Five cationic iridium(III) complexes (1–5) were synthesized exploiting two triazole-based cyclometalating ligands, namely, 1-methyl-4-phenyl-1H-1,2,3-triazole (A) and the corresponding mesoionic carbene 1,3-dimethyl-4-phenyl-1H-1,2,3-triazol-5-ylidene (B). From the combination of these two ligands and the ancillary one, i.e., 4,4′-di-tert-butyl-2,2′-bipyridine (for 1–3) or tert-butyl isocyanide (for 4 and 5), not only the typical bis-heteroleptic complexes but also the much less explored tris-heteroleptic analogues (2 and 5) could be synthesized. The redox and emission properties of all of the complexes are effectively fine-tuned by the different ligands: (i) cyclometalating ligand A induces a stronger highest occupied molecular orbital (HOMO) stabilization compared to B and leads to complexes with progressively narrower HOMO–lowest unoccupied molecular orbital (LUMO) and redox gaps, and lower emission energy; (ii) complexes 1–3, equipped with the bipyridine ancillary ligand, display fully reversible redox processes and emit from predominantly metal-to-ligand charge transfer (MLCT) states with high emission quantum yields, up to 60% in polymeric matrix; (iii) complexes 4 and 5, equipped with high-field isocyanide ligands, display irreversible redox processes and high-energy emission from strongly ligand-centered triplets with long emission lifetimes but relatively low quantum yields (below 6%, both in room-temperature solution and in solid state). This work demonstrates the versatility of phenyl-triazole derivatives as cyclometalating ligands with different chelation modes (i.e., C^∧N and C^∧C:) for the synthesis of photoactive iridium(III) complexes with highly tunable properties.

中文翻译：

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4-Phenyl-1,2,3-triazoles 作为阳离子环金属化铱 (III) 配合物的多功能配体

利用两个基于三唑的环金属化配体，即 1-甲基-4-苯基-1 H -1,2,3-三唑 ( A ) 和相应的中间离子卡宾，合成了五种阳离子铱 (III) 配合物 ( 1 – 5 ) 1,3-二甲基-4-苯基-1 H -1,2,3-三唑-5-亚基 ( B )。从这两种配体和辅助配体的组合，即 4,4'-二叔丁基-2,2'-联吡啶（用于1 – 3）或叔丁基异氰化物（用于4和5），不只有典型的双杂配复合物，还有较少探索的三杂配类似物（2和5 )可以合成。所有配合物的氧化还原和发射特性都通过不同的配体进行了有效的微调：(i) 环金属化配体A与B相比诱导更强的最高占据分子轨道 (HOMO) 稳定性，并导致配合物的 HOMO-最低值逐渐变窄未占分子轨道（LUMO）和氧化还原间隙，以及较低的发射能量；( ii) 配备联吡啶辅助配体的配合物1-3显示出完全可逆的氧化还原过程，并从主要金属到配体电荷转移 (MLCT) 状态发射，具有高发射量子产率，在聚合物基质中高达 60%；(iii) 配合物4和5，配备高场异氰化物配体，显示出不可逆的氧化还原过程和来自强配体中心三重态的高能发射，具有较长的发射寿命但相对较低的量子产率（在室温溶液和固态下均低于 6%） . 这项工作证明了苯基-三唑衍生物作为具有不同螯合模式（即^C∧N和^C∧C :）的环金属化配体的多功能性，可用于合成具有高度可调特性的光活性铱(III)配合物。