Structure of acetyl chloride molecule isotopomers CH<Subscript>3</Subscript>COCl and CD<Subscript>3</Subscript>COCl in the ground and lowest excited singlet and triplet electronic states: a quantum mechanical study

The structures of isotopomers of conformationally flexible acetyl chloride molecule, CH₃COCl and CD₃COCl, in the ground (S₀ and lowest excited singlet (S₁) and triplet (T₁) electronic states were calculated by the RHF, MP2, and CASSCF methods. The equilibrium geometric parameters and harmonic vibrational frequencies of the molecules in these electronic states were estimated. According to calculations, electronic excitation causes considerable conformational changes involving rotation of the CH₃ (CD₃) top and a substantial deviation of the CCOCl fragment from planarity. The results of calculations agree with experimental data. Two dimensional torsional inversion sections of the potential energy surface were calculated and analyzed. Vibrational problems for large amplitude vibrations (torsional vibration in the S₀ state and both torsional and inversion vibrations in the T₁ and S₁ states) were solved in one- and two-dimensional approximations.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 62–70, January, 2005.     

S1←S0 Vibronic spectra and the structure of acetyl fluoride-h3 and acetyl fluoride-d3 molecules

UV absorption spectra of acetyl fluoride-h₃ and -d₃ (CH₃COF and CD₃COF) molecules in the region of S₁S₀ electronic transitions are investigated. The origins (0⁰ ₀ or 14^0± ₀) of these transitions are observed at 39912 and 39904 cm^–1, respectively, and some of the fundamental frequencies of these molecules in the s₀ and S₁ states are determined. In particular, the systems of torsion and inversion (out-of-plane C=O vibrations) energy levels are studied. The geometric parameters of an acetyl fluoride-h₃ molecule in the S₁ state are estimated by the theoretical simulation of the rotational contours of the 0⁰ ₀ (14^0± ₀) band. These data are used to evaluate the potential barriers to internal rotation in the S₀ and S₁ states, which were found to be 360 and 560 cm^–1 for acetyl fluoride-h₃ and 380 and 770 cm^–1 for acetyl fluoride-d₃, respectively, as well as the potential barriers to inversion in the S₁ states, which were found to be 2090 and 2370 cm^–1 for acetyl fluoride-h₃ and acetyl fluoride-d₃, respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1957–1964, November, 1994.In conclusion, the authors would like to acknowledge T. S. Kuznetsova for the synthesis and purification of the AF samples.The research presented here was supported in part by the International Science Foundation under grant No. MJ 1000.     

S1←S0 vibronic spectra and the vapor-state molecular structure of propanal and 2-methylpropanal

The vapor-state absorption spectra have been recorded for propanal PA and 2-methylpropanal MP with path lengths up to 120 m. The initial points in the S₁S₀ electronic transitions have been identified together with various fundamental vibrational frequencies of the PA and MP conformers. They contain nonplanar aldehyde groups in the S₁ states with inversion potential barriers of about 600 cm^–1. The parameters of the internal-rotation potential functions in the S₁ states have been determined, and the corresponding potential functions in the S₀ states have been refined.Chemical Faculty, Lomonosov Moscow University. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 1, pp. 20–25, January–February, 1993.     

The internal rotation potential functions of the methacryloyl chloride molecule in the ground and excited electronic states

The systems of torsional vibration levels of the trans and cis methacryloyl chloride isomers in the ground (S ₀) and excited (S ₁) electronic states obtained by analyzing the vibrational structure of the gas-phase UV spectrum were used to reproduce the internal rotation potential functions of the molecule in both electronic states. The kinematic F factor in the S ₀ and S ₁ electronic states was calculated taking into account the relaxation of geometric parameters depending on the internal rotation angle. The internal rotation potential function parameters in the S ₀ state are substantially different from the parameters obtained using the torsional levels of the IR Fourier transform spectrum; at the same time, they are substantiated by quantum-mechanical calculations.     

Analysis of the Vibrational Structure of the <Emphasis Type="Italic">n</Emphasis>–π* Transition in the High-Resolution UV Absorption Spectrum of Methacryloyl Fluoride in the Gas Phase

The UV absorption spectrum of methacryloyl fluoride molecule in the gas phase is obtained in the wavenumber range of 32300–35900 cm^?1. The resolved vibrational structure of this spectrum consists of 153 absorption bands. The assignment of all bands has been made for the first time. Values ν_00trans = 35670.0 сm^?1 and ν_00cis = 35371.1 cm^?1 are determined. The fundamental frequencies for isomers in the S₀ and S₁ states are found. Several Deslandres Tables (DTs) are constructed for the torsional vibration of the s-trans- and s-cis-isomers of the investigated molecule using the NONIUS program. The origins in these DTs correspond to bands attributed to ν₀₀, and to the fundamental frequencies of each isomer in states S₀ and S₁. These DTs are used to determine harmonic frequencies ω_e, anharmonicity coefficients х₁₁, and the frequencies of torsional vibration 0–v transitions up to high values of vibrational quantum number v for s-trans- and s-cis-isomers in both electronic states. The frequencies of torsional vibrations for the s-trans-isomer and the s-cis-isomer in the S₀ state are ν″₁ = 80.9 сm^?1 and ν″₁ = 59.8 сm^?1, respectively. The frequencies for the s-trans- isomer and the s-cis-isomer in the S₁ state are ν′₁ = 134.1 сm^?1 and ν′₁ = 103.6 cm^?1, respectively.     

S 1←S 0 vibronic spectra and inversion potentials in theS 1 states of acetyl and formyl halides

The potential functions of inversion in the S₁ states are determined from the inversion transitions (out-of-plane C=O vibrations) found in the S₁←S₀ vibronic spectra of acetyl halide molecules. The high intensities of the hot inversion transitions are explained by the high probabilities of these transitions. The literature values of the inversion potentials (equilibrium values of angles formed by the C=O bonds deviating from the planes) of formyl halide molecules in the S₁ states are refined. The inversion potentials of formyl and acetyl halides are similar. M. V. Lomonosov Moscow State University, Chemical Faculty. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 316–321, March–April, 1995. Translated by L. Smolina     

S1←S0 Vibronic spectrum and structure of 2,2-difluoroethanal in the S1 state

The vibronic spectrum of the 2,2-difluoroethanal vapor was recorded using a multipass optical cell with an optical length of at least 140 m. The spectrum in the region of 300—364 nm was assigned to the S₁S₀ electronic transition (from the ground S₀ to the first excited singlet S₁ electronic state); the vibrational structure of the spectrum was analyzed. The spectrum bands were assigned to two systems of vibronic transitions, namely, transitions between the levels of the cis-conformer (S₀) and of the S₁ conformers, with the origins (0₀ ⁰ transitions between the zero vibrational levels of conformers) at 29192 and 29087 cm^–1, respectively. Analysis of the spectrum showed that the S₁S₀ electronic excitation of the cis-conformer was followed by rotation of the CHF₂ top and pyramidal distortion of the carbonyl fragment. A number of fundamental frequencies were found for S₁ conformers, in particular, torsion and inversion energy levels. The experimental data are in satisfactory agreement with the results of quantum-chemical calculations for the 2,2-difluoroethanal molecule in the S₀ and S₁ states.     

Internal rotation potential functions of the acryloyl chloride molecule in the ground (<Emphasis Type="Italic">S</Emphasis><Subscript>0</Subscript>) and excited (<Emphasis Type="Italic">S</Emphasis><Subscript>1</Subscript>) electronic states

The internal rotation potential function of the acryloyl chloride molecule in the S ₀ and S ₁ electronic states was reproduced using systems of torsional vibration levels obtained for its trans and cis isomers by analyzing the vibrational structure of the UV spectrum of the molecule. The kinematic factor F in the S ₀ ground state was calculated including geometric parameter relaxation as a function of internal rotation angle. The torsional potential parameters in the S ₀ state obtained in this work were substantially different from those determined from the infrared Fourier-transform spectrum ignoring the resonance perturbation of the level with v = 3. The form of the internal rotation potential function and the higher stability of the trans isomer (the main isomer) were substantiated by high-level quantum-mechanical calculations.     

Radiochemical and spectrophotometric investigations on the extraction equilibrium of ternary ion association thiocyanate complexes of cobalt(II) with nitrobluetetrazolium chloride (NBT) and triphenyltetrazolium chloride (TTC)

Extraction radiochemical investigations of ternary ion-association thiocyanate complexes of Co(II) with nitroblue tetrazolium chloride (NBT) [(3,3-dianizol-4,4-bis) 2-(4-nitrophenyl)-5-phenylnitrotetrazolium chloride] and triphenyltetrazolium chloride (TTC) [2,3,5-triphenyltetrazolium chloride] have been carried out. Molar ratios of the reacting components have been determined as NBT/[Co (SCN)₄]^2–=11 and TTC/[Co(SCN)₄]^2–=21. Using a chemical model and the method of Likussar — Boltz we have determined the values , K_ex and K_D, characterizing the extraction process. The results have been statistically treated. The relative standard deviation S_r has been calculated at a confidence level of 95%.     

An analysis of the vibrational structure of the UV absorption spectrum of methacryloyl chloride vapor

An analysis of the vibrational structure of the UV spectrum of methacryloyl chloride vapor was performed. The spectrum contained unique information about the torsional vibration levels of the trans and cis isomers in the ground (S ₀) and excited (S ₁) electronic states. 136 absorption bands were revealed, and ～85% of them were assigned. The 0-0 transition frequencies of the trans and cis isomers were found. Several Deslandres tables were constructed for torsional vibrations from 0-0 transition frequencies and “local origins” corresponding to fundamental and combined frequencies of both isomers. Systems of torsional levels up to high quantum number values (v ≈ 6–8) were determined, and the ω_e harmonic frequencies and χ ₁₁ anharmonicity coefficients were calculated for both isometric forms in the ground (S ₀) and excited (S ₁) states. The results were substantially different from those obtained in an analysis of Fourier-transform IR spectra.     

Microwave spectrum of propionyl chloride

The microwave spectrum of propionyl chloride has been investigated in the region 18.0–40.0 GHz, and transitions due to a cis conformer have been assigned. This form has a heavy atom planar configuration and the methyl group and the carbonyl oxygen atom are cis to each other. Using the substitution structures of propionic acid and acetyl chloride as molecular models for the propionyl chloride molecule, good agreement is found between observed and calculateò effective rotational constants. For the ³⁵Cl species satellite spectra assigned to the first four excited states of the C-C torsional mode have been observed together with the first excited state of the methyl torsional mode. The ground state spectrum has also been assigned for the ³⁷Cl species. Relative intensity measurements yielded the lowest C-C torsional vibration frequency of 86 ± 10 cm^?1. The CH₃ internal rotation frequency was found to be 197 cm^?1. Nuclear quadrupole coupling constants were determined for the ground state of the ³⁵Cl and ³⁷Cl species. From observed A-E splittings of ^bQ-branch transitions of the first excited state of the methyl torsional mode a barrier to internal rotation was estimated to be V₃ = 2480 ± 40 cal mol^?1 (867 ± 14 cm^?1).     

Structure and spectra of 1,3,2-dioxaphospholenes. 1. Microwave spectra of 2-chloro-4,5-dimethyl-1,3,2-dioxaphospholene and its isotopomers in the ground and excited vibrational states

The microwave spectrum of 2-chloro-4,5-dimethyl-1,3,2-dioxaphospholene (1) was studied in the frequency range from 7 to 53 GHz. Rotational transitions of the parent molecule in the ground and eleven excited vibrational states and those of its mono-substituted ³⁷Cl, ¹³C_Me, and ¹³C_Cycle isotopomers in the ground vibrational state were identified. Rotational constants and partial r _s-structure were obtained. The quartic centrifugal distortion constants, dipole moment components _a = 3.8D and _c = 0.24D (the total dipole moment is 3.81D), and the ³⁵Cl quadrupole coupling constants were determined for the parent molecule. The fine structure of the microwave transitions in the parent molecule was analyzed under the assumption of noninteracting methyl groups. The height of the barrier to internal rotation (V ₃₀ = V ₀₃ = 665 cm^–1) and the frequency of torsional vibrations ( = 167 cm^–1) were found. The frequencies of two lowest vibrational modes corresponding to deformation vibrations of the five-membered ring were estimated (100 cm^–1) from the relative intensities of rotational transitions for different vibrational states.     

Electronic structure and luminescence-spectroscopic properties of triphenylboron

The luminescence-spectroscopic properties of the triphènylboron (TPB) molecule, which belongs to the v_p class, have been studied experimentally and theoretically. The electronic structure of TPB in the ground and excited electronic states has been calculated in the framework of the CNDO/S-CI method. The electron density on the atoms, the first ionization potential, the dipole moment, the energies and matrices of the change in the electron density of the S_n and T_n states, the matrix elements of the spin-orbit coupling operator $$ " align="middle" border="0"> and $$ " align="middle" border="0"> , the intensities and directions of polarization of the S_n S_o and T_i S_o transitions, and the phosphorescence lifetime have been calculated. The experimental data are in qualitative agreement with the calculated data.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 4, pp. 468–472, July–August, 1985.     

Cleavage ofβ -propiothiolactones with methanesulfenyl chloride and acetyl sulfur chloride

-Propiothiolactones are cleaved at the S-CO bond by methanesulfenyl chloride and acetyl sulfur chloride to form mixed disulfides — derivatives of the acid chlorides of -mercapto-isobutyric acid. The mixed disulfides readily disproportionate on heating under acid or base catalysis conditions to give the corresponding symmetrical disulfides. A convenient method was found for obtaining the previously hard-to-obtain symmetrical disulfides.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 475–478, April, 1972.     

Reaction of acetyl chloride with triphenylarsine oxide

Conclusions The reaction of acetyl chloride with triphenylarsine oxide (21 molar ratio) in anhydrous toluene leads to formation of triphenylarsine dichloride and acetic anhydride.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1432–1434, June, 1970.     

Quantum-chemical investigation of the influence of the vacant orbitals of the heteroatom on the shaping of the electronically excited states and luminescence-spectroscopic properties of triphenylgallium

The electronic structure of the triphenylgallium molecule in the ground and electronically excited states has been calculated in the framework of the CNDO/S-CI method in sp and spd bases. The electron density in the AO's and atoms, the first ionization potential the energies and matrices of the changes in the electron density of the S_n and T_n states, the matrix elements of the spin-orbit coupling operator $$ " align="middle" border="0"> and $$ " align="middle" border="0"> , the intensities and directions of polarization of the S_n S_o and T₂ T_n transitions, and the phosphorescence lifetimes have been calculated. The following spectroscopic parametrization has been proposed for the Ga atom in the sp and spd bases: 1/2(I_s + a_s) = 10.075 eV, 1/2(I_p + A_p) = 4.265 eV, 1/2(I_d + A_d)=0, _Ga ^p =5 eV, _Ga ^d =O, _Ga ^sp =–7 eV, _Ga ^spd =–10 eV, and _s,p,d=1.433. The influence of the d AO's on the shaping of the orbital nature of the S₁ and T₂ states has been analyzed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 584–590, September–October, 1985.     

Application of symmetry coupling coefficients in the evaluation of the electronic spectra of d 7 ions

The optical absorption spectrum of cobalt chloride thiourea has been studied at room and liquid air temperatures. The results have been interpreted using group theoretical methods taking into account all the quartet states and several doublet states. Crystal field, electrostatic, and spin-orbit coupling interactions were included to yield the allowed transitions with the relative transition probabilities. The experimental results were interpreted for the following set of parameters: B = 750cm^–1, C = 3100cm^–1, = 7370cm^–1, = -200 cm^–1, = 500cm^–1, and = 450 cm^–1.     

Molecular Structure of Chloral (CCl3CHO) in the Lowest Excited Singlet State

The structure and the conformational behavior of the chloral CCl₃CHO molecule in the lowest excited singlet state (S₁) was investigated by CASSCF and CI ab initio quantum-chemical methods. It is shown that electronic excitation S₁S₀ causes significant changes in the molecular structure, namely, CCl₃ top rotation and pyramidalization of the carbonyl (CCHO) fragment. A relationship between the torsional and inversion vibrations of chloral in the S₁ state has been found. For large-amplitude nuclear motions corresponding to the torsional and inversion vibrations, the corresponding one- and two-dimensional problems were solved. The results are compared with the experimental data and with the results of previous calculations for the lowest excited triplet (T₁) state.     

Interaction of tin (IV) chloride with sulfolane and between tin (IV) chloride and lithium chloride in sulfolane solution

Tin (IV) chloride reacts with sulfolane (S) to form a cis-octahedral adduct SnCl₄·S₂. Solutions of lithium chloride and tin (IV) chloride in sulfolane contain the complex ions SnCl ₅ ^– and SnCl ₆ ^2– at 11 and 21 mole ratios of constituents, respectively. The complexes are characterized by conductimetry and by Mössbauer, IR, and Raman spectroscopy.     

Synthesis of a liquid crystal paramagnetic copper complex with Aminovinylketone and the structural study of its single crystal and mesophase

We have synthesized a mesogenic copper complex with aminovinylketone. The X-ray structural analysis has shown that the molecules of the complex in a single crystal (a=9.107, b=11.446, c=11.496 , =81.06, =73.20, =80.72°, and Z=1) form sheets with thickness determined by the cross molecular sizes. When the substance is heated, phase transitions are observed: Cr196Cr X128 S₁187 S_A189 N192°C i. We have carried out EPR studies of various phase states of the complex. It is shown that in the mesophase, the diamagnetic component of magnetic anisotropy is larger than the paramagnetic component resulting in the orientation of the long molecular axes along the outer magnetic field.Kazan Physicotechnical Institute. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 6, pp. 49–55, November–December, 1993.Translated by T. Yudanova