Crystallographic insight into the binding modes of group 12 metal cations with N7-alkylated purines

Abstract

This study explores the complexation behavior of previously unexplored N7-alkylated 6-chloropurine derivatives with group 12 metal cations (Zn²⁺, Cd²⁺, and Hg²⁺), where N9 is free to coordinate. Notably, with high basicity, the N9 nitrogen atoms serve as the primary coordination sites for all investigated metal ions. The N1 position does not coordinate with any metal ions under this study. Interestingly, N3 participates in binding with Cd²⁺ and Hg²⁺ ions, resulting in the formation of a 1D linear coordination polymer bridged by chloride anions. The observed polymeric structure exhibits further extension through intermolecular non-classical hydrogen bonding and π–π stacking interactions. In contrast, Zn²⁺ forms discrete coordination complexes that extend in the lattice due to hydrogen bonding interactions. The observed consistency in coordination preferences of metal–purine complexes translates to predictable motifs, and this reliable binding can serve as a synthon for the targeted construction of MOFs.