Organolithium-Mediated Postfunctionalization of Thiazolo[3,2-c][1,3,5,2]oxadiazaborinine Fluorescent Dyes.

An effective method for transition-metal-free postfunctionalization of thiazolo[3,2-c][1,3,5,2]oxadiazaborinine dyes via direct lithiation of the 1,3-thiazole ring was developed. The reaction allows valuable regioselective C-H modification of these N,O-chelated organoboron chromophores incorporating different groups, including C-, Hal-, Si-, S-, Se-, and Sn-substituents. As a result, a library of novel fluorescent 1,3-thiazole-based organoboron complexes has been synthesized and characterized. The influence of the donor/acceptor strength of the substituent E on the photophysical properties has been established. The compound with a bulky lipophilic substituent (SnBu3) exhibits a relatively high solid-state photoluminescence quantum yield of 44%.

Application of the Suzuki-Miyaura Reaction for the Postfunctionalization of the Benzo[4,5]thiazolo[3,2- c][1,3,5,2]oxadiazaborinine Core: An Approach toward Fluorescent Dyes.

A fluorescent dye based on the 8-brominated benzo[4,5]thiazolo[3,2- c][1,3,5,2]oxadiazaborinine core was synthesized from benzo[ d]thiazol-2-amine. The new boron complex can be effectively modified by a palladium-catalyzed Suzuki-Miyaura cross-coupling reaction with (het)arylboronic acids. This reaction allows a valuable regioselective postfunctionalization of 1,3,5,2-oxadiazaborinine chromophores with different aromatic substituents. The solutions of obtained target complexes in organic solvents demonstrate high fluorescence quantum yields. The compound with a 4-cyanophenyl group at benzothiazole unit (Ar = 4-C6H4CN) exhibits a comparatively high fluorescence quantum yield of 0.31 in the solid state.

Benzo[4,5]thiazolo[3,2- c][1,3,5,2]oxadiazaborinines: Synthesis, Structural, and Photophysical Properties.

A family of highly emissive benzo[4,5]thiazolo[3,2- c][1,3,5,2]oxadiazaborinines, conjugated with the donor 4-dimethylaminophenyl group, was designed and synthesized. Their photophysical, both in solution and in the solid state, and structural properties were investigated. The influence of donor and acceptor substituents (R) in the benzothiazole unit on photophysical properties of complexes was found out. The tetrafluorobenzothiazole analogue exhibits nonbonded nuclear spin-spin coupling between fluorines from the BF2 group and α-fluorine atom at the benzene ring. Additionally, this boron complex demonstrates a comparatively high solid-state fluorescence quantum yield (Φ = 0.34).