Theophylline alkaloid as glue of paddle-wheel copper(II)-adenine entities to afford a rhomboid chain

Abstract This work is aimed at the analysis of the interactions that drive the assembling of coordination metal-organic polymers based on biological molecules. Single-crystal X-ray diffraction data show that the compound 1D-{[Cu 2 (μ-ade) 4 (H 2 O) 2 ]·2[Cu(theoph) 2 ]·∼10H 2 O} n ( 1 ) contains neutral rhomboid shaped chains sustained by the tridentate μ 3 -κ N3 :κ N7 :κ N9 coordination mode of the adenine nucleobase. These chains are formed by dimeric copper/adeninato (ade) cores doubly bridged by monomeric copper/theophyllinato (theoph) entities with the alkaloid acting as peripheral ligand. The lack of direct intermolecular nucleobase···nucleobase interactions, due to their disruption by the crystallization water molecules, does not provide a highly porous material, but the irregular shape of the polymeric chain hinders their packing and allows the presence of a moderate amount of voids (16% of the unit cell volume) in good accordance with its adsorption capacity of 0.38 mmol CO 2 /g at 273 K. Thermogravimetric and variable temperature X-ray diffraction analyses show that the compound retains its structure up to 110 °C whereas above this temperature the release of the coordination water molecules produces a significant loss of crystallinity. Magnetic measurements indicate an overall antiferromagnetic behavior with a J value of −267 cm −1 within the dimeric entity.