Solid‐State Emission and Aggregate Emission of Aroyl‐ S,N‐Ketene Acetals Are Controlled and Tuned by Their Substitution Pattern

Abstract

Aroyl‐S,N‐ketene acetals are a novel highly diverse class of aggregation‐induced emission fluorogens (AIEgens) with a plethora of interesting properties. An expanded compound library of more than 110 dyes set the stage for the first qualitative control and tuneability of all aspects of their photophysical properties. The interplay of substituents not only allows tuning and prediction of the emission color, but also of the intensity, and quantum yields both in solids and in the aggregated state; these can be rationalized by scrutinizing intermolecular interactions in the crystalline solid state.

Alkynylated and triazole-linked aroyl-S,N-ketene acetals: one-pot synthesis of solid-state emissive dyes with aggregation-induced enhanced emission characteristics

“…Since the AIE or AIEE properties are largely defined by the aroyl- S , N -ketene acetal component, the aggregation behavior of compounds 3 is mostly relatively similar, especially with respect to the observed emission color. Again, the presence of the N -benzyl moiety sets the stage for occurrence of AIE as previously shown 36 , 37 . The aggregation-induced enhanced emission results as a consequence of the more extended alkynylated π-systems that also possess some inherent emission and solution, which enhances upon aggregation.…”

“…The quantum yields Φ f of both the TMS-protected and deprotected systems are 0.09 to 0.10, which are also higher than the other alkyne systems. This can be explained by the correlation between solid-state fluorescence quantum yield and substituent size established for the core systems 1 36 , 37 . Since the substituents of systems 4 are comparatively small substituents, a similar relationship can be assumed.…”

“…The importance, in particular, of the para -position of the benzyl moiety of the aroyl S , N -ketene acetals has been emphasized previously 36 , 37 . One possibility to introduce further functionalities and to modify the benzyl moiety is the Sonogashira reaction.…”

“…Since the factors influencing the substitution of the aroyl- S , N -ketene acetal core motif were discussed extensively in previous works, the focus is now on the influence of the variation of the alkynyl moiety on the photophysical properties. The longest wavelength absorption maximum λ abs,max occurs at wavelengths from 380 to 383 nm, which can be attributed to the aroyl- S , N -ketene acetal motif 36 , 37 . Only for the cyano-substituted derivatives 3t and 4c , as expected, a bathochromic shift of the longest wavelength absorption maximum to 400 nm can be observed.…”

“…Aroyl- S , N -ketene acetals have been proven since their recent renaissance as versatile and easily accessible AIEgens with a rich bouquet of properties 36 , 37 . In previous works, we already succeeded in expanding the reaction sequence in a one-pot fashion to synthesize bi- and multichromophores 38 , 39 .…”