Structure-activity relationships of arylamine-substituted pyrene derivatives: From molecular planarity to optoelectronic properties

In this study, we investigate the regulatory effects of substituent effects and molecular conformation on the photoelectric properties of pyrene-based luminescent materials, including a series of arylamine-substituted pyrene derivatives, N¹,N¹,N⁶,N⁶-tetraphenylpyrene-1,6-diamine (FBD001) to N,N'-((Pyrene-1,6-diyl)bis(1,4-phenylene))bis(4-methyl-N-(4-methyl-[1,1′-biphenyl]-3-yl)-[1,1′-biphenyl]-3-amine) (FBD006). Systematic first-principles calculations were performed using Gaussian, PySCF, and ORCA software, combined with wavefunction analysis using Multiwfn. Experimental validation yielded a series of compounds with high fluorescence quantum efficiency, with the highest value reaching 37.6%. The results indicate that the phenyl group is the key factor inducing molecular conformational distortion and reducing the molecular planarity parameter (MPP), whereas the steric hindrance effect of the methyl group has a limited influence on molecular planarity. The electron-donating methyl group induces red shifts in both absorption and emission peaks, whereas the synergistic effect of diphenyl and electron-donating alkyl groups leads to blue shifts and significantly enhances the oscillator strength. Moderate conformational distortion effectively suppresses aggregation-caused quenching (ACQ). The synergistic effect of diphenyl groups and electron-donating alkyl groups greatly enhances the radiative transition rate while suppressing non-radiative losses, thereby optimizing the fluorescence quantum efficiency. At the same time, the asymmetric structure (FBD003) exhibits excellent fluorescence quantum efficiency (34%) due to the large dipole moment and the solvation effect of polar solvents. And it has been proven that FBD005 and FBD006 have the potential to serve as excellent TADF materials. This study provides a clear structure-regulation strategy and theoretical support for the molecular design of high-efficiency blue luminescent materials.