Search results for " interaction"
showing 10 items of 5187 documents
The Nonlocal Correlation Density Functional VV10
2015
Abstract In this chapter, we review the most relevant attempts to merge the Vydrov and van Voorhis nonlocal density-dependent functional kernel (VV10) with modern density functionals to accurately describe van der Waals interactions with a reasonable computational cost. The chapter is organized by providing first an introduction of the relevance of van der Waals interactions and the difficulties of common density functionals to describe these forces. Second, the historical developments that eventually give rise to the most modern formulation of the nonlocal density functional VV10 are briefly addressed. Then, an overview of its technical formulation, adjustable parameters, and implementatio…
Discrete supramolecular donor-acceptor complexes
2009
The renewed interest in noncovalently associating electroactive molecules arises in part from the quest for new organic materials that convert solar energy into electrical/ chemical equivalents. In this context, the formation of charge-separated states is a key prerequisite. Charge-transfer events triggered by light have been studied in supramolecular donor–acceptor systems based on hydrogen bonds and coordinative metal bonds. Although many of the most widely utilized electroactive fragments feature large pconjugated surfaces, to date the use of p–p aromatic interactions has mainly been limited to the construction of semi-infinite ensembles of chromophores either to achieve charge transport…
The use of topological models in analytical chemistry
2005
In the present paper, the possible analytical applications of two toplogical models, the DARC model and the group contribution model, are discussed. Both models are applied to obtain calibration laws, which relate UV and IR characteristics with the chemical structure of ethylene oxide condensates. The group contribution model is also applied to determine the contribution of each part of the different compounds involved in a chemical interaction process, having established the sensitization parameters of benzodiazepines and anionic surfactants from the micellar enhancement fluorescence.
Excited states of [3.3](4,4')biphenylophane: the role of charge-transfer excitations in dimers with pi-pi interaction.
2010
The singlet and triplet electronic excitation manifold of [3.3](4,4')biphenylophane (BPP), an intramolecular dimer, and 4,4'-dimethylbiphenyl (DMBP), the corresponding monomer, has been analyzed by employing the approximate coupled-cluster singles and doubles model (CC2). The calculated triplet-triplet and singlet-singlet transient absorption spectra show good agreement with recent experimental results. The calculations suggest a strong interaction of the two biphenyl moieties of BPP in the first singlet and triplet excited states due to the overlapping pi-electron systems, and Forster-Dexter theory for weak coupling cannot be applied. Both the first excited singlet and triplet states of BP…
Towards a converged barrier height for the entrance channel transition state of the N(2D)+CH4 reaction and its implication for the chemistry in Titan…
2011
Abstract The N( 2 D) + CH 4 reaction appears to be a key reaction for the chemistry of Titan’s atmosphere, opening the door to nitrile formation as recently observed by the Cassini–Huygens mission. Faced to the controversy concerning the existence or not of a potential barrier for this reaction, we have carried out accurate ab initio calculations by means of multi-state multi-reference configuration interaction (MS-MR-SDCI) method. These calculations have been partially corrected for the size-consistency errors (SCE) by Davidson, Pople or AQCC corrections. We suggest a barrier height of 3.86 ± 0.84 kJ/mol, including ZPE, for the entrance transition state, in good agreement with the experime…
Photochemistry of the H2O/CO System Revisited : The HXeOH···CO Complex in a Xenon Matrix
2017
We report on the complex of a noble-gas hydride HXeOH with carbon monoxide. This species is prepared via the annealing-induced H + Xe + OH···CO reaction in a xenon matrix, the OH···CO complexes being produced by VUV photolysis of the H2O···CO complexes. The H–Xe stretching mode of the HXeOH···CO complex absorbs at 1590.3 cm–1 and it is blue-shifted by 12.7 cm–1 from the H–Xe stretching band of HXeOH monomer. The observed blue shift indicates the stabilization of the H–Xe bond upon complexation, which is characteristic of complexes of noble-gas hydrides. The HXeOH···CO species is the first complex of a noble-gas hydride with carbon monoxide and the second observed complex of HXeOH. On the ba…
The hedgehog receptor patched is involved in cholesterol transport.
2011
International audience; BACKGROUND: Sonic hedgehog (Shh) signaling plays a crucial role in growth and patterning during embryonic development, and also in stem cell maintenance and tissue regeneration in adults. Aberrant Shh pathway activation is involved in the development of many tumors, and one of the most affected Shh signaling steps found in these tumors is the regulation of the signaling receptor Smoothened by the Shh receptor Patched. In the present work, we investigated Patched activity and the mechanism by which Patched inhibits Smoothened. METHODOLOGY/PRINCIPAL FINDINGS: Using the well-known Shh-responding cell line of mouse fibroblasts NIH 3T3, we first observed that enhancement …