Photophysical Properties of Chiral Tetraphenylethylene Derivatives with the Fixed Propeller-Like Conformation

Abstract

The recent synthesized helical tetraphenylethylene (TPE) exhibits broad application prospects such as display, catalysis, and medical imaging. A full understanding of the intricate relation between structure and property is rather important to structural design and performance improvement. Here, we employed density functional theory (DFT) and timedependent DFT to calculate their ground-and excited-state structures, electron transition properties, optical rotation (OR), and second-order nonlinear optical (NLO) properties. For compound 1, the simulated UV−vis/CD spectra and calculated OR value are in reasonable agreement with the experimental ones, allowing us to reliably assign the electron transition and determine the absolute configuration. Intriguingly, TPE derivatives are excellent candidates for the second-order NLO materials in view of the large first hyperpolarizability values and intrinsic asymmetric structures. The intramolecular charge transfer cooperativity for this kind of compound was achieved through involvement of the donor and acceptor substituent groups or their combinations. The charge transfer within TPE plays a key role in determining the chiral origin and electron transition properties, whereas the contribution of peripheral phenyl rings is fairly small. Moreover, the designed compounds 5 and 7 are potential materials for the fluorescent probe.

Nonlinear nanophotonic devices in the ultraviolet to visible wavelength range

“…It has previously been used successfully as an imaging agent [155,155,180], and, in contrast to many fluorophores, it is well-known for exhibiting aggregation-induced-emission (AIE) [171,181] in which the emission intensity increases as the molecules aggregate. One study measured the nonlinear optical activity of a series of TPE structures ( Figure 6) [170]. In this study of eight different structures, the second-order NLO polarizabilities was increased as much as 27 times by tuning the substituent groups and their positions even when the primary chemical composition (the TPE core) was relatively unchanged.…”

“…As mentioned, the n2 depends on the molecular density and molecular orientation with the optical field. One study measured the nonlinear optical activity of a series of TPE structures (Figure 6) (170). In this study of eight different structures, the second-order NLO polarizabilities was increased as much as 27 times by tuning the substituent groups and their positions even when the primary chemical composition (the TPE core) was relatively unchanged.…”

“…TPE is an intriguing material with a unique chemical structure. In previous work, it has demonstrated large NLO coefficients, particularly the first hyperpolarizability or the second-order NLO coefficient, and the four-leaf clover architecture facilitates the design of push-pull chromophores that allows electron charge transfer across the π conjugation of the TPE molecule [170][171][172][173][174][175][176][177][178][179]. It has previously been used successfully as an imaging agent [155,155,180], and, in contrast to many fluorophores, it is well-known for exhibiting aggregation-induced-emission (AIE) [171,181] in which the emission intensity increases as the molecules aggregate.…”

Aggregation‐induced emission materials for nonlinear optics

“…For instance, Liu et al designed the helical TPE compound with the inherent chirality and fixed propeller-like conformation, and predicted its second-order NLO properties via density functional theory (DFT) and time-dependent DFT calculations. [128] Nevertheless, the realistic reports about AIE molecules exhibiting SHG responses are rare. The classical AIEgen TPE also has been certified to be the SHG active.…”

Design and Development of Axially Chiral Bis(naphthofuran) Luminogens as Fluorescent Probes for Cell Imaging

“…[17][18][19][20][21][22][23][24][25][26][27][28] Nevertheless, designs trategies that employa mino acids and sugars lead to AIEgens with poor thermal stability that lacks cope forw avelengthtunability.B INOL, vastly explored in asymmetric catalysis [29][30][31][32][33] and bearing at remendous resemblance to the rotorlike structures of typical AIEgens such as tetraphenylethene (TPE) or tetraphenylsiloles, has been used to design chiralluminogens through the appendage of well-known AIEgensa ta ppropriate positions of BINOL ( Figure 1). [34][35][36] However, these existing design strategies are mostly limited to scaffolds such as TPE or tetraphenylsiloles. The dearth of protocols to generate chiral AIEgens withouta ny AIEgens (e.g.,T PE or tetraphenylsilole) externally tagged to the chiral scaffold remains al ongstanding challenge.…”