Experimental and Computational Study of Solid Solutions Formed between Substituted Nitrobenzoic Acids

We present an experimental and computational study of solid solution formation in binary systems of substituted nitrobenzoic acids. Different isomers with methyl group, hydroxyl group, and chlorine substituents are studied. We show that the solid solution formation likelihood evaluated based on the observed solubility limit is notably affected by both - the exchanged functional groups and the location of the substituents in the molecular structure. This demonstrates that the component solubility limit strongly depends on the intermolecular interactions present in the crystal structure and altered by the molecule replacement. Solid solutions form in all of the studied crystalline phases. Component solubility limits from around 5% up to 50% were observed. The obtained results indicated that the calculated intermolecular interaction energy change by the functional group replacement does not allow to rationalize the experimentally observed solubilities neither considering the molecules adjacent to the replace group nor all the molecules within a 15 Å radius. The relative energy of the experimental structures and isostructural phases obtained from the computationally generated structure landscapes calculated at the level providing accurate energy ranking was found to be mostly consistent with the experimentally observed component solubilities.