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SPIN-SPIN COUPLING ACROSS INTERMOLECULAR F-Cl...N HALOGEN BONDS
No full textAuthor Institution: Department of Chemistry, Youngstown State University, Youngstown, OH 44555; Instituto de Qu\imica Medica, CSIC, Juan de la Cierva, 3, E-28006 Madrid, SpainAb initio EOM-CCSD calculations have been performed to determine one- and two-bond spin-spin coupling constants J(F-Cl), J(Cl-N), and J(F-N) across F-Cl...N halogen bonds in complexes with F-Cl as the Lewis acid and N, FCN, HCN, (CH)CN, LiCN, Z-HNNH, HCNH, NHF, NH, cyclic NH(CH), and NH(CH) as Lewis bases. The structures of these complexes were optimized at MP2 with the aug'-cc-pVTZ basis set. The absolute value of J(F-N) increases in these complexes as the F-N distance decreases, a behavior similar to that of J(F-N) for complexes stabilized by F-H...N hydrogen bonds. J(Cl-N) also tends to increase in absolute value with decreasing F-N distance. J(F-Cl) is always positive, decreases upon complex formation as the F-Cl distance increases, and appears to be sensitive to the nature of the nitrogen base. The relatively large differences in the values of these coupling constants in the various complexes and their variation along the chlorine-transfer coordinate for F-Cl...NH suggest that they should be amenable to experimental investigation
Spin-spin coupling across intermolecular F-Cl⋯N halogen bonds
No full textAb initio EOM-CCSD calculations have been performed to determine one- and two-bond spin-spin coupling constants 1J(F-Cl), 1XJ(Cl-N), and 2XJ(F-N) across F-Cl⋯N halogen bonds in complexes with F-Cl as the Lewis acid and N2, FCN, HCN, (CH3)CN, LiCN, Z-HNNH, H2CNH, NH2F, NH3, cyclic-NH(CH 2)2, and NH2(CH3) as Lewis bases. The structures of these complexes were optimized at MP2 with the aug′-cc-pVTZ basis set. The absolute value of 2XJ(F-N) increases in these complexes as the F-N distance decreases, a behavior similar to that of 2hJ(F-N) for complexes stabilized by F-H⋯N hydrogen bonds. 1XJ(Cl-N) also tends to increase in absolute value with decreasing F-N distance. 1J(F-Cl) is always positive, decreases upon complex formation as the F-Cl distance increases, and appears to be sensitive to the hybridization of the nitrogen base. The relatively large differences in the values of these coupling constants in the various complexes and their variation along the chlorine-transfer coordinate for F-Cl⋯NH3 suggest that they should be amenable to experimental investigation. © 2008 American Chemical Society.Peer Reviewe
Spin−Spin Coupling across Intermolecular F−Cl···N Halogen Bonds
No full textAb initio EOM-CCSD calculations have been performed to determine one- and two-bond spin−spin coupling constants 1J(F−Cl), 1XJ(Cl−N), and 2XJ(F−N) across F−Cl···N halogen bonds in complexes with F−Cl as the Lewis acid and N2, FCN, HCN, (CH3)CN, LiCN, Z-HNNH, H2CNH, NH2F, NH3, cyclic-NH(CH2)2, and NH2(CH3) as Lewis bases. The structures of these complexes were optimized at MP2 with the aug′-cc-pVTZ basis set. The absolute value of 2XJ(F−N) increases in these complexes as the F−N distance decreases, a behavior similar to that of 2hJ(F−N) for complexes stabilized by F−H···N hydrogen bonds. 1XJ(Cl−N) also tends to increase in absolute value with decreasing F−N distance. 1J(F−Cl) is always positive, decreases upon complex formation as the F−Cl distance increases, and appears to be sensitive to the hybridization of the nitrogen base. The relatively large differences in the values of these coupling constants in the various complexes and their variation along the chlorine-transfer coordinate for F−Cl···NH3 suggest that they should be amenable to experimental investigation
The electronic structure of the xenon insertion compounds XXe–MX2 (X = F, Cl, Br, I; M = B, Al, Ga)
No full textNature of chemical bonding in the XXe–MX2 (X = F, Cl, Br, I; M = B, Al, Ga) molecules have been investigated using topological analysis of Electron Localisation Function (ELF) and electron density. The wave function has been approximated by the DFT(B3LYP, M062X) and the CCSD methods using all-electron basis sets (TZVPPall, TZVall+) and the ecp-28 approximation for Xe, I with Def2-TZVPPD basis set. Electronic structure of the XXeMX2 consists of the [Xe–MX2] fragment, bound non-covalently to the halogen atom, Xδ−⋯[Xe–MX2]δ+ (δ = 0.4–0.7e). The xenon–icosagen bond, Xe–M displays covalent nature in all studied molecules, confirmed by bonding disynaptic attractor V(Xe,M) for the ELF field with basin population ranging from 1.1 to 1.8e. The basin population of the Xe–M bond decreases together with the r(Xe–M) bond length increase and the increase of the polarisability of the respective halogen. The Xe–X bond always shows a non-covalent nature, confirmed by an absence of bonding attractor in the region between the core basins C(Xe) and C(X). M–X bonds can have either covalent or ionic nature depending on the type of icosagen and halogen involved in bonding. The Al–F and Ga–X (X = F, Cl, Br) bonds have ionic nature, except for the Ga–I bond, showing slightly covalent but highly delocalised character, confirmed by the presence of the bonding basin V(Ge,X) with the population of 0.64e. In addition to bonding population calculations, the analysis of the bond polarity, based on topological analysis of electron density combined with ELF fields, and delocalisation of electron density in bonding basins has been performed and discussed
DataSheet1_CH4 activation by PtX+ (X = F, Cl, Br, I).PDF
No full textReactions of PtX+ (X = F, Cl, Br, I) with methane have been investigated at the density functional theory (DFT) level. These reactions take place more easily along the low-spin potential energy surface. For HX (X = F, Cl, Br, I) elimination, the formal oxidation state of the metal ion appears to be conserved, and the importance of this reaction channel decreases in going as the sequence: X = F, Cl, Br, I. A reversed trend is observed in the loss of H2 for X = F, Cl, Br, while it is not favorable for PtI+ in the loss of either HI or H2. For HX eliminations, the transfer form of H is from proton to atom, last to hydride, and the mechanisms are from PCET to HAT, last to HT for the sequence of X = F, Cl, Br, I. One reason is mainly due to the electronegativity of halogens. Otherwise, the mechanisms of HX eliminations also can be explained by the analysis of Frontier Molecular Orbitals. While for the loss of H2, the transfer of H is in the form of hydride for all the X ligands. Noncovalent interactions analysis also can be explained the reaction mechanisms.</p
The nature of inter- and intramolecular interactions in F2OXe…HX (X= F, Cl, Br, I) complexes
Get PDFElectronic structure of the XeOF2 molecule and its two complexes with HX (X= F, Cl, Br, I) molecules have been studied in the gas phase using quantum chemical topology methods: topological analysis of electron localization function (ELF), electron density, ρ(r), reduced gradient of electron density |RDG(r)| in real space, and symmetry adapted perturbation theory (SAPT) in the Hilbert space. The wave function has been approximated by the MP2 and DFT methods, using APF-D, B3LYP, M062X, and B2PLYP functionals, with the dispersion correction as proposed by Grimme (GD3). For the Xe-F and Xe=O bonds in the isolated XeOF2 molecule, the bonding ELF-localization basins have not been observed. According to the ELF results, these interactions are not of covalent nature with shared electron density. There are two stable F2OXe…HF complexes. The first one is stabilized by the F-H…F and Xe…F interactions (type I) and the second by the F-H…O hydrogen bond (type II). The SAPT analysis confirms the electrostatic term, Eelst (1) and the induction energy, Eind (2) to be the major contributors to stabilizing both types of complexes
Theoretical Study on Cyclopeptides as the Nanocarriers for Li+, Na+, K+ and F-, Cl-, Br-
No full text
The interaction process between a series of cyclopeptide compounds cyclo(Gly)(n) (n = 4, 6, 8) and monovalent ions (Li+, Na+, K+, F-, Cl-, and Br-) was studied using theoretical calculation. The mechanism of combination between the cyclo(Gly)(n) and ions was discussed through binding energy, Mulliken electron population, and hydrogen bond. It was found that for the same cyclopeptide the binding energy has the order of cyclo(Gly)(n)-Li+ > cyclo(Gly)(n)-Na+ > cyclo(Gly)(n)-K+ and cyclo(Gly)(n)-F- > cyclo(Gly)(n)-Br- > cyclo(Gly)(n)-Cl-. The binding energy manifests the stable complex of cyclo(Gly)(n) and ions can be formed, and the different energy shows the potential use of cyclo(Gly)(n) as nanocarriers for metal ions or the extractant for ions separation.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
H-X (X=H, F, Cl, Br, I) iki atomlu moleküllerin anharmonik potansiyel parametrelerinin tayini
No full textBu çalışmada H-X (X=H, F, Cl, Br, I) moleküllerin anharmonik potansiyel parametreleri, Morse potansiyelinin seri açılımı ve perturbasyon teorisi yardımıyla hesaplandı. Elde edilen k2 ve k4 değerleri kullanılarak H-X (X=H, F, Cl, Br, I) moleküllerin titreşim enerjileri hesaplandı ve bulunan değerler spektroskopik titreşim enerjileri ile karşılaştırıldı. H-X (X=H, F, Cl, Br, I) moleküllerin enerji özdeğerleri De ayrışma enerjileri ile karşılaştırılarak molekülerin alabilecekleri enerji özdeğerleri (açık kanal sayıları) belirlendi. H-X (X=H, F, Cl, Br, I) moleküllerin titreşim enerjilerini hesaplamak ve Morse potansiyel enerji grafiklerini çizdirmek üzere bir MATLAB® bilgisayar programı yazıldı. Elde edilen sonuçlar tablolar ve grafikler halinde verildi. Özellikle n kuantum sayısının büyük değerleri için, hesapladığımız k2 ve k4 anharmonik potansiyel parametrelerinin güvenilir olduğu tespit edildi.In this thesis, anharmonic potential parameters of H-X (X=H, F, Cl, Br, I) molecules are calculated by using series expansion of Morse potential and perturbation theory. Vibrational energies of H-X (X=H, F, Cl, Br, I) molecules are calculated by using the determined k2 and k4 values and results are compared with spectroscopic vibrational energies. The allowed vibrational energy levels (number of open channels) of H-X (X=H, F, Cl, Br, I) molecules are determined by comparing these energy levels with De dissociation energies. A MATLAB® computer program is written in order to calculate vibrational energies of H-X (X=H, F, Cl, Br, I) molecules and to plot the graph of Morse potential energy. The results obtained from calculations are given in tabular form and in graphics. It is determined, in particularly for big values of n quantum number, that the calculated k2 and k4 anharmonic potential parameters are reliable
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