@article{KleinpeterKlodKoch2007, author = {Kleinpeter, Erich and Klod, Sabrina and Koch, Andreas}, title = {Visualization of through space NMR shieldings of aromatic and anti-aromatic molecules and a simple means to compare and estimate aromaticity}, issn = {0166-1280}, doi = {10.1016/j.theochem.2007.02.049}, year = {2007}, abstract = {Through space NMR shieldings of aromatic (benzene, mono-substituted and annelated benzenes, ferrocene, [14]- and [18]-annulenes, phenylenes and tetra- to heptahelicene) and anti-aromatic molecules (cyclobutadiene and pentalene) were assessed by ab initio molecular-orbital calculations. Employing the nucleus-independent chemical shifts (NICS) concept, these through space NMR shieldings were visualized as iso-chemical-shielding surfaces (ICSSs) and can be applied quantitatively to determine the stereochemistry of proximal nuclei. In addition, the distances in {\AA} at ICSS values of ±0.1 ppm in-plane and perpendicular-to-center of the aromatic ring system were employed as a simple means to compare and estimate qualitatively the aromaticity of the systems at hand.}, language = {en} } @article{LaschewskyPoundSkrabaniaetal.2007, author = {Laschewsky, Andr{\´e} and Pound, Gwenaelle and Skrabania, Katja and Holdt, Hans-Joachim and Teller, Joachim}, title = {Unsymmetrical bifunctional trithiocarbonate as unexpected by-product in the synthesis of a dithioester RAFT agent}, issn = {0303-402X}, doi = {10.1007/s.00396-007-1653-5}, year = {2007}, abstract = {The trithiocarbonate 2-(benzylsulfanylthiocarbonylsulfanyl) propanoic acid is formed as minor by-product in the synthesis of the dithioester 2-((2-phenylthioacetyl)sulfanyl) propanoic acid via the Grignard route. The mechanism for this side reaction is not clear. The isolated trithiocarbonate may act as unsymmetrical but bifunctional RAFT agent in the aqueous polymerization of N,N-dimethyl acrylamide. Therefore, it is important to separate it completely from the dithioester before engaging the latter in controlled free radical polymerization to guarantee a maximum control.}, language = {en} } @article{RudershausenDrexlerBansseetal.2007, author = {Rudershausen, S. and Drexler, Hans-Joachim and Banße, Wolfgang and Kelling, Alexandra and Schilde, Uwe and Holdt, Hans-Joachim}, title = {Three polymorphs of bis(5-methylthio-1,2-dithiole-3-thione)-disulfide}, doi = {10.1002/crat.200610776}, year = {2007}, abstract = {The title compound, bis(5-methylthio-1,2-dithiole-3-thione)-disulfide, was yielded for the first time as by- product of the reaction of nickel(II) and cobalt(II) ions with 5-methylthio-1,2-dithiole-3-thione-4-thiolate. The compound can be obtained directly by oxidation of the ammonium salt of the ligand. C8H6S10 forms three polymorphs: (I), which crystallizes in the orthorhombic space group P212121, (II) and (III), which crystallize in the monoclinic space groups P21/c and P21/n, respectively. The crystal and molecular structures are presented here. The determination of the absolute configuration of (I) indicated the P-helical enantiomer. In contrast to this, the crystals of (II) und (III) are racemic, containing P- and M-helical enantiomers. The polymorphs differ in the kind of skewing around the disulfide bond and of the positions of the both dithiole rings to the S-S-moiety}, language = {en} } @article{ShainyanUshakovMeshcheryakovetal.2007, author = {Shainyan, Bagrat A. and Ushakov, Igor A. and Meshcheryakov, Vladimir I. and Schilde, Uwe and Koch, Andreas and Kleinpeter, Erich}, title = {The stereodynamics of 3,5-bis(trifluoromethylsulfonyl)-1,3,5-oxadiazinane and 1,3,5- tris(trifluoromethylsulfonyl)-1,3,5-triazinane- an experimental and theoretical study}, doi = {10.1016/j.tet.2007.09.041}, year = {2007}, abstract = {Multinuclear dynamic NMR spectroscopy of 3,5-bis(trifluoromethylsulfonyl)-1,3,5-oxadiazinane (3) revealed the existence of two conformers with differently oriented CF3 groups with respect to the ring, and two dynamic processes: ring inversion and restricted rotation about the N-S bond. Two transition states connecting the two conformers and corresponding to clockwise and counterclockwise rotations about the N-S bond were found; the calculated activation barriers of about 12 kcal/mol are in excellent agreement with those measured experimentally for the related molecule 1,3,5-tris(trifluoromethylsulfonyl)-1,3,5-triazinane (1). X-ray analysis proved the existence of the symmetric isomer of 3, which is the minor isomer in solutions but the only one in the crystal due to packing effects. The normal Perlin effect (JCHax < JCHeq)observed for 2(6)-CH2 in 3, whereas the reversed Perlin effect was found for the 4-CH2 group in 3 as well as for all CH2 groups in 1 both experimentally and theoretically. The latter effect in compounds 1, 3, and 1- (methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane (2) can be considered as a genuine reverse Perlin effect since larger values of 1JCH are observed for longer C-H bonds.}, language = {en} } @phdthesis{You2007, author = {You, Liangchen}, title = {Synthesis and characterization of novel glycopolymers}, address = {Potsdam}, pages = {116 S. : graph. Darst.}, year = {2007}, language = {en} } @article{Kleinpeter2007, author = {Kleinpeter, Erich}, title = {Syntheses and conformational analyses of mono- and trans-1,4-dialkoxy substituted cyclohexanes : the steric substituent/skeleton interactions}, issn = {0040-4020}, doi = {10.1016/j.tet.2007.06.094}, year = {2007}, abstract = {Mono- and trans-1,4-dialkoxy substituted cyclohexanes (alkyl=Me, Et, i-Pr, t-Bu) were prepared using the solvomercuration-demercuration (SM-DM) procedure. The axialaxial and axial,axialequatorial, equatorial conformational equilibria of the products were studied by low temperature 1H and 13C NMR spectroscopy in CD2Cl2. The structures and relative energies of the participating conformers were calculated at both the B3LYP (6-311G*//6-311+G*) and MP2 (6-311+G*//6-311G*) levels of theory. In the case of DFT, good correlations of ;Gocalcd versus ;Goexptl were obtained. Both the structures and the energy differences of the conformers have been discussed with respect to established models of conformational analysis, viz. steric and hyperconjugative interactions. In addition, 1JH,C coupling constants were considered with respect to the hyperconjugation present.}, language = {en} } @phdthesis{Kaper2007, author = {Kaper, Helenea}, title = {Structure control of nanoscaled inorganic matter by ionic liquids}, address = {Potsdam}, pages = {138 S. : Ill., graph. Darst.}, year = {2007}, language = {en} } @article{WackerKleinpeter2007, author = {Wacker, Philipp and Kleinpeter, Erich}, title = {Stoichiometry, complex stability, molecular size and conformational variations of metal ion crown ether complexes subject to diffusion coefficients in nonaqueous solutions}, doi = {10.1007/s10847-007-9332-1}, year = {2007}, abstract = {Both the stoichiometry and complex stability constants of crown ether complexes with metal ions have been determined by examining gradual changes in their diffusional behavior in nonaqueous solution. Diffusion coefficients, D, were evaluated by pulsed field gradient (PFG) NMR titration experiments whilst complex stability constants were determined by nonlinear curve-fitting procedures, D versus csol., which also allow the treatment of multiple complexation equilibria (1:1 to 1:2 stoichiometries). Differences in the diffusion coefficients of the various free crown ethers with respect to their metal ion complexes indicate great sensitivity to both conformational changes and changes in molecular size upon complexation.}, language = {en} } @article{RasovicSteelKleinpeteretal.2007, author = {Rasovic, Aleksandar and Steel, Peter J. and Kleinpeter, Erich and Markovic, Rade}, title = {Regioselective synthesis of 1,3-thiazines by sequential 4-oxothiazolidine to 1,2-dithiole to 1,3-thiazine transformations : role of intramolecular non-bonded S...O interactions}, doi = {10.1016/j.tet.2006.12.075}, year = {2007}, abstract = {A new synthetic approach to 2,3-dihydro-4H-1,3-thiazine derivatives based upon reductive rearrangement of 1,2- dithiole-3-ylidene thiones has been developed. In turn, the 1,2-dithiole derivatives were prepared by an efficient ring- opening-closing process of 2-alkylidene-4-oxothiazolidines, induced in the presence of Lawesson's reagent by intramolecular non-bonded 1,5-type S...O interactions in the 4-oxothiazolidine precursors.}, language = {en} } @phdthesis{Nest2007, author = {Nest, Mathias}, title = {Quantum dynamics for large systems: System-bath type situations and correlated dynamics of many electrons}, address = {Potsdam}, pages = {176 S., I-V, graph. Darst.}, year = {2007}, language = {en} }