91093-21-9Relevant articles and documents
Regulation of an Ambient-Light-Induced Photocyclization Pathway (Norrish–Yang Versus 6π) by Substituent Choice
Liu, Hui,Gao, Hu,Wang, Sisi,Yao, Shengxin,Wu, Fan,Zhao, Yue,Chan, Kin Shing,Shen, Zhen
supporting information, p. 12418 - 12430 (2020/09/07)
Photocyclization, irrespective of whether multiple steps (e.g., Norrish–Yang cyclization) or a single concerted step (e.g., 6π photocyclization) are involved, is an intramolecular photochemical process resulting in the formation of one new single bond to afford a ring system. In particular, visible-light-induced photocyclization offers a green and sustainable route to organic cyclic compounds that are difficult to access by thermal reactions. Herein, we describe the ambient light-induced intramolecular photocyclization of a series of donor/acceptor chromophores 1 d–3 d containing two types of photoresponsive motifs, namely an electron-deficient BF2-chelated ketone fused with an electron-rich thiophene, and probe the solution-phase and solid-state photochromic performance of these compounds. The results reveal that simple variation of R substituents on the diaryl moiety allows one to control the intramolecular photocyclization mechanism with high photochemical selectivity, e.g., under ambient light, methyl-substituted 1 d and 2 d undergo reversible 6π photocyclization, whereas ethyl-substituted 3 d exclusively undergoes irreversible Norrish–Yang photocyclization. Single-crystal X-ray analysis of Norrish–Yang cyclization products reveals the formation of four pairs of conformational enantiomers differing in the dihedral angle between benzothiophene and the BF2 core, namely (±)N-3 d@68°, (±)N-3 d@-77°, (±)N-3 d@-78°, and (±)N-3 d@-102°. The UV/Vis absorption spectra of 1 d–3 d cover a broad visible-light region (380–572 nm), while DFT and TD-DFT calculations reveal that absorption in this region is dominated by the charge-transfer (CT) transition from the thiophene-centered HOMO to the LUMO of the electron-deficient π-conjugated BF2-chelated unit and the n→π* and π→π* transitions within the latter unit. The spatial separation of the HOMO and LUMO of these dyes promotes triplet-state generation and self-photosensitizes intramolecular photocyclization in the visible-light region. Three-dimensional time-resolved and steady-state emission spectra of 3 d show that the Norrish–Yang photocyclization takes place within milliseconds with excellent conversion efficiency (96 %).
Thermally Irreversible Photochromic Systems. Reversible Photocyclization of 1,2-Bis(benzothiophen-3-yl)ethene Derivatives
Uchida, Kingo,Nakayama, Yasuhide,Irie, Masahiro
, p. 1311 - 1315 (2007/10/02)
1,2-Bis(benzothiophen-3-yl)ethene derivatives, which possess thermally irreversible and fatique resistant photochromic properties, were synthsized. cis-1,2-Dicyano-1,2-bis(2-methylbenzothiophen-3yl)ethene Ia and 2,3-bis(2-methylbenzothiophen-3-yl)maleic anhydride 2a underwent reversible photocyclization to produce red-colored closed-ring forms with λmax at 507 and 544 nm, respectively.The closed-ring forms were stable for more than 3 weeks at 80 deg C.The coloration/decoloration (ring closure/opening)cycles were able to be repeated more than 1E4 times with keeping the adequate photochromic performance.
