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Mechanism of Host–Guest Complex Formation and Identification of Intermediates through NMR Titration and Diffusion NMR Spectroscopy
Authors:M. Sc. Jan‐Hendrik Lamm  B. Sc. Philipp Niermeier  Dr. Andreas Mix  Dr. Jasmin Chmiel  Beate Neumann  Dr. Hans‐Georg Stammler  Prof. Dr. Norbert W. Mitzel
Affiliation:Lehrstuhl für Anorganische Chemie und Strukturchemie, Universit?t Bielefeld, Fakult?t für Chemie, Universit?tsstrasse 25, 33615 Bielefeld (Germany) http://www.uni‐bielefeld.de/chemie/arbeitsbereiche/ac3‐mitzel/
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?H2κ1‐G1?HG2 is observed (in the second step a host dimer coordinates one guest molecule); for pyrimidine the equilibrium H2→H1κ2‐G1?HG2 is observed (the formation of a 1:1 aggregate is the second step).
Keywords:anthracenes  diffusion NMR spectroscopy  gallium  host–  guest systems  poly‐Lewis acids
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