Festkörperemittierende Aroyl‐S,N‐Ketenacetale mit steuerbaren aggregationsinduzierten Emissionseigenschaften

Abstract

N‐Benzyl‐aroyl‐S,N‐ketenacetale können durch die Kondensation von Aroylchloriden und N‐Benzyl‐2‐methylbenzothiazolium‐Salzen in guten bis ausgezeichneten Ausbeuten dargestellt werden, wodurch eine Substanzbibliothek bestehend aus 35 Chromophoren mit intensiver Festkörperemissions‐ und aggregationsinduzierten Emissions‐Eigenschaften aufgebaut werden konnte. Mittels Variation des Substituenten von elektronenschiebend bis elektronenziehend kann die Emissionsfarbe der Festkörperfluoreszenz gezielt von blau bis rot eingestellt werden.

Communication of Bichromophore Emission upon Aggregation – Aroyl‐S,N‐ketene Acetals as Multifunctional Sensor Merocyanines

“…While the triarylamine and phenylene carbazol bichromophores 4 h and 4 t exhibit only low Φ f values of 0.01, the tetraphenylethene bichromophore 4 ad has an increased Φ f of 0.06, presumably due to the solid‐state emission of both chromophores. [ 9a , 15 ] Three model bichromophores 4 h , 4 t , and 4 ad were selected as combinations of the red emissive p ‐cyano‐phenyl‐substituted aroyl‐ S,N ‐ketene acetal component and a blue luminescent chromophore, representing complementary emission partners. While compounds 4 t and 4 ad have lifetimes τ of 1.51 ( λ em =555 nm) and 2.34 ns ( λ em =566 nm) at λ exc =330 nm, para ‐cyanophenyl triarylamine bichromophore 4 h reveals a lifetime τ of 13.1 ns, which is astonishingly long for a red emitting fluorophore ( λ em =600 nm) (Figure 2 ).…”

“…The absorption maxima of the series of aroyl‐ S,N ‐ketene acetal bichromophores 4 vary between 290 and 400 nm. While maxima around 400 nm can be ascribed to the aroyl‐ S,N ‐ketene acetal, [15] maxima covering a wavelength region from 290 to 330 nm can be unequivocally attributed to various blue emitters. Indeed, the bichromophores′ absorption spectra match with the sum of the constituting chromophores.…”

“…Optimization of a model reaction (see Supporting Information, chapter 3) with tetrakis(triphenylphosphane)palladium(0) as a catalyst and cesium carbonate as a base set the stage for concatenating a condensation-Suzuki coupling sequence in the sense of a consecutive three-component reaction in a one-pot fashion. Employing acid chlorides 1 bearing electron-donating or electron-withdrawing substituents or heterocyclic moieties (see Supporting Information, Table S7), N-(p-bromobenzyl) 2-methyl benzothiazolium bromide (2) [15] and different boronic acid esters 3 comprising of blue-emitting core structures, such as triphenylamine, tri-phenylethene-dicarbazole, phenylcarbazole, perylene, and tetraphenyl-ethene, [17] a library of 31 aroyl-S,Nketene acetal bichromophores 4 was synthesized in moderate to excellent yields of 31-96 % (Figure 1).…”

“…Absorption and emission studies in the solid state Previously, we showed that aroyl-S,N-ketene acetals account for a rainbow-type tuning of solid-state emission color [15] by variation of the electronic nature of the substituents in paraposition of the aroyl moiety. [15,18] In a similar fashion, the bichromophores 4 can be readily distinguished by their solidstate emission color ranging from blue to orange-red depending both on the substituents in para-position of the aroyl moiety (R 1 ) and the second chromophore (R 2 ) (Figure 2).…”

“…Absorption and emission studies in the solid state Previously, we showed that aroyl-S,N-ketene acetals account for a rainbow-type tuning of solid-state emission color [15] by variation of the electronic nature of the substituents in paraposition of the aroyl moiety. [15,18] In a similar fashion, the bichromophores 4 can be readily distinguished by their solidstate emission color ranging from blue to orange-red depending both on the substituents in para-position of the aroyl moiety (R 1 ) and the second chromophore (R 2 ) (Figure 2). Phenylene carbazole bichromophore 4 r exhibits the shortest wavelength emission maximum (λ em = 497 nm), while the paracyanophenyl triarylamine bichromophore 4 h displays the most red-shifted emission maximum (λ em = 600 nm) (Figure 2; for details see Supporting Information, chapter 7).…”