Dendritic Supramolecular Assembly with Multiple Ru(II) Tris(bipyridine) Units at the Periphery: Synthesis, Spectroscopic, and Electrochemical Study

Synthesis and comparison study of electrochemiluminescence from mononuclear and corresponding heterodinuclear Ir-Ru complexes via an amide bond as a bridge

A mononuclear iridium-based complex with a primary amine group (named Ir-NH₂), a mononuclear ruthenium-based complex with a butanoic acid group (named Ru-COOH) and the corresponding heterodinuclear complex containing an iridium and ruthenium center via an amide bond bridge (named Ir-Ru) were designed and successfully synthesized in this study. The photophysical and electrochemical properties and ECL performances of these three metal complexes under various experimental conditions were well characterized. For the first time, the insights from this comprehensive comparison study indicate that the two metal-based subunits with comparable luminescent properties are significant in the design of bimetallic-based multicolor luminophores at the molecular level, which helps us to further understand the emission performances of bimetallic complexes and to rationally design more efficient corresponding organometallic luminophores with multicolor emission for wide applications in the future.

Dinuclear metal complexes: multifunctional properties and applications

Dinuclear metal complexes have enabled breakthroughs in OLEDs, photocatalytic water splitting and CO₂reduction, DSPEC, chemosensors, biosensors, PDT and smart materials.

Phosphorus dendrimers functionalised with nitrogen ligands, for catalysis and biology

Phosphorus dendrimers (dendrimers having one phosphorus atom at each branching point) possess versatile properties, depending on the type of their terminal functions.

Novel ruthenium and iridium complexes of N-substituted carbazole as triplet photosensitisers

Novel mono- and di-nuclear Ru(ii) and Ir(iii) complexes, bearing a modified carbazole moiety are synthesised. In comparison to their mononuclear analogues, the homonuclear diatomic complexes (RuCRu and IrCIr), in which the carbazole containing-ligand functions as a bridge, display increased absorbance in the visible region, and give rise to higher singlet oxygen quantum yields.

Electrogenerated chemiluminescence of iridium-containing ROMP block copolymer and self-assembled micelles

The electrochemical properties and electrogenerated chemiluminescence (ECL) of an Ir(ppy)2(bpy)(+)-containing ROMP monomer, block copolymer (containing Ir(ppy)2(bpy)(+) complexes, PEG chains, and butyl moieties), and self-assembled micelles were investigated. Following polymerization of the iridium complex, we observed multiple oxidation peaks for the block copolymer in cyclic voltammograms (CV) and differential pulse voltammograms (DPV), suggesting the presence of multiple environments for the iridium complexes along the polymer backbone. The ECL signals from monomer 1 and polymer 2 were reproducible over continuous CV cycles and stable over prolonged potential biases, demonstrating their robustness toward ECL-based detection. Comparison of the ECL signal of the block copolymer, containing multiple iridium complexes attached to the backbone, and the monomeric complex showed enhanced signals for the polymer. In fact, formation and reopening of the self-assembled micelles allowed recovery of the polymer and near complete retention of its original ECL intensity.

Applications of tris(2,2'-bipyridyl)ruthenium(II) in electrochemiluminescence

Electrochemiluminescence (ECL) of tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)(3)(2+)] has received considerable interest over broad applications due to its remarkably high sensitivity and extremely wide dynamic range. After a brief introduction of the ECL of Ru(bpy)(3)(2+), an overview of our recent research on enhanced ECL, fabrication of solid-state ECL sensors, analytical application of an effective bioassay, and alignment of ECL with capillary electrophoresis (CE) and microchip CE is discussed in detail. Finally, we conclude with a look at the future challenges and prospects of the development of ECL.

Ultrasensitive electrogenerated chemiluminescence biosensor for the determination of mercury ion incorporating G4 PAMAM dendrimer and Hg(II)-specific oligonucleotide

A novel electrogenerated chemiluminescence (ECL) biosensor for highly sensitive and selective detection of mercury ion was developed on the basis of mercury-specific oligonucleotide (MSO) served as a molecular recognition element and the ruthenium(II) complex (Ru1) as an ECL emitting species. The biosensor was fabricated on a glassy carbon electrode coated with a thin layer of single wall carbon nanotubes, where the ECL probe, NH(2)-(CH(2))(6)-oligo(ethylene oxide)(6)-MSO↔Dend-Ru1, was covalently attached. The Dend-Ru1 pendant was prepared by covalent coupling Ru1 with the 4th generation polyamidoamine dendrimer (Dend), in which each dendrimer contained 35 Ru1 units so that a large amplification of ECL signal was obtained. Upon binding of Hg(2+) to thymine (T) bases of the MSO, the T-Hg-T structure was formed, and the MSO changed from its linear shape to a "hairpin" configuration. Consequently, the Dend-Ru1 approached the electrode surface resulting in the increase of anodic ECL signal in the presence of the ECL coreactant tri-n-propylamine. The reported biosensor showed a high reproducibility and possessed long-term storage stability (92.3% initial ECL recovery over 30 day's storage). An extremely low detection limit of 2.4 pM and a large dynamic range of 7.0 pM to 50 nM Hg(2+) were obtained. An apparent binding constant of 1.6 × 10(9)M(-1) between Hg(2+) and the MSO was estimated using an ECL based extended Langmuir isotherm approach involving multilayer adsorption. Determination of Hg(2+) contents in real water samples was conducted and the data were consistent with the results from cold vapor atomic fluorescence spectroscopy.

Development of electrogenerated chemiluminescence-based enzyme linked immunosorbent assay for sub-pM detection

This paper reports the development and characterization of a highly sensitive enzyme linked immunosorbent assay realized by the electrogenerated chemiluminescence (ECL) detection of a thiol monolayer formed by an enzyme labeled antibody. We used two monoclonal anti tumor necrosis factor-alpha (TNF-alpha) antibodies for a sandwich immunoassay. One was a capture antibody, and the other was a detection antibody labeled with an enzyme via an avidin-biotin interaction. Acetylcholinesterase was used as the labeling enzyme to convert acetylthiocholine to thiocholine. Then the thiocholine was collected on a gold electrode surface by gold-thiol binding. A bright and distinctive emission was observed at 1150 mV (vs Ag-AgCl) on the gold electrode with a thiocholine monolayer as a coreactant in the presence of tris(2,2'-bipyridyl)ruthenium complex. This method can greatly enhance the immunoassay signal since a large number of coreactant molecules can be generated by the enzymatic reaction, which is advantageous compared with a previously reported ECL based immunoassay that directly labels the detection antibody with a coreactant or luminophore. In addition, a surface accumulated coreactant is superior to the previously reported coreactant system in a bulk solution, because ECL emission occurs only very close to an electrode surface. As a result, high sensitivity and a low detection limit of 0.2 pM (3.4 pg/mL) TNF-alpha were achieved with excellent reproducibility by optimizing the conditions for the immuno-reaction, thiocholine accumulation, and ECL generation.

Electrogenerated chemiluminescence

In electrogenerated chemiluminescence, also known as electrochemiluminescence (ECL), electrochemically generated intermediates undergo a highly exergonic reaction to produce an electronically excited state that then emits light. These electron-transfer reactions are sufficiently exergonic to allow the excited states of luminophores, including polycyclic aromatic hydrocarbons and metal complexes, to be created without photoexcitation. For example, oxidation of [Ru(bpy)(3)](2+) in the presence of tripropylamine results in light emission that is analogous to the emission produced by photoexcitation. This review highlights some of the most exciting recent developments in this field, including novel ECL-generating transition metal complexes, especially ruthenium and osmium polypyridine systems; ECL-generating monolayers and thin films; the use of nanomaterials; and analytical, especially clinical, applications.

Enhanced Electrogenerated Chemiluminescence in the Presence of Fluorinated Alcohols

The electrochemistry, UV-vis absorption, photoluminescence (PL), and coreactant electrogenerated chemiluminescence (ECL) of Ru(bpy)3(2+) (where bpy=2,2'-bipyridine) have been obtained in a series of hydroxylic solvents. The solvents included fluorinated and nonfluorinated alcohols and alcohol/water mixtures. Tri-n-propylamine was used as the oxidative-reductive ECL coreactant. Blue shifts of up to 30 nm in PL emission wavelength maximums are observed compared to a Ru(bpy)3(2+)/H2O standard due to interactions of the polar excited state (i.e., *Ru(bpy)3(2+)) with the solvent media. For example, Ru(bpy)3(2+) in water has an emission maximum of 599 nm while in the more polar hexafluoropropanol and trifluoroethanol it is 562 and 571 nm, respectively. ECL spectra are similar to PL spectra, indicating the same excited state is formed in both experiments. The difference between the electrochemically reversible oxidation (Ru(bpy)3(2+/3+)) and first reduction (Ru(bpy)2(2+/1+)) correlates well with the energy gap observed in the luminescence experiments. Although the ECL is linear in all solvents with [Ru(bpy)3(2+)] ranging from 100 to 0.1 nm, little correlation between the polarity of the solvent and the ECL efficiency (phiecl=number of photons per redox event) was observed. However, dramatic increases in phiecl ranging from 6- to 270-fold were seen in mixed alcohol/water solutions.

Tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence

This paper critically reviews analytical applications of the chemiluminescence from tris(2,2'-bipyridyl)ruthenium(II) and related compounds published in the open literature between mid-1998 and October 2005. Following the introduction, which summarises the reaction chemistry and reagent generation, the review divides into three major sections that focus on: (i) the techniques that utilise this type of detection chemistry, (ii) the range of analytes that can be determined, and (iii) analogues and derivatives of tris(2,2'-bipyridyl)ruthenium(II).

Synthesis of carbosilane dendritic wedges and their use for the construction of dendritic receptors

A divergent route for the synthesis of carbosilane wedges that contain either a bromine or amine as focal point has been developed. These new building blocks enable the construction of various core-functionalized carbosilane dendrimers. As a typical example carbosilane dendrimers up to the third generation containing a N,N',N''-1,3,5-benzenetricarboxamide core (G1-G3) have been synthesized. This new class of molecules has been studied as host molecules and they have been found to bind protected amino acids as guest molecules via hydrogen bonding interactions. A decrease in the association constants was observed for the higher generation dendritic hosts, which is attributed to the increased steric hindrance around the core where the binding site is located. The binding properties of the dendritic host molecules can be tuned by modifying the binding motif at the core of the carbosilane dendrimers. A higher association constant for N-CBZ-protected glutamic acid 1-methyl ester (5) was observed when the third generation N,N',N''-1,3,5-tris(L-alaninyl)benzenetricarboxamide core-functionalized carbosilane dendrimer (G3') was used as the host molecule compared to G3. Different association constants for the formation of the diastereomeric G3'.L-5(K=295 M(-1)) and G3'.(D-5)(2) (K=236 M(-1)) host-guest complexes were observed, pointing to a small enantioselective recognition effect. The difference between the association constants for the formation of the G3'.(L-5)(2) and G3'.(D-5)(2) host-guest complexes was much more pronounced, K=37 M(-1)versus K=10 M(-1), respectively.

Microfluidic chip with electrochemiluminescence detection using 2-(2-aminoethyl)-1-methylpyrrolidine labeling

A tertiary amine derivative, 2-(2-aminoethyl)-1-methylpyrrolidine (AEMP) was successfully developed as electrochemiluminescence (ECL) probe within microfluidic chip using ECL detection in this paper. The system was characterized by the interaction between biotin and avidin. In principle, tertiary amine derivatives containing active group can be used as a potential alternative of traditional tris(2,2'-bipyridine)ruthenium(II) [Ru(bpy)3(2+)] label. Firstly, The ECL efficiency of AEMP was characterized via comparing with that of two coreactants enhancing Ru(bpy)3(2+) ECL, TPA and proline. At same condition, AEMP has a similar ECL efficiency to TPA, and much higher than proline. After AEMP reacted with NHS-LC-biotin (succinimidyl-6-(biotinamido) hexanoate), the products and their ECL were analyzed by directly injecting it in the microfluidic chip. A 4.5 cm microchannel was used to separate the mixture of AEMP and biotinylated AEMP. The present works indicated that AEMP has a good reactivity to the analytes containing carboxyl group with a similar ECL efficiency to TPA. Under optimal condition, the detection limits (based on 3 S/N) of AEMP was 2.7 microM. The system was also validated by the reaction between biotin and avidin. The calculated binding ratio between avidin and biotin based on the present method was 4.4.