Silver mediated duplex-type complexes of pyrimidinophanes and their acyclic counterparts

Abstract

Complexation of metal cations with acyclic and macrocyclic nucleobase derivatives containing uracil and 2-thiocytosine units linked by polymethylene spacers was studied. The investigated compounds have demonstrated high extraction selectivity for the Ag⁺ ion over a large number of competitive cations (Na⁺, Ca²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺). The structure and composition of Ag⁺ complexes have been investigated by a variety of physical-chemical methods. The crystal structures of three Ag⁺ complexes with 2-thiocytosine have been established by X-ray analysis. To refine the composition of the complexes formed in solution, the self-diffusion coefficients have been determined by NMR spectroscopy. For the estimation of the most reliable complex structures, the combined analysis of NMR data and DFT calculations was successfully applied. It was shown that the tendency of 2-thiocytosine moieties to form N1-nitrogen coordinated complexes and the presence of a polymethylene spacer between amine groups in the pyrimidinophanes provides the formation of Ag⁺ mediated duplex-type multi-component complexes.