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便高效的合成工具——布赫沃尔德-哈特维希交叉偶联反应，用于对1,2,4,5-四嗪进行官能化。影响布赫沃尔德-哈特维希交叉偶联反应的重要因素已得到优化。成功制备了七种新的供体-受体四嗪分子（TA1-TA7），其收率良好至高（61%-72%）。这些分子随后参与了与环辛炔的逆电子需求狄尔斯-阿尔德反应（iEDDA）。对所获得的新型吡啶嗪的光物理和电化学性质进行了研究。其中一些表现出荧光特性，可作为开启型探针。尤为重要的是，两种吡啶嗪（DA3和DA6）展现了室温磷光（RTP）特性。