title: Preferred dimerization of tetra-tolyl- and tetra-tosylurea derivatives of flexible and rigidified calix[4]arenes.
abstract: The dimerization of tetratolyl- and tetratosyl-urea derivatives 1 and 2, derived from a tetrapentoxy calix[4]arene in the cone conformation and of the corresponding tetra-urea derivatives 3 and 4, in which the cone conformation is rigidified by the two crown-3 tethers, have been studied. All six possible equimolar mixtures were examined by 1H NMR using CDCl3 and CD2Cl2 as solvents. While no heterodimers are found for the combinations 1/3 and 2/4 in either solvent, all remaining combinations lead to the (exclusive) formation of heterodimers in CD2Cl2. In CDCl3 heterodimers are only observed for the combinations of 3 with 2 or 4. These results are discussed in terms of entropic and enthalpic contributions and compared with MD-simulations in a box of chloroform solvent molecules.
authors.affiliation: Abteilung Lehrant Chemi, Fachbereich Chemie und Pharmazie, Johannes Gutenberg-Universität Mainz, Germany.
authors.forename: Yuliya
authors.initials: Y
authors.lastname: Rudzevich
authors.forename: Myroslav O
authors.initials: MO
authors.lastname: Vysotsky
authors.forename: Volker
authors.initials: V
authors.lastname: Bohmer
authors.forename: Marcus S
authors.initials: MS
authors.lastname: Brody
authors.forename: Julius
authors.initials: J
authors.lastname: Rebek
authors.forename: Frank
authors.initials: F
authors.lastname: Broda
authors.forename: Iris
authors.initials: I
authors.lastname: Thondorf
mesh_terms: D047250:Calixarenes / Q000737:chemistry*; D003198:Computer Simulation; D019281:Dimerization; D019277:Entropy; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D018583:Pliability; D013237:Stereoisomerism; D014508:Urea / Q000031:analogs & derivatives* / Q000737:chemistry*
chemical_list: D047250:Calixarenes; D014508:Urea