Tuning Proton Behavior in a Ternary Molecular Complex

The multicomponent ternary complex of 4-dimethylaminobenzoic acid (4-DABA), 3,5-dinitrobenzoic acid (3,5-DNBA), and 4,4'-bipyridine (BIPY) has been studied by variable temperature X-ray and neutron diffraction. Proton disorder is observed within the 4-DABA homodimers present and quantitatively evaluated from neutron data. The effect of the crystal environment and in particular the pyramidalization of the nitrogen atom within the 4-DABA molecule and the consequential effect on the presence of hydrogen atom disorder are discussed with reference to the previously determined pure 4-DABA structure and the binary cocrystal with 3,5-DNBA.