The Variance of Photophysical Properties of Tetraphenylethene and Its Derivatives during Their Transitions from Dissolved States to Solid States

Abstract

The study of aggregation-induced emission luminogens (AIEgens) shows promising perspectives explored in lighting, optical sensors, and biological therapies. Due to their unique feature of intense emissions in aggregated solid states, it smoothly circumvents the weaknesses in fluorescent dyes, which include aggregation-caused quenching of emission and poor photobleaching character. However, our present knowledge of the AIE phenomena still cannot comprehensively explain the mechanism behind the substantially enhanced emission in their aggregated solid states. Herein, to systematically study the mechanism, the typical AIEgens tetraphenylethene (TPE) was chosen, to elucidate its photophysical properties, the TPE in THF/H2O binary solvents, TPE in THF solvents depending on concentration, and the following direct conversion from a dissolved state to a precipitated solid state were analyzed. Moreover, the TPE derivatives were also investigated to supply more evidence to better decipher the generally optical behaviors of TPE and its derivatives. For instance, the TPE derivative was homogeneously dispersed into tetraethyl orthosilicate to monitor the variance of photophysical properties during sol–gel processing. Consequently, TPE and its derivatives are hypothesized to abide by the anti-Kasha rule in dissolved states. In addition, the factors primarily influencing the nonlinear emission shifting of TPE and its derivatives are also discussed.

Tetraphenylethene Derivatives Bearing Alkylammonium Substituents: Synthesis, Chemical Properties, and Application as BSA, Telomere DNA, and Hydroxyl Radical Sensors

“…Figure 5c shows the changes in the PL spectra of aqueous solutions of TPE-C(4)N + Me 3 Br − with the addition of Fenton's reagent. The computational calculations revealed that the PL peaks of TPE at 459 nm and 540 nm corresponded to the S 3 → S 0 and S 1 → S 0 transitions, respectively [33]. As shown in Figure 5c, the peak at approximately 470 nm, which corresponds to S 1 → S 0 transition, disappeared with the addition of four equimolar amounts of Fenton's reagent.…”

To unravel the factor to dominantly impact the emission energy of crystal diphenyldibenzofulvene derivatives

“…Generally, the AIEgens are typically built in the π -conjugated molecular architectures with a lot of branching groups to prevent fluorescence quenching in aggregated states. [22][23][24][25] Additionally, the expanded π -conjugated molecular structures are commonly believed to produce the emission with a longer wavelength (lower energy), which can be used to modify the emission wavelength of AIEgens. [26][27][28][29] The optical behaviors ofπ -conjugated AIEgens, however, are considerably more complex and do not simply follow this empirical principle.…”

The crucial role of planar π-conjugated segment in the molecular conformation of diphenyldibenzofulvene derivatives in crystals contributing to reducing emission energy

“…Generally, the AIEgens are designed in the π -conjugated molecular structures with a lot of branched groups to prevent fluorescent quenching in aggregated states. [32][33][34][35][36][37][38] In addition, to adjust the emission wavelength of AIEgens, the expanded π -conjugated molecular structures are commonly believed to result in the emission with a longer wavelength (lower energy). [39][40][41][42] However, the optical behaviors of π -conjugated AIEgens perform much more complicated and do not simply follow this empirical principle.…”