selected AbstractsSingle End-to-End Azidocopper(II) Chain Based on an Electroactive Ligand: A Structural, Electrochemical, Magnetic and Ab Initio StudyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 31 2009Guillaume Pilet Abstract By combining azide and the (Z)-1,1,1-trifluoro-4-(quinolin-8-ylamino)but-3-en-2-one enaminone ligand, HL, an azido-bridged copper(II) one dimensional polymer was synthesized in a one-pot reaction. The solved and refined crystal structure evidenced the unusual single and asymmetric end-to-end coordination mode of the azide ion. The redox properties of this complex were studied by cyclic voltammetry, andoxidation of the azido bridge was evidenced. Magneticmeasurements, combined with magnetostructural-driven analysis revealed a weak ferromagnetic interaction between the copper(II) ions within the N3, -bridged chains, complemented by an antiferromagnetic interaction between the chains mediated by ,,, interactions. A survey of the scarce literature of single end-to-end azido bridges, associated with quantum chemical ab initio calculations, was carried out to tentatively identify the relevant parameters driving the weak intrachain exchange interaction.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Reactivity of (Mono- tert -butyloxiranyl)lithium: A Theoretical Ab Initio StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 26 2008Abdelatif Bouyacoub Abstract The reactivity of the lithiated tert -butyloxiranyl anion has been studied by means of ab initio calculations at the CCSD(T)//MP2 level of theory. Four reaction paths have been studied (three ring-opening reactions and one addition reaction). All extrema were located and characterised. The effects of solvation by one or two MeLi molecules were studied for each reaction path by reoptimising the various extrema. It was found that the addition reaction path becomes competitive when at least two MeLi molecules are taken into account. This shows the catalytic effect of alkyllithium on this reaction path. In no case could a free carbene be characterised as a reaction intermediate. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Ab Initio Study on Interactions in Difluoroamine Clusters from one to four MoleculesPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2002Xue-Hai Ju Ab initio calculations at HF, MP2 levels of theory with 6-311G* basis set in combination with counterpoise procedure for BSSE correction have been performed on difluoroamine clusters consisting of up to four molecules. The dimer, trimer and tetramer were all found to exhibit two minima. There are two types of clusters: cyclic and chain. The corrected bond energies are 9.19, 19.22 and 33.67,kJ/mol at the MP2/6-311G*//HF/6-311G* level for the more stable dimer, trimer and tetramer, respectively. The contribution of cooperative effect to the interaction energy is quite significant in the cyclic clusters, but negligible in the chain ones. There exist H-bonds which involve six and eight F,,,H contacts at ca. 0.23,0.24,nm in cyclic trimer and cyclic tetramer, respectively. The intermolecular interaction is an exothermic process under 400.0,K accompanied by a decrease in the probability of complex formation, and the interactions become weak as temperature increases. [source] High-Level Ab Initio Study of Anion,, Interactions in Pyridine and Pyrazine Rings Coordinated to AgICHEMPHYSCHEM, Issue 3 2008David Quiñonero Dr. Enhanced binding: High-level ab initio calculations (RI,MP2(full)/aug-cc-pVQZ) demonstrate that the anion binding properties of pyridine and pyrazine are dramatically enhanced when it is coordinated to AgI, as shown in the picture. [source] ChemInform Abstract: Ab initio Study of the Geometry, Stability, and Aromaticity of the Cyclic S2N+3 Cation Isomers and Their Isoelectronic Analogues.CHEMINFORM, Issue 38 2009Guo-Hua Zhang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Ab initio Study of Small Coinage Metal Telluride Clusters AunTem (n, m: 1, 2)CHEMINFORM, Issue 21 2009Q.-M. S. Rong Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Ab initio Study of Structural, Dielectric, and Dynamical Properties of Zinc-Blende ZnX (X: O, S, Se, Te).CHEMINFORM, Issue 21 2009You Yu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Ab initio Study on Structure and Phase Transition of A- and B-Type Rare-Earth Sesquioxides Ln2O3 (Ln: La,Lu, Y, and Sc) Based on Density Function Theory.CHEMINFORM, Issue 19 2008Bo Wu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Ab initio Study of the Electronic Structure and Bonding of Aluminum Nitride.CHEMINFORM, Issue 4 2008Apostolos Kalemos Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Ab initio Study of Structure and Stability of M2Al2 (M: Cu, Ag, and Au) ClustersCHEMINFORM, Issue 27 2007FengLi Liu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Electronic Structure, Equilibrium and Magnetic Properties of Ni2MnGe: Ab initio Study.CHEMINFORM, Issue 13 2007Maria Pugaczowa-Michalska Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Ab initio Study of Energetic Solids: Cupric Azide, Mercuric Azide, and Lead AzideCHEMINFORM, Issue 50 2006Weihua Zhu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Ab initio Study of the Fluoride,Ammonia Clusters: F - ,(NH3)n, n = 1,3CHEMINFORM, Issue 8 2005D. A. Wild Abstract For Abstract see ChemInform Abstract in Full Text. [source] Ab initio Study of the Electronic Structure of Rhodium Based Intermetallic Compounds under PressureCHEMINFORM, Issue 46 2004M. Rajagopalan Abstract For Abstract see ChemInform Abstract in Full Text. [source] Infrared Spectra of Hydrogen-Bonded Ionic Crystals: Ab initio Study of Mg(OH)2 and ,-Be(OH)2.CHEMINFORM, Issue 45 2004Piero Ugliengo Abstract For Abstract see ChemInform Abstract in Full Text. [source] Ab initio Study of the Ground and Excited States of Zinc Carbide, ZnC.CHEMINFORM, Issue 42 2003Andromache Tsouloucha No abstract is available for this article. [source] Search for Ionic Orthocarbonates: Ab initio Study of Na4CO4.CHEMINFORM, Issue 51 2002Musstafa Al-Shemali Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Ab initio Study of the Atmospheric Oxidation of CS2.CHEMINFORM, Issue 22 2001Michael L. McKee Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Ab initio Study of the Interactions between CO2 and N-Containing Organic HeterocyclesCHEMPHYSCHEM, Issue 2 2009Konstantinos D. Vogiatzis Abstract In the garden of dispersion: High-accuracy ab initio calculations are performed to determine the nature of the interactions and the most favorable geometries between CO2 and heteroaromatic molecules containing nitrogen (see figure). Dispersion forces play a key role in the stabilization of the dimer, because correlation effects represent about 50,% of the total interaction energy. The interactions between carbon dioxide and organic heterocyclic molecules containing nitrogen are studied by using high-accuracy ab initio methods. Various adsorption positions are examined for pyridine. The preferred configuration is an in-plane configuration. An electron donor,electron acceptor (EDA) mechanism between the carbon of CO2 and the nitrogen of the heterocycle and weak hydrogen bonds stabilize the complex, with important contributions from dispersion and induction forces. Quantitative results of the binding energy of CO2 to pyridine (C5H5N), pyrimidine, pyridazine, and pyrazine (C4H4N2), triazine (C3H3N3), imidazole (C3H4N2), tetrazole (CH2N4), purine (C5H4N4), imidazopyridine (C6H5N3), adenine (C5H5N5), and imidazopyridamine (C6H6N4) for the in-plane configuration are presented. For purine, three different binding sites are examined. An approximate coupled-cluster model including single and double excitations with a perturbative estimation of triple excitations (CCSD(T)) is used for benchmark calculations. The CCSD(T) basis-set limit is approximated from explicitly correlated second-order Møller,Plesset (MP2-F12) calculations in the aug-cc-pVTZ basis in conjunction with contributions from single, double, and triple excitations calculated at the CCSD(T)/6-311++G** level of theory. Extrapolations to the MP2 basis-set limit coincide with the MP2-F12 calculations. The results are interpreted in terms of electrostatic potential maps and electron density redistribution plots. The effectiveness of density functional theory with the empirical dispersion correction of Grimme (DFT-D) is also examined. [source] Ab initio Study of Mechanism of Forming a Germanic Hetero-Polycyclic Compound between Germylidene (H2C=Ge:) and AcetoneCHINESE JOURNAL OF CHEMISTRY, Issue 8 2010Xiuhui Lu Abstract The mechanism of the cycloaddition reaction of forming a germanic hetero-polycyclic compound between singlet germylidene (R1) and acetone (R2) has been investigated with CCSD(T)//MP2/6-31G* method. From the surface energy profile, it can be predicted that the dominant reaction pathway for this reaction consists of three steps: (1) the two reactants (R1, R2) firstly form a twisted four-membered ring intermediate (INT2); (2) the intermediate (INT2) reacts further with acetone (R2) to give another intermediate (INT4); (3) intermediate (INT4) isomerizes to a hetero-polycyclic germanic compound (P4) via a transition state TS4. The presented rule of this reaction: the [2+2] cycloaddition effect between the , orbital of germylidene and the , orbital of ,-bonded compounds leads to the formation of four-membered ring intermediate (INT2). The 4p unoccupied orbital and the lone-pair sp electrons of Ge in the four-membered ring intermediate (INT2) react with the , orbital and the antibonding ,* orbital of ,-bonded compounds, respectively, forming the ,,p and sp, ,* cyclic donor-acceptor bonds, resulting in the generation of a stable germanic hetero-polycyclic compound (P4). [source] Ab initio study of the OH + CH2O reaction: The effect of the OH··OCH2 complex on the H-abstraction kineticsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2006Shucheng Xu Kinetics for the reaction of OH radical with CH2O has been studied by single-point calculations at the CCSD(T)/6-311+G(3df, 2p) level based on the geometries optimized at the B3LYP/6-311+G(3df, 2p) and CCSD/6-311++G(d,p) levels. The rate constant for the reaction has been computed in the temperature range 200,3000 K by variational transition state theory including the significant effect of the multiple reflections above the OH··OCH2 complex. The predicted results can be represented by the expressions k1 = 2.45 × 10 -21T2.98 exp (1750/T) cm3 mol,1 s,1 (200,400 K) and 3.22 × 10 -18T2.11 exp(849/T) cm3 mol,1 s,1 (400,3000 K) for the H-abstraction process and k2 = 1.05 × 10 -17T1.63 exp(,2156/T) cm3 mol,1 s,1 in the temperature range of 200,3000 K for the HO-addition process producing the OCH2OH radical. The predicted total rate constants (k1 + k2) can reproduce closely the recommended kinetic data for OH + CH2O over the entire range of temperature studied. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 322,326, 2006 [source] Reorganization of highly preorganized hosts upon cation complexation: Ab initio study of fluorospherandsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4 2007Shabaan A. K. Elroby Abstract Fluorospherands (F-spherands) are highly preorganized hosts composed of fluorobenzene or 4-methylfluorobenzene units attached to one another at their 2,6-positions. To understand the intrinsic factors affecting cation complexation, we investigated the complexation behavior between F-spherands and cations using density functional theory (DFT) at the level of B3LYP/6-31G**. The F6-spherand (C6H3F)6, (1) has a highly preorganized spherical cavity, which can encapsulate Li+ and Na+. Its cavity is not big enough for K+ and NH, which prefer external binding. Plausible conformations were studied for F8-spherand (C6H3F)8. Conformer of D2d symmetry (2b) is more stable than that of D4d (2a), in agreement with NMR experiments. The cavity size of F8-spherand is big enough to encapsulate all cations studied. However, the cavity size of 2b is smaller than that of 2a, which resulted in the guest selectivity. Upon complexation, 2b conformation is more stable for Li+ and Na+, while 2a conformation is preferred for larger cations such as K+ and NH. Thus, the ab initio calculations over these highly preorganized fluorospherands give important insights into their host,guest chemistry. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Ab initio study on the photochemical behavior of styreneJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2002Yoshiaki Amatatsu Abstract Ab initio complete active space self-consistent field (CASSCF) and the second order multireference Møller-Plesset calculations have been performed to examine the photochemical behavior of styrene upon the strong S0 -S2 electronic excitation in the low-lying excited states. The optimized structure at the S2/S1 conical intersection (CIX) is characterized by a quinoid structure. The transition state (TS) in S1 is in the vicinity of the S2/S1 -CIX. At the S1 -TS, two reaction paths branch. One is the relaxation into the stable structure in S1 and then emission into S0. The other is the radiationless decay through the S1/S0 -CIX. © 2002 Wiley Periodicals, Inc. J Comput Chem 10: 950,956, 2002 [source] Ab initio study on N,N,,N, -triaminoguanidineJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 2007Pansy Iqbal Abstract Electronic structure calculations and second-order delocalizations in N,N,,N,,-triaminoguanidine (TAG) have been studied by employing ab initio MO and density functional methods. There are total 10 rotational isomers on the potential energy (PE) surface of TAG. The effect of three amino groups substitution on guanidine (Gu) has been studied in terms of the primary and the secondary electron delocalizations in TAG by employing Natural Population Analysis (NPA). An increased electron delocalization is observed in protonated triaminoguanidine (TAGP) due to the three strong intramolecular hydrogen bonds and hence accounts for its extra stability. The increase in the electron delocalization upon protonation in TAG can be compared to that in guanidine. The absolute proton affinity (APA) of TAG is less than that of Gu. HOMA and NICS studies have been carried out to understand electron delocalization in TAGP. Copyright © 2007 John Wiley & Sons, Ltd. [source] Ab initio study of spinodal decomposition in (Zn, Cr)TePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2006T. Fukushima Abstract The spinodal decomposition in (Zn, Cr)Te is simulated by using first principles calculations and Monte Carlo simulation. It is found that the chemical pair interaction between Cr atoms in (Zn, Cr)Te is attractive interaction and leads to spinodal decomposition. Curie temperatures in decomposed situation are estimated by the random phase approximation with taking the magnetic percolation effect into account. This decomposed phase makes the random pattern of high concentration regions which connect each other and have possibility to realize high Curie temperature. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] ChemInform Abstract: Ab initio study of the Two Iso-electronic Molecules NpO - 4 and UO2- 4O.CHEMINFORM, Issue 2 2002Helene Bolvin Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] A Theoretical ab initio Study of the Capacity of Several Binding Units for the Molecular Recognition of AnionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2005Carolina Garau Abstract Noncovalent bonding between anions and the ,-cloud of electron-deficient aromatic rings has recently attracted considerable attention. Complexes of bromide with different electron-deficient aromatic rings and with other binding units based on hydrogen bonding (urea, thiourea and squaramide) have been studied and compared using high level B3LYP/6-31++G** ab initio and Molecular Interaction Potential with polarization (MIPp) calculations. Our findings reveal that electron-deficient aromatic rings are excellent candidates for constructing anion receptors and that the interaction strength can be modulated by the nature of the ring. Supporting experimental evidence has been obtained from X-ray structures retrieved from the Cambridge Structural Database. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] ChemInform Abstract: An ab initio Study of Possible Pathways in the Thermal Decomposition of NaAlH4CHEMINFORM, Issue 9 2009J. G. O. Ojwang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: BX4 - and AlX4 - Superhalogen Anions (X: F, Cl, Br): An ab initio StudyCHEMINFORM, Issue 43 2008Celina Sikorska Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Photoelectron Spectroscopy and ab initio Study of the Structure and Bonding of Al7N - and Al7N.CHEMINFORM, Issue 21 2008Boris B. Averkiev Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] | |||||||||||||||||||||||||||||||