Boosting The Solid-State Luminescence of Phenazine Derivatives by Enhancing Intermolecular Hydrogen Bonds and π-π...

Six monosubstituted phenazine derivatives were designed and synthesized for constructing cocrystals to investigate their structure-property relationship. It was found that 2-substituted phenazines could form cocrystals with 2,6-dimethylphenylboronic acid (DBA). These cocrystals exhibited red-shifted and enhanced luminescence relative to their individual components, especially 2NP-DBA whose luminescence efficiency was nearly 100 times higher than that of 2NP. By analyzing the single-crystal structures of the cocrystals and their components, enhanced hydrogen bonds and π-π interactions between molecules were detected in cocrystals, which suppressed the nonradiative transition pathways. Consequently, all three cocrystals demonstrated enhanced luminescence with strong continuous π-π interactions, which differed from the previously reported luminescence enhancement resulting from the destruction of π-π interactions. An in-depth investigation of these cocrystals can not only provide a better understanding of the structure-property relationship of organic luminescent materials, but also help develop organic luminescent materials with intense solid-state luminescence and strong π-π interactions. In addition, the optical response of these cocrystals to acidic vapors has been successfully applied in anti-counterfeiting.