A New Strategy for the Synthetic Assembly of Inorganic-Organic Silver(I)-Polyoxometalate Hybrid Structures Employing Noncovalent Interactions between Theobromine Ligands

A new strategy for the synthesis of inorganicorganic silver(I)-polyoxometalate materials was developed. The approach takes advantage of the ability of purine bases to build strong networks using them as ligands to silver(I). Its major experimental strong point is the facile preparation of target compounds from aqueous solutions from basic starting materials. Proof of concept was accomplished by using theobromine as the purine base. Seven new compounds containing silver(I) theobromine building blocks were characterized by single crystal X-ray diffraction: [Ag(thb)(2)]ClO4 (2), [Ag(thb)(2)(H2O)]ClO4 (3), [Ag(thb)(2)](2)(H4V10O28)center dot 3H(2)O (4), [Ag(thb)(2)](2)(Cr2O7)center dot 0.5H(2)O (5), [Ag(thb)(2)(H2O)](2)(H3O)[Ag(beta-Mo8O26)]center dot 4H(2)O (6), [Ag(thb)](2)[Ag(Cr(OH)(6)Mo6O18)]center dot 2H(2)O (7), and [Ag(thb)(2)](2)(H3O)(4)[Ni(OH)(6)Mo6O18](CO3)center dot 13H(2)O (8) (thb = theobromine). The purity of compounds 27 was confirmed by powder X-ray diffraction and elemental analysis. They were also characterized by IR and UV/vis spectroscopy and thermal analysis (DTA/TG). The main structural traits in all of the polyoxometalate containing compounds are coordination polymers running along the direction of one of the crystallographic axes. These chains are interconnected by a framework of strong hydrogen bonds and stacking interactions. The thermodynamic rationalization of these crystal structure landscapes is thoroughly discussed.