Triazolylidene Metal Complexes Tagged with a Bodipy Chromophore: Synthesis and Monitoring of Ligand Exchange Reactions

The
alkyne azide “click” reaction was successfully used
to prepare new Bodipy-functionalized triazoles and triazolium salts.
The Bodipy functionality was compatible with cyclometalation conditions
as well as with transmetalation procedures involving a triazolyldene
silver intermediate, as demonstrated by the successful formation of
a metallacyclic palladium dimer and an iridium chelate. Both complexes
were characterized by X-ray diffraction, and spectroscopic studies
demonstrate unperturbed photoluminescence of the Bodipy chromophore
(emission around 545 nm, quantum yields in the 0.35–0.7 range,
and excited-state lifetimes between 3 and 7 ns). The palladium dimer 4 was cleaved using N,N-dimethylaminopyridine
(dmap) and acridine to afford monomeric triazolylidene palladium complexes 5 and 6. While dmap is a classical spectator
ligand, acridine acts as photoluminescence quencher and quenching
constants were determined as KSV = 0.86
and 1.6 × 104 M–1 for complexes 4 and 5, respectively. This dual reactivity of
acridine as ligand and quencher was utilized for a ligand displacement
assay that allowed modification of the organometallic site of the
hybrid complex to be monitored by emission spectroscopy.

炔烃-叠氮“点击”反应（alkyne azide “click” reaction）已被成功用于制备新型氟化硼二吡咯（Bodipy）功能化三唑及三唑鎓盐。氟化硼二吡咯官能团可兼容环金属化（cyclometalation）条件及涉及三唑卡宾银中间体的金属转移（transmetalation）步骤，这一点可通过环金属钯二聚体与铱螯合物（iridium chelate）的成功合成得到验证。两种配合物均通过X射线衍射（X-ray diffraction）进行表征，光谱学研究表明，氟化硼二吡咯生色团的光致发光（photoluminescence）未受干扰：发射波长约为545 nm，量子产率处于0.35~0.7区间，激发态寿命介于3~7 ns之间。使用N,N-二甲基氨基吡啶（N,N-dimethylaminopyridine，缩写dmap）与吖啶（acridine）对钯二聚体4进行裂解，可得到单核三唑卡宾钯配合物5与6。其中dmap为经典的旁观配体（spectator ligand），而吖啶则充当光致发光猝灭剂（photoluminescence quencher），配合物4与5的猝灭常数分别为KSV=0.86与1.6×10^4 M^–1。利用吖啶兼具配体与猝灭剂的双重反应活性，可构建配体置换测定（ligand displacement assay）体系，通过发射光谱法（emission spectroscopy）实现对杂化配合物有机金属位点修饰过程的监测。