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In this work, prereactive complexes, reaction products, and conformational preferences derived from the photochemical reaction between CS2 and ClF were analyzed following the codeposition of the reactants trapped in argon matrices at cryogenic temperatures. After codeposition of CS2 and ClF diluted in Ar, the formation of van der Waals complexes is observed. When the mixture is subsequently irradiated by means of broad-band UV-visible light (225 ≤ λ ≤ 800 nm), fluorothiocarbonylsulfenyl chloride (FC(S)SCl) and chlorothiocarbonylsulfenyl fluoride (ClC(S)SF) are produced. These species exist as two stable planar anti- and syn-conformers (anti- and syn- of the C=S double bond with respect to the S–Cl or S–F single bond, respectively). For both novel molecules, anti-FC(S)SCl and anti-ClC(S)SF are the lowest-energy computed rotamers. As expected due to the photochemical activity of these species, additional reaction products due to alternative or subsequent photochannels are formed during this process. [ABSTRACT FROM AUTHOR]

FC(O)Br has been synthesized, and its IR spectrum in the gas phase and isolated in an Ar matrix, as well as, its Raman spectrum in the solid state at -196 °C has been analyzed. Its molecular structure has been determined and its UV has been measured. FC(O)Br and FC(O)Cl has been photodissociated in an argon matrix at 17 K with a 193 nm laser. The photolysis produces CO and XF which recombine to form CO/XF complexes. The formation of complexes are followed by the shift of the normal vibration modes with respect to CO and XF isolated in argon matrix. In the case of FC(O)Br, three isomers are identified, OC...BrF, OC...FBr, and CO...BrF, whereas for FC(O)Cl only one isomer is observed, OC...ClF. High level quantum chemical calculations are used to help the assignment of the different isomers. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

By oxidation of selenoacetic acid, CH3C(O)SeH, we have prepared the hitherto unknown diacetyl diselenide, [CH3C(O)Se]2. Its vibrational properties were studied experimentally, both in neat liquid (Fourier transform infrared spectroscopy and Raman) with the molecule isolated in argon matrix at low temperatures and theoretically using MP2 and B3LYP methods in combination with 6‐31+G(d), 6‐311++G(3df,3dp) or aug‐cc‐pvDZ basis sets. Analysis of Ar matrix spectra reveals a conformational equilibrium in gas phase at room temperature, which was interpreted by considering only two of the three stable rotamers predicted by our three‐dimensional potential energy surface scans. Energetic properties of three minima found theoretically were further studied in terms of donor–acceptor interactions by using natural bond orbital calculations at the same levels of theory. From this, it was possible to rationalize the conformational stability order and molecular structures by means of vicinal hyperconjugative delocalizations involving lone pairs on selenium or oxygen atoms and C=O, C–C or Se–C antibonding orbitals. The photochemistry of the compound in the argon matrix in the range between 200 and 800 nm was also investigated, revealing only one photochemical path to produce ketene, H2C=C=O, methylselane, CH3SeH, and carbonyl selenide, OCSe. [ABSTRACT FROM AUTHOR]

The methylsulfonyloxyl radical, CH3SO3, one of the key intermediates in the atmospheric oxidation of dimethyl sulfide (DMS), was generated by flash pyrolysis of CH3SO2OOSO2CH3 and subsequently isolated in solid noble-gas matrices. The radical has been characterized by UV/Vis and IR spectroscopy and its tautomerization to CH2SO3H observed upon irradiation with light of λ≥360 nm. [ABSTRACT FROM AUTHOR]

UV photolysis ( λ=248 or 255 nm) of cyclic S2N2 isolated in solid argon matrices yields two open-shell S2N2 isomers, trans SNSN (3A′′) and cis SNSN (3A′′), as well as a closed-shell C2v dimer (SN)2 (1A1). These novel isomers have been characterized by their IR spectra and mutual photo-interconversion reactions. Quantum chemical calculations support the experimental results and also provide insight into the complex potential energy surface of S2N2. [ABSTRACT FROM AUTHOR]

Two hitherto unknown difluoromethylselanes, HCF2SeH and ClCF2SeH, were formed by photolysis of difluoroselenoacetic and chlorodifluoroselenoacetic acids isolated in solid argon. The progress of the photolysis was monitored by FTIR spectroscopy. The photoproducts were identified by comparison of experimental with theoretically predicted spectra and reported spectra for known species. The photochemical decomposition mechanisms of HCF2C(O)SeH and ClCF2C(O)SeH is presented. [ABSTRACT FROM AUTHOR]

The novel iminyl radical O2SN, a SO3 analogue, was produced by flash vacuum pyrolysis of gaseous alkyl sulfonyl azides RSO2N3 (R=CF3, CH3) mixed with argon. Photoisomerization (λ>360 nm) of O2SN into planar syn‐OSNO and anti‐OSNO (see picture) was observed in solid noble‐gas matrices. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis of the new compound, bis(trifluoromethyl)dicarbonate, CF3OC(O)OC(O)OCF3, is carried out by reduction of bis(trifluoromethyl)trioxidicarbonate with excess of CO at 0°C. The product is characterized by IR, Raman, 13C and 19F NMR spectroscopy and its properties are compared with those of the other members of the series CF3OC(O)O x C(O)OCF3, x =0–3. Single crystals are grown at −25°C and the X-ray diffraction analysis shows the packing of syn–syn rotamers exhibiting C 2 symmetry. DFT calculations predict this rotamer as the most stable one and also structural and vibrational data are predicted reasonably well. [Copyright &y& Elsevier]

For two decades, the peroxychloroformyl radical, ClC(O)OO, has played a central role in models of the chemical stability of the Venus atmosphere. No confirmation, however, has been possible in the absence of laboratory measurements for ClC(O)OO. We report the isolation of ClC(O)OO in a cryogenic matrix and its infrared and ultraviolet spectral signatures. These experiments show that ClC(O)OO is thermally and photolytically stable in the Venus atmosphere. These experimental discoveries validate the existence of ClC(O)OO, confirm several longstanding model assumptions, and provide a basis for the astronomical search for this important radical species. [ABSTRACT FROM AUTHOR]

The article presents the journal's frontispiece highlighting the methylsulfonyloxyl radical and the atmospheric oxidation of dimethyl sulfide (DMS).

The cover picture shows the decay of high-energy diazirinone (cyclic N2CO). At room temperature this violet gas has a half life of 30 h. The IR, Raman, and electronic spectra were analyzed, and the photochemistry was studied in a solid argon matrix at 16 K. Details are discussed in the article by X. Zeng, J. F. Stanton et al. on p. 3403 ff. [ABSTRACT FROM AUTHOR]

Thephotochemistry of matrix isolated (trifluoromethylsulfonyl)azide, CF3SO2N3, has been studiedat low temperatures. Upon ArF laser irradiation (λ = 193 nm),the azide eliminates N2and furnishes triplet [(trifluoromethyl)sulfonyl]nitrene,CF3SO2N, which has been characterized by IRand EPR spectroscopy. Upon subsequent UV light irradiation (λ= 260–400 nm) the nitrene converts to CF3NSO2and CF3S(O)NO through a Curtius-type rearrangement.Further two new species CF2NSO2F andFSNO were identified together with CF2NF, SO2, F2CO, CF3NO, and SO as side products. Inaddition, triplet nitrene CF3N was detected by its EPRand IR spectra. The complex stepwise photodecomposition of matrixisolated CF3SO2N3is discussed interms of the observed photolysis products and quantum chemical calculations. [ABSTRACT FROM AUTHOR]

TheIR spectra of S-ethyl fluorothioformate, FC(O)SCH2CH3, were recorded in the vapor phase and compared withthe Raman spectrum in the liquid state. Additional IR spectra of thecompound isolated in argon and nitrogen matrices at ca. 12 K werealso recorded. The title compound exhibits rich conformational equilibriaat room temperature being C1the moststable symmetry with a synperiplanar orientation of the carbonyl doublebond (CO) with respect to the S–C(sp3) singlebond, while the C–C bond of the ethyl group presents a gaucheorientation with respect to the C–S single bond. Several bandsassigned to a second conformer were also observed in the IR matrixspectra. This second rotamer presents a planar skeleton (Cspoint group) retaining the prevalentsyn orientation of the FC(O)SCH2CH3moleculewith an antiperiplanar orientation of the C–C bond of the ethylgroup with respect to the C–S bond. The variation of the nozzletemperature before matrix gas deposition gives rise to different conformerratios. With these data an enthalpy difference of 0.45 kcal mol–1can be calculated between the more stable C1and the Csconformers. A third form, corresponding to the anti-gaucheconformer, is also detected when the matrix is exposed to broad-bandUV–visible irradiation. Moreover, the photochemistry of theAr and N2matrix-isolated species is studied. Conformationalinterconversion is observed at short irradiation times, whereas adecarbonylation process with the concomitant formation of a HC(S)CH3:HF molecular complex dominates the photochemistry of FC(O)SCH2CH3of longer irradiation times. The new ethylfluoro sulfide, FSCH2CH3, is proposed as anintermediate species. [ABSTRACT FROM AUTHOR]

Abstract: The photochemical reactions between OCSe and Cl2 or Br2 isolated in solid argon at cryogenic temperatures were studied by means of FTIR spectroscopy. The OCSe⋯Cl2, OCSe⋯Br2 and SeCO⋯Br2 molecular complexes were identified by the shifts of the OCSe IR absorptions on complexation, and also by the IR activation of the Cl–Cl vibration in the first adduct. The hitherto unknown ClC(O)SeCl and BrC(O)SeBr molecules were formed upon UV–Vis irradiation of the matrix. The former was firstly obtained in the anti form, and subsequently photochemically transformed into the thermodynamically more stable syn conformation, while only the syn rotamer of BrC(O)SeBr was produced. The characterization of the novel species through their IR spectra was supported by the comparison with results of quantum chemical calculations. [Copyright &y& Elsevier]

The synthesis of ClC(O)OONO2 is accomplished by photolysis of a mixture of Cl2, NO2, and CO in large excess of O2 at about -70 °C. The product is isolated after repeated trap-to-trap condensation. The solid compound melts at -84 °C, and the extrapolated boiling point is 80 °C. ClC(O)OONO2 is characterized by IR, Raman, ¹³C NMR, and UV spectroscopy. According to the IR matrix spectra, the compound exists at room temperature only as a single conformer. The molecular structure of ClC(O)OONO2 is determined by gas electron diffraction. The molecule possesses a gauche structure with a dihedral angle of φ (COON) = 86.7(19) °, and the C=O bond is oriented syn with respect to the O-O bond. The short O-O bond (1.41 B(6) Å) and the long N-O bond (1.511(8) Å) are consistent with the facile dissociation of ClC(O)OONO2 into the radicals ClC(O)OO and NO2. The experimental geometry of ClC(O)OONO2 is reproduced reasonably well by B3LYP/6-311+G(2df) calculations, whereas the MP2 approximation predicts the N-O bond considerably too long and the dihedral angle too small. [ABSTRACT FROM AUTHOR]

The photochemistry of OCSe with ClF trapped together in argon matrices at cryogenic temperatures has been explored and the first interhalogen representatives of the elusive XC(O)SeY family, namely syn-ClC(O)SeF, anti-ClC(O)SeF, syn-FC(O)SeCl, and anti-FC(O)SeCl, as well as the hitherto triatomic species ClSeF complexed by a CO molecule, were obtained. Both ClC(O)SeF conformers appear to be produced independently by photolysis of the respective precursors; while formation of both FC(O)SeCl structures is ruled by the presence of an angular molecular complex OCSe⋯Cl-F formed prior to photolysis. This latter photochemical pathway seems to favor the formation of the less stable anti-FC(O)SeCl structure instead of the more stable syn-one. With the aid of quantum chemical calculations, using ab initio, DFT, TDDFT, and CASSCF methods, the mechanism for this photochemical reaction is rationalized both in terms of radical processes as well as a photoinduced electron transfer occurring into the OCSe⋯Cl-F complex. Also a singlet-triplet conical intersection between anti and syn rotamers of the FC(O)SeCl molecule is theoretically explored. [ABSTRACT FROM AUTHOR]

By oxidation of selenoacetic acid, CH3C(O)SeH, we have prepared the hitherto unknown diacetyl diselenide, [CH3C(O)Se]2. Its vibrational properties were studied experimentally, both in neat liquid (Fourier transform infrared spectroscopy and Raman) with the molecule isolated in argon matrix at low temperatures and theoretically using MP2 and B3LYP methods in combination with 6‐31+G(d), 6‐311++G(3df,3dp) or aug‐cc‐pvDZ basis sets. Analysis of Ar matrix spectra reveals a conformational equilibrium in gas phase at room temperature, which was interpreted by considering only two of the three stable rotamers predicted by our three‐dimensional potential energy surface scans. Energetic properties of three minima found theoretically were further studied in terms of donor–acceptor interactions by using natural bond orbital calculations at the same levels of theory. From this, it was possible to rationalize the conformational stability order and molecular structures by means of vicinal hyperconjugative delocalizations involving lone pairs on selenium or oxygen atoms and C=O, C–C or Se–C antibonding orbitals. The photochemistry of the compound in the argon matrix in the range between 200 and 800 nm was also investigated, revealing only one photochemical path to produce ketene, H2C=C=O, methylselane, CH3SeH, and carbonyl selenide, OCSe. [ABSTRACT FROM AUTHOR]

The methylsulfonyloxyl radical, CH3SO3, one of the key intermediates in the atmospheric oxidation of dimethyl sulfide (DMS), was generated by flash pyrolysis of CH3SO2OOSO2CH3 and subsequently isolated in solid noble-gas matrices. The radical has been characterized by UV/Vis and IR spectroscopy and its tautomerization to CH2SO3H observed upon irradiation with light of λ≥360 nm. [ABSTRACT FROM AUTHOR]

UV photolysis ( λ=248 or 255 nm) of cyclic S2N2 isolated in solid argon matrices yields two open-shell S2N2 isomers, trans SNSN (3A′′) and cis SNSN (3A′′), as well as a closed-shell C2v dimer (SN)2 (1A1). These novel isomers have been characterized by their IR spectra and mutual photo-interconversion reactions. Quantum chemical calculations support the experimental results and also provide insight into the complex potential energy surface of S2N2. [ABSTRACT FROM AUTHOR]

The vapor of acetyl isocyanide, CH3C(O)NCS, and trifluoroacetyl isocyanide, CF3C(O)NCS,were isolated in solid Ar at 15 K. The existence of rotational isomerismwas confirmed when the matrixes were irradiated with broad-band UV–vislight (200 ≤ λ ≤ 800 nm) and also by temperature-dependentAr-matrix IR spectroscopy. The initial spectra showed the vapor ofCH3C(O)NCS and CF3C(O)NCS consist of two conformerssyn–syn and syn–anti(with the CO bond syn with respect to the C–H or C–Fbond and syn or anti with respect to the NC double bond).When CH3C(O)NCS is irradiated, simultaneously with therandomization process, H2CCO and HSCN are produced. Inthe case of the photolysis of CF3C(O)NCS, the main productsare CF3NCS and CO. The assignment of the IR bands to thedifferent photoproducts was made on the basis of the usual criteria,taking account reported antecedents in the literature. [ABSTRACT FROM AUTHOR]

Chlorodifluoroacetyl isothiocyanate,ClF2CC(O)NCS, wassynthesized by the reaction of ClF2CC(O)Cl with an excessof AgNCS. The colorless product melts at −85 °C, and itsvapor pressure follows the equation ln p= −4471.1(1/T) + 11.35 (p[atm], T[K]) in the range −38 to 22 °C. The compoundhas been characterized by IR (gas phase, Ar matrix, and matrix photochemistry),by liquid Raman, by 19F and 13C NMR, gas UV–vis,and photoelectron spectroscopy (PES), by photoionization mass spectrometry(PIMS), and by gas electron diffraction (GED). The conformationalproperties of ClF2CC(O)NCS have been analyzed by jointapplication of vibrational spectroscopy, GED and quantum chemicalcalculations. The existence of two conformers has been detected inthe gas and liquid phases, in which the C–Cl bond adopts agauche orientation with respect to the CO group; the COgroup is in syn- or anti-position with respect to the NC doublebond of the NCS group. The computed ΔG°difference between these two gauche–syn and gauche–antiforms is ΔG° = 0.63 kcal mol–1in the B3LYP/6-31G(d) approximation. The most significant gas-phasestructural parameters for gauche–syn ClF2CC(O)NCSare re(NCS) 1.559(2) Å, re(NCS) 1.213(2) Å, re(NC) 1.399(7) Å, re(CO) 1.199(2) Å, and ∠e(CNC) 134.7(13)°. Photolysis of ClF2CC(O)NCSusing an ArF excimer laser (193 nm) mainly yields ClF2CNCS,CO, and ClC(O)CF2NCS. The valence electronic propertiesof the title compound were studied using PES and PIMS. The experimentalfirst vertical ionization energy of 10.43 eV corresponds to the ejectionprimarily of the sulfur lone-pair electrons of the in-plane nonbondingorbital on the NCS group. [ABSTRACT FROM AUTHOR]

The synthesis of pentafluoronitrosulfane, SF5NO2, is accomplished either by reacting N(SF5)3 with NO2 or by the photolysis of a SF5Br/NO2 mixture using diazo lamps. The product is purified by treatment with CsF and repeated trap-to-trap condensation. The solid compound melts at -78 °C, and the extrapolated boiling point is 9 °C. SF5NO2 is characterized by 19F, 15N NMR, IR, Raman, and UV spectroscopy as well as by mass spectrometry. The molecular structure of SF5NO2 is determined by gas electron diffraction. The molecule possesses C2v symmetry with the NO2 group staggering the equatorial S-F bonds and an extremely long 1.903(7) Å S-N bond. Calculated bond enthalpies depend strongly on the computational method: 159 (MP2/6-311G++(3df)) and 87 kJ mol-1 (B3LYP/6-311++G(3df)). The experimental geometry and vibrational spectrum are reproduced reasonably well by quantum chemical calculations. [ABSTRACT FROM AUTHOR]

The synthesis of CF[sub 3]OC(O)OOC(O)F is accomplished by the photolysis of a mixture of (CF[sub 3]CO)[sub 2]O, FC(O)C(O)F, CO, and O[sub 2] at -15 °C using a low-pressure mercury lamp. The new peroxide is obtained in pure form in low yield after repeated trap-to-trap condensation and is characterized by NMR, IR, Raman, and UV spectroscopy. Geometrical parameters were studied by ab initio methods [B3LYP/6-311+G(d)]. At room temperature, CF[sub 3]OC(O)OOC(O)F is stable for many days in the liquid or gaseous state. The melting point is -87 °C, and the boiling point is extrapolated to 45 °C from the vapor pressure curve log p = 8.384 - 1715/T (p/mbar, T/K). A possible mechanism for the formation of CF[sub 3]OC(O)OOC(O)F is discussed, and its properties are compared with those of related compounds. [ABSTRACT FROM AUTHOR]

The article presents the journal's frontispiece highlighting the methylsulfonyloxyl radical and the atmospheric oxidation of dimethyl sulfide (DMS).