Vibrational spectra in cyclopropane series: II. Symmetry and conformation in the gas phase of the monomer and dimer of cyclopropanecarboxylic acid

Infrared and Raman spectra of gaseous cyclopropanecarboxylic acid (C₃H₅COOH and C₃H₅COOD) were measured from 250 to 4000 cm^?1. The bands were assigned respectively to the monomer and to an associate. The depolarization ratio measurement, the vib—rot envelope study and the detailed analysis of the v(CO) and v(CH) regions enabled the symmetry and the conformation of the molecular entities in equilibrium to be determined. The monomer belongs to the C_s symmetry group and the conformation of its predominant fraction is trans/trans. The associate is a centrosymmetrical dimer (C_i symmetry) having (trans/cis)₂ conformation. Some features of the geometry of the pseudocycle are discussed.     

Atmospheric pressure chemical vapour deposition of selenium and tellurium films by UV laser photolysis of diethyl selenium and diethyl tellurium

Excimer laser‐induced photolysis of gaseous diethyl selenium and diethyl tellurium (C₂H₅)₂M (M = Se, Te) is controlled by cleavage of both M? C bonds, it yields C₁–C₄ hydrocarbons (ethene as major product) and results in chemical vapour deposition of selenium films and nanosized tellurium powder. The selenium and tellurium properties were characterized by X‐ray photoelectron spectroscopy and Scanning electron Microscopy techniques. Copyright © 2001 John Wiley & Sons, Ltd.     

Hydrogen bond effect on the bonding and B2 molecular vibrations of pyrrole

The influence of the hydrogen bond on the infrared B₂ symmetry modes of pyrrole (C_2ν) has been studied. CNDO/2 calculations suggest that the most probable structure for the associated pyrrole involves the interaction NH ⋯ π. The shortest distance between the nitrogen atom and the ring of the nearest neighbor molecule is about 2.9 Å. The absorption bands of pyrrole in the gaseous state at 474, 626 and 720 and 826 cm⁻¹ have been assigned to the NH, ring and CH out-of-plane deformation modes.     

IR matrix spectra of CsNO2, RbNO2, KNO2, and NaNO2. The structure of CsNO2

The IR spectra of alkali nitrites were studied in Ar matrices at the temperature of 7 K. The spectra of CsNO₂ were investigated with the aid of ¹⁵N and ¹⁸O isotopes in order to determine the structure of the gaseous molecules. The IR spectra of ¹⁸O-enriched CsNO₂ samples were recorded and the results interpreted by means of normal coordinate calculations. CsNO₂ has a planar ring structure of C_2v, symmetry. The bond angle ONO of this molecule was calculated to be 116 ± 5°. NaNO₂ as well as the remaining alkali nitrites have C_2v, symmetry structures. Far-IR spectra of alkali nitries were recorded in order to measure the interionic stretching vibrations; in some case low-frequency bands were observed and assigned to the A₁ and B₁ interionic stretching modes.     

Structural and spectral consequences of ion pairing II. a theoretical study of CIO−3Li+ and ClO−3Na+

The structure of ClO⁻₃M⁺ ion pairs (M = Li, Na) has been examined with the aid of ab initio molecular orbital calculations. The calculations support recent experimental findings that ClO⁻₃ M ion paris have C_3v rather than C_s configurations. Results from these studies also show that the metal cation prefers to coordinate at the base of the chlorate anion pyramidal structure along the C₃ axis. Calculated vibrational frequencies, intensities, isotopic frequency shifts, and isotopic substituted frequency and intensity patterns render support to this conclusion. New vibrational assignments of observed and some unassignable bands from previous matrix-isolation and molten gas phase spectroscopic studies of ClO⁻₃M⁺ ion pairs are provided.     

Vibrational spectra and conformational behavior of 1,1- diethylcyclopropane

Infrared spectra (from 4000 to 400 cm⁻¹) of solid, liquid and gaseous 1,1-diethylcyclopropane and Raman spectra of the condensed phases of this compound have been recorded. Evidence for two conformational isomers, one of which vanishes in the polycrystalline solid phase, is found in the spectral data for the liquid phase. It has been concluded that these two rotational isomers are the gauche/gauche conformers which arise when the two methyl groups are displaced in a conrotatory sense (C₂ symmetry) and a disrotatory sense (C_s symmetry) from a hypothetical cis/cis (C_2υ) structure. These conclusions are consistent with the conformational results previously obtained for ethylcyclopropane and ethyloxirane. In addition, from the variable temperature liquid phase Raman intensity measurements, the C₂ rotamer of 1,1- diethylcyclopropane has been calculated to be 1.1 ± 0.2 kcal/mole more stable than the C_s form, and is the sole conformer remaining in the solid phase. Tentative vibrational assignments, in agreement with those for related molecules, are proposed for the major spectral bands of 1,1-diethylcyclopropane.     

The electronic and spin properties of excited Se-O<Subscript>2</Subscript> intermediates

Nonempirical calculations performed by various methods were used to estimate the structure and stability of Se-O₂ intermediates containing active oxygen forms and reveal possible channels of their formation. The electronic and spin properties of ground and excited states of the SeOO (C _s ) superoxocomplex, Se(O₂) (C _2v) peroxocomplex, and SeO₂ (C _2v) selenium dioxide were analyzed. Calculations revealed rules that governed changes in the spectral and spin properties of oxygen in the formation of such systems.     

A theoretical comparison of the lowest-lying singlet and triplet states of H2CBe and of HCBeH

The low-lying singlet and triplet states of H₂CBe and HCBeH are examined using ab inito molecular orbital theory. In agreement with earlier results, the lowest-lying structure of H₂CBe has C_2v symmetry and is a triplet with one π electron (³ B₁). The results presented here suggest that the lowest-energy singlet structure is the (¹B₁) open-shell singlet, also with C_2v symmetry, at least 2.5 kcal/mol higher in energy. The singlet C_2v structure with two π electrons (¹A₁) is 15.9 kcal/mol higher than ³B₁. All of these structures are bound with respect to the ground state of methylene and the beryllium atom. In HCBeH, linear equilibrium geometries are found for the triplet (³Σ) and singlet (¹Δ) states. The triplet is more stable than the singlet (¹Δ) by 35.4 kcal/mol, and is only 2.9 kcal/mol higher in energy than triplet H₂ CBe. Since the transition structure connecting these two triplet molecules is found to be 50.2 kcal/mol higher in energy than H₂ CBe, both triplet equilibrium species might exist independently. The harmonic vibrational frequencies of all structures are also reported.     

Darstellung von [(C2H5)2NH2]3[PS3F]F und [(C2H5)2NH2]3[PS2SeF]F und Kristallstruktur der selenhaltigen Phase

Preparation of [(C₂H₅)₂NH₂]₃[PS₃F]F and [(C₂H₅)₂NH₂]₃ [PS₂SeF]F and Crystal structure of the Phase with Selenium The title compounds were prepared by reaction of diethylammon ium-trithiophosphite with fluoride ions (as diethylammonium fluoride) and sulfur and selenium, respectively. The crystal structure of the selenium containing phase was determined. It does not represent a phosphoranate with a [PS₂SeF₂]^3? anion, but a double salt of [PS₂SeF]^2? with F^?.     

Structure,Optical, and Magnetic Properties of (PPN+)2(C702−)⋅2 C6H4Cl2, which Contains Dianionic Polymeric (C702−)n Chains

A new salt, (PPN⁺)₂(C₇₀^2?) ? 2 C₆H₄Cl₂ ( 1 ), which contains C₇₀^2? dianions, has been obtained as single crystals (PPN⁺=bis(triphenylphosphine)iminium cation). The C₇₀^2? dianions form polymeric zigzag (C₇₀^2?)_n chains, in which the fullerene units are bonded through single C? C bonds of length 1.581(5)–1.586(6) Å. The distance between the centers of neighboring C₇₀^2? units is 10.441 Å. The optical and magnetic properties of (C₇₀^2?)_n have also been studied. Decreasing the symmetry of C₇₀ in the polymer activate about 20 new IR bands in addition to the 10 IR‐active bands of the starting C₇₀. The polymeric structure shows absorptions in the visible and NIR regions, with three main bands at 890, 1200, and 1550 nm, instead of one band of isolated C₇₀^2? dianions at 1165–1184 nm. We concluded that the (C₇₀^2?)_n polymer was diamagnetic, with a negative molar magnetic susceptibility of ?3.82×10^?4 emu mol^?1 per C₇₀^2? dianion. The polymer is EPR silent and a weak narrow EPR signal in salt 1 is due to impurities, which only constitute 0.84 % of spin S=1/2 of the total amount of fullerene C₇₀.     

Formation,Structural Characterization,and Calculated NMR Chemical Shifts of Selenium‐Nitrogen Compounds from SeCl4 and ArNHLi (Ar = supermesityl,mesityl)

Supermesityl selenium diimide [Se{N(C₆H₂^tBu₃‐2, 4, 6)}₂; Se{N(mes*)}₂] can be prepared in a good yield from the reaction of SeCl₄ and (mes*)NHLi. The molecule adopts an unprecedented anti, anti‐conformation, as deduced by DFT calculations at PBE0/TZVP level of theory and supported by ⁷⁷Se NMR spectroscopy and a crystal structure determination. An analogous reaction involving (C₆H₂Me₃‐2, 4, 6)NHLi [(mes)NHLi] unexpectedly lead to the reduction of selenium and afforded the selenium diamide Se{NH(mes)}₂ that was characterized by X‐ray crystallography and ⁷⁷Se NMR spectroscopy. The Se‐N bonds of 1.847(3) and 1.852(3) Å show normal single bond lengths. The <NSeN bond angle of 109.9(1)° also indicates a tetrahedral AX₂E₂ bonding arrangement around selenium. Two N‐H···N hydrogen bonds link the Se{NH(mes)}₂ molecule with two discrete (mes)NH₂ molecules. In the solid state selenium diamide adopts the anti‐conformation, whereas in solution the presence of both syn‐ and anti‐isomers could be observed. PBE0/TZVP calculations of the shielding tensors of 28 different types of selenium‐containing molecules, for which the ⁷⁷Se chemical shifts are unambiguously known, were carried out to assist the spectral assignment of Se{N(mes*)}₂ and Se{NH(mes)}₂.     

Vibrational spectra and conformational behavior of dicyclopropylmethane

Raman spectra of the condensed phases of dicyclopropylmethane have been recorded. In addition, i.r. spectra of this compound have been obtained for all three phases. From the appearance of spectral doublets in the liquid phase Raman (and i.r.) spectra, one member of each of which vanishes upon crystallization, it has been concluded that, in the liquid state, DCPM exists as an equilibrium mixture of at least two conformers. Based upon the spectral results for DCPM, and upon the conformational preferences of a number of related molecules, it has been concluded that these two conformers are the C₂ and C_sgauche/gauche rotational isomers, with the C₂ form being the one which remains in the solid phase. From a variable temperature study of liquid phase Raman peaks, it has been determined that the C₂ conformer of DCPM is more stable than the C_s conformer by 0.93 ± 0.10 kcal/mole. In addition, it appears that the C₂ rotamer of DCPM also predominates in the gaseous phase. Tentative assignments of the major spectral bands of DCPM have also been proposed.     

The use of 18O substitution in the characterization of MReO4 molecules. The IR spectrum of matrix-isolated CsReO4

The molecular structure of gaseous CsReO₄ has been studied by matrix isolation IR spectroscopy. The ¹⁸O substitution experiments indicate a bidentate structure of C_2v symmetry in which the perrhenate anion is slightly distorted from the tetrahedral geometry.     

The reactions between SO2 and C2H2 (and C2H4) at elevated temperatures. A single-pulse shock tube investigation

The high-temperature reaction between sulfur dioxide and acetylene in an excess of argon was studied in a 1?in. i.d. single-pulse shock tube. Mixtures ranging from 1.81% to 5.40% SO₂ and 1.60% to 4.90% C₂H₂ were heated to reflected shock temperatures of 1550°–2150°K, for dwell times of about 0.6 msec and gas dynamically quenched. Total reaction densities were 0.89 to 5.4 × 10^?2 moles/1. The reaction products were analyzed by gas chromatography. A technique was developed for separating Ar, C₂H₄, C₂H₂, SO₂, CO, CO₂, H₂S, COS, and CS₂. The major products of the reaction are CO, H₂, CS₂, and sulfur. The products observed were compared with those predicted on the assumption that equilibrium was attained. Several preliminary experiments were carried out with ethylene-sulfur dioxide mixtures, and the results indicated that for this combination the sulfur dioxide probably reacted with the acetylene generated from the decomposition of the ethylene, rather than directly with the ethylene. The rate of decline in the sulfur dioxide content in C₂H₂-SO₂ mixtures was found to be approximately second order (total) and can be empirically represented by A mechanism is proposed to account for the overall reaction kinetics.     

Far-infrared studies of ethanols and fluoroethanols trapped in low-temperature matrices

Ethanol, its deuterated derivatives (C₂H₅OD, C₂D₅OD) and fluoroethanols (CFH₂CH₂OH, CF₃CH₂OH) have been isolated in low temperature matrices and investigated in the far-infrared region. From the concentration dependency of the observed bands and from studies of the pure alcohols in the gaseous, liquid, and solid phase it was found that the hydrogen bond stretching frequencies ν_σ associated with the hydrogen bonded system OH?O appear in the 100 – 160 cm^?1 range. At higher M/A ratios the OD(OD) torsion modes τ_OH are dominating and were identified in the 200 – 300 cm^?1 region. The influence of various matrix materials like argon, krypton, xenon, nitrogen and methane on the low frequency spectra of ethanol have also been studied. It was found, that nitrogen and methane matrices produce significant changes in the far infrared spectra.     

Deduction of structures of lanthanoid coordination compounds from absorption spectra

The nepheloxetic effect (reduction in the electron repulsion parameter B in a coordination compound relative to that in the gaseous ion) indicates that the bond type deviates from ionic. There is a linear relation between the long-wave shift v (difference in wave-numbers for the bands in the compound and aqua-ion) and B for the d-transition metals; v is dependent on the type of bond from the metal to the addend.These v have been measured for the ⁴J_9/2²P_1/2 bond (which corresponds to a bond from Nd to a dissociated carboxyl, alcohol, or other OH group) and have been found to be additive; the increments correponding to these groups have been deduced and used to deduce the structure of the internal sphere for Nd and Eu coordinated with hydroxy-acids, EDTA, and other substances in aqueous solution.The splitting of the ⁴J_9/2(Nd³⁺) and ⁵D₂(Eu³⁺) levels has given the symmetry of the aqua-ion (C₄), of the EDTA one (C_4V), of the cyanotriacetate one (C_3V), and of the diethylenetriaminepentacetate one (C_3V) for Nd and Eu.Read at the Eighth International Conference on the Chemistry of Coordination Compounds, Vienna, 10 September 1964.     

马来腈二硫纶·邻菲咯啉镍(II)配合物的电子光谱和理论研究

测量了标题配合物Ni(mnt)(phen)在多种介质中的电子吸收光谱和发射光谱, 使用密度泛函理论的B3LYP方法和分子轨道理论的PM3方法研究了其气态分子几何构型、电子结构和成键, 用ZINDO/S方法通过多组态的组态相互作用(CI)计算解释了实验光谱. 结果表明: 该配合物分子为平面结构, 对称性属于点群C_2v, 基态为自旋三重态, 配位键Ni—N和Ni—S为典型的共价结合, Ni的3d电子反馈效应较显著; 可见区的吸收带和发射带(对应于基态电子组态到较低能量激发态组态的跃迁)本质上属于配体phen到mnt^2－的荷移跃迁(LL'CT), 紫外区的吸收带本质上属于配体的π→π*跃迁.     

Radiochemical determination of oxygen traces in selenium

A sensitive method for determination of oxygen in selenium is described. Oxygen is converted into the gaseous compound sulfur dioxide labelled with³⁵S. The β-radiation of³⁵S is measured by liquid scintillation counting. The detection limit is 0.02 ppm. The efficiency of vacuum distillation in the purification of selenium, and the influence of air, dry oxygen and water on the absorption of oxygen by selenium have been investigated.     

Spectral properties of the C60 complex with dibenzenechromium

The product of the interaction of fullerene C₆₀ with dibenzenechromium (DBC) was studied by ESR and IR spectroscopy. The ESR spectrum contains a signal of the radical cation DBC⁺. A signal of the C₆₀ ^? anion is virtually absent, which is most likely related to its broadening. The IR spectrum contains bands characteristic of the DBC⁺ cation in the (DBC)I molecule and four bands characteristic of C₆₀ ^?. The data obtained indicate the interaction of C₆₀ molecules with the environment in the crystal structure of the complex.     

Standard Chemical Thermodynamic Properties of Perfluoro N-Alkanes

The chemical thermodynamic properties C_p°, ΔH_f° S°, ΔG_r° and K_p of gaseous perfluoro n-alkanes, P(CF₂)n F(2≤n≤10), have been calculated from 298.15 to 1000 K using the Benson method with C_p° = a″;b/T + c/T², C_p°=a+bT+c+/T² and C_p°=a″ + bT +cT². Better results are obtained for C_p°=a+b/T+c/T². The calculated chemical thermodynamic properties of C₂ F₆ (g) are in excellent agreement with the literature data of Stull, Westrum, and Sinke under IBM/PC microcomputer with STEP data base management system.