Biquinolino-modified beta-cyclodextrin dimers and their metal complexes as efficient fluorescent sensors for the molecular recognition of steroids

作者：Liu Y^*; Song Y; Chen Y; Li XQ; Ding F; Zhong RQ

来源：Chemistry - A European Journal, 2004, 10(15): 3685-3696.

DOI：10.1002/chem.200305724

• cyclodextrins
• fluorescent sensors
• molecular recognition
• steroids
• supramolecular chemistry

A series of bridged beta-cyclodextrin (beta-CyD) dimers possessing functional tethers of various lengths was synthesized in moderate yield by the treatment of 2,2'-biquinoline-4,4'-dicarboxylic dichloride with beta-CyD or mono[6-oligo(ethylenediamino)-6-deoxy]-beta-CyDs. The products were 2,2'-biquinoline-4,4'-dicarboxy-bridged bis(6-O-beta-CyD) (8), N,N'-bis(2-aminoethyl)-2,2'-biquinoline-4,4'-dicarboxamide-bridged bis(6-amino-6-deoxy-beta-CyD) (9), and N,N'-bis(5-amino-3-azapentyl)-2,2'-biquinoline-4,4'-dicarboxamide-bridged bis(6-amino-6-deoxy-beta-CyD) (10). The reaction of 8-10 with copper perchlorate give their copper(II) complexes 11-13 in satisfactory yields of over 77%. All the bis(beta-CyD)s 8-13 act as efficient fluorescent sensors and display remarkable fluorescence enhancement upon addition of optically inert steroids. The inclusion complexation behaviors of 8-13 when treated with the representative steroids cholate (14), deoxycholate (15), and glycocholate (16) in aqueous solution at 25degreesC were investigated by means of UV/Vis spectroscopy, conductivity and fluorescence measurements, circular dichroism spectroscopy, and 2D NMR spectroscopy. The tether length of bis(beta-CyD) 9 allows it to adopt a cooperative host-tether-guest binding mode in which the spacer and guest are co-included in the two CyD cavities. As a result of this cooperation, 9 has a stability constant (K-s) about 2 x 10(2) times higher than that of monomodified beta-CyD 4 for inclusion complexation with cholate. Metallooligo(beta-CyD)s with four beta-CyD units have enhanced binding abilities compared with monomodified beta-CyDs. These metallo compounds have binding affinities for guest steroids that are up to 50-4.1 x 10(3) times higher than those of CyDs 2-4. The guest-induced fluorescence enhancement of his(CyD)s opens a new channel for the design of sensor materials. The complex stability constants of these compounds are discussed from the viewpoint of induced-fit interaction and cooperative multiple binding between host and guest.

• 出版日期2004-8-6
• 单位南开大学