title: Absorption, fluorescence, and cd spectroscopic study of chiral recognition by a binaphthyl-derived chromogenic calixcrown host.
abstract: The (R)- and (S)-enantiomers of a binaphthyl-appended calix[4]crown-6 ether with two 2,4-dinitrophenylazo chromophore units ((R)-1 and (S)-1) as chiral hosts were tested in their reactions with the enantiomers of alpha-methylbenzylamine ((R)-MBA, (S)-MBA)) and phenylglycinol ((R)-PGL, (S)-PGL) as chiral guests. The visible absorption spectra indicate a two-step process: the first is a nonenantioselective proton transfer from the host to the guest, which is followed by the enantioselective real complexation. In the visible range of the CD spectra a positive/negative band belongs to the absorption of pure (R)-1/(S)-1, and a negative/positive exciton couplet to the absorption of (R)-1-(S)-MBA/(S)-1-(R)-MBA complexes. The latter phenomenon suggests that the complexation of amines is accompanied by a chiral arrangement of the two chromophore units in the hosts. The UV fluorescence of (R)-1/(S)-1 arising from the binaphthyl moiety is quenched by K+ ions, but not by the amine guests, showing that the interaction between the binaphthyl group and the complexed amines is weak.
authors.affiliation: Department of Physical Chemistry, Budapest University of Technology and Economics, 1521 Budapest, Hungary. kubinyi@mail.bme.hu
authors.forename: Miklós
authors.initials: M
authors.lastname: Kubinyi
authors.forename: Krisztina
authors.initials: K
authors.lastname: Pál
authors.forename: Péter
authors.initials: P
authors.lastname: Baranyai
authors.forename: András
authors.initials: A
authors.lastname: Grofcsik
authors.forename: István
authors.initials: I
authors.lastname: Bitter
authors.forename: Alajos
authors.initials: A
authors.lastname: Grün