@article{NorledgeLambeirAbagyanetal.2001, author = {Norledge, Brian V. and Lambeir, Anne M. and Abagyan, Ruben and Rottmann, Antje and Fernendez, Anna M. and Filimonov, Vladimir V. and Peter, Martin G. and Wierenga, Rik K.}, title = {Modeling, mutagenesis, and structural studies on the fully conserved phoshate-binding loop (Loop 8) of triosephosphate isomerase : toward a new substrate specificity}, issn = {0887-2585}, year = {2001}, language = {en} } @article{GrotjahnLehmannAurichetal.2001, author = {Grotjahn, Manuela and Lehmann, S. and Aurich, Ines and Holdt, Hans-Joachim and Kleinpeter, Erich}, title = {NMR spectroscopic and molecular modelling studies of the solution structure and complexational behaviour of some bis(benzocrown ether)s}, year = {2001}, abstract = {Structural information about the bis(benzo crown ether)s I-VI and their complexes with alkali metal cations was deduced from the 13C NMR chemical shifts, the salt-induced 1H and 13C chemical shifts and the vicinal 1H,1H coupling constants. Especially the isomerism with respect to the amide O=C - NH bonds and imine fragments were assigned by various useful NMR parameters ( C=O, 1JN,H, 1JC,H) and proved to be E,E-anti,anti. Furthermore, stereochemical information about preferred conformations about flexible bonds was obtained from 2D ROESY NMR experiments. The complex formation (2:1 complexes and sandwich-like 1:1 complexes, respectively) were determined also by 23Na NMR spectroscopy. The conformational study of the crown ethers was accompanied and corroborated by molecular dynamics and quantum chemical calculations.}, language = {en} } @article{JansenBuschmannWegoetal.2001, author = {Jansen, K. and Buschmann, Hans-J{\"u}rgen and Wego, A. and Dopp, D. and Mayer, C. and Holdt, Hans-Joachim and Schollmeyer, E.}, title = {Curcubit[5]uril, decamethylcururbit[5]uril and curcurbit[6]uril : synthesis, solubility and amin complex formation}, year = {2001}, abstract = {A simple way to prepare cucurbit[5]uril is described. The macrocycles of the cucurbituril type are nearly insoluble in water. The solubilities of cucurbit[5]uril, decamethylcucurbit[5]uril and cucurbit[6]uril in hydrochloric acid, formic acid and acetic acid of different concentrations have been investigated. Due to the formation of complexes between cucurbit[n]urils and protons the solubility increases in aqueous acids. The macrocyclic ligands are able to form complexes with several organic compounds. Thus, the complex formation of the cucurbituril macrocycles with different amines has beenstudied by means of calorimetric titrations. The reaction enthalpy gives noevidence of the formation of inclusion or exclusion complexes. 1H-NMR measurements show that in the case of cucurbit[5]uril and cucurbit[6]uril the organic guest compound is included within the hydrophobic cavity. Decamethylcucurbit[5]uril forms only exclusion complexes with organicamines. This was confirmed by the crystal structure of the decamethylcucurbit[5]uril-1,6- diaminohexane complex. complex formation - cucurbit[5]uril - cucurbit[6]uril - decamethylcucurbit[5]uril - solubility - synthesis}, language = {en} } @article{HoldtDrexlerStarkeetal.2001, author = {Holdt, Hans-J{\"u}rgen and Drexler, Hans-Joachim and Starke, Ines and Grotjahn, Manuela and Kleinpeter, Erich}, title = {Homologous series of the PdCl2 and PtCl2 complexes of maleonitrile-dithiacrown ethers : synthesis, crystal structures, NMR spectroscopy and mass spectrometry}, year = {2001}, language = {en} } @article{KleinpeterGrotjahnKlinkaetal.2001, author = {Kleinpeter, Erich and Grotjahn, Manuela and Klinka, Karel D. and Drexler, Hans-Joachim and Holdt, Hans-J{\"u}rgen}, title = {Conformational and complexational study of some maleonitrile mixed oxadithia crown ethers by NMR spectroscopy and molecular modelling}, year = {2001}, abstract = {The macrocyclic ring interconversion of four maleonitrile mixed oxadithia crown ethers of variable ring size, mn-12-S2O2, mn-15-S2O3, mn-18-S2O4 and fn-12-S2O2, were studied by 1H and 13C NMR spectroscopy and by molecular modelling. The barriers to ring interconversion were estimated using variable temperature NMR spectroscopy and from the calculated activation energies, together with the spin-lattice relaxation times of the CH2 carbon atoms, conclusions were drawn regarding the intramolecular flexibility of the crown ethers in both the free state as well as the complexed state incorporating either AgI, BiIII, SbIII, PdII or PtII metal cations. Furthermore, both the stoichiometry of the complexes and the coordination sites of the crown ethers to the various cations were also clearly implicated. Molecular modelling was also utilised to ascertain the preferred conformers of the four compounds and their corresponding complexes, the results of which corroborated the experimental NMR results to a high degree.}, language = {en} } @article{RitschelMahapatraZuelicke2001, author = {Ritschel, Thomas and Mahapatra, Susanta and Z{\"u}licke, Lutz}, title = {Quasiclassical dynamics of proton scattering by N2 on an improved ab initio potential energy surface}, year = {2001}, abstract = {An improved analytical representation of the ground electronic potential energy surface (PES) of the (H+, N2) system is generated using the ab initio data reported in our earlier work. The new analytical PES function describes adequately the global behavior and in particular the angular dependence of the interaction as well as the long-range part so that it is amenable to scattering studies. We investigate the elastic and inelastic H+-N2 scattering dynamics on this PES by the quasiclassical trajectory method for center-of-mass collision energies in the range 29-144 eV. The trajectory results thus obtained are compared with the available experimental findings and with recent quantum-mechanical (vibrational close-coupling rotational infinite-order sudden) results. Despite some differences, the experimental data are well reproduced by the present calculations.}, language = {en} } @article{StrehmelHenbestSarkeretal.2001, author = {Strehmel, Bernd and Henbest, K. B. and Sarker, A. M. and Malpert, J. H. and Chen, D. Y. and Rodgers, M. A. J. and Neckers, D. C.}, title = {Ion induced man ipulation of photochemical pathways in crown ether compounends based on fluorinated oligophenylenevinylenes}, publisher = {Journal of nanoscience and nanotechnology. - 1 (2001), 1, S. 107 - 124}, year = {2001}, language = {en} } @article{Mickler2001, author = {Mickler, Wulfhard}, title = {Reactive Liquid-liqudi-extraction of heavy metals from landfill leachates}, year = {2001}, abstract = {Toxic heavy metals are extracted simultaneously by reactive liquid-liquid-extraction from a model landfill leachate. This is taken as an example to generate an unproblematic waste water. Alkylphosphoric acids (commercial D2EHPA and D2EHTPA), ß-diketones, 4-Acyl-5-pyrazolones and a novel commercial alkyl-methyl-phosphonic acid are used as extractants. By means of the functions E\%=f (pH, t) and lg D=f (pH, cL) some thermodynamic parameters of the extraction are determined. In the case of the alkylthiophosphoric acid the thiophilic cations are extracted advantageously in contrast to chromium, magnesium or calcium. There is no significant separation between the heavy metals and the alkaline earth metals. The complexes are extracted with the composition ML(HL)n. According to their ligand force, the presence of complexing agents in the aqueous phase (for example cyanide, tartrate, ammonia or chloride) hinders the extraction. The influence of humic acid is comparable to that of tartaric acid. Because of the formation of less soluble compounds, sulphate ions make the extraction of calcium more difficult. The extraction data points out that aromatic or chloric solvents are not advantageous in contrast to the non toxic aliphatic hydrocarbons. With the novel aminomethylphosphonic acid (ironex, BASF) the extraction of iron, indium and gallium is possible at a pH > 1.5 as ML2(HL) and ML(HL)2 resp. Copper and zinc were extracted quantitatively as 1:2 complexes only in a small pH-range between 4 to 6. Generally, the best results were found for the ß-diketones (LIX 54 included) and 4-acyl-5-pyrazolones. In these cases the toxic heavy metals could be separated quantitatively. Only 6\% of calcium and 23\% of magnesium are coextracted by the ligands. The extraction process can further be optimized by synergistic effects.}, language = {en} } @article{Illenseer2001, author = {Illenseer, C.}, title = {Investigation of ion-molecule collisions with laser-based ion mobility spectrometry}, year = {2001}, language = {en} } @article{KalliesMeier2001, author = {Kallies, Bernd and Meier, R.}, title = {The electronic structure od 3 [M(H20)6)3+ions from Sc(III)till Fe (III) : a quantum mechanical study based on DFT computations and natural bond orbital analyses}, year = {2001}, language = {en} }