Electron Push-Pull Effects for Solution and Solid-State Emission Control in Naphthalene 2,7-Position-Based Donor-Acceptor-Donor

Organic luminescent materials have garnered significant attention owing to their potential applications, particularly due to their inherent flexibility and ease of processability. Accordingly, the development of strategies that enable precise control over both intra- and intermolecular interactions, which directly influence their emission properties, is of paramount importance. In this study, a series of naphthalene (NAP) 2,7-position-based donor-acceptor-donor (D-A-D) compounds were designed and synthesized to investigate the electron push-pull effect on intramolecular and intermolecular interactions. The energy bandgaps of the compounds were controlled by the electron push-pull effect, resulting in red-shifted emission within 48 nm in the order of increasing electron-donating ability in solution state. Experimental data and theoretical calculations show that the intramolecular charge transfer (ICT) properties of D-A-D compounds are systematically controlled by electron push-pull effects. In particular, the solid-state emission of the compounds showed a redshift in the same order as that observed in solution. This solid-state emission behavior is explained by the electron push-pull effect-dependent intermolecular interactions. Consequently, an efficient single-molecule and multi-molecule emission control strategy by electron push-pull effect in NAP 2,7-position-based D-A-D was successfully demonstrated.