Engineering of Solvatomorphs of the Luminescent Complex ofortho-Phenylenediboronic Acid and 8-Hydroxyquinoline

ortho-Phenylenediboronic acid reacts efficiently with 8-hydroxyquinoline yielding a luminescent yellowish complex soluble in a number of typical organic solvents. Through a solvent-evaporation method, five solvatomorphs and one structure of an ester of the studied compound were crystallized. Four of the solid-state forms (i.e., crystals containing acetone, tetrahydrofuran (THF), 1,4-dioxane, and acetonitrile) are isostructural, whereas the presence of dichloromethane leads to a different crystal structure. In turn, methanol, instead of being incorporated into the structural voids, reacts with the complex molecule which results in a methyl ester derivative. All crystals were characterized by X-ray diffraction, differential scanning calorimetry, theoretical computations, and solid-state timeresolved spectroscopy. Acetone and THF are located at the center of symmetry and are disordered, while symmetric dioxane fits perfectly into such structural voids, which enhances the crystal quality. It is reflected in a more energetically stable crystal structure containing dioxane and in the fact that this solvatomorph is most preferably formed from various mixtures of the examined solvents. Different solvent content does not influence the spectroscopic properties significantly. The determined lifetimes are of nanosecond order (∼15 ns), which is similar to that determined for solution samples.