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Ground-state Geometry (ground-state + geometry)
Selected AbstractsComputational study of titanium (IV) complexes with organic chromophoresINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2006Ivan Kondov Abstract A computational study of small titanium complexes with the chromophores catechol, alizarin, and coumarin 343 is presented. Employing density functional theory (DFT), the ground-state geometries, energies, and harmonic frequencies of the different compounds are calculated. Furthermore, time-dependent DFT and the configuration interaction singles (CIS) method are used to determine excitation energies and excited-state gradients. Based on these results, the character of the excited states as well as electronic-vibrational coupling strengths are analyzed, and the implications for electron-transfer reactions at dye,semiconductor interfaces are discussed. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Ab initio investigation of the solvent and electron correlation effects on the geometries and first hyperpolarizabilities of push,pull oligomersINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 11 2007Eric A. Perpète Abstract Using the HF and MP2 approaches, we have determined the ground-state geometry and first hyperpolarizability of increasingly long push,pull polyacetylene oligomers. The bulk solvent effects have been assessed at both levels of theory through the Polarizable Continuum Model. For the first hyperpolarizability, the resulting 16 combination of theoretical levels of computation have been compared to evaluate the importance of individual corrections, as well as their additive/ multiplicative character. It turns out that the inclusion of bulk solvent effects is essential for an accurate estimate of the nonlinear optics properties of these push,pull derivatives. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Electrochemistry and Photophysics of Donor-Substituted Triarylboranes: Symmetry Breaking in Ground and Excited StateCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2006Rainer Stahl Dipl.-Chem. Abstract We synthesized a series of amino substituted triarylboranes (TABs) 1,3 by copper(I)-catalyzed cross-coupling reactions. The title compounds were investigated by means of cyclic voltammetry (CV) and UV-visible absorption and fluorescence spectroscopy. Electrochemical oxidation of tris(4-carbazolyl-2,6-dimethylphenyl)borane (3) leads to the formation of an electroactive polymer film on the electrode surface. The charge-transfer (CT) absorption band of all three TABs shows a pronounced negative solvatochromism, while the emission is positively solvatochromic. By combining Jortner's theory, AM1 computations, and electrooptical absorption measurements (EOAM), this unexpected behavior was shown to be due to a dipole inversion upon S0,S1 excitation. Furthermore, polarized steady-state fluorescence spectroscopy and EOAM prove that the ground-state geometry of 3 is of lower symmetry than D3 and that the excitation energy can be transferred from one subchromophore to another within the lifetime of the excited state. Exciton-coupling theory was used to quantitatively analyze this excitation transfer. [source] Disproving a Silicon Analog of an Alkyne with the Aid of Topological Analyses of the Electronic Structure and Ab Initio Molecular Dynamics CalculationsCHEMPHYSCHEM, Issue 9 2005Carlo A. Pignedoli Dr. Abstract A silicon compound has recently been synthesized that was claimed to exhibit the first realization of a silicon,silicon triple bond. We debate this classification on the basis of a thorough investigation of the nature of the chemical bond, using the rigorous topological analysis of the electron density as developed in Bader's atoms-in-molecules theory, that of the electron localization function and the related orbital-independent definitions of the bond order. Our results refer both to the ground-state geometry and to nonequilibrium configurations, which are accessed by the system in a room-temperature ab initio molecular dynamics simulation. We also use the reciprocal compliance force constant as an independent chemical descriptor. All the above procedures are in agreement and do not support the classification of the silicon,silicon central bond as triple. The characterization which consistently emerges from the present study is one in which two electron pairs participate in the bonding and the other pair belongs mainly to nonbonding regions. [source] |