title: Mechanism of host-guest complex formation and identification of intermediates through NMR titration and diffusion NMR spectroscopy.
abstract: The formation of host-guest (H-G) complexes between 1,8-bis[(diethylgallanyl)ethynyl]anthracene (H) and the N-heterocycles pyridine and pyrimidine (G) was studied in solution using a combination of NMR titration and diffusion NMR experiments. For the latter, diffusion coefficients of potential host-guest structures in solution were compared with those of tailor-made reference compounds of similar shape (synthesized and characterized by NMR, HRMS, and in part XRD). Highly dynamic behavior was observed in both cases, but with different host-guest species and equilibria. With increasing concentrations of the pyridine guest, the equilibrium H2⇄H2κ(1)-G1⇄HG2 is observed (in the second step a host dimer coordinates one guest molecule); for pyrimidine the equilibrium H2→H1κ(2)-G1⇄HG2 is observed (the formation of a 1:1 aggregate is the second step).
authors.affiliation: Lehrstuhl für Anorganische Chemie und Strukturchemie, Universität Bielefeld, Fakultät für Chemie, Universitätsstrasse 25, 33615 Bielefeld (Germany) http://www.uni-bielefeld.de/chemie/arbeitsbereiche/ac3-mitzel/
authors.forename: Jan-Hendrik
authors.initials: JH
authors.lastname: Lamm
authors.forename: Philipp
authors.initials: P
authors.lastname: Niermeier
authors.forename: Andreas
authors.initials: A
authors.lastname: Mix
authors.forename: Jasmin
authors.initials: J
authors.lastname: Chmiel
authors.forename: Beate
authors.initials: B
authors.lastname: Neumann
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Stammler
authors.forename: Norbert W
authors.initials: NW
authors.lastname: Mitzel
keywords: anthracenes; diffusion NMR spectroscopy; gallium; host-guest systems; poly-Lewis acids