Vibrational spectroscopy of triacetone triperoxide (TATP): anharmonic fundamentals, overtones and combination bands

The vibrational spectrum of triacetone triperoxide (TATP) is studied by the correlation-corrected vibrational self-consistent field (CC-VSCF) method which incorporates anharmonic effects. Fundamental, overtone, and combination band frequencies are obtained by using a potential based on the PM3 method and yielding the same harmonic frequencies as DFT/cc-pVDZ calculations. Fundamentals and overtones are also studied with anharmonic single-mode (without coupling) DFT/cc-pVDZ calculations. Average deviations from experiment are similar for all methods: 2.1-2.5%. Groups of degenerate vibrations form regions of numerous combination bands with low intensity: the 5600-5800 cm(-1) region contains ca. 70 overtones and combinations of CH stretches. Anharmonic interactions are analyzed.     

Microwave spectrum, structure, and internal dynamics of the nitric acid dihydrate complex

A-type rotational spectra of the complex HNO3-(H2O)2 have been observed by rotational spectroscopy in a supersonic jet. Extensive isotopic substitution and analysis of the resulting moments of inertia reveals that the complex adopts a cyclic geometry in which a second water inserts into the weak secondary hydrogen bond of the (also cyclic) HNO3-H2O dimer. The complex is planar, except for one free proton from each water unit that lies above or below the plane. The primary hydrogen bond, formed between the HNO3 proton and the first water molecule in the trimer, is 1.643(76) A in length. All intermolecular distances are smaller than those of the constituent dimers. Internal motion, inferred from spectral doubling and studied by isotopic substitution experiments, likely corresponds to proton interchange involving the second water unit, but no such motion is revealed by the a-type spectrum for the first water unit. The degree of proton transfer across the hydrogen bond is discussed in terms of the proton-transfer parameter, rhoPT, which assesses the degree of ionization on the basis of interatomic distances. Measured in this way, the complex is best described as hydrogen bonded, in accord with numerous theoretical predictions. However, an increase in the degree of ionization relative to that in HNO3-H2O is discernible. Using rhoPT as a metric, two water molecules do less to ionize nitric acid than one water does to ionize sulfuric acid.     

A remark on the paper of H. H. Schaefer Abschätzung der nichttrivalen eigenwerte stochastischer matrizen

It is shown that one of the results of Schaefer can be obtained in a more elementary way and can be improved. This is an immediate corollary of a paper of the author Duke Math. J.19, 75–91 (1952).Lothar Collatz belatedly on his 60th birthday     

Influence of the Water Content on the Thermal Behaviour of β-Cyclodextrin at Low and Very Low Temperature

Heat capacities of -CD·9.7H₂O weremeasured by adiabatic calorimetry in the temperature range10–300 K. Differential scanning calorimetry wasused to follow the evolution of the thermalbehaviour versus hydration ratio between 170 and300 K. At least three different behaviours wereobserved, according to the number, n, of watermolecules: 0 < n < 7, 7 < n < 10, and n > 10.These macroscopic results are discussed in terms oforganization differences between the most or theleast hydrated -CD. The structuring effectof the hydration water molecules is emphasised. Theexistence of two energetically distinct -CDhydrates (n < 10 and n > 10) seems to be confirmed. Thishypothesis is discussed in comparison with previousspectroscopic and structural studies.     

Solid cobalt(III) and iron(II) complexes and mercury salts investigated by positron annihilation and Mössbauer effect

Measurements of the Doppler effect of the annihilation -line and of the positron lifetime were carried out in three series of solid coordination complexes; the Mössbauer spectra of the iron-containing samples were also recorded. The lack of correlation between the Móssbauer and positron annihilation parameters suggests that electrons of the ligands rather than those of the central atoms dominate in positron annihilation processes.     

Titan—sticksoff-verbindungen XXIX. Kristall- und molekülstruktur spicocyclischer amide von titan und zirkonium mit dem liganden meSi(N-t-Bu)2

The compounds M[(N-t-Bu)₂SiMe₂]₂ (I M = Ti; II, M = Zr) were prepared by treatment of dilithiated Me₂Si(NH-t-Bu)₂ with TiCl₄ and ZrCl₄, respectively. Crystals of I and II belong to the space groups P2₁2₁2₁ and C2/c, respectively. The spirocyclic molecules possess approximate D_2d symmetry with planar MN₂Si rings. Important ring dimensions are d(MN) 1.890(4)/2.053(2) » (I/II). d(SiN) 1.742(10)/1.753(2) », angle NMN 83.4(2)/77.9(1)° and angle NSiN 92.4(2)/94.8(1)°.     

Milch

Ohne Zusammenfassung     

Über Irreduzibilitätskriterien von I. Schur und G. Pólya

Ohne ZusammenfassungHerrn I. Schur zum 60. Geburtstage gewidmet     

Untersuchungen über die arithmetischen Eigenschaften von Gruppen linearer Substitutionen

Ohne Zusammenfassung     

Microsolvation of a partially bonded complex by non-polar and weakly polar microsolvents: a microwave and ab initio study of HCN–SO3–Ar and HCN–SO3–CO – ARTICLE WITHDRAWN

WITHDRAWN TO APPEAR IN SPECIAL ISSUE IN 2007