Electrochemiluminescence of Thienyltriazoles, Iridium Complexes, Au25 Clusters and PbS Nanoparticles

Electrogenerated chemiluminescence or electrochemiluminescence (ECL), produces light in the vicinity of a working electrode by the excited species of a luminophore formed via electron transfer between radical cations and anions, which are electrogenerated. In order for the ECL system to be efficient, the radicals must be stable in solution. This can be enhanced by adding co-reactants such as benzoyl peroxide (BPO) and tri-n-propylamine (TPrA) that produce strong oxidizing or reducing radicals upon redox reactions. ECL pairs electrochemical and spectroscopic methods and is a powerful analytical technique that is highly sensitive and selective. A comprehensive, mechanistic study of ECL generation via annihilation and co-reactant paths has been completed for modified deoxycytidine (dC) nucleosides, thienyltriazole ligands, metal complexes containing iridium(III) and ruthenium(II), Au25 clusters, and boron-dipyrromethene (BDY) capped PbS nanoparticles (NPs). Spooling ECL spectroscopy was developed during this thesis work, and was used to future understand sophisticated mechanisms for ECL generation, tuning and controlling. Specifically, the electrochemistry and spectroscopy of four modified dC nucleosides were studied to correlate their electronic structures with blue ECL. Four thienyltriazole ligands were synthesized and their electrochemical properties were analyzed and relative efficiencies determined. Eight iridium(III) complexes, four containing aryltriazole cyclometalled ligands, were found to show bright ECL while three iridium(III) complexes containing two dimethylamino substituents on the 2,2\u27-bipyridine ligand displayed self-enhancing ECL intensity up to 16 times with multiple excited states for light emission. A soft salt containing Ir(III) Ru(II) Ir(III) complexes demonstrated electronic communication between the [Ru]2+ and [Ir]- moieties thus reducing the energy required to produce ECL. Au25 clusters were discovered to emit in the near-infrared (NIR) region in both annihilation and co-reactant paths. Co-reactant BPO resulted in multiple strong excited states and the ECL mechanisms were elucidated using our newly developed spooling ECL spectroscopy. And lastly, BDY-capped PbS NPs were interrogated in the generation of both visible and NIR ECL via annihilation and co-reactant routes

Enhanced electrochemiluminescence from a stoichiometric ruthenium(II)-iridium(III) complex soft salt

The authors thank NSERC, CFI, FQRNT, PREA, and The University of Western Ontario for generous financial support to this research.Electrochemiluminescence (ECL) and electrochemistry are reported for a heterometallic soft salt, [Ru(dtbubpy)3][Ir(ppy)2(CN)2]2 ([Ir][Ru][Ir]), consisting of a 2:1 ratio of complementary charged Ru and Ir complexes possessing two different emission colors. The [Ru]2+ and [Ir]− moieties in the [Ir][Ru][Ir] greatly reduce the energy required to produce ECL. Though ECL intensity in the annihilation path was enhanced 18× relative to that of [Ru(bpy)3]2+, ECL in the co-reactant path with tri-n-propylamine was enhanced a further 4×. Spooling spectroscopy gives insight into ECL mechanisms: the unique light emission at 634 nm is due to the [Ru]2+* excited state and no [Ir]−* was generated in either route. Overall, the soft salt system is anticipated to be attractive and suitable for the development of efficient and low-energy-cost ECL detection systems.PostprintPeer reviewe

Enhanced electrochemiluminescence from a stoichiometric ruthenium(II)-iridium(III) complex soft salt

Electrochemiluminescence (ECL) and electrochemistry are reported for a heterometallic soft salt, [Ru(dtbubpy)3][Ir(ppy)2(CN)2]2 ([Ir][Ru][Ir]), consisting of a 2:1 ratio of complementary charged Ru and Ir complexes possessing two different emission colors. The [Ru]2+ and [Ir]− moieties in the [Ir][Ru][Ir] greatly reduce the energy required to produce ECL. Though ECL intensity in the annihilation path was enhanced 18× relative to that of [Ru(bpy)3]2+, ECL in the co-reactant path with tri-n-propylamine was enhanced a further 4×. Spooling spectroscopy gives insight into ECL mechanisms: the unique light emission at 634 nm is due to the [Ru]2+* excited state and no [Ir]−* was generated in either route. Overall, the soft salt system is anticipated to be attractive and suitable for the development of efficient and low-energy-cost ECL detection systems.</p

Bright electrochemiluminescence of iridium(III) complexes

Electrochemiluminescence (ECL) of four bright iridium(III) complexes containing aryltriazole cyclometallated ligands is reported. The ECL mechanisms, spectra and high efficiencies via annihilation and coreactant paths have been investigated.</p

Bright electrochemiluminescence of iridium(III) complexes

Electrochemiluminescence (ECL) of four bright iridium(III) complexes containing aryltriazole cyclometallated ligands is reported. The ECL mechanisms, spectra and high efficiencies via annihilation and coreactant paths have been investigated.</p

Interrogating Near-Infrared Electrogenerated Chemiluminescence of Au₂₅(SC₂H₄Ph)₁₈⁺ Clusters

The electrochemistry, near-infrared photoluminescence (NIR-PL) spectroscopy, and electrogenerated chemiluminescence (ECL) of Au₂₅­(SC₂H₄Ph)₁₈⁺­C₆F₅CO₂^– (Au₂₅⁺) clusters were investigated. For the first time, NIR-ECL emission was observed in both annihilation and coreactant paths. Our newly developed spooling spectroscopy was employed during the ECL evolution and devolution processes along with explicit NIR-PL spectroscopy to elucidate light generation mechanisms. It was discovered that the electronic relaxation of the Au₂₅^– excited state to the ground state plays a key role in giving off ECL at 893 nm, while intermediate, strong, and weak NIR-PL emissions at 719/820, 857, and 1080 nm can be attributed to the excited states higher than the HOMO-LUMO gap, across the HOMO-LUMO gap, and of semi-rings, respectively

Synthesis, Structure, Electrochemistry, and Electrochemiluminescence of Thienyltriazoles

Four blue-emitting thienyltriazoles with desired N and O coordination atoms were prepared in high yield via click chemistry for potential incorporation into metal complexes. Three of their crystal structures were determined by X-ray crystallography. The electrochemical properties, electronic structures of these thienyltriazoles, <b>1</b>–<b>4</b>, and their correlations were studied using cyclic voltammetry and differential pulse voltammetry techniques along with density function theory (DFT) calculations. All of the compounds underwent irreversible redox reactions, leading to unstable electrogenerated radical cations and anions. Electrochemical gaps determined from the differences between first formal reduction and oxidation reactions were correlated to HOMO–LUMO energy gaps obtained from UV–vis spectroscopy and the DFT calculations as well as energies of excited states measured from photoluminescence spectroscopy. We observed weak electrochemiluminescence (ECL) from annihilation of these thienyltriazole radicals in acetonitrile containing 0.1 M tetra-<i>n</i>-butylammonium perchlorate as electrolyte. An enhancement in ECL efficiency ranging from 0.16 to 0.50% was observed upon addition of benzoyl peroxide as a coreactant in the above electrolyte solutions. The generation of excimers in solutions of <b>1</b>–<b>4</b> was observed as seen by the red-shift in ECL maxima relative to their corresponding photoluminescence peak wavelengths. Our work is of importance for the development of efficient blue-emitting fluorophores via click chemistry that could be potential luminophores in metal complexes