Donor–Acceptor 1,2,4,5-Tetrazines Prepared by the Buchwald–Hartwig Cross-Coupling Reaction and Their Photoluminescence Turn-On Property by Inverse Electron Demand Diels–Alder Reaction

A facile efficient
synthetic tool, Buchwald–Hartwig cross-coupling
reaction, for the functionalization of 1,2,4,5-tetrazines is presented.
Important factors affecting the Buchwald–Hartwig cross-coupling
reaction have been optimized. Seven new donor–acceptor tetrazine
molecules (TA1–TA7) were conveniently
prepared in good to high yields (61–72%). They have been subsequently
engaged in the inverse electron demand Diels–Alder (iEDDA)
reaction with cyclooctyne. The photophysical and electrochemical properties
of the new pyridazines have been studied. Some are fluorescent acting
as turn-on probes. More importantly, two pyridazines (DA3 and DA6) exhibit room-temperature phosphorescence (RTP)
properties.

本论文提出了一种简易高效的合成工具——布赫沃尔德-哈特维格交叉偶联反应，用于对1,2,4,5-四嗪进行官能化。影响布赫沃尔德-哈特维格交叉偶联反应的关键因素已得到优化。七种新的供体-受体四嗪分子（TA1-TA7）得以便捷合成，收率良好至高（61%-72%）。随后，这些分子被用于与环辛炔的逆电子需求狄尔斯-阿尔德反应（iEDDA）。新型吡啶甲烷的光物理性质和电化学性质得到了研究。其中一些分子表现出荧光，可作为开关闭合探针。更重要的是，两种吡啶甲烷（DA3和DA6）展现了室温磷光（RTP）特性。