Molecular structure and vibrational characteristics of thorium tetrafluoride

The molecular structure of ThF₄ is studied by synchrotron electron diffractometry and mass spectrometry. The thermally mean values of internuclear distances are found at a temperature of 1370±20 K: r_g(Th-F) = 2.124(5) å, r_g(F-F) = 3.418(31) å, δ(F-F) = 0.049(32) å, and LF-Th-F = 107.2(1.7)?. These distances agree with the tetrahedral structure of the molecule. The missing vibration frequencies of the ThF₄ molecule are calculated in a combined analysis of electron diffraction and spectroscopic data: v₁ = 620(30) cm^-1 and v₂ = 115(15) cm^-1.     

Investigation of the structure and energetics ofΒ-diketonates. VI. Molecular structure of calcium dipivaloylmethanate Ca(DPM)2 according to gas phase electron diffraction data

Combined mass spectrometric and electron diffraction study of the overheated vapor over calcium dipivaloylmethanate was performed. It was established that one molecular form, Ca(DPM)₂, predominates in the vapor at 420–460‡C. The r_a, r_g and r_a parameters of the Ca(DPM)₂ molecule were determined, and the symmetry of the molecule was found to be D_2d.     

Structure of SmCl3, DyCl3, and HoCl3 molecules based on the data of synchronous electron diffraction and mass-spectrometric experiment

Saturated vapors of SmCl₃, DyCl₃, and HoCl₃ have been studied in the framework of a synchronous electron diffraction and mass-spectrometric experiment at temperatures 1205 K, 1160 K, and 1148 K, respectively. In vapors of all compounds, along with monomer molecular forms, an insignificant (up to 2 mol.%) amount of dimers was detected. Parameters of the effective configuration of monomer molecules were determined. For molecules SmCl₃, DyCl₃, and HoCl₃ values of internuclear distances r _g(Ln-Cl) were 2.511(5) Å, 2.453(5) Å, and 2.444(5) Å, values of valence angles ∠_g(Cl-Ln-Cl) were 115.6(11)°, 116.8(10)°, and 116.6(10)°, respectively. It is shown that parameters of the r _g-structure are not incompatible with the notion of a planar equilibrium geometrical configuration of molecules SmCl₃, DyCl₃, and HoCl₃. Main tendencies in the change of structural and vibration characteristics in the series of lanthanide trichlorides are considered.     

Gas electron diffraction and quantum chemical study of the structure of a 2-nitrobenzenesulfonyl chloride molecule

A combined gas electron diffraction and quantum chemical (B3LYP/6-311+G**, B3LYP/cc-pVTZ, B3LYP/cc-pVTZ, midix (Cl), and MP2/cc-pVTZ) study of the structure of a 2-NO₂-C₆H₄-SO₂Cl molecule is performed. It is found experimentally that at a temperature of 345(5) K the gas phase contains two conformers of the C ₁ symmetry. Conformer I with a nearly perpendicular arrangement of the S-Cl bond with respect to the benzene ring plane (the C(NO₂)-C-S-Cl torsion angle is 84(3)°) is contained predominantly (69(12)%). In conformer II, the S-Cl bond is located near the benzene ring plane (the C(NO₂)-C-S-Cl angle is 172(3)°). The following experimental internuclear distances (Å) are obtained for conformer I: r _h1(C-H) = 1.064(15), r _h1(C-C)_av = 1.397(3), r _h1(C-S) = 1.761(6), r _h1(S-O)_av = 1.426(4), r _h1(S-Cl) = 2.043(5), r _h1(N-O)_av = 1.222(4), r _h1(C-N) = 1.485(16). In both conformers, the NO₂ group is turned by more than 30° relative to the benzene ring plane.     

Sublimation Enthalpies of Substituted Pyridine N-Oxides

Russian Journal of General Chemistry - The enthalpies of sublimation of five substituted pyridine N-oxides were determined by the Knudsen effusion method with mass spectrometric control of the...     

STRUCTURAL ASPECTS OF trans–cis ISOMERIZATION OF AZOBENZENE, 4,4′-AZOPYRIDINE,AND AZOXYBENZENE

Journal of Structural Chemistry - Processes of trans–cis isomerization of azobenzene (AZB), 4,4′-azopyridine (AZP), and azoxybenzene (AZOB) are studied using quantum chemical...     

Gas-Phase Structures of Potassium Tetrakis(hexafluoro- acetylacetonato) Lanthanide(III) Complexes [KLn(C5HF6O2)4] (Ln=La,Gd, Lu)

The molecular structures of potassium tetrakis(hexafluoroacetylacetonato)lanthanide(III) complexes [KLn(hfa)₄] (Ln=La, Gd, Lu; hfa=C₅HF₆O₂,) were studied by synchronous gas-phase electron diffraction/mass spectrometry (GED/MS) supported by quantum-chemical (DFT/PBE0) calculations. The compounds sublime congruently and the vapors contain a single molecular species: the heterobinuclear complex [KLn(hfa)₄]. All molecules are of C₁ symmetry with the lanthanide atom in the center of an LnO₈ coordination polyhedron, while the potassium atom is coordinated by three ligands with formation of three K−O and three K−F bonds. One hfa ligand is not bonded to the potassium atom. Topological analysis of the electron-density distributions confirmed the existence of ionic-type K−O and K−F bonding. The structures of the free [KLn(hfa)₄] molecules are compared with those of the related compounds [KDy(hfa)₄] and [KEr(hfa)₄] in their crystalline state. The complex nature of the chemical bonding is discussed on the basis of electron-density topology analyses.     

Effect of an External Heavy Atom on the Product Yield of Photoinduced Heterocyclization of 2-Azidobenzoic Acid

High Energy Chemistry -