Universität Hannover, Germany

I began the studies to get my PhD in chemistry at the Universität Hannover, Germany, in 1988. I worked in the group of Prof. Helge Willner in the inorganic chemistry institute. The main objectives were the sythesis and characterization of chlorine oxides, preferrably those which may play a role in atmospheric chemistry and which were not known experimentally at that time. Using a halogen exchange reaction, I was able to obtain chloryl chloride, ClClO2 for the first time. The reaction proceeds schematically via

FClO2  +  XCl --> ClClO2  +  XF ;
where XCl can be, for example, AlCl3, BCl3, or HCl. ClClO2 was characterized by IR and UV/vis spectroscopy in neon and argon matrices and also in the gas phase. From the 35/37Cl and 16/18O isotopic shifts of n5 and n6 structural parameters of ClClO2 could be derived.

It was impossible to synthesize the molecule on a preparative scale; thus, it has to be generated in situ. However, ClClO2 isolated in an argon matrix can be photo-isomerized to chlorine chlorite, ClOClO, and subsequently to dichlorine peroxide, ClOOCl. Both molecules were identified and characterized by IR spectroscopy.

Publications related to ClClO2

  1. H. S. P. Müller and H. Willner,
    Gas Phase Studies on Chloryl Chloride, ClClO2,
    Proceedings of the Bunsen Discussion-Meeting "Physics and Chemistry of the Atmosphere", October 6 — 9, 1991, Schliersee, Germany;
    Ber. Bunsenges. Phys. Chem. 96 (1992) 427 — 431.  View abstract.
  2. H. S. P. Müller and H. Willner,
    Synthesis and Properties of Chloryl Chloride, ClClO2,
    Inorg. Chem. 31 (1992) 2527 — 2534.
  3. J. Jacobs, M. Kronberg, H. S. P. Müller, and H. Willner,
    An Experimental Study on the Photochemistry and Vibrational Spectroscopy of Three Isomers of Cl2O2 Isolated in Cryogenic Matrices,
    J. Am. Chem. Soc. 116 (1994) 1106 — 1114.
  4. H. S. P. Müller and E. A. Cohen,
    The Submillimeter Spectrum and Structure of Chloryl Chloride, ClClO2,
    J. Phys. Chem. A 101 (1997) 3049 — 3051.
  5. H. S. P. Müller, E. A. Cohen, and D. Christen,
    The Rotational Spectrum of Chloryl Chloride, ClClO2, in its Ground Vibrational State,
    J. Chem. Phys. 110 (1999) 11865 — 11875.
  6. D. Christen, H.-G. Mack, and H. S. P. Müller,
    Quantum Chemical Calculations of Spectroscopic Properties for Chloryl Chloride, ClClO2, and other Cl2O2 Isomers,
    J. Mol. Struct. 509 (1999) 137 — 151.
  7. H. S. P. Müller, E. A. Cohen, and D. Christen,
    The Rotational Spectrum of ClClO2 in its v4 = 1 and v6 = 1 Vibrationally Excited States: An Example of Strong Coriolis Interaction,
    J. Mol. Spectrosc., in press.

Other projects included the spectroscopic characterization of OClO and ClOO in a neon matrix, the preparation of covalent perchlorates XOClO3 (X = H, F, Cl) for an electron diffraction study, the preparation of FCl18O3 for a high resolution infrared study, and the participation in the spectroscopic characterization of CrF4 and CrF5.

Other publications related to work in Hannover

  1. J. Jacobs, H. S. P. Müller, H. Willner, E. Jacob, and H. Bürger,
    Vibrational and Electronic Spectra of Molecular Chromium Tetrafluoride, CrF4, and Chromium Pentafluoride, CrF5. Comments on the Existence of Chromium Hexafluoride, CrF6,
    Inorg. Chem. 31 (1992) 5357 — 5363.
  2. H. S. P. Müller and H. Willner,
    Vibrational and Electronic Spectra of Chlorine Dioxide, OClO, and Chlorine Superoxide, ClOO, Isolated in Cryogenic Matrices,
    J. Phys. Chem. 97 (1993) 10589 — 10598.
  3. F. Meguelatti, G. Graner, H. Bürger, K. Burczyk, H. S. P. Müller, and H. Willner,
    High-Resolution Infrared Study of FCl18O3. Rovibrational Analysis of the v1 and v2 Bands and Ground State Constants,
    J. Mol. Spectrosc. 164 (1994) 368 — 378.
  4. B. Casper, H.-G. Mack, H. S. P. Müller, H. Willner, and H. Oberhammer,
    Molecular Structures of Perchloric Acid and Halogen Perchlorates ClOClO3 and FOClO3,
    J. Phys. Chem. 98 (1994) 8339 — 8342.
  5. F. Aubke, B. Casper, H. S. P. Müller, H. Oberhammer, and H. Willner,
    Vibrational Spectra and Gas Phase Structures of Fluorine Fluorosulfate (FOSO2F) and Chlorine Fluorosulfate (ClOSO2F),
    J. Mol. Struct. 346 (1995) 111 — 120.
  6. U. Rockland, H. Baumgärtel, E. Rühl, O. Lösking, H. S. P. Müller, and H. Willner,
    Ionic Fragmentation and Ion-Pair-Formation in Chlorine Dioxide,
    Ber. Bunsenges. Phys. Chem. 99 (1995) 969 — 975.
  7. H. S. P. Müller,
    Rotational and Vibrational Spectra of Chloryl Fluoride, FClO2. Nuclear Quadrupole, Spin-Rotation, and Shielding Tensors and the Harmonic Force Field,
    J. Mol. Struct. 517—518 (2000) 335 — 350.