Porous Supramolecular Architectures Based on π-Stacking Interactions between Discrete Metal-Adenine Entities and the Non-DNA Theobromine/Caffeine Nucleobases

This work is aimed at the analysis of the π–π stacking interactions as the driving force to develop porous supramolecular metal–organic frameworks (SMOFs) as an alternative to more directional hydrogen bonding interactions. Four compounds based on the interaction between rigid copper/adenine entities and theobromine/caffeine molecules have been synthesized: [Cu7(μ-ade)6(μ3-OH)6(μ-H2O)6](theo)2·∼28H2O (1), [Cu2(μ-ade)4(H2O)2]·3Htheo·∼7H2O (2), [Cu2(μ-ade)4(H2O)2]·2Htheo·∼18H2O (3), and [Cu2(μ-ade)4(H2O)2]·(caf)·∼6H2O (4). The blue compound 1 is formed by wheel-shaped cationic heptameric units where the copper atoms are bridged by hydroxide anions, water molecules, and adeninato ligands with a μ-κN3:κN9 coordination mode. The assembly of the heptameric entities and the theobrominate anions takes place mainly through π–π stacking interactions involving the adeninato ligands and theobrominate moieties. Although compound 1 exhibits an open-framework with voids representing 37% of the unit cell, the plasticity ...