Water-Soluble Iridium(III) Complexes Containing Tetraethylene-Glycol-Derivatized Bipyridine Ligands for Electrogenerated Chemiluminescence Detection

Abstract

Four cationic heteroleptic iridium(III) complexes containing a 2,2 ′-bipyridine (bpy) ligand with one or two tetraethylene glycol (TEG) groups attached in the 4 or 4,4 ′ positions were synthesized to create new water-soluble electrogenerated chemiluminescence (ECL) luminophores bearing a convenient point of attachment for the development of ECL-labels. The novel TEG-derivatized bipyridines were incorporated into [Ir(C ∧ N) 2 (R-bpy-R ′)]Cl complexes, where C ∧ N = 2-phenylpyridine anion (ppy) or 2-phenylbenzo[d]thiazole anion (bt), through reaction with commercially available ([Ir(C ∧ N) 2 (µ-Cl)] 2 dimers. The novel [Ir(C ∧ N) 2 (Me-bpy-TEG)]Cl and [Ir(C ∧ N) 2 (TEG-bpy-TEG)]Cl complexes in aqueous solution largely retained the redox potentials and emission spectra of the parent [Ir(C ∧ N) 2 (Me-bpy-Me)]PF 6 (where Me-bpy-Me = 4,4 ′ methyl-2,2 ′-bipyridine) luminophores in acetonitrile, and exhibited ECL intensities similar to those of [Ru(bpy) 3 ] 2+ and the analogous [Ir(C ∧ N) 2 (pt-TEG]Cl complexes (where pt-TEG = 1-(TEG)-4-(2-pyridyl)-1,2,3-triazole). These complexes can be readily adapted for bioconjugation and considering the spectral distributions of [Ir(ppy) 2 (Me-bpy-TEG)] + and [Ir(ppy) 2 (pt-TEG)] + , show a viable strategy to create ECL-labels with different emission colors from the same commercial [Ir(ppy) 2 (µ-Cl)] 2 precursor.

Reinterpreting the Fate of Iridium(III) Photocatalysts─Screening a Combinatorial Library to Explore Light-Driven Side-Reactions

“… a Metal complexes at 10 μM in acetonitrile at ambient temperature. b Corrected for the change in instrument sensitivity over the wavelength range. c Metal complexes at 5 μM in 4:1 EtOH/MeOH at 85 K. d Energy between the zeroth vibrational levels of the ground and excited states, estimated from the highest energy band of the low-temperature emission spectrum, unless otherwise indicated. e Estimated using E 0 (M + * /0 ) = E 0 ′(M +/0 ) + E 0–0 . f Estimated using E 0 (M 2+/+ *) = E 0 ′(M 2+/+ ) – E 0‑0 . g Commonly reported potentials for the excited state of [Ir­(ppy) 2 (dtb-bpy)] + were established using a first approximation of E 0–0 (2.17 eV) from the spectral distribution at ambient temperature . Subsequent estimation (2.62 eV) based on the emission at 77 K, however, may be an overestimate, due to the contribution of higher energy transitions. − Our estimate of ∼2.4 eV was based on spectra under multiple conditions and values obtained for related complexes. , …”

“… g Commonly reported potentials for the excited state of [Ir­(ppy) 2 (dtb-bpy)] + were established using a first approximation of E 0–0 (2.17 eV) from the spectral distribution at ambient temperature . Subsequent estimation (2.62 eV) based on the emission at 77 K, however, may be an overestimate, due to the contribution of higher energy transitions. − Our estimate of ∼2.4 eV was based on spectra under multiple conditions and values obtained for related complexes. , …”

Water-Soluble Tris(cyclometalated) Iridium(III) Complexes for Aqueous Electron and Energy Transfer Photochemistry

“…20 The incorporation of an aldehyde group on one of the cyclometalating ligands furthermore permitted their covalent attachment to proteins and amine-containing polymers, to result in some of the first PEGylation reagents based on luminescent transition metal complexes. The teams of Francis and Hayne used PEG substituents to obtain water-soluble iridium(III)-based emitters for electrogenerated chemiluminescence (Figure 1c), 21 and in related earlier studies furthermore employed a combination of sulfonation and PEGylation strategies for the same purpose. 22 In contrast, the Roelfes group introduced quaternary ammonium groups at the 2,2′-bipyridine backbone to obtain a water-soluble iridium(III) complex that acted as photocatalyst for modification of dehydroalanine residues in peptides and proteins (Figure 1d).…”

“…Previously explored water-soluble cyclometalated iridium­(III) complexes (left) and the corresponding cyclometalating ligands (right); R = H, CF 3 , t Bu. − ,− …”

Progress in spectrum-based electrochemiluminescence quantitative analysis

“…由于缺乏商品化的ECL光谱 分析仪 [25] , 现阶段的ECL光谱分析主要依靠自制与组 装ECL光谱装置的方式实现, 导致只有少数课题组具 备独立采集ECL光谱、开展ECL光谱分析与应用研究 的能力 [26~28] . 无论是直接采用商品化CCD光栅光谱仪 检测ECL光谱 [29] , 还是采用CCD与单色仪耦合的方式 检测ECL光谱 [30,31] 分析的简易型ECL光谱仪原型机 [34] , 在国内较早地开 展了ECL光谱的基础研究工作 [34,35] ; 于2015年攻克了 准确和灵敏检测ECL光谱的关键技术, 通过设计并采 用提高信噪比、构建精密光路、整机运行一体化等措 施, 研发出适用于定量分析的ECL光谱仪原型机 [36] . 本 文综述了ECL光谱定量分析的研究进展.…”