Acetylene Derivatives of Cationic Diazaoxatriangulenes and Diaza [4]Helicenes ‐ Access to Red Emitters and Planar Chiral Stereochemical Traits

Article Article scientifique Article Acetylene Derivatives of Cationic Diazaoxatriangulenes and Diaza [4]Helicenes ‐ Access to Red Emitters and Planar Chiral Stereochemical Traits eng 2022-02-09 2022-03-10 author Ondrisek Pavol 0000-0003-4648-6352 864061 author Elie Margaux 0000-0002-1424-9144 886073 author Pupier Marion 0000-0001-6033-2910 812717 author de Aguirre Adiran 0000-0001-7991-6406 935526 author Poblador Bahamonde Amalia Isabel 0000-0002-5266-914X 797442 author Besnard Céline 0000-0001-5699-9675 682138 author Lacour Jérôme 0000-0001-6247-8059 99165 e202104405 10.1002/chem.202104405 35040214 0947-6539 https://onlinelibrary.wiley.com/doi/10.1002/chem.202104405 Cationic triangulenes, and related helicenes, constitute a rich class of dyes and fluorophores, usually absorbing and emitting light at low energy, in the orange to red domains. Recently, to broaden the scope of applications, regioselective late-stage functionalizations on these core moieties have been developed. For instance, with the introduction of electron-donating groups (EDGs), important bathochromic shifts are observed pushing absorptions towards or in the near-infrared (NIR) spectral domain while emissive properties disappear essentially completely. Herein, to upset this drawback, acetylene derivatives of cationic diazaoxa triangulenes (DAOTA) and [4]helicenes are prepared (16 examples). Contrary to other EDG-functionalized derivatives, C≡C− functionalized products remain broadly fluorescent, with red-shifted absorptions (Δλabs up to 25 nm) and emissions (Δλem up to 73 nm, ΦPL up to 51 %). Quite interestingly, a general dynamic stereoisomerism phenomenon is evidenced for the compounds derived from achiral DAOTA cores. At low temperature in 1H NMR spectroscopy (218 K), N−CH2 protons become diastereotopic with chemical shifts differences (Δδ) as high as +1.64 ppm. The signal coalescence occurs around 273 K with a barrier of ∼12 kcal mol−1. This phenomenon is due to planar chiral conformations (Sp and Rp configurations), induced by the geometry of the alkyl (n-propyl) side-chains next to the acetylenic substituents. Ion pairing studies with Δ-TRISPHAT anion not only confirm the occurrence of the chiral conformations but evidence a moderate but definite asymmetric induction from the chiral anion onto the cations. Finally, DFT calculations offer a valuable insight on the geometries, the corresponding stereodynamics and also on the very large difference in NMR for some of the diastereotopic protons. NIR dyes and fluorophores VT NMR Cationic helicenes Planar chirality Stereodynamics Triangulenium cations Dewey 540 36 Département de chimie organique 141 false 760 Groupe Lacour 1055 Groupe Poblador Bahamonde https://doi.org/10.26037/yareta:7iyohmxz7fgcjjuked6ivbog6u Chemistry 28 15 81871323-58b5-4e9c-9f85-4d084e7b2974 Article (Published version) Public 1234.pdf 8847953 application/pdf CC BY-NC-4.0 Vignette Public chem202104405-toc-0001-m.jpg 251416 image/jpeg openAccess Faculté des sciences / Section de chimie et biochimie / Département de chimie organique

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Acetylene Derivatives of Cationic Diazaoxatriangulenes and Diaza [4]Helicenes ‐ Access to Red Emitters and Planar Chiral Stereochemical Traits	Chemistry			2022	273	98

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