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

Abstract

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 (SnBu 3 ) exhibits a relatively high solid-state photoluminescence quantum yield of 44%.

Recent advances in the synthesis of luminescent tetra-coordinated boron compounds

“…From these results it was concluded that the cyano group plays an important role in acquiring strong ICT behavior and AIE and mechanochromic properties. Among the seven BF 2 -compounds (186)(187)(188)(189)(190)(191)(192) studied by Lu and co-workers 176 186 and 189 exhibited the AIE phenomenon and mechanochromism, respectively. In 2017, Gao et al 178…”

“…In an analogous fashion benzothiazole, pyrazoline, oxadiazole, benzimidazole, benzoxazole, thiadiazole, imidazole, thiazole, imidazole-pyridine and phenanthroimidazole based B-N coordinated tetra-coordinated boron compounds were synthesized and studied for their optical properties. [170][171][172][173][174][175][176][177][178][179][180][181][182][183][184][185][186][187][188][189] Among the different boron-compounds reported: 180, 181, 188 184, 185, 177 186-192, 176 and 193 178 (Fig. 20) exhibited aggregation induced emission (AIE) and reversible mechanochromic properties.…”

“…Solid state emission experiments revealed that 197 exhibited high contrast reversible mechanochromic behaviour as well. In 2020, the Potopnyk group 187 developed a transition-metal-free post-functionalization of thiazole based organoboron compounds by the direct lithiation of the 1,3-thiazole ring. This method allowed a variety of substitutions including –C, –Hal, –Si, –S, –Se and –Sn substituents by the regioselective C–H modification of the organoboron compounds ( 198 ).…”

Triphenylamine-based N,O-bidentate BF2 complexes: synthesis and photophysical properties

“…Organoboron fluorescent dyes with unique optical properties such as high molar extinction coefficients, fluorescent quantum yields, and photostability have attracted much attention in the past decade. [1][2][3][4][5] These have found widespread application in biological imaging, molecular sensors, and optoelectronic devices. [6][7][8][9][10] Currently, the most investigated organoboron complexes are based on the boron dipyrromethene (BODIPY) skeleton.…”