Absorption, fluorescence, and cd spectroscopic study of chiral recognition by a binaphthyl-derived chromogenic calixcrown host

• Published in: Chirality (New York, N.Y.) N.Y.), 2004-03, Vol.16 (3), p.174-179
• Main Authors: Kubinyi, Miklós, Pál, Krisztina, Baranyai, Péter, Grofcsik, András, Bitter, István, Grün, Alajos
• Format: Article
• Language: English
• Subjects: chiral amine; exciton chirality; fluorescence quenching; solvent effect; supramolecular complex
• ISSN: 0899-0042; 1520-636X
• DOI: 10.1002/chir.20003

The (R)‐ and (S)‐enantiomers of a binaphthyl‐appended calix4crown‐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 α‐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. Chirality 16:174–179, 2004. © 2004 Wiley‐Liss, Inc.