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

• Published in: Crystal growth & design Vol. 17; no. 12; pp. 6836 - 6851
• Main Authors: Jarzembska, Katarzyna N, Kamiński, Radosław, Durka, Krzysztof, Kubsik, Marcin
• Format: Journal Article
• Language: English
• Published: American Chemical Society 06.12.2017
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/acs.cgd.7b01420

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 time-resolved 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.