Modular three-component synthesis, photophysics, and electronic structure of solid-state and aggregate luminescent α-sulfenylated aroyl-S,N-ketene acetals

Abstract

α-Sulfenylated aroyl-S,N-ketene acetals are accessible from acyl chlorides, benzothiazolium salts, and N-thiosuccinimides via consecutive one-pot three-component synthesis in a modular fashion. The resulting merocyanines are prone to equilibrating E–Z-isomerization in solution, whereas preferred configurations can be found in the crystal structures. TD-DFT calculations indicate that the longest wavelength absorption bands of the chromophores in solution can be rationalized as HOMO–LUMO charge-transfer transitions of the energetically favored E-configurations. The α-sulfenylated aroyl-S,N-ketene acetals exhibit pronounced solid-state emission, with emission colors ranging from blue to orange and emission upon induced aggregation is observed in acetonitrile/water mixtures with significant quantum yields at water contents of 80%.