Any Old Radical Won’t Do: An EPR Study of the Selective Excitation and Quenching Mechanisms of [Ru(bipy)<sub>3</sub>]<sup>2+</sup> Chemiluminescence and Electrochemiluminescence

Hindson, Christopher M.; Hanson, Graeme R.; Francis, Paul S.; Adcock, Jacqui L.; Barnett, Neil W.

doi:10.1002/chem.201100877

Cited by 25 publications

(21 citation statements)

References 31 publications

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“…Equations (6) and (8) are not feasible for most of the iridium complexes examined in this study. Conversely, in systems in which the metal complex is used for the ECL detection of an amine analyte, both species can be oxidized at the electrode surface and pathways analogous to Equations (1)–(5) become more important. When comparing relative ECL intensities, it is therefore also important to consider the influence of experimental conditions on the relative contribution of multiple reaction pathways that may be available for complexes within the study.…”

Section: Discussionmentioning

confidence: 99%

Co‐reactant Electrogenerated Chemiluminescence of Iridium(III) Complexes Containing an Acetylacetonate Ligand

et al. 2017

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We examine the electrogenerated chemiluminescence (ECL) of three Ir(C^N) 2 (acac) complexes, where acac = acetylacetonate anion and C^N = 2-phenylpyridine (ppy), 2-phenylbenzothiazole (bt), or 2-phenylquinoline (pq) anions, with tri-n-propylamine co-reactant in acetonitrile under a range of chemical and instrumental conditions; this follows somewhat conflicting recent claims of the ECL intensities from complexes of this type. Relevant electrochemical, spectroscopic, and ECL properties are evaluated in direct comparison with those of Ir(ppy) 3 and [Ru(bpy) 3 ](PF 6 ) 2 , as well as data from previous publications. DFT calculations on the Ir(C^N) 2 (acac) complexes show the HOMOs to be composed of both the metal and the C^N ligand, and the LUMOs almost exclusively on the C^N ligand. The ECL intensities of the Ir(C^N) 2 (acac) complexes (relative to [Ru(bpy) 3 ](PF 6 ) 2 ) were dependent on experimental conditions and, in some cases, the ECL intensities reported for iridium complexes may have been derived using conditions that unintentionally disadvantaged the reference electrochemiluminophore.

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Section: Discussionmentioning

confidence: 99%

Co‐reactant Electrogenerated Chemiluminescence of Iridium(III) Complexes Containing an Acetylacetonate Ligand

et al. 2017

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“…Changes in the relative emission intensities from various metal complexes (in separate solutions) with different co‐reactants have been observed,13, 20 but the changes are difficult to predict because the reactivity of both the co‐reactant and its radical oxidation products must be considered19, 21 and they cannot be modified without replacing the reaction media. On the other hand, the electrode potential can be easily tuned and applied at multiple levels to the same system.…”

Section: Methodsmentioning

confidence: 99%

Selective Excitation of Concomitant Electrochemiluminophores: Tuning Emission Color by Electrode Potential

et al. 2012

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The electrogenerated chemiluminescence (ECL) of tris(2,2'bipyridine)ruthenium(II) ([Ru(bpy) 3 ] 2+ ) ions with co-reactants in aqueous solution [1] is a remarkably sensitive and versatile detection system [2] that is now exploited in commercial instrumentation throughout the world for rapid screening and quantification of clinical biomarkers, food borne pathogens and biowarfare agents. [3] New applications of the ECL of [Ru(bpy) 3 ] 2+ and related complexes continue to appear in areas as diverse as light-emitting devices, [4] anion sensing, [5] multiplexed (microarray) immunoassays, [6] detection of damaged or sequence-specific DNA, [7] and molecular encodingdecoding. [8] The pursuit of superior ECL reagents and strategies that underpin such applications remains intensive, [2f,h] and is spurred by advances in the manipulation of reagent properties (for example ECL efficiency, solubility, spectral distribution) derived from extensive investigation of ruthenium, iridium, and other metal complexes, [9] and innovations in nanotechnology. [10] Considerable attention has been focused on controlling the emission color, [9d,e, 11] with the enticing prospect of simultaneously detecting multiple, spectrally distinct electrochemiluminophores for multi-analyte quantification or internal standardization. [2e, 9e, 11, 12] The implementation of these approaches, however, is complicated by the small number of available complexes with high ECL efficiency and solubility in analytically useful solvents, [10c, 13] and is fundamentally limited by the width of the emission bands, [11a, 14] which can span hundreds of nanometers. ECL spectra obtained by Richter et al. using a mixture of [Ru(bpy) 3 ] 2+ and either [Ir(ppy) 3 ] (ppy = 2-phenylpyridine) or [Ir(df-ppy) 2 (pic)] (dfppy = 2-(2,4-difluorophenyl)pyridine, pic = 2-carboxypyridine; see Scheme 1) in acetonitrile with tripropylamine (TPA) as a co-reactant show considerable spectral overlap despite differences in emission maxima of 100 and 150 nm, respectively. [11a, 12a, 15] If we compare ECL with photoluminescence, where selectivity is routinely derived not only from the wavelengths of emission, but also the energy required to attain the electronically excited state of the fluorophore, [16] the question arises of whether the excitation processes of ECL can also be exploited for selectivity between multiple emitting species. Herein we demonstrate that such systems can indeed be controlled through electrode potential (Figure 1). We then extend this concept through the repeated acquisition of ECL spectra during cyclic voltammetry experiments to derive three-dimensional (intensity versus wavelength and potential) resolution of electrochemiluminophores.The ECL of metal complexes with an oxidative-reduction co-reactant, such as TPA, involves several interrelated pathways, [19] the most dominant of which is dependent upon reaction conditions. Inspection of several key reaction steps Scheme 1. Metal complexes selected for dual-emitter investigations (L = N 4 ,N 4' -bis((2S)-1-me...

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“…9a). 30,31,40 Oxidation of the tertiary amine by cerium(IV) or by the oxidised metal complex (M + ) initially forms an aminium radical cation that decomposes to form a highly reductive alkyl radical species. The reaction of this intermediate with the oxidised metal complex can generate the electronically excited emissive species.…”

Section: Mechanism Considerationsmentioning

confidence: 99%

Chemiluminescence detection with water-soluble iridium(iii) complexes containing a sulfonate-functionalised ancillary ligand

Truong

Spilstead

Barbante

et al. 2014

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The chemiluminescence from four cyclometalated iridium(III) complexes containing an ancillary bathophenanthroline-disulfonate ligand exhibited a wide range of emission colours (green to red), and in some cases intensities that are far greater than the commonly employed benchmark reagent, [Ru(bpy)3](2+). A similar complex incorporating a sulfonated triazolylpyridine-based ligand enabled the emission to be shifted into the blue region of the spectrum, but the responses with this complex were relatively poor. DFT calculations of electronic structure and emission spectra support the experimental findings.

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Any Old Radical Won’t Do: An EPR Study of the Selective Excitation and Quenching Mechanisms of [Ru(bipy)₃]²⁺ Chemiluminescence and Electrochemiluminescence

Cited by 25 publications

References 31 publications

Co‐reactant Electrogenerated Chemiluminescence of Iridium(III) Complexes Containing an Acetylacetonate Ligand

Co‐reactant Electrogenerated Chemiluminescence of Iridium(III) Complexes Containing an Acetylacetonate Ligand

Selective Excitation of Concomitant Electrochemiluminophores: Tuning Emission Color by Electrode Potential

Chemiluminescence detection with water-soluble iridium(iii) complexes containing a sulfonate-functionalised ancillary ligand

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Any Old Radical Won’t Do: An EPR Study of the Selective Excitation and Quenching Mechanisms of [Ru(bipy)3]2+ Chemiluminescence and Electrochemiluminescence

Cited by 25 publications

References 31 publications

Co‐reactant Electrogenerated Chemiluminescence of Iridium(III) Complexes Containing an Acetylacetonate Ligand

Co‐reactant Electrogenerated Chemiluminescence of Iridium(III) Complexes Containing an Acetylacetonate Ligand

Selective Excitation of Concomitant Electrochemiluminophores: Tuning Emission Color by Electrode Potential

Chemiluminescence detection with water-soluble iridium(iii) complexes containing a sulfonate-functionalised ancillary ligand

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Any Old Radical Won’t Do: An EPR Study of the Selective Excitation and Quenching Mechanisms of [Ru(bipy)₃]²⁺ Chemiluminescence and Electrochemiluminescence