Dendron‐Containing Tetraphenylethylene Compounds: Dependence of Fluorescence and Photocyclization Reactivity on the Dendron Generation

Abstract

The synthesis and characterization of four dendron-containing tetraphenylethylenes (TPEs), 1(1)-1(4), were synthesized, along with a TPE compound that contained four OCH(2) Ph groups (referred to as 1(0)) for comparison. Photophysical studies revealed that the TPE core became emissive after linking dendrons onto its periphery. Moreover, the fluorescence intensity was significantly enhanced when high-generation dendrons were linked onto the TPE core; the fluorescence intensity increased in the following order: 1(1)<1(2)<1(3)<1(4). This phenomenon was tentatively attributed to an enhancement in the energy barrier for internal rotation and torsion of the TPE core to which four dendrons were connected. In addition, the photocyclization of the TPE core into the respective 9,10-diphenylphenanthrene was facilitated when high-generation dendrons were linked to the TPE core. Again, the photocycliztion reactivity increased in the following order: 1(1)<1(2)<1(3)<1(4). We found that the fluorescence and photocyclization reactivity of TPE could be modulated by covalent interactions with dendrons, and such modulation was strongly dependent on the dendron-generation.

Mitochondrion‐Specific Live‐Cell Bioprobe Operated in a Fluorescence Turn‐On Manner and a Well‐Designed Photoactivatable Mechanism

“…This result is different from the previous reports, in which phenyl rings are mainly involved in the photocyclodehydrogenation reaction. [ 32,39,40 ] c -TPP3M is less conjugated than o -TPP3M, as revealed by its bluer absorption maximum (Table 1 ). However, it shows a much effi cient light emission in solution with a Φ F as high as 69% due to the activation of the RIM process by the photocyclodehydrogenation reaction.…”

“…The pyridinium ring is thus comparatively more reactive than the other phenyl rings in the excited state, making its preferred participation in the photocyclodehydrogenation reaction. If the photocyclodehydrogenation of o -TPP3M occurs in a general way, [ 32,39,40 ] a product, named as c -TPP3M(b), will be obtained. Its structure was simulated, optimized, and provided in Figure 2 e. Comparing c -TPP3M with c -TPP3M(b) in their most optimized confi guration, it was found that c -TPP3M was thermodynamically more stable than c -TPP3M(b) with 21.47 kJ mol −1 lower energy.…”

“…Besides aggregation, many physical and chemical methods have been developed to activate the RIR process. [29][30][31][32] Among them, photocyclodehydrogenation has attracted our attention due to the participation of light with appropriate wavelengths. [ 29,32 ] On the other hand, some AIE molecules with electron-donating (D) and accepting (A) groups also show the twisted intramolecular charge-transfer (TICT) effect.…”

“…[29][30][31][32] Among them, photocyclodehydrogenation has attracted our attention due to the participation of light with appropriate wavelengths. [ 29,32 ] On the other hand, some AIE molecules with electron-donating (D) and accepting (A) groups also show the twisted intramolecular charge-transfer (TICT) effect. [ 25,33 ] As stated in the literature, the TICT effect will redshift and quench the light emission of a luminophore when the surrounding environment becomes Photoactivatable fl uorophores that can convert from a weakly emissive or nonemissive state to a fl uorescent state upon irradiation, operated in a fl uorescence turn-on manner, are powerful tools in biochemical and biological research such as cell lineage in development, [ 1,2 ] macromolecule tracking in living cells, [ 1,2 ] …”

Photoinduced Synthesis of Dual‐Emissive Tetraphenylethene‐Based Dendrimers with Tunable Aggregates and Solution States Emissions

“…To tackle our challenge, we constructed dendrimers that were multifunctionalized at the periphery with TPE and, in a step, photoconvert some of the TPE to DPP units. The fundamentals of photoinduced conversion of TPE to DPP are well established, and the conversion is controlled by the irradiation time and solvent. We used irradiation time to control the conversion of TPE to DPP in order to access heterofunctional dendrimers that were dual emissive.…”