Metal binding properties of pyrimidinophanes and their acyclic counterparts

A series of acyclic and macrocyclic nucleobase derivatives that contain uracil and 2-thiocytosine units linked by polymethylene spacers was prepared. The length of spacers as well as the oxidation number of sulfur atoms entering into the structure of the compounds was varied. The crystal structure of pyrimidinophane with hexa- and heptamethylene linkers was established by X-ray analysis. The metal ion-binding properties of pyrimidinophanes and their acyclic counterparts were investigated by liquid extraction and super(1)H NMR titration experiments. The compounds with 2-thiocytosine fragments revealed a high selectivity of extraction towards Ag super(+) ions. The stoichiometry of silver complexes and the binding constants have been determined. The antibacterial activity of these complexes was also discussed.