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Synthesis and Complexation Studies between Trifluoromethylammonium Threads and Dibenzo[24]Crown‐8
Author(s) -
Johnsen Carsten,
Stein Paul C.,
Nielsen Kent A.,
Bond Andrew D.,
Jeppesen Jan O.
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201001277
Subject(s) - chemistry , ammonium , trifluoromethyl , polar effect , titration , stereochemistry , proton nmr , crystallography , medicinal chemistry , inorganic chemistry , organic chemistry , alkyl
Two new ammonium threads were synthesized and characterized. They are composed of either one or two bis‐alkylammonium sites that can act as recognition elements for dibenzo[24]crown‐8 (DB24C8) and are both appended with two electron‐withdrawing trifluoromethyl (CF 3 ) groups. The pseudorotaxanes formed between the trifluoromethyl ammonium threads and DB24C8 were characterized by single‐crystal X‐ray diffraction analyses and studied by NMR spectroscopy. The NMR spectroscopic data reveal that attachment of two electron‐withdrawing trifluoromethyl groups to the single‐site ammonium thread enhances the binding strength between the DB24C8 ring and the ammonium thread. Investigations carried out between the double‐site ammonium thread and DB24C8 reveal that the relative amount between the [2]pseudorotaxane and the [3]pseudorotaxane can be controlled by changing the ratio between the double‐site ammonium thread and DB24C8. Quantitative studies carried out by NMR titrations indicate at weak( K 2 / K 1 = 0.24) anticooperative effect in the formation of the [3]pseudorotaxane.