Ferrocene-modified artificial ditopic nucleobase receptors capable of serving both hydrogen-bonding and π-stacking interactions

Ferrocene-modified artificial ditopic nucleobase receptors were designed and synthesized. The ditopic receptors possess two hydrogen-bonding and one pi-stacking interaction sites that act simultaneously for the binding to 1-butylthymine utilizing the pivot character of the ferrocene skeleton. Diamidopyridine was chosen for the hydrogen-bonding moiety, and 2,7-disubstituted pyrene was used for pi-stacking one. The ditopic receptors bound 1-butylthymine, and the stoichiometry for the complexation was found to be 1:2 in CDCl3. In the H-1 NMR spectrum of the mixture for the receptors and 1-butylthymine, large downfield shifts of the NH protons on both diamidopyridine and 1-butylthymine revealed the complementary hydrogen bonds between them, while upfield shifts were observed for CH protons of the pyrene and the thymine nuclei reflecting from the close approach of the bound 1-butylthymine to the pyrene. Binding affinities of the ditopic receptors for 1-butylthymine were discussed on the basis of the total association constants.