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A hydrogen-bonded CHF⋯HF complex was characterized by FTIR matrix isolation spectroscopy and ab initio calculations. Three possible structures of this complex were found at the coupled-cluster with single, double, and perturbative triple excitations [CCSD(T)/L3a_3] level of theory. The comparison between the experiment and theory reveals that the most stable structure with the binding energy of 6.48 kcal/mol is formed upon x-ray irradiation of isolated CH2F2 molecules in noble gas matrices (Ne, Ar, Xe). This species appears to be the first known intermolecular complex of monofluorocarbene, and its identification was unambiguously proved by IR absorptions corresponding to HF deformation (libration), CF stretching, H–C–F bending, and CH and HF stretching modes. It is worth noting that the corresponding spectral features in an argon matrix were previously tentatively ascribed to CH2F2+· and HF⋯CHF−· [L. Andrews and F. T. Prochaska, J. Chem. Phys. 70, 4714 (1979)], but the calculations performed in the present study definitely support the re-assignment. The observed CHF⋯HF complex can be converted to the parent CH2F2 under the action of light with λ < 525 nm. The plausible mechanism of this conversion using the conical intersection concept is discussed. [ABSTRACT FROM AUTHOR]

We report on the preparation and vibrational characterization of the C2H3...CO2 complex, the first example of a stable intermolecular complex involving vinyl radicals. This complex was prepared in Ar and Kr matrices using UV photolysis of propiolic acid (HC3OOH) and subsequent thermal mobilization of H atoms. This preparation procedure provides vinyl radicals formed exclusively as a complex with CO2, without the presence of either CO2 or C2H3 monomers. The absorption bands corresponding to the v5(C2H3), v7(C2H3), v8(C2H3), v2(CO2), and v3(CO2) modes of the C2H3...CO2 complex were detected experimentally. The calculations at the UCCSD(T)/L2a level of theory predict two structures of the C2H3...CO2 complex with Cs and C1 symmetries and interaction energies of -1.92 and -5.19 kJ mol-1. The harmonic vibrational frequencies of these structures were calculated at the same level of theory. The structural assignment of the experimental species is not straightforward because of rather small complexation-induced shifts and matrix-site splitting of the bands (for both complex and monomers). We conclude that the C1 structure is the most probable candidate for the experimental C2H3...CO2 complex based on the significant splitting of the bending vibration of CO2 and on the energetic and structural considerations. [ABSTRACT FROM AUTHOR]

Spectroscopic characteristics and X-ray induced transformations of the HCN... CO2 complex in solid Ar and Kr matrices were studied by FTIR spectroscopy and ab initio calculations at the CCSD(T) level. The complexwas prepared by deposition of the HCN/CO2/Ng gas mixtures (Ng = Ar or Kr). The comparison of the experiment and calculations prove formation of a linear, H-bonded NCH... OCO complex with a substantial red shift of the C-H stretching band and a blue shift of the H-C-N bending band in respect to the monomer. This result is in contrast with the previous gas-phase observations, where only T-shape complex was found. Irradiation of deposited matrices leads to formation of CN radicals and HNC molecules and subsequent annealing results in appearance of H2CN and trans-HCNH in both matrices plus HKrCN in the case of Kr. In the presence of CO2, the strongest absorption of trans-HCNH radical demonstrates an additional blue-shifted (by 6.4 cm-1) feature, which was assigned to the N-coordinated complex of this radical with CO2 on the basis of comparison with calculations. To our knowledge, it is the first experimentally observed complex of this radical. No evidence was found for HKrCN... CO2 complex, which was explained tentatively by steric hindrance. [ABSTRACT FROM AUTHOR]

The radiation-induced transformations of isolated dimethyl disulphide molecules in a solid argon matrix occurring under the action of X-rays at 4.5 K were studied by FTIR spectroscopy. It was shown that decomposition was quite efficient (the corresponding radiation-chemical yield of Me 2 S 2 degradation was estimated as 4.5 molecules per 100 eV). The radiolysis proceeds via two primary channels yielding CH 3 SH plus H 2 CS and CH 4 plus H 2 CSS, respectively. These two channels of dimethyl disulphide decay during radiolysis lead to various secondary products appearing during prolonged radiolysis. Spectroscopic characteristics of the observed products and possible implications of the results are discussed. • Efficient radiolysis of isolated dimethyl disulphide molecules in solid argon was showed. • Two primary channels of radiolysis of dimethyl disulphide molecules were discovered. • With prolonged radiolysis of dimethyl disuphide molecules, a variety set of products is discovered. [ABSTRACT FROM AUTHOR]

The structural and spectroscopic features of the CHF3...H2O complex have been investigated using high-level ab initio calculations and IR matrix isolation spectroscopy. In contrast to previous findings, the computations at the CCSD(T)/L3a_3 and MP2/L3a_3 levels of theory revealed only one structure of the complex stabilized by two C-H...O and O-H...F hydrogen bonds. The interaction energy extrapolated to a complete basis set with ZPVE and BSSE corrections is 2.73 kcal/mol at the CCSD(T) level, taking into account the zero-point vibrational energy (ZPVE) and basis set superposition error (BSSE) corrections. According to Bader's analysis, complex exhibits a cyclic structure, which confirms the existence of ring critical point as well as bond critical points in the system. The calculated complexation-induced shifts of the fluoroform fundamentals are in good agreement with the matrix isolation results. In addition to previously reported IR absorptions of the complex, the feature corresponding to the C-F bending mode of CHF3...H2O was first observed, in good correlation with the computational predictions. [ABSTRACT FROM AUTHOR]

Formyl radical HCO is an important reactive intermediate in combustion, atmospheric and extraterrestrial chemistry. Like in the case of other transients, the lack of knowledge of the absolute IR intensities limits the quantitative spectroscopic studies on this species. We report the first experimental determination of the absorption intensities for the fundamental vibrational bands of HCO. The measurements have been performed using matrix-isolation FTIR spectroscopy. Determination of the values was based on the repeated photodissociation and thermal recovery of the HCO radical using the known value of the absorption coefficient of CO. The experimentally determined values (93.2 ± 6.0, 67.2 ± 4.5, and 109.2 ± 6.6 km mol − 1 for the ν 1 , ν 2 , and ν 3 modes, respectively) have been compared to the calculated IR intensities obtained by DFT and UCCSD(T) computations. [ABSTRACT FROM AUTHOR]

The X-ray-induced transformations of simple chlorofluorocarbons (CFCl3 and CF2Cl2) in solid noble-gas matrixes (Ne, Ar, Kr, and Xe) at 7 K were studied in order to elucidate basic mechanisms of the radiation-chemical degradation with possible implications for stratospheric and extraterrestrial ice chemistry. The decomposition of parent molecules and formation of products were monitored by FTIR spectroscopy, and the identification was supported by ab initio calculations at the CCSD(T) level. It was shown that the ionic reaction channels were predominating in most cases (except for CF2Cl2/Xe system). The primary radical cations (CFCl3+• and CF2Cl2+•) are either stabilized in matrixes or undergo fragmentation to yield the corresponding secondary cations (CFCl2+, CCl3+, CF2Cl+) and halogen atoms. The probability of fragmentation through different channels demonstrates a remarkable matrix dependence, which was explained by the effect of excess energy resulting from the exothermic positive hole transfer from matrix atoms to freon molecules. A qualitative correlation between "hot" ionic fragmentation at low temperatures and gas-phase ion energetics was found. However, dissociative electron attachment leads to formation of neutral radicals (CFCl2• or CF2Cl•) and chloride anions. One more possible way of dissociative electron attachment in the case of CF2Cl2 is formation of CF2•• and Cl2-•. A general scheme of the radiation-induced processes is proposed. [ABSTRACT FROM AUTHOR]

The α-hydroxyethyl radical (CH3·CHOH, 2A) is a key intermediate in ethanol biochemistry, combustion, atmospheric chemistry, radiation chemistry, and astrochemistry. Experimental data on the vibrational spectrum of this radical are crucially important for reliable detection and understanding of the chemical dynamics of this species. This study represents the first detailed experimental report on the infrared absorption bands of the α-hydroxyethyl radical complemented by ab initio computations. The radical was generated in solid para-H2 and Xe matrices via the reactions of hydrogen atoms with matrix-isolated ethanol molecules and radiolysis of isolated ethanol molecules with x rays. The absorption bands with maxima at 3654.6, 3052.1, 1425.7, 1247.9, 1195.6 (1177.4), and 1048.4 cm−1, observed in para-H2 matrices appearing upon the H· atom reaction, were attributed to the OHstr, α-CHstr, CCstr, COstr + CCObend, COstr, and CCstr + CCObend vibrational modes of the CH3·CHOH radical, respectively. The absorption bands with the positions slightly red-shifted from those observed in para-H2 were detected in both the irradiated and post-irradiation annealed Xe matrices containing C2H5OH. The results of the experiments with the isotopically substituted ethanol molecules (CH3CD2OH and CD3CD2OH) and the quantum-chemical computations at the UCCSD(T)/L2a_3 level support the assignment. The photolysis with ultraviolet light (240–300 nm) results in the decay of the α-hydroxyethyl radical, yielding acetaldehyde and its isomer, vinyl alcohol. A comparison of the experimental and theoretical results suggests that the radical adopts the thermodynamically more stable anti-conformation in both matrices. [ABSTRACT FROM AUTHOR]

In this work we report the results of systematic studies on the radiation-induced transformations in HCN/Ng systems (Ng=Ne, Ar, Kr or Xe) at 7 K using a combination of FTIR and EPR spectroscopy. It was shown that HCN underwent efficient decomposition producing H atoms, CN radicals and HNC isomer. The thermally induced reactions of H atoms in different matrices result in the formation of two isomeric radicals, H 2 CN and trans-HCNH, the former being predominated. The temperature dependent dynamics of CN and H 2 CN radicals in a krypton matrix was observed by EPR spectroscopy in solid krypton. The vibrational frequencies, IR intensities and magnetic resonance parameters of H 2 CN and trans-HCNH radicals calculated at the CCSD(T) level are in reasonable agreement with the experimental results. It was found that HCNH radical could be effectively bleached with visible light. The comparison of experimental and computational data made it possible to assign a new vibrational band at 918 cm −1 in an Ar matrix (and the corresponding bands in Kr and Xe) to trans-HCNH radical. In addition, HKrCN was found in the case of krypton, whereas HXeCN and HXeNC were produced in solid xenon. The reaction mechanisms and contribution of different channels are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The primary radical cation of cyclopropylacetylene was first characterized by EPR spectroscopy in low-temperature freon matrices. The assignment was confirmed by specific deuteration and quantum-chemical calculations at PBE0 and CCSD(T) levels. Photolysis with visible light led to irreversible transformation of the initial species to a ring-open structure. Detailed computational analysis of energy and magnetic resonance parameters of possible reaction products justified formation of pent-3-en-1-yne radical cation (presumably, a (Z)-isomer). This conclusion was also supported by the effect of specific deuteration. [Copyright &y& Elsevier]

Abstract: Diels–Alder reactions of thiophene-1,1-dioxides with strong electron withdrawing groups (EWG) were studied experimentally and theoretically. Thiophene-1,1-dioxides with two strong EWG behave as dienophiles and regio- and stereoselectively react with cyclopentadiene to give [2+4] cycloadducts 2a–c , which are derivatives of benzothiophene. In contrast, thiophene-1,1-dioxides with one EWG behave as dienes in the inverse electron demand Diels–Alder reaction yielding dihydro-1H-indenes derivatives. Cope [3,3]-sigmatropic rearrangement of adducts 2a–c was also demonstrated. MP2 calculations successfully rationalize the contrasting regioselectivities of these cycloaddition reactions. [Copyright &y& Elsevier]

Abstract: The structures of a series of metallatranes, N(CH2CH2O)3M–X (I–IV), where M=Si, Ge, Sn and Pb, and X=H, F, Cl, Br, HO, CH3, (CH3)2N, (CH3)3N+ were studied using DFT calculations with full geometry optimization. The obtained results are in good agreement with gas electron diffraction data. The transannular bond M←N length depends on the nature of M and axial X substituent and the strength of M←N bond increases in Si&#60;Ge&#60;Sn order. The structures of tetracoordinated species, HC(CH2CH2O)3M–X and N(CH2CH2O)3C–X, were calculated for comparison. Possible mechanisms of transannular bond formation in I–IV are also discussed. [Copyright &y& Elsevier]

Structure and spectroscopic features of the CF2⋯HFcomplexes were studied by ab initio calculations at the CCSD(T) level and matrix isolation FTIR spectroscopy. The calculations predict three stable structures. The most energetically favorable structure corresponds to hydrogen bonding of HF to the lone pair of the C atom (the interaction energy of 3.58 kcal/mol), whereas two less stable structures are the H⋯F bonded complexes (the interaction energies of 0.30 and 0.24 kcal/mol). The former species was unambiguously characterized by the absorptions in the FTIR spectra observed after X-ray irradiation of fluoroform in a xenon matrix at 5 K. The corresponding features appear at 3471 (H–F stretching), 1270 (C–F symmetric stretching, shoulder), 1175 (antisymmetric C–F stretching), and 630 (libration) cm-1, in agreement with the computational predictions. To our knowledge, it is the first hydrogen-bonded complex of dihalocarbene. Possible weaker manifestations of the H⋯F bonded complexes were also found in the C–F stretching region; however, their assignment is tentative. The H⋯C bonded complex is protected from reaction yielding a fluoroform molecule by a remarkably high energy barrier (23.85 kcal/mol), so it may be involved in various chemical reactions. [ABSTRACT FROM AUTHOR]

The structure and spectroscopy of hydrogen-bonded complexes of partially fluorinated methanes attract considerable interest from both fundamental and applied points of view. Here we report an experimental and theoretical study on CH 2 F 2 ⋯CO complex, which represents the first example of difluoromethane complex characterized by matrix isolation vibrational spectroscopy. According to the computations at the CCSD(T)/CBS (MP2/CBS) level of theory with ZPVE correction, the interaction energy of the most stable structure is 0.78 (0.84) kcal/mol. The calculated complexation-induced shifts for this structure are in reasonable agreement with experiment. The complex exhibits characteristic blue shifts of the C–H stretching modes (by 3.8 and 10.4 cm−1 for symmetrical and antisymmetrical vibrations, respectively) and red shifts of the C–F stretching modes (by −0.8 and −4.2 cm−1 for symmetrical and antisymmetrical vibrations, respectively); the C–O stretching is blue-shifted (+5.4 cm−1). The comparison of new complex with previously known species of this kind is discussed. • A matrix isolated CH 2 F 2 ⋯CO complex was characterized by FTIR spectroscopy. • CH 2 F 2 ⋯CO complexes were examined by ab initio calculations (MP2 and CCSD(T)). • Calculated complexation-induced shifts are in reasonable agreement with experiment. [ABSTRACT FROM AUTHOR]

• FKrCF and FXeCF were synthesized in the noble gas matrices. • CH 2 F 2 was used as a precursor generating CF under X-ray irradiation. • New compounds were identified through comparison with ab initio calculations. • FNgCF molecules were found to decay under near IR, visible and UV light. FKrCF and FXeCF were synthetized in solid krypton and xenon matrices at cryogenic temperatures. These molecules representing a new class of noble-gas compounds are formed as a result of reaction between mobile F atoms and trapped CF fragment in solid Kr and Xe, which occur after X-ray radiolysis of CH 2 F 2 in the corresponding matrices. The assignment was based on comparison with previously published computational data (Chopra et al., Chem. Phys., 2017, 494, 20) and the results of additional quantum chemical calculations. New molecules were found to be sensitive to near-IR, visible and UV light. [ABSTRACT FROM AUTHOR]

In this work, we have examined the radiation-induced synthetic chemistry occurring in an astrochemically important C2H2–CO system at the molecular level using a matrix isolation approach. The 1:1 C2H2···CO intermolecular complex of linear structure was obtained in the solid low-temperature (5 K) noble gas matrices by deposition of the C2H2/CO/Ng (Ng = Ar, Kr, Xe) gaseous mixtures and characterized by Fourier-transform infrared spectroscopy. It was found that the X-ray radiolysis of the C2H2···CO complex resulted in formation of C3O (tricarbon monoxide), HCCCHO (propynal), c-H2C3O (cyclopropenone), H2CCCO (propadienone), and HC3O (oxoprorynyl radical). This means that the studied complex may be considered as the simplest building block (or minimal size of intermolecular reactor) for cold astrochemistry occurring in mixed interstellar ices. Remarkably, the discovered transformations of the complex actually represent synthetic routes leading to various C3 species, whereas the acetylenic C–H bond cleavage yielding ethynyl radical appears to be a minor process. Prolonged irradiation results in dehydrogenation, while the C3 skeleton is retained. The interpretation of the C2H2···CO radiolysis mechanism (possible reactions pathways) is provided based on the analysis of kinetic curves and matrix effect. Astrochemical implications of the results are discussed. [ABSTRACT FROM AUTHOR]

Investigations of the low-temperature radiation-induced transformations in the C2H2–H2O system are relevant to the chemistry occurring in interstellar and cometary ices. In this work, we applied a matrix isolation technique to study the radiation-driven evolution of this system at molecular level in order to get new mechanistic insight. The 1:1 C2H2⋅ ⋅ ⋅H2O complexes were prepared in various solid noble-gas matrices (Ar, Kr, Xe) and these icy matrices were subjected to X-ray irradiation at 5 K. Decomposition of initial complex and formation of products were monitored by Fourier-transform infrared (FTIR) spectroscopy. It was found that complexation with H2O resulted in significant enhancement of the radiolytic decay of C2H2 molecules and provided new channels for its radiation-induced transformations. Ketene (both isolated H2CCO and in the form of H2CCO–H2 pair), ketenyl radical (HCCO), carbon monoxide (CO), and methane (CH4) were observed as main products of the C2H2⋅ ⋅ ⋅H2O radiolysis. In addition, vinyl alcohol (CH2CHOH) was detected in an Ar matrix. The mechanistic interpretation (reaction routes leading to formation of these products) is discussed on the basis of consideration of kinetic dependences and matrix effects. Conversion of C2H2⋅ ⋅ ⋅H2O to CH4 is a prominent example of water-mediated cleavage of the C≡C triple bond, which may occur under prolonged irradiation in rigid media. Possible astrochemical implications of the obtained results are highlighted. [ABSTRACT FROM AUTHOR]

The structure of the 3,3-dimethylbut-1-yne radical cation and its unusual photochemical rearrangement to the trimethylallene radical cation have been characterized by low-temperature matrix EPR spectroscopy and DFT calculations. [Copyright &y& Elsevier]

The radiation-induced transformations of isolated phosphine molecules in a series of solid noble gas matrices occurring under the action of X-rays at 4.5 K were studied by FTIR spectroscopy. It was shown that decomposition was quite efficient (the corresponding radiation-chemical yields of PH 3 degradation were estimated as 5.8, 4.2, 3.5, and 2.0 molecules per 100 eV for neon, argon, krypton, and xenon, respectively). The radiolysis proceeds via two channels yielding PH 2 • and PH, respectively (the spectroscopic and kinetic data suggest that the latter species is partially trapped in the same cage with hydrogen molecules). Comparative studies using direct activation of isolated phosphine molecules in matrices at λ = 185 nm revealed similarity in the degradation pathways under radiolysis and VUV photolysis. Spectroscopic characteristics of the observed products and possible astrochemical implications of the results are discussed. • Degradation of matrix isolated PH 3 under the action of X-ray and VUV radiation at 4.5 K was studied. • PH 2 and PH species are efficiently produced in both cases. • PH originates from both single-step and two-step decomposition of PH 3 molecules. • A complex structure of infrared absorption bands was attributed to matrix site splitting. [ABSTRACT FROM AUTHOR]

Intermolecular complexes between CHF3 and CO have been studied by ab initio calculations and IR matrix isolation spectroscopy. The computations at the MP2 and CCSD(T) levels of theory indicated five minima on the potential energy surface (PES). The most energetically favorable structure is the C(CO)-H(CHF3) coordinated complex (Cs symmetry) with the stabilization energy of 0.84 kcal/mol as computed at the CCSD(T) level (with ZPVE and BSSE corrections). This is the only structure experimentally found in argon and krypton matrixes, whereas the weaker non-hydrogen-bonded complexes predicted by theory were not detected. The vibrational spectrum of this complex is characterized by a red-shift of the CF3 asymmetric stretching, splitting of the C-H bending mode, and blue-shifts of the C-H and C-O stretching vibrations as compared to the monomer molecules. The observed complexation-induced shifts of CHF3 and CO fundamentals are in good agreement with the computational predictions. It was shown that both MP2 and CCSD(T) calculations generally provided a reasonable description of the vibrational properties for the weak intermolecular complexes of fluoroform. [ABSTRACT FROM AUTHOR]

The radical cations of piperazine, morpholine, thiomorpholine, and thioxane were investigated by electron paramagnetic resonance (EPR) and electron−nuclear double resonance (ENDOR) spectroscopy in a solid Freon matrix. Optimized geometry and magnetic parameters of the radical cations were calculated using a density functional theory (DFT)/Perdew−Burke−Ernzerhof (PBE) method. Both experimental and theoretical results suggest that all the studied species adopt chair (or distorted chair) conformations. No evidence for the boat conformers with intramolecular σ*-bonding between heteroatoms were obtained. In the cases of morpholine and thioxane, the oxygen atoms are characterized by relatively small spin populations, whereas a major part of spin density is located at N and S atoms, respectively. The thiomorpholine radical cation exhibits nearly equal spin population of N and S atoms. In most cases (except for thioxane), the calculated magnetic parameters agree with the experimental data reasonably well. [ABSTRACT FROM AUTHOR]

The transformations of isolated toluene molecules under X-ray radiolysis in solid noble gas matrices at 6 K were characterized by FTIR spectroscopy. It was found that the efficiency of the radiation-induced decomposition of toluene was generally comparable to that of benzene. Meanwhile, a remarkable matrix effect was observed: toluene is more stable than benzene in an argon matrix, whereas it becomes more sensitive in the case of xenon matrix. This result was ascribed to the increasing role of upper triplet excited states in a xenon matrix. In all the matrices two main radiolysis products observed at moderate absorbed doses were benzyl radical and 5-methylene-1,3-cyclohexadiene (MCHD). Benzyl radical predominates in all the cases, while the relative contribution of MCHD strongly decreases in the row Ar-Kr-Xe. On the basis of this comparison, the formation of MCHD was tentatively attributed to the rearrangement of excited primary toluene radical cations. Possible scheme of the radiation-induced processes is discussed. • Radiation chemistry of isolated toluene molecules was studied at 6 K. • Two main primary products are benzyl radical and 5-methylene-1,3-cyclohexadiene. • Inert matrix has strong impact on the distribution of degradation channels. • The radiation sensitivity of toluene and benzene at molecular level was compared. [ABSTRACT FROM AUTHOR]

Vinyl radicals produced by annealing-induced reaction of mobilized hydrogen atoms with acetylene molecules in solid noble-gas matrices (Ar, Kr, and Xe) were characterized by Fourier transform infrared and electron paramagnetic resonance (EPR) spectroscopies. The hydrogen atoms were generated from acetylene by UV photolysis or fast electron irradiation. Two vibrational modes of the vinyl radical (ν7 and ν5) were assigned in IR absorption studies. The assignment is based on data for various isotopic substitutions (D and 13C) and confirmed by comparison with the EPR measurements and density-functional theory calculations. The data on the ν7 mode is in agreement with previous experimental and theoretical results whereas the ν5 frequency agrees well with the computational data but conflicts with the gas-phase IR emission results. [ABSTRACT FROM AUTHOR]

Abstract: Germylenes based on substituted diethylenetriamine (1), diethanolamines (2, 3) and pyridine-containing dialcohols (4, 5) were used as ligands in molybdenum and tungsten carbonyl complexes. Synthesis of new mono- and disubstituted (cis- or trans-) germanium(II) containing molybdenum (8, 9, 14, 15, 17) and tungsten (6, 7, 10–13, 16) carbonyl complexes were described. Composition of the complexes obtained was established by elemental analysis data and their structures were investigated by multinuclear NMR spectroscopy, IR and X-ray diffraction analysis (7, 13 and 17). The germylenes based on dialkanolamines and pyridine-containing dialcohols (O-ligands) give cis-digermanium complexes in contrast to the germylenes based on diethylenetriamines (N-ligands) which form trans-digermanium complexes. [Copyright &y& Elsevier]

Xenon trifluoride radicals were generated by the solid slate chemical reaction of mobile fluorine atoms with XeF2 molecules isolated in a solid argon matrix. On the basis of spectroscopic and kinetic FTIR measurements and performed quantum chemical calculations, two intrared absorption bands at 568 (strong) and 523 (very weak) cm-1 have been assigned to asymmetric and symmetric Xe-F stretching vibrational modes of radical XeF3, respectively. Chemical reaction of fluorine atom with XeF2 in a solid argon cage obeys Specific kinetic behavior indicating the formation of- a long-lived intermediate complex under the condition that the diffusing fluorine atom is attached to isolated XeF2 at temperatures 20 K < T< 27 K. Subsequent thermally acrivafed conversion in the complex is the main source ot novel xenon-containing radical species XeF3. The rate constant and energy barrier are estimated for the reaction in an argon cage, [XeF2-F]→Kr [XeF3], as Kr∼ 7 × 10-5 c-1 at 27 K and E ≈ 1.2 kcal/mol, respectively. Quantum chemistry calculations reveal that radical XeF3 has a planar C2v structure. DFT calculations show that formation of the third Xe-F bond in the XeF3 radical is exothermic, and the binding energy of the third Xe-F bond is 8-20 kcal/mol. [ABSTRACT FROM AUTHOR]

Abstract: Chemical reactions induced by fast electron irradiation of benzene in solid xenon were studied by EPR and FTIR spectroscopy. Irradiation at 16K leads to H atoms and phenyl radicals. Annealing at 45K results in formation of HXeH and cyclohexadienyl radical ( C6H7). A strong IR absorption at 618/620cm−1 and several weaker bands were assigned to cyclohexadienyl radical from comparison with EPR data and DFT calculations. A computationally stable molecule HXeC6H5 was not found experimentally, which means that it is either not formed or not stabilized under the experimental conditions used. [Copyright &y& Elsevier]

Single crystal structures of N(CH2CH2NSiMe3)3Si-Vinyl (1) and N(CH2CH2NSiMe3)3Si-n-Butyl (2) were determined by X-ray diffraction studies: both compounds show weak transannular Nax→M interactions (1, d(Nax→Si)=2.712(1) A˚, 2, d(Nax→Ge)=2.743(3) A˚). General trends for molecular structures of the group 14 elements (Si, Ge, Sn) azametallatranes are discussed with also included DFT calculations data. [Copyright &y& Elsevier]

Syntheses of title compounds, viz. N(CH[sub 2]CH[sub 2]NR)[sub 3]E (1, E = Sb, R = Me; 4, E = Bi, R: Me; 6, E = Sb, R = SiMe[sub 3]; 8, E = Bi, R = SiMe[sub 3]), by the reaction of E(NAlk[sub 2])[sub 3] (3, E = Sb, Alk = Et; 5, E = Bi, Alk = Me) with N(CH[sub 2]CH[sub 2]NMeH)[sub 3] (2) or N(CH[sub 2]CH[sub 2]NSiMe[sub 3]H)[sub 3] (7) are reported. The reactions of SbCl[sub 3] with N[CH[sub 2]CH[sub 2]N(Me)Li][sub 3] or N[CH[sub 2]CH[sub 2]N(SiMe[sub 3])Li][sub 3] and BiCl[sub 3] with N[CH[sub 2]CH[sub 2]N(SiMe[sub 3])Li][sub 3] resulted in compounds 1, 6, and 8, respectively. Composition and structures of all novel compounds were established by ¹H and [sup 13]C NMR spectroscopy and mass spectrometry. The X-ray structural study of 8 clearly indicated the presence of transannular interaction Bi←N[sub dat] in this compound, while 6 possesses a long Sb···N[sub dat] distance. The structural data obtained from geometry optimizations on 6 and 8 reproduce experimental trends, i.e., a decrease in the E-N[sub dat] distance from Sb to Bi. The values of electron density in E-N[sub dat] critical point and the Laplacian of charge density for 8 indicate that a closed-shell interaction exists between the metal atom and N[sub dat] atom. [ABSTRACT FROM AUTHOR]

New assignment of EPR spectra of low-temperature F + C70 reaction products shows an unexpectedly high selectivity of the addition of the F atom to the asymmetric C=C bonds of C70 to form three C70F regioisomers only among the five possible ones. [Copyright &y& Elsevier]

The reversible photoinduced transformations of 2,3-dimethyloxirane radical cations in freonic matrices at 77K are related to the conversion between the cis- and trans-isomers of an open form and a cyclic form. [ABSTRACT FROM AUTHOR]

The X-ray irradiation of 2,2-dimethyloxirane in freonic matrices at 77K results in the trapping of a cyclic radical cation form, presumably, complexed with a matrix molecule, which transforms into a C-centered distonic radical cation under the action of light. [ABSTRACT FROM AUTHOR]

Radical cations of trimethylene oxide under photobleaching at 77K could form either distonic radical cations ·CH2CH2CH=OH+/·CH2CH2O+=CH2 or oxetan-2-yl radicals depending on the Freon matrix used. [Copyright &y& Elsevier]

Photobleaching (λ =436nm) of trimethylene sulfide radical cations (λ max ≈460nm, ɛmax ≈345dm3 mol–1 cm–1) stabilised in different Freon matrices at 77K results in the formation of distonic radical cations CH2CHSHCH2 ·+. [Copyright &y& Elsevier]