The molecular structure and conformational properties of gaseous dimer of copper (I) pivalate, Cu2piv2, have been studied by gas electron diffraction (GED) at 413(5) K and quantum chemical calculations (DFT and MP2). The molecule possesses a planar eight-membered skeleton. Two conformers, “staggered” of C2h symmetry and “eclipsed” of C2v symmetry, were found for Cu2piv2 in the gas phase. The following geometric parameters of the skeleton ring and the tert-butyl groups have been determined from the GED experiment for the “staggered” form: rg(Cu···Cu) = 2.520(8) Å, rg(Cu–O)ave = 1.871(4) Å, rg(C–O)ave = 1.273(3) Å, rg(C–C)ring-tert = 1.531(4) Å, rg(C–C)tert-out-of-plane-ring = 1.536(4) Å, rg(C–C)tert-in-the-plane-ring = 1.527(4) Å, rg(C–H)ave = 1.087(5) Å, (O–Cu–O) = 172.12°(3). Computations predict the internal rotation of the tert-butyl groups to be independent. The value of calculated Wiberg bond index for Cu···Cu testifies the existence of weak bonding between two copper atoms.
A combined gas electron diffraction and quantum chemical (B3LYP/6-311+G**, B3LYP/cc-pVTZ) study of the molecular structure of 2-nitrobenzenesulfonic acid (2-NBSA) is performed. Quantum chemical calculations show that the 2-NBSA molecule has five conformers, and the Gibbs energy of one of them is lower by more than 4.5 kcal/mol than the energy of the other conformers. It is found experimentally that the saturated vapor of 2-NBSA at T = 394(5) K contains only the low-energy conformer that has an intramolecular hydrogen bond between the H atom of the hydroxyl group and one of the O atoms of the NO2 group. The C-C-S-O(H) torsion angle determining the position of the S-O(H) bond is ?72(7)°, while the NO2 group is substantially turned relative to the benzene ring plane (C1-C2-N-O = 40(5)°). The following experimental values of the internuclear distances are obtained for this conformer (Å): rh1(C-H)av = 1.07(2), rh1(C-C)av = 1.401(4), rh1(C-S) = 1.767(6), rh1(S=O)av = 1.412(4), rh1(S-O) = 1.560(6), rh1(N-O)av = 1.217(5), rh1(C-N) = 1.461(8), rh1(O-H) = 0.99(3). 相似文献
In the framework of synchronous gas-phase electron diffraction and mass spectrometry experiment, the saturated vapor of N,N′-ethylenebis(salicylaldiminate) copper(II) CuO2N2C16H14 is studied at a temperature T 574(5) K. It is found that evaporation is congruent and the saturated vapor consists of monomeric molecules. Electron diffraction data are proved to correspond to the geometric model for the CuO2N2C16H14 molecule of C2 symmetry with an almost planar structure of the CuN2O2 coordination fragment and internuclear distances \(r_{h_1 } \)(Cu-O) = 1.917(13) Å and \(r_{h_1 } \)(Cu-N) = 1.931(15) Å. The stuctural parameters obtained are compared to those quantum chemically calculated and molecular parameters in crystals. 相似文献
The saturated vapors of ErCl3 and YbCl3 were studied in a simultaneous electron diffraction and mass spectrometric experiment at 1165 K and 1170 K, respectively. In the vapors of these compounds, we found up to 3 mol.% dimers along with the monomers. The parameters of the rg effective configuration of the monomer molecules were determined. For ErCl3 and YbCl3, the internuclear distances rg(Ln-Cl) were 2.436(5) Å and 2.416(5) Å, and the bond angles ∠g(Cl-Ln-Cl) were 117.0(10)° and 117.2(10)°, respectively. The equilibrium configurations and vibration frequencies of the monomer and dimer molecules were calculated by the HF, B3LYP, and MP2 methods using the combination of the ECPD energy-consistent quasirelativistic core potential, including 4f electrons [Kr4d104fn], and the contracted [5s4p3d] valence basis set for Er and Yb atoms and the MIDIX [4s3p1d] basis set for Cl atoms. The parameters of the effective rg configuration of the monomer molecules corresponding to the temperature of the experiment were calculated. The difference between the calculated equilibrium re(Ln-Cl) and temperature-averaged rg(Ln-Cl) distances was found to be 0.001–0.002 Å and did not exceed the error of the rg(Ln-Cl) parameter determined in the electron diffraction experiment. The experimental parameters of the rg structure were shown to be consistent with the idea about the planar equilibrium geometrical configuration of ErCl3 and YbCl3 molecules. 相似文献
Particular features of the geometrical and electronic structure of six possible conformers of dansylamide ((CH3)2N–C10H6–SO2NH2) are considered. The electronic absorption spectra of the conformers of dansylamide in the free state and taking into account the influence of an aqueous solvent (in terms of the PCM model) are calculated by the TDDFT method. It is shown that, as a result of taking into account solvation, the electronic absorption spectra of the conformers exhibit a bathochromic shift, and the difference in the values of λ of the conformers reaches 16 nm. The calculated electronic absorption spectra in an aqueous medium agree qualitatively with the obtained experimental spectra. An analysis of molecular orbitals involved in the first three electronic transitions of the conformers is carried out. It is suggested that the broadening of the band with λmax = 326 nm in the experimental spectrum may be caused by the presence of dansylamide conformers in the aqueous solution. It is shown that the calculated values of λ in the electronic absorption spectra of dansylamide in the aqueous solvent depend substantially on the DFT functional type. 相似文献
Geometrical and electronic structure and optical properties of several substituents and derivatives of 1,8-naphthosultam are studied by quantum-chemical DFT and TDDFT. It is found that the substituents –NO2, –CF3, and –N(CH3)2 affect the geometrical and electronic structure the most. It is shown that the Stokes shift is greatest (≈260 nm) for compounds with the strong donor substituent –N(CH3)2, while strong acceptor substituents provide a quite small Stokes shift. The dependence of the Stokes shift on the difference in energies of the frontier orbitals of the ground and excited states of molecules is found. Of the 1,8-naphthosultam substituents considered, compounds with –N(CH3)2 substituent, which emit in the biological window region, can be advised for use in optical bioimaging. The results can be used as a basis for the development and creation of new functional materials and biologically active compounds. 相似文献
The saturated vapor over solid W2O4F has been studied by electron diffractometry. Structure analysis was fulfilled assuming complex composition of the vapor. It has been established that at T=1043±30 K the vapor consists of WO2F2 and WOF4 molecules in amounts of 90 and 10 more % respectively. There are two alternative models describing the geometrical structure of the WO2F2 molecule (C2v symmetry) which fit experimental data equally well. In one model, the valence OWO angle is greater than the FWF angle, while in the other, the inverse relation is observed.Ivanovo State University. Moscow Mendeleev Chemical Engineering Institute. Ivanovo Chemical Engineering Institute. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 3, pp. 41–46, May–June 1993.Translated by L. Smolina 相似文献
The structural investigation of molecules in the vapor over neodymium tribromide was performed by synchronous gas-phase electron diffraction and mass spectrometric (GED/MS) experiments at 1110(10) K. Besides the monomeric molecules (NdBr3), a small amount (0.7%) of the dimer (Nd2Br6) was detected. For NdBr3, the thermal-average bond length rg(Nd–Br) of 2.675(6) Å was determined. The equilibrium structure was estimated to be planar (or nearly planar) with re(Nd–Br) of 2.659(7) Å. Three vibrational frequencies were estimated using the GED data: 1 = 193 cm–1, 2 = 35 cm–1, 4 = 41 cm–1. The structural parameters of Nd2Br6 could not be refined and were constrained at the estimated values during the analysis. 相似文献