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  • 1
    Electronic Resource
    Electronic Resource
    Matrix-Isolation of Iodine Superoxide and Iodine Dioxide (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 179-181 
    Details
    ISSN: 0009-2940
    Keywords: Matrix isolation ; Pyrolysis ; Photochemistry ; Iodine compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Flash pyrolysis of a gas mixture containing iodine, oxygen and argon yields the hitherto unknown iodine superoxide, which can be identified by its UV absorption (λ max= 254 nm) after trapping the pyrolysate at 12 K. Irradiation converts iodine superoxide into iodine dioxide, identified by its IR and UV spectra.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300207
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  • 2
    Electronic Resource
    Electronic Resource
    Flash Pyrolysis of 1,1,1-Trimethyltetrasilane - Evidence for the Formation of Dibridged Si2H2 (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1043-1046 
    Details
    ISSN: 0009-2940
    Keywords: Matrix isolation ; Ab initio calculations ; Oligosilanes ; Silicon atoms ; Reaction mechanisms ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pulsed flash pyrolysis of 1,1,l-trimethyltetrasilane (5) led to trimethylsilane, silane and a further species which is believed to be dibridged Si2H2 (13). Another route to 13 was found in the cocondensation of hydrogen and silicon atoms in an argon matrix at 12 K. The identification of matrix-isolated 13 is based on observed IR bands at 1475.6, 1092.8 and 890.3 cm-1. These positions are in good agreement with the ab initio calculated wavenumbers for the strongest absorptions of 13. The band shifts for the mono- and dideuterated isotopomers support this assignment.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300804
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  • 3
    Electronic Resource
    Electronic Resource
    Isofulminic Acid - Phantom or Reality?Dedicated to Professor Dieter Seebach on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2505-2517 
    Details
    ISSN: 0947-3440
    Keywords: Matrix isolation ; Photochemistry ; CHNO isomers ; Hydrogen-bonded complexes ; Density functional calculations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complex photochemistry of matrix-isolated dihaloformoximes 8a, 8b, and 8c, which are transformed upon irradiation into the new hydrogen-bonded complexes HalCN…HOHal 10a-c′, identified by their IR spectra, has been unveiled. An earlier assignment of the experimental IR absorptions to isofulminic acid HONC (4) must be withdrawn. A competitive reaction to the formation of complexes 10a-c′ produces the hydrogen-bonded complexes HalNCO/HHal 12a-c′, which can be regarded as intermediates on the photochemical pathway to the final product isocyanic acid HNCO (1), and are tentatively identified by their IR absorptions. Our findings are supported by deuteration experiments and theoretical calculations using the density functional method BLYP/6-311G*.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971213
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  • 4
    Electronic Resource
    Electronic Resource
    Bromine Complexes of Ethylene and Cyclopropene: Matrix-IR-Spectroscopic Identification, Photochemical Reactions, Ab Initio Studies (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 317-326 
    Details
    ISSN: 0947-3440
    Keywords: Matrix isolation ; IR spectroscopy ; Photochemistry ; Ab initio calculations ; Alkene complexes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The matrix-isolated ethylene-bromine complex (1) and the cyclopropene-bromine complex (8) have been chosen to examine which ab initio method (MP2 or BLYP) is more suitable to calculate the IR spectra and structures of π complexes. In addition the photochemistry of 1 and 8 has been investigated and the mechanism of the photochemically induced reactions is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970208
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  • 5
    Electronic Resource
    Electronic Resource
    2,3-Dihydroimidazol-2-ylidene (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1517-1520 
    Details
    ISSN: 1434-193X
    Keywords: Nucleophilic carbenes ; Heterocycles ; Decarboxylation ; Photochemistry ; Matrix isolation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Irradiation of imidazole-2-carboxylic acid (3) - matrix-isolated in argon at 10 K - with a wavelength of 254 nm leads to decarboxylation and the formation of a complex between 2,3-dihydroimidazol-2-ylidene and carbon dioxide (1·CO2). Upon irradiation of 2,3-dihydroimidazol-2-ylidene (1) with λ = 254, 193, and 185 nm no imidazole can be detected. On the other hand flash vacuum pyrolysis of imidazole-2-carboxylic acid (3) produces imidazole and carbon dioxide. 2,3-Dihydroimidazol-2-ylidene (1) - the possible intermediate - cannot be trapped under these conditions.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    The Thermally and Photochemically Induced Ring Opening of cis-3,4-Dichlorocyclobutene and trans-3,4-Dichlorocyclobutene: New Insights from a Matrix-Spectroscopic Study (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2063-2072 
    Details
    ISSN: 1434-193X
    Keywords: Matrix isolation ; Ring opening ; Flash pyrolysis ; Photochemistry ; Cyclobutenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermally induced ring opening of 1 and 5 proceeds with high stereospecifity in a conrotatory fashion in agreement with the Woodward-Hoffmann rules. Upon flash pyrolysis of 1 the matrix-isolated (Xe, 12 K) products 2a and 2b were found, whereas the corresponding reaction of 5 yielded 3a and 3b. The s-cis conformers 2b and 3b were identified for the first time by comparison of the experimental and calculated (BLYP-6-311G*) IR absorptions. A non-stereospecific photochemical reaction could be observed if matrix-isolated (Ar or Xe, 12 K) 1 was excited directly with λ = 193 nm. Products of the allowed disrotatory pathway as well as those of the forbidden conrotatory reaction were found, a behaviour that corresponds with the known photochemistry of cyclobutenes. A surprising reaction was found if 1 and 5 were irradiated in a xenon matrix with λ 〉 270 nm. The precursors, which were photostable in an argon matrix, opened the ring in a conrotatory fashion, the expected pathway for a thermal reaction. In this case the light is absorbed by the solid xenon in a cooperative process with the precursor molecules. A detailed discussion of the possible energy transfer mechanisms is given. Most probably, a hot ground-state reaction of vibrationally excited 1 and 5 occurs, although the reaction of the radical cations cannot be excluded.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Laser Irradiation of Monomeric Acetylene and the T-Shaped Acetylene Dimer in Xenon and Argon Matrices (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 769-776 
    Details
    ISSN: 1434-193X
    Keywords: Matrix isolation ; IR spectroscopy ; Photochemistry ; Two-photon process ; Excitons ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Irradiation of acetylene (4) in an argon matrix with an ArF laser (λ = 193 nm) yields the ethynyl radical C2H· (5) and C2 (6). If the same wavelength is used to irradiate 4 in a xenon matrix, only the infrared signal of the compound Xe-C2 (7) can be detected. The same band is found on irradiation at λ = 248 nm (KrF laser) in a xenon matrix, despite the fact that acetylene (4) does not absorb light of this wavelength. Irradiation of the T-shaped acetylene dimer 9 in an argon or xenon matrix at λ = 193 nm yields butadiyne (11) and vinylacetylene (12). However, irradiation with a KrF laser (λ = 248 nm) in a xenon matrix additionally yields cyclobutadiene (13). The dependence of the mechanisms of the fragmentation and dimerization of acetylene (4) on the matrix material is discussed.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Silylenes of the Elemental Composition C4H2Si: Generation and Matrix-Spectroscopic Identification (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1285-1290 
    Details
    ISSN: 1434-193X
    Keywords: Matrix isolation ; Silicon π systems ; Silacyclopropenylidenes ; Photochemistry ; Density functional calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Flash pyrolysis of 1,1-diethynyl-2,2,2-trimethyldisilane (16) and triethynylsilane (18) led to the formation of two silylenes of the elemental composition C4H2Si, namely diethynylsilylene (10) and ethynylsilacyclopropenylidene (7), which were isolated in an argon matrix at 10 K. Both compounds could be photoconverted into another isomer, butadiynylsilylene (9). The identification of these reactive intermediates is based on the comparison between the experimental and calculated IR spectra for the parent compounds as well as for their dideuterated and fully 13C-labeled isotopomers.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Photoisomerization of Bicyclopropylidene and 1,2-Dimethylenecyclobutane in Rare-Gas Matrices: Towards the IR-Spectroscopic Identification of Tetramethyleneethane (2,3-Dimethylenebutane-1,4-diyl) (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1291-1294 
    Details
    ISSN: 1434-193X
    Keywords: Matrix isolation ; IR spectroscopy ; Photochemistry ; Diradicals ; Isomerizations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Bicyclopropylidene (3) and 1,2-dimethylenecyclobutane (7) have been irradiated in rare-gas matrices. If 1,2-dimethylenecyclobutane (7) is exposed to the light of a KrF excimer laser (λ = 248 nm), an isomeric species is produced, showing an absorption at 793.1 cm-1 (argon matrix) or 791.2 cm-1 (xenon matrix) in the IR spectrum. The back reaction can be induced with light of λ = 254 nm. This photochemical interconversion, together with the comparison between the experimental and calculated band positions, supports the assignment of the IR absorption near 790 cm-1 to tetramethyleneethane (5).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    C3H4Si Species: Generation and Matrix-Spectroscopic Identification of Some Silacyclobutadiene Isomers (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1297-1305 
    Details
    ISSN: 1434-193X
    Keywords: Matrix isolation ; Ab initio calculations ; Photochemistry ; Silylenes ; Silaethenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Flash pyrolyses of four suitable precursors - namely 1,1,1-trimethyl-2-propargyldisilane (32), its allenyl (34) and propynyl isomer (35), as well as 2-ethynyl-1,1,1,2-tetramethyldisilane (31) - lead to the formation of three C3H4Si species (7, 11, and 15). By examination of their photochemistry five additional compounds of the same composition (12, 13, 14, 17, and 18) were identified. Except ethynylsilaethene (18), all compounds observed are silylenes. Their identification is based on the comparison of the experimental and calculated (BLYP-6-31G*) IR spectra. Silacyclobutadiene (4) or silatetrahedrane (25) could not be detected.
    Type of Medium: Electronic Resource
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