inclusion compound
The mechanical trapping of small molecules within spaces between other molecules; e.g., the inclusion of iodine molecules by starch molecules to form the well-known red-to-black "addition compound"
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The role of stereochemistry to elucidate reaction patterns and physicochemical properties in topical subjects ranging from inorganic to organic chemistry is the focus of this volume, the last in the series. Detailed accounts are given to study: chaining in polyphosphates. electron-transfers in carbonyl clusters, inclusion of organometallic molecules in cyclodextrins, stereochehmistry of paramagnetic metal complexes by labeling with nitroxyl radicals, stereocontrol in organic syntheses assisted by inorganic complexes.![]()
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This thesis work deals with the investigation of the structural and dynamic properties of various guest species in urea inclusion compounds. Urea inclusion compounds are widely used in chemical analyses and syntheses. Studies of the molecular properties of the guest and host components are therefore of intrinsic scientific interest. Solid-state NMR spectroscopy is particularly suitable for the evaluation of the guest dynamics as well as the structural properties in such materials.
The molecular behavior (dynamics, molecular order) of ?, ?-dibromoalkanes/urea inclusion compounds (CnH2nBr2, n = 6, 10, 11) with different selectively deuterated guest components was studied via solid-state 2H NMR spectroscopy, comprising variable-temperature line shape studies, spin-lattice and spin-spin relaxation experiments. In addition, the conformational properties were probed by high resolution solid-state 13C and 1H NMR experiments. For the long-chain guest systems (n = 10, 11), the guest dynamics at best can be described by the presence of overall reorientations around the channel axis (modeled by a non-degenerate jump motion) along with chain fluctuations. For the dibromohexane/urea inclusion compound, the guest species exclusively exist in distinct gauche conformations, which undergo exchange with rate constants that match the NMR time-scale. For comparison, the molecular properties of 1-bromodecane in urea have been studied as well. Both the molecular order and dynamics can be described in quite the same way as found for 1, 10-dibromodecane or 1, 11-dibromo- undecane in urea.
Furthermore, this work reports on 1H and 13C CP/MAS NMR studies on urea inclusion compounds with various types of guest species (n-alkanes, alkane derivatives of different chain lengths)...![]()