Designing Hydrogen Bonds with Temperature-Dependent Proton Disorder: The Effect of Crystal Environment

Two crystal structures, each containing a 4-dimethylaminobenzoic acid dimer (4-DABA), have been studied by multitemperature X-ray diffraction methods. In form I of pure 4-DABA, temperature-dependent proton disorder is observed. In the molecular complex with 3,5-dinitrobenzoic acid, no such disorder is observed in the 4-DABA dimer but is observed in the 3,5-dinitrobenzoic acid dimer. The effect of the crystal environment perturbing the local symmetry of apparently similar molecular structures is discussed in relation to this change in observed proton disorder.