Molecular structure and selective theophylline complexation by conformational change of diethyl N,N′-(1,3-phenylene)dicarbamate

The receptor ability of diethyl N , N ′-(1,3-phenylene)dicarbamate ( 1 ) to form host–guest complexes with theophylline (TEO) and caffeine (CAF) by mechanochemistry was evaluated. The formation of the 1 –TEO complex (C 12 H 16 N 2 O 4 ·C 7 H 8 N 4 O 2 ) was preferred and involves the conformational change of one of the ethyl carbamate groups of 1 from the endo conformation to the exo conformation to allow the formation of intermolecular interactions. The formation of an N—H...O=C hydrogen bond between 1 and TEO triggers the conformational change of 1 . CAF molecules are unable to form an N—H...O=C hydrogen bond with 1 , making the conformational change and, therefore, the formation of the complex impossible. Conformational change and selective binding were monitored by IR spectroscopy, solid-state 13 C nuclear magnetic resonance and single-crystal X-ray diffraction. The 1 –TEO complex was characterized by IR spectroscopy, solid-state 13 C nuclear magnetic resonance, powder X-ray diffraction and single-crystal X-ray diffraction.