A series of electrochemiluminescent (ECL) iridium(III) complexes with the general formula [Ir(C^∧N)₂(pim)]⁺ (where C^∧N = cyclometalating ligands 2-phenylpyridinato (ppy) or 2-(2,4-difluorophenyl)pyridinato (dFppy), and pim = 2-(2-pyridyl)imidazole) have been synthesized. In each case, the 2-(2-pyridyl)imidazole ancillary ligand has been modified to facilitate bioconjugation and ECL label development. All complexes exhibit blue-shifted optical and electro-generated phosphorescence relative to the archetypal complex [Ir(ppy)₂(bpy)]⁺ (bpy = 2,2′-bipyridine). The emission energies for the complexes were unperturbed by functionalization of the imidazole unit of the pim ligand, whereas the emission energy was significantly blue-shifted when the pyridyl group was modified with an electron-donating oxyethanol unit. Cyclic voltammetric studies provide results consistent with fluorine substituents on the cyclometalating ligands, or an oxyethanol substituent on the neutral pim ligand, widening the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap of these complexes. Most of the complexes have high photoluminescence quantum yields (Φ_PL) in acetonitrile (up to 0.91), and some have higher ECL efficiencies than [Ru(bpy)₃]²⁺ in both acetonitrile (up to 177%) and ProCell buffer (up to 202%). Theoretical studies provide additional insights into the photophysical and electrochemical properties of this series of compounds.

中文翻译：

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双功能 2-（2-吡啶基）咪唑配体的铱 （III） 配合物：水性介质中的电化学发光发射器


已经合成了一系列电化学发光 （ECL） 铱 （III） 配合物，通式为 [Ir（C^∧N）₂（pim）]⁺（其中 C^∧N = 环金属化配体 2-苯基吡啶 （ppy） 或 2-（2,4-二氟苯基）吡啶 （dFppy） 和 pim = 2-（2-吡啶基）咪唑）。在每种情况下，2-（2-吡啶基）咪唑辅助配体都经过修饰，以促进生物偶联和 ECL 标记开发。所有复合物都表现出相对于原型复合物 [Ir（ppy）₂（bpy）]⁺ （bpy = 2,2′-bipyridine） 的蓝移光学和电生成磷光。配合物的发射能量不受 pim 配体的咪唑单元官能化的影响，而当吡啶基用电子供体氧乙醇单元修饰时，发射能量显着蓝移。循环伏安法研究提供的结果与环金属化配体上的氟取代基或中性 pim 配体上的氧乙醇取代基一致，拓宽了这些复合物的最高占据分子轨道 （HOMO） – 最低未占据分子轨道 （LUMO） 间隙。大多数复合物在乙腈中具有高光致发光量子产率 （Φ_PL）（高达 0.91），有些复合物在乙腈（高达 177%）和 ProCell 缓冲液（高达 202%）中的ECL效率高于[Ru（bpy）₃]²⁺。理论研究为这一系列化合物的光物理和电化学性质提供了更多见解。