Complex and mixture of β-cyclodextrin with diazepam characterised by 1H NMR and atom–atom potential methods

•Combined use of solid-state 1H NMR spectroscopy and atom–atom potential methods.•The magnetisation recovery indicated a formation of diazepam–cyclodextrin complex.•Activation energy for motion of CH3 in diazepam did not change in inclusion complex.•The phenyl ring of diazepam is located inside the β-cyclodextrin cavity. Inclusion complex of β-cyclodextrin with diazepam and a physical mixture of these components were studied by solid-state 1H NMR. The activation barrier for reorientation of the methyl group in the diazepam molecule was found not changed by complex formation with β-cyclodextrin. The complex formation resulted in a decrease in the number of water molecules and affected the relaxation time of β-cyclodextrin. By the atom–atom potential method the most probable configuration of the diazepam molecule inside β-cyclodextrin cavity was proposed.