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Initio Study (initio + study)
Kinds of 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] 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: 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: 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] 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] Structure and Stability of VO2+ in Aqueous Solution: A Car,Parrinello and Static ab initio Study.CHEMINFORM, Issue 34 2007Aymeric Sadoc 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 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] An ab initio Study of the Silicon,Oxygen,Sulfur Oligomers (SiOS)n (n , 6)CHEMINFORM, Issue 43 2003Thomas Krueger 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] An ab initio Study of the Ligand Field and Charge-Transfer Transitions of Cr(CN)3- 6 and Mo(CN)3- 6.CHEMINFORM, Issue 25 2003Marc F. A. Hendrickx 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: An ab initio Study of the NMR Properties (Absolute Shieldings and NICS) of a Series of Significant Aromatic and Antiaromatic Compounds.CHEMINFORM, Issue 42 2001Ibon Alkorta 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] 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] pKa optimized catalysis in serine proteinases, an ab initio study on the catalaytic HisINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 11 2007Péter Hudáky Abstract First principle models of catalytic apparatus of enzymes can be used for studying stability as well as the atomic details of a catalytic mechanism. For example, the catalytic triad of chymotrypsin was recently investigated by using an ab initio geometry optimized (Hudáky and Perczel, Proteins: Struct Funct Genet, 2006, 62, 749) self-stabilizing molecule ensemble without the presence of the complete enzyme and substrate. Several parameters of the above catalytic reaction turned out to be the same within the model and the in vitro enzymatic reaction. Among the numerous parameters of the catalytic process geometrical changes of the catalytic histidine was investigated here and the variation of its pKa value was determined. A relatively large range, 3.5 unit, was determined as the variation of pKa as function of the conformational subspace available in serine proteases. Comparing PDB structures of the free and the complex enzymes it was shown, that histidine, after accepting the proton from the OH group of the catalytic serine, undergoes a minor conformational change accompanied by a 2.5 unit decrease in pKa. We conclude that the changes of pKa during catalysis are predominantly determined by the geometrical arrangement of the histidine moiety and this change serves as a significant driving force in the catalytic process. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] | |||||||||||||||||||||||||||||||