Yonggang Yang,Tingting Ye,Yang Liu,Zhinan Jiang,Tiantian Guan,Chaochao Qin,Chunsheng Zhuang,Yufang Liu
Triphenylamine (TPA) molecules are extensively employed in optoelectronic materials and photochemical reactions. The present research examines the ultrafast dynamics of photocyclization reaction utilizing transient absorption (TA) spectroscopy. In the femtosecond TA spectrum, the excited state absorption (ESA) signal for TPA at 627 nm diminishes within 2.5 ns, while a triplet-triplet absorption (TTA) signal emerges at 524 nm, gradually decaying over 25.2 ns in the subsequent nanosecond TA spectrum. As the TTA signal diminishes, a new positive TTA signal corresponding to the photocyclization intermediate, N-phenyl-4a,4b-dihydrocarbazole (NPDHC), appears at 426 nm. Following the decay of the TTA signal of NPDHC over 494.5 ns, another positive absorption signal is observed at 612 nm, which is associated with the ESA signal from both NPDHC and N-phenylcarbazole. In contrast, Tetra-N-phenylbenzidine (TPB) and N,N′-Bis(3-methylphenyl)-N,N′-bis(phenyl)benzidine (TPB-CH 3 ) exhibit only a positive ESA signal and a negative stimulated emission (SE) signal, with no detectable TTA signal or cyclization product signal. Theoretical simulations reveal that the spin-orbit coupling (SOC) constant of TPA (0.26 cm −1 ) is higher than that of the two other molecules (0.09 cm −1 ). This research presents direct observations of the triplet-triplet intermediates in the photocyclization reaction of TPA in real-time.
ABSTRACT The extensive use of dihydrocoumarins across several fields has spurred the need to develop innovative and efficient synthetic strategies for their synthesis. In this work, we present a novel chemo-enzymatic cascade system for the synthesis of dihydrocoumarin derivatives from biomass-derived cinnamic acid and its derivatives. The key features of this approach include the photochemical E → Z isomerization/photocyclization of cinnamic acid derivatives and the enzymatic (OYE1) reduction of the intermediate coumarins to the target dihydrocoumarin derivatives. Remarkably, the utilization of microreactors in the photochemical process facilitated a complete photocyclization transformation within 1 hour under continuous flow conditions. In contrast, the batch reaction achieved a 97 % conversion but took 6 hours to accomplish. Furthermore, deep eutectic solvents (DESs) were introduced to effectively overcome the incompatibility issues between the catalysts and solvents in chemo-enzymatic cascade reactions. Our platform showcases a promising model for rationalizing incompatibilities in other such reactions, setting the stage for the development of more efficient chemo-biocatalytic synthesis strategies.
Ye Du,Chao-Ran Huang,Zhe-Kun Xu,Wei Hu,Peng-Fei Li,Ren-Gen Xiong,Zhong-Xia Wang
Organic photochromic compounds have been widely investigated for optical memory storage and switches. Very recently, we pioneeringly discovered optical control of ferroelectric polarization switching in organic photochromic salicylaldehyde Schiff base and diarylethene derivatives, differently from the traditional ferroelectrics. However, the study of such intriguing photo-triggered ferroelectrics is still in its infancy and relatively scarce. In this manuscript, we synthesized a pair of new organic single-component fulgide isomers, (E and Z)-3-(1-(4-(tert-butyl)phenyl)ethylidene)-4-(propan-2-ylidene)dihydrofuran-2,5-dione (1E and 1Z). They undergo prominent photochromism from yellow to red. Interestingly, only polar 1E has been proven to be ferroelectric, while the centrosymmetric 1Z does not meet the basic requirement for ferroelectricity. Besides, experimental evidence shows that the Z-form can be converted to the E-form by light irradiation. More importantly, the ferroelectric domains of 1E can be manipulated by light in the absence of an electric field, benefiting from the remarkable photoisomerization. 1E also adopts good fatigue resistance to the photocyclization reaction. As far as we know, this is the first example of organic fulgide ferroelectric reported with photo-triggered ferroelectric polarization response. This work has developed a new system for studying photo-triggered ferroelectrics and would also provide an expected perspective on developing ferroelectrics for optical applications in trap future.
危险品化学品经营许可证（带存储）