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

Ferrocene-modified artificial ditopic nucleobase receptors were designed an d synthesized. The ditopic receptors possess two hydrogen-bonding and one p i-stacking interaction sites that act simultaneously for the binding to 1-b utylthymine utilizing the pivot character of the ferrocene skeleton. Diamid opyridine was chosen for the hydrogen-bonding moiety, and 2,7-disubstituted pyrene was used for pi-stacking one. The ditopic receptors bound 1-butylth ymine, and the stoichiometry for the complexation was found to be 1:2 in CD Cl3. In the H-1 NMR spectrum of the mixture for the receptors and 1-butylth ymine, large downfield shifts of the NH protons on both diamidopyridine and 1-butylthymine revealed the complementary hydrogen bonds between them, whi le upfield shifts were observed for CH protons of the pyrene and the thymin e 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.