Boron complexes of thiazole-bridged 1,5-bidentate nitrogen ligands: synthesis and acid-responsive photophysical properties
Boron complexes of thiazole-bridged 1,5-bidentate nitrogen ligands: synthesis and acid-responsive photophysical properties
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噻唑桥 1,5-二齿氮配体的硼配合物：合成和酸响应光物理性质
DOI：
10.1039/d1ob00828e
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Murai Toshiaki
中科院分区：
文献类型：
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作者：
Puji Pamungkas Khurnia Krisna;Maruyama Toshifumi;Murai Toshiaki
采用5-H噻唑卤化、Buchwald-Hartwig胺化、BF3·Et2O络合的方法合成了1,5-双齿氮配体与噻唑连接的硼配合物。这些硼配合物表现出高达125 nm的大斯托克斯位移，这与普通的BODIPYs形成了明显的对比。硼配合物的吸收和发射光谱几乎与配合物中的取代基以及用于测量的溶剂无关。与噻唑环相连的吡啶基的氮原子作为刘易斯碱，接受刘易斯酸和Brønsted酸，导致吸收带明显红移。在硼配合物中加入三（五氟苯基）硼烷B(C6F5)3导致吸收带发生明显的红移。同样，三氟乙酸（TFA）和三氟酸（TfOH）的加入导致在更长的波长上出现新的吸收带，并伴有荧光猝灭现象。DFT计算表明，在硼配合物的受体单元中氮原子质子化后，配合物的HOMO和LUMO之间的能隙显著减小。
Boron complexes of 1,5-bidentate nitrogen ligands with a thiazole linker were synthesized by the halogenation of 5-H thiazoles followed by Buchwald–Hartwig amination and complexation with BF3·Et2O. These boron complexes showed a large Stokes shift of up to 125 nm, which is in marked contrast to that observed for ordinary BODIPYs. The absorption and emission spectra of the boron complexes were almost independent of the substituents in the complexes as well as the solvents used for the measurement. The nitrogen atom of the pyridyl group attached to the thiazole ring acted as a Lewis base which accepted Lewis and Brønsted acids to lead to a prominent red-shift of the absorption bands. Addition of tris(pentafluorophenyl)borane, B(C6F5)3, to the boron complex led to a significant red-shift of the absorption band. Likewise, addition of triflic acid (TfOH) and trifluoroacetic acid (TFA) resulted in the emergence of a new absorption band at a longer wavelength accompanied by fluorescence quenching phenomena. DFT calculations show that the energy gap between HOMO and LUMO of the complex significantly decreases after protonation of the nitrogen atom in the acceptor unit of the boron complex.