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The relativistic correction to the s2p2-sp3 energy separation in the carbon atom is shown to be 120 cm?1 which is too small to resolve the discrepancies between theory and experiment for the 1A1-3B1 energy separation in methylene. 相似文献
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Duygu İNCİ 《应用有机金属化学》2020,34(12):e6016
NOO-type tridentate Schiff base, N-salicylidene-2-aminobenzoic acid, (H2L), and its ternary Cu (II) complex containing H2L Schiff base and 4,7-dimethyl-1,10-phenanthroline (4,7-dmphen), [Cu(4,7-dmphen)(H2L)]27H2O, have been synthesized and characterized by CHN analysis, ESI-MS, FTIR, and single-crystal X-ray diffraction techniques. The interaction of alone H2L Schiff base ligand and ternary Cu (II) complex with biomacramolecules {calf thymus DNA (CT-DNA) and bovine serum albumin (BSA)} has been investigated by electronic absorption and fluorescence spectroscopy. The experimental results indicate that H2L Schiff base ligand and ternary Cu (II) complex bind to CT-DNA by means of a moderate intercalation mode. Furthermore, the fluorescence quenching mechanism between H2L Schiff base ligand and ternary Cu (II) complex with BSA possesses a static quenching process. Radical scavenging activity of H2L Schiff base ligand and ternary Cu (II) complex was measured in terms of EC50, using the DPPH and H2O2 methods. Biomacromolecule interactions and scavenging activity studies revealed that ternary Cu (II) complex yielded better results than H2L Schiff base ligand alone. 相似文献
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The relativistic correction to the s 2 p 2-sp 3 excitation energy in the carbon atom is shown to be 120 cm-1 rather than 500 cm-1 as reported by Desclaux et al. This is too small to explain the 8 kJ mol-1 discrepancy between theory and experiment for the 1 A 1-3 B 1 energy separation in methylene. Two pitfalls that can arise when calculating relativistic corrections from approximate wavefunctions are discussed. 相似文献
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The results of some minimal basis set valence bond calculations, with an antibonding midbond molecular orbital (πm*) included, are reported for the D2h isomer of O4. The in-plane πm*←π* excitations describe the charge transfer from each monomer, while the π*←π excitations on each monomer partially describe the intermolecular dispersive attractions. It is found that the charge-transfer interactions by themselves are insufficient to stabilize the S=0 spin D2h dimer of O4 relative to two O2 monomers when a correction is included for basis set superposition error. The inclusion of both the charge transfer and dispersion terms yields an estimate of 14 cm−1 for the binding energy (De) at an equilibrium separation (Re) of 3.29 Å. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 68: 129–134, 1998 相似文献
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N.C. Pyper 《Molecular physics》2013,111(6):1367-1390
The equation of motion of a reduced spin density operator characterizing the state of a group of spins scalar coupled to a second group of spins which are either relaxing rapidly and/or irradiated with a strong radiofrequency field is derived within the framework of the non-viscous liquid approximation. An analytic expression for the spectral densities entering this equation is derived within the extreme narrowing approximation for the case in which the relaxation rates of the nuclei in the second group of spins are much greater than any scalar couplings between them. The resultant equation is used to discuss the conditions needed in a high resolution nuclear magnetic double resonance experiment to decouple a spin-½ nucleus (A) from a rapidly relaxing quadrupolar nucleus (X) in the fast relaxation limit, defined by |2πJAX T 1X | ? 1, in which the A resonance consists of a single broadened line. It is found that, if (ω A - ω X )2 ? T 1X -2 so that the x and y components of the JAX coupling can be neglected, decoupling, in the sense that all broadening of the A resonance is removed, occurs only when the strength of the B 2 field be such that γ X 2 B 2 2 ? T 1X -2 and that the conventional decoupling criterion γ X 2 B 2 2 ? 4π2 JAX 2 is not applicable. However, if the x and y components of the A-X scalar coupling cannot be neglected because the condition (ω A - ω X )2 ? T 1X -2 is not satisfied, it is found that the X spin can never be entirely decoupled. It is shown that such double resonance experiments enable both the coupling constants between spin-½ and quadrupolar nuclei and the relaxation times of the latter nuclei to be extracted in situations in which measurement of the half-widths of spin-1/2 transitions can only yield the product JAX 2 T 1X in the absence of irradiation of the quadrupolar nuclei. 相似文献
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The interactions of the noble gases with a graphene sheet are investigated theoretically. The short range repulsive interaction between the noble gas and each carbon atom is described using Hartree-Fock atomic densities and a local density functional theory with the exchange functional corrected for the finite range of the interaction by introducing a Rae-type correction depending on the effective number of electrons. The long range interactions are introduced as the sum of the Axilrod-Teller triple-dipole interaction plus the dipole-dipole and dipole-quadrupole dispersive attractions damped according to the theory of Jacobi and Csanak. The energy arising from the interactions between the permanent quadrupoles on the carbon atoms with the dipole they induce on the noble gas is negligible, being nonzero only on account of the atomistic structure of graphene. The mobile and delocalized nature of the graphene pi electrons causes the effective number of electrons to be around 500 rather than that of 12 appropriate for a system of entirely localized interactions with individual carbon atoms. Inclusion of the Axilrod-Teller term is required to obtain reliable predictions for the binding energies and equilibrium geometries. Absorption of a noble gas atom is predicted to occur at the site above the center of a six membered ring although this is preferred over two other sites by only about 5 meV. The methods presented for generating all the potentials can be applied to derive the interactions between any ion and carbon atom in the wall of a single-walled nanotube. Knowledge of these interactions is required to study the alkali halide nanocrystals encapsulated in single-walled carbon nanotubes of current interest. 相似文献