Molecular structure of nickel(II) and copper(II) N,N′-ethylene-bis(acetylacetoneiminates) MO2N2C12H18 according to gas-phase electron diffraction data and quantum-chemical calculations

The molecular structure of nickel(II) and copper(II) N,N′-ethylene-bis(acetylacetoneiminates), NiO₂N₂C₁₂H₁₈ and CuO₂N₂C₁₂H₁₈, at 442(5) K and 425(5)K, respectively. Both molecules have C ₂ symmetry with a nearly planar MN₂O₂ coordination site and internuclear distances r _h1(M-O) = 1.862(10)/1.923(17) Å and r _h1(M-N) = 1.879(10)/1.947(18) Å for Ni(acacen) and Cu(acacen), respectively. The structure of free molecules is close to the structure of molecules in crystal. The DFT/3LYP quantum-chemical calculations (CEP-31G and 6-31G* basis sets) gave a molecular structure that agreed satisfactorily with the one found in experiment. The low-spin ¹ A and high-spin ³ A states of the Ni(acacen) molecule were considered. It was found that a change in multiplicity caused significant changes in the geometrical and electronic structure of the MN₂O₂ coordination site. As shown by experiment and calculations for the NiO₂N₂C₁₂H₁₈ molecule, the low-spin ¹ A state is the ground state. The internal rotation of CH₃(CN) and CH₃(CO) methyl groups was studied by the 3LYP/CEP-31G method. It was shown that steric hindrances led to a high rotation barrier of the CH₃(CN) group.     

Water-Promoted Photochemical Synthesis of 12-Oxo-6,12-Dihydroazepino[2,1-b]quinazolines with Competitive Formation of 3H-Azepine-2(1H)-Ones

High Energy Chemistry - The effect of an organo-aqueous solvent on the yields of 12-oxo-6,12-dihydroazepino[2,1-b]quinazoline-6-carboxylic acid methyl ester and 3H-azepine-2(1H)-one-3-carboxylic...     

One-Step Synthesis of 2-[(2-Carboxyphenyl)amino]-6-formylnicotinic Acid via Photolysis of 2-Azidobenzoic Acid in the Presence of Weak Bases

Russian Journal of General Chemistry - 2-Azidobenzoic acid has undergone rearrangement into 2-[(2-carboxyphenyl)amino]-6-formylnicotinic acid under irradiation in aqueous-organic media in the...     

Influence of Solvents on the Efficiency of Photoinitiated Formation of 2,3- and 2,7-Substituted 3H-Azepines

High Energy Chemistry -     

Structural dependence of the fragmentation of naphthalenesulfonyl halide and naphthalenesulfonamide molecules under electron ionization

By mass spectrometry it is found that naphthalene, 1-naphthalenesulfonyl chloride, 2-naphthalenesulfonyl fluoride, 2-naphthalenesulfonyl chloride, 1,5-naphthalenedisulfonyl chloride, 1-naphthalenesulfonamide, and 2-naphthalenesulfonamide evaporate congruently on heating and their saturated vapor is presented by the corresponding monomeric molecular forms. The relationship is established between the character of the fragmentation of molecules during electron ionization and the specific features of their geometric and electronic structures.     

The molecular structure of selenium dibromide as determined by combined gas-phase electron diffraction-mass spectrometric experiments and quantum chemical calculations

The vapour over solid SeBr(4) at 10 degrees C was investigated with a combined gas-phase electron diffraction/mass spectrometric (GED/MS) method. The composition of the vapour derived from the mass spectra (43% SeBr(2), 56.7% Br(2) and 0.3% Se(2)Br(2)) was in agreement with the composition obtained from the analysis of the simultaneously recorded GED intensities (41(3)% SeBr(2), 59(3)% Br(2)). The GED study results in the following geometric parameters (r(g), angle(g) values with total uncertainties): Se-Br = 2.306(5) A and Br-Se-Br = 101.6(6) degrees . Most quantum chemical approximations (B3LYP, MP2, CCSD and CCSD(T) with relativistic effective core potentials and cc-pVTZ as well as aug-cc-pVTZ basis sets for the outer shells) overestimate the Se-Br bond length by 0.01 to 0.03 A. All methods reproduce the bond angle correctly, except for the B3LYP method. Gas phase vibrational frequencies estimated from experimental vibrational amplitudes agree well with those measured by Raman spectroscopy in acetonitrile solutions. All computational methods overestimate vibrational frequencies, especially that for the symmetric stretch vibration, by about or 8 to 13%.     

Investigation of the structure and energetics ofΒ-diketonates. VII. Molecular structure of Ga(DPM)3 according to gas phase electron diffraction data

A combined electron diffraction and mass spectrometric study of the saturated vapor over gallium tris-dipivaloylmethanate was performed. It was found that the vapor contains only the monomeric molecules Ga(DPM)₃ of C₃ symmetry, for which the r_a, r_g,and r_a parameters were determined. The force constant f(Ga-O) was estimated from the experimental value of the vibration amplitude 1(Ga-O). 1999.     

Structure and vibration frequencies of gaseous europium dibromide

Molecular structure of EuBr₂ was studied by electron diffraction and mass spectrometry at 1373(20) K. The molecule has a nonlinear equilibrium configuration and is characterized by the following effective parameters: r_g(Eu-Br) = 2.767(6) Å, r_g(Br-Br) = 5.11(5) Å, l_g(Eu-Br) = 0.109(2) Å, l_g(Br-Br) = 0.388(5) Å, Z_g(Br-Eu-Br) = 135.0(3.5)°. The vibration frequencies v₁ = 225(10) cm^-1 and v₂ = 40(4) cm^-1 were found using electron diffraction data.     

Structure of a zinc(II) N,N’-ethylene-bis (acetylacetoniminate) molecule,ZnO<Subscript>2</Subscript>N<Subscript>2</Subscript>C<Subscript>12</Subscript>H<Subscript>18</Subscript>, according to gas electron diffraction data and quantum chemical calculations

Gas electron diffraction is used to study the structure of a zinc(II) N,N’-ethylene-bis(acetylacetoniminate) molecule, ZnO₂N₂C₁₂H₁₈, at a temperature T = 503(5) K. It is found that the molecule has the symmetry of the C₂ equilibrium configuration with a nonplanar structure of the ZnN₂O₂ coordination fragment and internuclear distances r_h1(Zn-O) of 1.958(13) ? and _h1(Zn-N) of 2.012(16) ?. Quantum chemical calculations by the DFT/B3LYP/CEP,TZV method gives the molecular structure consistent with that found in the experiment.     

Molecular structure of LuBr<Subscript>3</Subscript> according to the data of the simultaneous electron diffraction and mass spectrometric experiment

The saturated vapor of lutetium tribromide was studied in the simultaneous electron diffraction and mass spectrometric experiment at 1161(10) K. Along with the monomer molecular forms, the vapor contained an insignificant (up to 3 mol.%) amount of dimers. The parameters of the effective configuration of the monomer molecule were determined. The internuclear distance r _g(Lu-Br) is 2.553(5) Å, and the effective bond angle ∠_g(Br-Lu-Br) is 115.3(10)°. The temperature-averaged r _g parameters were calculated by the B3LYP method using the potential functions obtained by scanning the PES along the vibration coordinates and compared with similar experimental values. It was shown that the geometrical model of the LuBr₃ molecule of D _3h symmetry was consistent with the experimental data. The dependence of the r _g parameters of the LuBr₃ molecule on the vapor temperature was studied theoretically.