Luminescent iridium(III) complexes with nitrogen-rich 1,2,3-triazoles: Synthesis, photophysics and electrochemistry

Nitrogen-rich metal complexes, which feature nitrogen-containing heterocycles with two or more N–N and C–N bonds, offer flexible coordination modes and notable structural stability. This study presents a straightforward synthesis of luminescent nitrogen-rich iridium(III) complexes (<b>NRIr1</b>–<b>NRIr4</b>) utilizing click chemistry-derived triazole chelates. Copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction has been utilized to synthesize triazole-based cyclometalated ligands (<b>L1</b>–<b>L4</b>), and imidazole-functionalized bipyridine ligand served as ancillary ligand (<b>AnL</b>). Comprehensive structural characterization through single-crystal X-ray diffraction and DFT calculation reveals a slightly distorted octahedral geometry around the iridium center. The photophysical studies show emission maxima ranging from 533 nm to 565 nm, with quantum yields varying from 0.1% to 7.2%. Electrochemical analysis reveals irreversible metal-based oxidation peaks with potentials around 1.30 V and reduction potentials from −1.14 V to −1.19 V. These results highlight the impact of nitrogen-rich ligands on the electronic properties of the iridium center, leading to enhanced luminescent performance and efficient energy transfer.

富含氮的金属配合物，其结构特征为带有两个及以上N-N与C-N键的含氮杂环，具备灵活的配位模式与优异的结构稳定性。本研究采用点击化学衍生的三唑螯合配体，实现了发光型富氮铱(III)配合物（<b>NRIr1</b>–<b>NRIr4</b>）的简便合成。通过铜催化叠氮-炔环加成（CuAAC）反应合成了三唑类环金属化配体（<b>L1</b>–<b>L4</b>），并以咪唑功能化联吡啶配体作为辅助配体（<b>AnL</b>）。通过单晶X射线衍射与密度泛函理论（DFT）计算开展的全面结构表征结果显示，铱中心周围呈现轻微扭曲的八面体几何构型。光物理性能研究表明，该系列配合物的发射峰值波长介于533 nm至565 nm之间，量子产率范围为0.1%至7.2%。电化学分析结果显示，存在以金属为中心的不可逆氧化峰，峰电位约为1.30 V，还原电位范围为-1.14 V至-1.19 V。上述结果凸显了富氮配体对铱中心电子性质的调控作用，可提升发光性能并实现高效能量传递。