Unveiling the Donor-Modulated Intramolecular Charge Transfer Phenomenon in the Excited-State Dynamics of Tetraphenylbuta-1,3-diene-Based Donor–Acceptor Derivatives

Abstract

Precise modulation of charge transfer (CT) characteristics in the excited state of aggregation-induced emission (AIE)-active organic emitters is essential for optimizing their performance mainly in optoelectronic applications such as organic light emitting diodes (OLEDs). In this work, two tetraphenylbuta-1,3-diene (TPB)-based donor–π–acceptor (D–π–A) derivatives, TPB–CHO–CBZ and TPB–CHO–PXZ, are designed by modifying the previously reported TPB–CHO–TPA, with the aim of systematically tuning the CT characteristics of the TPB backbones. Comprehensive photophysical and computational investigations reveal that the variation of the donor strength enables the fine control over the intramolecular CT behavior of these TPB derivatives, thereby influencing their excited-state properties such as solvatochromism, photoluminescence quantum yield, and emission lifetimes in both solution and solid states. Interestingly, temperature-dependent emission results provide an unusual enhancement of emission intensity accompanied by a blue shift for TPB–CHO–PXZ, suggesting the involvement of a twisted intramolecular charge transfer (TICT) state. Polarity and viscosity-dependent transient absorption spectroscopic studies have confirmed the presence of TICT character and its linear dependence of donor strength. Overall, the present findings demonstrate for the first time the significant structure–property correlations in TPB-based AIE systems, contributing to the rational design of high-performance optoelectronic materials for next-generation OLEDs and molecular electronics.