Details

Autor(en) / Beteiligte

• Bałczewski, Piotr
• Kowalska, Emilia
• Różycka‐Sokołowska, Ewa
• Skalik, Joanna
• Owsianik, Krzysztof
• Koprowski, Marek
• Marciniak, Bernard
• Guziejewski, Dariusz
• Ciesielski, Witold

Titel

Mono‐Aryl/Alkylthio‐Substituted (Hetero)acenes of Exceptional Thermal and Photochemical Stability by the Thio‐Friedel–Crafts/Bradsher Cyclization Reaction

Ist Teil von

• Chemistry : a European journal, 2019-11, Vol.25 (62), p.14148-14161

Ort / Verlag

Germany: Wiley Subscription Services, Inc

Erscheinungsjahr

2019

Quelle

Wiley-Blackwell subscription journals

Beschreibungen/Notizen

• The highly substituted mono‐aryl/alkylthio‐(hetero)acenes prepared in this study have been found to be thermally more stable (Tdecomp.=331–354 °C) than the known di‐aryl/alkylthio‐substituted acenes by an average of 25 °C. They are also much more photostable at 254 and 365 nm (in both argon and air) than the parent anthracene and other reported anthracenes. The most photostable aryl/alkylthio‐anthracenes at 254 nm were found to be 60–70 (in air) and 130 (in argon) times more stable in solution than the unsubstituted anthracene, and much more stable than known EDG/EWG‐substituted anthracenes (EDG=electron‐donating group, EWG=electron‐withdrawing group) with an extended aromatic core. Furthermore, the acenes showed significantly higher photostability at 365 nm in both air and argon. The anthracenes were obtained by the novel thio‐Friedel–Crafts/Bradsher cyclization reaction of hitherto unknown [o‐(1,3‐dithian‐2‐yl)aryl](aryl)methyl thioethers. The developed approach provides a general access to mono‐aryl/alkylthio‐substituted (hetero)acene frameworks containing at least three fused (hetero)aromatic rings. The characteristic feature of this approach, which leads to highly substituted acenes, is that the substituents, unlike in other methods, may be introduced at an early stage of the synthesis. DFT and TD‐DFT calculations confirmed the stabilizing role of the aryl/alkylthio substituent in the mono‐aryl/alkylthio‐substituted anthracenes, which are the most stable anthracenes prepared to date. Their high photostability is mainly due to the quenching of singlet oxygen by the acene and the quenching of the acene S1 state by molecular oxygen. The leading role of one aryl/alkylthio group in the high photostabilization (254 and 365 nm, in both Ar and O2) of highly substituted and thermally stable mono‐aryl/alkylthio‐(hetero)acene fluorophores, obtained by a novel thio‐Friedel–Crafts/Bradsher cyclization reaction, has been examined and explained by means of DFT and TD‐DFT calculations (see figure).