Guest-directed assembly of caffeine and succinic acid into topologically different heteromolecular host networks upon grinding

Two alternative inclusion host lattices are formed upon cocrystallization of caffeine and succinic acid in the presence of an appropriate guest. The host lattices differ in topology as well as in the stoichiometric ratio of caffeine and succinic acid. Both host frameworks are based on the assembly of a common, dumbbell-shaped heteromolecular building block involving molecules of caffeine and succinic acid. A grinding-based screening procedure revealed that host formation is independent of the state of aggregation, allowing the inclusion of compounds that are either solids, liquids, or gases under ambient conditions. The selectivity to form a particular host is directed by the molecular recognition properties of the guest. The ability of the guest to form C-H center dot center dot center dot O and halogen bonds appears to be the key factor in controlling the topology of the inclusion matrix, allowing the stoichiometric ratio of caffeine and succinic acid to be varied by appropriate choice of the guest.