Search results for "FUNCTIONAL"
showing 10 items of 4822 documents
ChemInform Abstract: Weak Interactions Between Trivalent Pnictogen Centers: Computational Analysis of Bonding in Dimers X3E···EX3(E: Pnictogen, X: Ha…
2009
The nature of weak interactions in dimers X3E···EX3 (E = N−Bi, X = F−I) was investigated by wave function and density functional theory (DFT)-based methods. Out of the 20 systems studied, 10 are found to be bound at the CP-MP2 and LMP2 levels of theory. Detailed partition of the interaction energy into different components revealed that dispersion is the primary force holding the dimers together but there also exists an important ionic component whose contribution increases with increasing halogen size. As expected, standard density functionals fail to describe bonding in the studied systems. However, the performance of DFT methods can be easily improved via empirical dispersion correction …
A Density Functional Theory study on gold cyanide interactions: The fundamentals of ore cleaning
2010
We have employed Density Functional Theory calculations to study the adsorption of CN, CN− and KCN on Au(111) and Au(211) surfaces and compare the obtained results to CO. The adsorption of CN, CN−, and KCN are exothermic with respect to the gas-phase moieties, and the adsorption energy increases at steps. Our results show that the binding mechanism of CN− is different from that of CO. The projected LDOS indicates that the bond between the flat surface and CN shows very small overlap between metal and CN states. This overlap increases provided that extra charge is present or low-coordinated Au atoms are available. Charge transfer is analyzed via the Bader method and the Electron Localization…
Electron Energy Loss and DFT/SCI Study of the Singlet and Triplet Excited States of Aminobenzonitriles and Benzoquinuclidines: Role of the Amino Gro…
1999
Spectroscopic consequences of varying the twist angle of the amino group in aminobenzonitrile systems in the electronic ground state are investigated by applying electron energy loss (EEL) spectroscopy and density functional theory to 4-N,N-dimethylaminobenzonitrile (DMABN), 4-N,N-dimethylamino-3,5-dimethylbenzonitrile (MMD), benzoquinuclidine (BQ), and 6-cyanobenzoquinuclidine (CBQ). A number of singlet and triplet excited states was observed and assigned with the help of DFT/SCI theory. The results characterize the gas-phase spectroscopy of the molecules and verify to within 0.3 eV the predictive power of DFT/SCI theory for vertical states over a wide range of twist and pyramidalization a…
Conventional, non-conventional extraction techniques and new strategies for the recovery of bioactive compounds from plant material for human nutriti…
2019
Considering a large number of variations in the chemical structures of bioactive compounds (BACs) that are valuable to humans and a large number of their sources, it is necessary to build a standard and integrated extraction and analytical approaches for obtaining these compounds. From this perspective, the main purpose of this Special Issue of Food Research International was to publish research related to the extractions with data about isolation of BACs from plant matrices for human nutrition. This Special Issue includes both, conventional and innovative extraction techniques, highlighting their characteristics and advantages in relation to the target matrix. Many of presented works conta…
Covalent and non-covalent chemistry of 2D black phosphorus
2021
The post-graphene era is undoubtedly marked by two-dimensional (2D) sheet polymers, such as black phosphorus (BP). This emerging material has a fascinating structure and outstanding electronic properties and has been postulated for a plethora of applications. The need to circumvent the pronounced oxophilicity of P atoms has dominated the research on this material in recent years, with the objective of finding the most effective method to improve its environmental stability. When it comes to chemical functionalization, the few approaches reported so far involve some drawbacks such as low degree of addition and low production ability. This review presents the concepts and strategies of our st…
ChemInform Abstract: New Reactions of Amino-Functionalized 3-Vinyl-1H-indoles and Tetrahydropyridin-4-yl Analogues with Dienophiles.
2010
Reactions of 3-[2-(morpholin-4-yl)vinyl]-1H-indole (1), the 1,2-dihydro-9H-carbazole 2, as well as the 3-(tetrahydropyridin-4-yl)-1H-indoles 3a and 3b with some carbo- and heterodienophiles are described. The scope and limitations of the synthetic utility of these amino- (or homoamino)-functionalized 3-vinyl-1H-indoles are reported and some MO calculations for the qualitative prediction of their reactivities are presented. The reactions gave rise to substitution products, redox products, Diels-Alder adducts, ene adducts, and Michael-type adducts (Schemes 2 and 3).
Oxide/water interfaces: how the surface chemistry modifies interfacial water properties
2012
The organization of water at the interface with silica and alumina oxides is analysed using density functional theory-based molecular dynamics simulation (DFT-MD). The interfacial hydrogen bonding is investigated in detail and related to the chemistry of the oxide surfaces by computing the surface charge density and acidity. We find that water molecules hydrogen-bonded to the surface have different orientations depending on the strength of the hydrogen bonds and use this observation to explain the features in the surface vibrational spectra measured by sum frequency generation spectroscopy. In particular, 'ice-like' and 'liquid-like' features in these spectra are interpreted as the result o…
3-Formyl-2-furanboronic acid: X-ray and DFT studies
2004
The molecule of the title compound, C5H5BO4, is almost planar with the boronic acid group inclined to the furan ring by 3.7 (1)°. DFT (density functional theory) calculations at the B3LYP/6-311+G** level of theory (with no imaginary frequencies) were used to approximate the influence of hydrogen bonding on the molecular geometry and have confirmed the planarity of the molecule. No significant differences in geometrical parameters in the solid state and in the gas phase are associated with the presence of the O—H⋯O intermolecular hydrogen-bonding network. The crystal packing is characterized by O—H⋯O hydrogen-bonded dimers, which are additionally linked by O—H⋯O, as well as C—H⋯O interactio…
Coordinating and hydrogen bonding ability of a bifunctional 2D paddle-wheel copper(II) coordination polymer
2015
abstract A new copper(II) complex of formula {[Cu 2 (H 2 btc) 2 (dmf) 2 ] 4dmf} n (1)[H 4 btc = 1,2,4,5-benzenetetracarb-oxylic acid, dmf = dimethylformamide] has been synthesised and its structure determined by X-raydiffraction. The structure displays a new square grid of ‘‘paddle-wheel’’ tetracarboxylate-bridgeddicopper(II) units with an intradimer copper–copper separation of 2.619(2) A. The dmf molecules areretained through weak axial coordinative bonds and hydrogen bonding interactions with the carboxylicgroups of the porous neutral network of 4 4 net topology. The magnetic behaviour of 1 corresponds to astrong antiferromagnetic coupling within each dicopper(II) unit (J = 343 cm 1 with …
Effect of hydrogen bonds on polarizability of a water molecule in (H2O)(N) (N = 6, 10, 20) isomers.
2010
Abstract: Polarizabilities of the low-lying isomers of (H2O)N (N = 6, 10, 20) clusters were computed by using Density Functional Theory. The global polarizabilities of the water isomers were found to depend mainly on the total number of water molecules rather than their cluster structures. We show that this result hides in fact a strong heterogeneity of the molecular polarizability within the different isomers. The global polarizability of a cluster was divided into a sum of molecular contributions by using the Hirshfeld partitioning scheme. We reveal that the value of the local polarizability of a molecule in the cluster is correlated with the number and type of the hydrogen bonds (HB) the…