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A series of N,N′‐diarylamine‐modified hemithioindigos (HTIs) were synthesized and characterized. Photochemical Z/E isomerization around the C=C double bond occurred for all novel HTIs in various solvents. Due to a strong donor–acceptor π‐conjugated structure, the novel HTIs exhibited a strong red shift and clear solvatochromism in steady‐state absorption and fluorescence spectroscopic measurements, respectively. An intramolecular charge transfer (ICT) from the diarylamine‐substituted stilbene component (donor) to the thioindigo part (acceptor) strongly affects the isomerization behavior. HTI is the dominating photochromic unit in this system but the substitution pattern on the triarylamine (TAA) moiety causes unusually strong changes in the photostationary states (PSS) and thermal stabilities. Electron‐withdrawing substituents (such as cyano groups) strongly improve thermal stabilities and enrich the E‐isomer content in the photostationary state, however electron‐donating substituents play a converse effect, for example, in the solvents hexane and tetrachloroethene. The low E ratio in the PSS in more polar solvents, such as acetonitrile, can be explained by a very fast thermal back reaction and formation of a new decay state in OMe‐substituted compounds.

SummaryPhotochromic pyrans for applications in material and life sciences were synthesized via palladium-mediated cyanation, carbonylation and Sonogashira cross-coupling starting from bromo-substituted naphthopyran 1 and benzopyrans 2a/b. A novel photoswitchable benzopyran-based ω-amino acid 6 for Fmoc-based solid-phase peptide synthesis is presented. The photochromic behaviour of the 3-cyano-substituted benzopyran 5a was investigated by time-resolved absorption spectroscopy in the picosecond time domain.

Amino acids U 0400Photomodulation of Ionic Current Through Hemithioindigo-Modified Gramicidin Channels. -A novel hemithioindigo-based amino acid (IV) is prepared and incorporated into the model ion channel gramicidin. The ionic current through the channel can be modulated by photoisomerization of that amino acid. -(LOUGHEED, T.; BORISENKO, V.; HENNIG, T.; RUECK-BRAUN, K.; WOOLLEY*, G. A.; Org.