Characterization of electrochemiluminescence of tris(2,2′-bipyridine)ruthenium(II) with glyphosate as coreactant in aqueous solution

Glyphosate, a phosphorus-containing amino acid type herbicide was used as a coreactant for studying of electrochemiluminescence (ECL) reaction of tris(2,2′-bipyridyl)ruthenium(II) [Ru(bpy)₃²⁺] in an aqueous solution. In a phosphate buffer solution of pH 8, glyphosate itself was known to be electrochemically inactive at glassy carbon electrode, however, it participated in a homogeneous chemical reaction with the electrogenerated Ru(bpy)₃³⁺, and resulted in producing Ru(bpy)₃²⁺ species at the electrode surface. Kinetic and mechanistic information for the catalysis of glyphosate oxidation were evaluated by the steady-state voltammetric measurement with an ultramicroelectrode. The simulated cyclic voltammogram based on this mechanism was in good agreement with that obtained experimentally. ECL reaction of Ru(bpy)₃²⁺/glyphosate system was found to be strongly dependent on the media pH. In a pH region of 5-9, an ECL wave appeared at ca. +1.1 V vs. Ag/AgCl, which was caused by the generation of *Ru(bpy)₃²⁺ via a Ru(bpy)₃³⁺-mediated oxidation of glyphosate. When pH >10, a second ECL wave was observed at ca. +1.35 V vs. Ag/AgCl, which was believed to be associated with a reaction between Ru(bpy)₃³⁺ and the species from direct oxidation of GLYP at a GC electrode surface.     

Ru(bpy)3-doped silica nanoparticle DNA probe for the electrogenerated chemiluminescence detection of DNA hybridization

A sensitive electrogenerated chemiluminescence (ECL) detection of DNA hybridization, based on tris(2,2′-bipyridyl)ruthenium(II)-doped silica nanoparticles (Ru(bpy)₃²⁺-doped SNPs) as DNA tags, is described. In this protocol, Ru(bpy)₃²⁺-doped SNPs was used for DNA labeling with trimethoxysilylpropydiethylenetriamine(DETA) and glutaraldehyde as linking agents. The Ru(bpy)₃²⁺-doped SNPs labeled DNA probe was hybridized with target DNA immobilized on the surface of polypyrrole (PPy) modified Pt electrode. The hybridization events were evaluated by ECL measurements and only the complementary sequence could form a double-stranded DNA (dsDNA) with DNA probe and give strong ECL signals. A three-base mismatch sequence and a non-complementary sequence had almost negligible responses. Due to the large number of Ru(bpy)₃²⁺ molecules inside SNPs, the assay allows detection at levels as low as 1.0 × 10⁻¹³ mol l⁻¹ of the target DNA. The intensity of ECL was linearly related to the concentration of the complementary sequence in the range of 2.0 × 10⁻¹³ to 2.0 × 10⁻⁹ mol l⁻¹.     

Layer-by-layer assembly of functional silica and Au nanoparticles for fabricating electrogenerated chemiluminescence sensor

We described the use of silica nanoparticles as building blocks for the immobilization of electrogenerated chemiluminescence (ECL) reagent Ru(bpy)₃²⁺ and the fabrication of layer-by-layer assembly film by alternating the deposition of the Ru(bpy)₃²⁺-doped silica nanoparticles and Au nanoparticles. UV-vis absorption spectroscopy, scanning electron microscopy (SEM), cyclic voltammetry and ECL were used to characterize the uniform growth of the multilayer film. Since Ru(bpy)₃²⁺ could still maintain its ECL property when doped into the silica nanoparticles, the as-prepared multilayer film could be used as an effective ECL sensor, and the sensor showed high sensitivity and good stability.     

Hydroxyl radical-related electrogenerated chemiluminescence reaction for a ruthenium tris(2,2′)bipyridyl/co-reactants system at boron-doped diamond electrodes

An electrogenerated chemiluminescence (ECL) reaction of the Ru(bpy)₃²⁺ (2,2′-bipyridyl, bpy)/co-reactant system in the extremely high-potential region (over 2.6 V versus Ag/AgCl) was probed using a boron-doped diamond (BDD) electrode. At the BDD electrode, three ECL waves (1.25, 2.30 and 3.72 V) were observed in cyclic voltammograms for 20 mM ascorbic acid (AA). For the ECL peaks observed at 1.25 V corresponding to the oxidation potential for Ru(bpy)₃²⁺ (1.15 V), the light intensities and current densities were found to depend on the square root of the AA concentration. This suggests that AA oxidation, followed by the formation of the reducing radical that is necessary for generating the excited state of Ru(bpy)₃^2+* occurred through homogeneous electron-transfer between Ru(bpy)₃³⁺ and the AA species. However, for the ECL peaks at 2.30 V, the current densities and light intensities linearly increased with increasing AA concentration, suggesting that the reducing radical was formed through the direct oxidation at the electrode surface. The ECL reaction at 3.72 V was observed only at the BDD electrode and not at other electrodes. The onset potentials for the light intensity were approximately 2.6 V, independently of the type of the co-reactants (e.g. 2-propanol and AA). The peak potentials exhibited linear relation with the co-reactant concentration. In the analysis of the ECL intensity for various co-reactants (alcohols) that show different reactivity for the hydrogen abstraction reaction, the order of the light intensities at the peaks for alcohols was found to be consistent with that for the rate constants of the hydrogen abstraction reaction. These results indicate that the co-reactant radical was formed through the hydrogen abstraction reaction with the hydroxyl radical (HO) generated during the oxygen evolution reaction.     

Electrochemiluminescent determination of nicotine based on tri(2,2′-bipyridyl) ruthenium (II) complex through flow injection analysis

This paper describes the electrogenerated chemiluminescence (ECL) processes of Ru(bpy)₃²⁺/nicotine system at ITO working electrode. An ECL-based method for rapid and sensitive detection of nicotine in phosphate buffer solution at pH 8.0 is established. Strong ECL emission was observed at a positive potential of 1.4 V vs. Ag/AgCl. A possible ECL mechanism is proposed for the Ru(bpy)₃²⁺/nicotine system, the oxidation product of nicotine at the electrode surface reacts with the 3+ state of ruthenium bipyridyl (2+) complex and form ruthenium complex exited state ions and thus releases photons. Effect of pH (medium/electrolyte), working potential, buffer composition, buffer concentration, reactant and co-reactant (nicotine) concentration, flow rate and loop size on the ECL spectrum of the Ru(bpy)₃²⁺/nicotine were studied. At the optimized experimental conditions, lower detection limit for nicotine was observed as 1.2 nmol L⁻¹ (S/N = 3). Linear relationship between ECL current and concentration of nicotine was observed (up to 100 μmol L⁻¹) with R-value of 0.997. The relative standard deviation with 5 μmol L⁻¹ concentration of nicotine for 20 analyses was only 1.4%. A 94% recovery rate was observed in a real sample analysis without any complications/disturbance in measurement. Interferences of humid acid, camphor and SDS were not observed in their presence in the sample solution. The established procedure for nicotine quantification manifests fascinating results and can be suggested for further applications.     

New mechanisms in DNA cleavage by metal complexes

The chemistry of new families of DNA cleavage agents based on oxoruthenium(IV) or diplatinum pyrophosphite complexes is reviewed. The ruthenium complexes derived from Ru(tpy)(bpy)O²⁺ (tpy, 2, 2, 2-terpyridine; bpy, 2, 2-bipyridine) are effective DNA cleavage agents both electrocatalytically or thermally. The stoichiometric reaction quantitatively produces Ru(II), which also binds to DNA covalently in a slow, follow-up reaction. The cleavage by Pt₂(pop)₄ ^4– (pop, P₂O₅H₂) is photoactivated and proceeds via H-atom abstraction by the platinum complex.     

A highly sensitive method for detection of protein based on inhibition of Ru(bpy)32+/TPrA electrochemiluminescent system

The detection of proteins is very important in the study of biochemistry procedure, and electrochemiluminescence method is a very practical tool for the study of protein folding, structure and quantification. In this work, bovine serum albumin (BSA) and casein were found to be able to significantly quench the electrochemiluminescence (ECL) of Ru(bpy)₃²⁺/TPrA system, based on which a highly sensitive approach for the detection of protein was proposed. Under the optimized conditions, the logarithmic plot of the inhibited ECL versus the concentration of BSA and casein were linear over the ranges of 1–30 μg/L and 0.1–1.6 μg/L, respectively. The corresponding limit of detection (LOD) was 0.45 μg/L for BSA and 0.026 μg/L for casein (S/N = 3). UV, ECL and fluorescence methods were used to investigate the mechanism of the inhibited ECL of Ru(bpy)₃²⁺/TPrA/BSA system. A mechanism based on the formation of protein-Ru(bpy)₃²⁺ super molecule was proposed, which would prevent Ru(bpy)₃²⁺ from reaching the working electrode surface so that induced ECL quenching.     

Electrochemical fabrication and potential-enhanced luminescence of [Ru(bpy)2tatp] incorporating DNA-stabilized single-wall carbon nanotubes on an indium tin oxide electrode

A simple method was developed for the preparation of [Ru(bpy)₂tatp]²⁺-based aggregates (where bpy = 2,2′-bipyridine, tatp = 1,4,8,9-tetra-aza-triphenylene) on an indium tin oxide (ITO) electrode in the presence of DNA-stabilized single-walled carbon nanotubes (DNA–SWCNTs). The presence of SWCNTs in the concentration range from 0.02 to 0.125 g L⁻¹ dispersed with 0.25 mmol L⁻¹ DNA was found to promote the immobilization of [Ru(bpy)₂tatp]²⁺ on the ITO electrode by the method of repetitive voltammetric sweeping. The photoluminescence of [Ru(bpy)₂tatp]²⁺ incorporating DNA–SWCNTs both in solution and on the ITO electrode was systematically investigated by emission spectra and fluorescence microscopic imaging. An excess amount of SWCNTs can quench the photoluminescence of [Ru(bpy)₂tatp]²⁺ enhanced by DNA. The anodic potentials combined with CW green laser via an optical microscope was found to significantly increase the emission intensity of [Ru(bpy)₂tatp]²⁺–DNA–SWCNTs aggregates on the ITO electrode. In addition, the electrochemical fabrication and photoluminescence principles of [Ru(bpy)₂tatp]²⁺–DNA–SWCNTs aggregates on the ITO electrode tuned by the external electric fields were discussed in detail.     

DNA-promoted electrochemical assembly of [Ru(bpy)2IP] at an ITO electrode

A controllable assembly technique of [Ru(bpy)₂IP]^3+/2+ (where bpy = 2,2′-bipyridine and IP = imidazo[4,5,f][1,10]phenanthroline) promoted by calf thymus DNA at an ITO electrode is proposed. The stable assembled layer containing [Ru(bpy)₂IP]^3+/2+ and double stranded DNA is obtained on the ITO electrode using repetitive voltammetric sweeping, confirmed by ex situ voltammetry, X-ray photoelectron spectroscopy (XPS) and the inverted fluorescence microscopy. There exist two pairs of diffusion-controlled waves and two pairs of prewaves for [Ru(bpy)₂IP]²⁺ in the voltammetric sweeping process. The half-wave potentials of the prewaves are far more negative than those of the diffusion-controlled waves. These experimental results suggest that double stranded DNA is enable to accelerate and increase the controllable assembly of Ru(bpy)₂IP]^3+/2+ by using the ITO surface. The fluorescence microscopy imaging reveals that [Ru(bpy)₂IP]^3+/2+ has the ability to bind with double strand DNA. The fluorescence intensity of [Ru(bpy)₂IP]^3+/2+ with DNA is stronger than that without DNA.     

EQCM study of the ECL quenching of the tris(2,2′-bipyridyl)ruthenium(II)/tris-n-propylamine system at a Au electrode in the presence of chloride ions

Significant effect of chloride ions on the electrogenerated chemiluminescence (ECL) behavior of the ruthenium(II)tris(2,2′-bipyridine) (Ru(bpy)₃²⁺)/tri-n-propylamine (TPrA) system at a Au electrode was reported. At low concentrations (e.g., [Cl⁻] < 5 mM), the ECL was enhanced; at relatively high concentrations, however, the ECL intensity decreased with the increase of the [Cl⁻]. At [Cl⁻] = 90 mM, ∼50% and 100% ECL inhibition was observed for the first and the second ECL wave, respectively. The electrogenerated gold-chloride complexes (AuCl₂⁻ and AuCl₄⁻) which were verified using an electrochemical quartz-crystal microbalance (EQCM) method were found to be responsible for the ECL inhibition. This study suggests that care must be taken when a Au working electrode is used for ECL studies in chloride-containing buffer solutions (widely used in DNA probes) and/or with the commonly used chloride-containing reference electrodes since in these cases the ECL behavior may significantly disagree with that obtained using other electrodes and reaction media.     

DNA-enhanced assembly of [Ru(bpy)2ITATP] on an ITO electrode

A novel technique for controllable assembly of [Ru(bpy)₂ITATP]^3+/2+ (where bpy = 2,2′-bipyridine, ITATP = isatino[1,2-b]-1,4,8,9-tetraazatriphenylene) on an ITO electrode in the absence and presence of calf thymus DNA is proposed. The [Ru(bpy)₂ITATP]^3+/2+ and double stranded DNA is assembled onto the ITO electrode using repetitive voltammetric sweeping. The assembly is confirmed by ex situ cyclic voltammetry and the fluorescence microscopy. A pair of diffusion-controlled waves and prewaves for [Ru(bpy)₂ITATP]^3+/2+ is observed in the voltammetric sweeping process. The formal potential of the prewaves is found to be much negative than that of the diffusion-controlled waves. The controllable assembly of [Ru(bpy)₂ITATP]^3+/2+ on the ITO surface is accelerated by DNA and affected by ionic strength. With this DNA-prompted electrochemical technique, a multifunctional biomolecular film containing surface-confined redox center of controllable thickness is fabricated.     

Mediated oxidation of guanine by [Ru(bpy)2dpp] and their electrochemical assembly on the ITO electrode

Electrochemical oxidation of guanine mediated by [Ru(bpy)₂dpp]²⁺ (where bpy = 2,2′-bipyridine, dpp = 2,3-bis (2-pyridyl) pyrazine) and their electrochemical assembly at an ITO electrode prompted by guanine have been investigated with cyclic voltammetry and differential pulse voltammetry. It is found that [Ru(bpy)₂dpp]²⁺ can serve as an excellent mediator to induce the oxidation of guanine, and the mediated peak currents increase linearly with the rise of guanine concentration in the range from 0.01 to 0.20 mmol L⁻¹. Interestingly, with the increase of repetitive voltammetric sweeping numbers, [Ru(bpy)₂dpp]^3+/2+ can be assembled onto the ITO electrode and guanine has the ability to enhance the peak currents of prewaves. Also, with the rise of guanine concentration from 0.01 to 0.15 mmol L⁻¹, the peak currents of prewaves increase gradually. Meanwhile, the mediated mechanism of guanine oxidation by [Ru(bpy)₂dpp]²⁺ and the assembled process of [Ru(bpy)₂dpp]^3+/2+ on the ITO surface in the presence of guanine are discussed in detail.     

Ditopic, flexible hydrazone-based building blocks with pendant 2,2′:6′,2′′-terpyridine metal-binding domains

The synthesis and characterization of three new bis(2,2′:6′,2′-terpyridine) (tpy) ligands containing different hydrazone spacers between the metal-binding domains are described. Treatment of 1,4-benzenedicarbaldehyde bis(2,2′:6′,2′′-terpyridin-4′-ylhydrazone) (1) with [(tpy)RuCl₃] in the presence of N-ethylmorpholine results in the formation of [(tpy)Ru(μ-1)Ru(tpy)]⁴⁺. Single crystal X-ray diffraction data for [(tpy)Ru(μ-1)Ru(tpy)][PF₆]₄·8MeCN confirm the ability of the hydrazone-based ligand to bridge two ruthenium(II) centres, providing proof-of-principle for the application of this class of flexible ligand in the design of coordination polymers.     

Detection of N-methyladenosine in urine samples by electrochemiluminescence using a heated ITO electrode

A sensitive and rapid electrochemiluminescence (ECL) method for the detection of N⁶-Methyladenosine (m6A) in urine samples on a heated indium-tin-oxide (ITO) electrode is presented. The ECL intensity of Tris(2,2′-bipyridyl) dichlororuthenium(II)hexahydrate (Ru(bpy)₃²⁺) can be enhanced by the presence of m6A. Experimental results showed that the change of ECL intensities (ΔI) of the Ru(bpy)₃²⁺ between before and after addition of m6A was affected by the working electrode surface temperature (T_e); the highest ΔI occurred at 31 °C. Under optimum conditions, the ΔI had a linear relationship with the m6A concentration in the range of 1.9 × 10⁻⁹-3.9 × 10⁻⁶ mol/L and a detection limit of 7.7 × 10⁻¹⁰ mol/L (S/N = 3) at T_e = 31 °C. The recovery of m6A standards added to urine samples verified the accuracy of the proposed method.     

Photochemically Induced Oxidative and Reductive Regeneration of NAD(P)+/NAD(P)H Cofactors: Applications in Biotransformations

Photosensitized regeneration of NAD(P)H cofactors is accomplished by biocatalyzed and artificially catalyzed transformations in photochemical assemblies. Photogenerated N,N'-dimethyl-4,4′-bipyridinium radical cation, MV^+., acts as electron carrier for the reduction of NADPH in the presence of the enzyme ferredoxin reductase and for the reduction of NADH in the presence of lipoamide dehydrogenase. For the photogeneration of MV^+. and subsequent NADPH formation, three different photosensitizers are applied: Ru(bpz)²₃⁺, Ru(bpy)²₃⁺, and Zn—TMPyP⁴⁺. The highest quantum yield for NADPH formation is observed with Ru(bpz)₃²⁺ and is ϕ = 1.7 × 10⁻¹. For NADH regeneration only Zn-TMPyP⁴⁺ can be applied. Ru(bpy)₃²⁺ and Ru(bpz)²⁺₃ interact with NADH in their excited or oxidized forms and therefore cannot be used as light-active compounds in the system. The NADPH regeneration cycle has been coupled to the biocatalyzed synthesis of glutamic acid. Although Ru(bpz)₃²⁺ is 42.5-fold more efficient than Ru(bpy)₃²⁺ in the regeneration of NADPH, the synthesis of glutamic acid is improved only by a factor of 2 in the presence of Ru(bpz)₃²⁺, implying that the coupled process is rate limiting. Oxidative regeneration of the NAD⁺ cofactor is accomplished in a photosystem that includes Ru(bpy)₃²⁺ as photosensitizer. The photoprocess is coupled to dehydrogenation of ethanol, propanol, lactic acid, and alanine with concomitant H₂ evolution. A photosystem that includes Ru(bpy)₃²⁺ as photosensitizer, ascorbate as electron donor, and chloro-tris-(3-diphenylphosphinobenzene sulfonate)Rh(I), RhCl(dpm)₃^3-, is catalytically active in the photoinduced regeneration of NAD(P)H cofactors. Mechanistic investigations show that photogenerated Ru(bpy)₃⁺ mediates the generation of a hydrido-rhodium complex that acts as a charge relay for the production of NAD(P)H.     

DNA-promoted electrochemical assembly of [Ru(bpy)2dpp] on the ITO electrode by introducing copper(II) ion

The electrochemical assembly of [Ru(bpy)₂dpp]^3+/2+ (where bpy = 2,2′-bipyridine, dpp = 2,3-bis (2-pyridyl) pyrazine) promoted by calf thymus DNA on an ITO electrode based on the introduction of copper(II) ion has been investigated. There exists a diffusion-controlled wave and two prewaves for the complex in the differential pulse voltammetric sweeping process. The formal potential of the high prewave shift ca. 0.530 V negatively compared with that of the diffusion-controlled wave. Dpp ligand with two vacant chelating N sites in the complex can bite Cu²⁺ and the resultant heterometallic complex shows a weakened assembly in contrast to that of [Ru(bpy)₂dpp]^3+/2+ alone. Furthermore, double stranded DNA is able to accelerate the assembly of the ruthenium complex and heterometallic complex generated by chelating with Cu²⁺ by using the ITO surface, the prompted strength of the latter is far stronger than the former. Their assembled mechanism enhanced by DNA is proposed.     

Aldehyde-decorated 2,2′-bipyridine and 2,2′:6′,2″-terpyridine ruthenium(II) complexes: Convenient scaffolds for supramolecular chemistry

Two new aldehyde-decorated tpy and bpy-containing ruthenium(II) complexes, [Ru(1)(bpy)₂][PF₆]₂ and [Ru(1)(tpy)Cl][PF₆] in which 1 is 5,5′-bis(4-formylphenyl)-2,2′-bipyridine, have been prepared and fully characterized. The packing in both solid state structures involves extensive O_aldehyde···HC_pyridine contacts, but π-stacking interactions are important only between [Ru(1)(tpy)Cl]⁺ cations.     

Influence of nature, concentration and pH of buffer acid-base system on rate determining step of the electrochemiluminescence of Ru(bpy)3 with tertiary aliphatic amines

The electrogenerated chemiluminescence (ECL) of Ru(bpy)₃²⁺ (bpy = 2,2′-bipyridyl) with tertiary aliphatic amines as co-reactants, was theoretically and experimentally studied as a function of the pre-equilibria involved in the ammonium proton lost and in relation to the nature of the rate determining step. Transient potential steps were used with a 3-mm glassy carbon disk electrode or carbon fiber ultramicroelectrodes array to investigate emission behavior in a variety of aqueous solution types, containing phosphate, tartrate and phthalate acid-base systems at differing pH values. The emission of Ru(bpy)₃²⁺ resulting from the reaction with n-tripropylamine (TPrA), tri-isobutylamine (TisoBuA), n-tributylamine (TBuA), methyl-di-n-propylamine (MeDPrA) and triethylamine (TEtA) in varying acid-base media was interpreted on the basis of the quoted pre-equilibria, ammonium pK_a being known. The nature of the rate determining steps changes depending on pH. Above pH ≈ 5 the amine neutral radical formation is the rate determining step and, is independent of pH with rate constant close to 10³ s⁻¹; below pH ≈ 5 the rate determining step becomes the deprotonation of the ammonium ion, operated by different bases present in solution. Different amines in the same acid-base system showed analogous ECL behavior, conditioned by the chosen acid base system. A single amine in different acid-base systems showed different kinetic behaviors, due to the dissociation constants of the chosen buffers. The concentration of the acid-base system also played an important role and influenced emission intensity and shape. ECL emission were simulated by finite difference methods, implementing a previously proposed mechanism by including the relevant pre-equilibria. Simulation may also give estimates of the pK_a values of the ammonium ions. An ion pair formation between R₃N⁺ and the mostly charged species present in solution is hypothesized to explain the contradictory experimental results concerning the reaction mechanism of the proton lost of the radical cation.     

Electrocatalytic activity of [Ru(bpy)<Subscript>3</Subscript>]<Superscript>2+</Superscript> toward guanine oxidation upon incorporation of surfactants and SWCNTs

The homogeneous and mediated oxidation of guanine by [Ru(bpy)₃]²⁺ (2,2′-bipypyridine) in the presence of surfactants and single-walled carbon nanotubes (SWCNTs) has been investigated using cyclic voltammetry, repetitive differential pulse voltammetry and rotating electrode method. In acidic medium, the oxidation of guanine was controlled by mass transport process of [Ru(bpy)₃]²⁺ in solution, leading to a homogeneous electrocatalysis. In neutral medium, the result from emission spectroscopy suggested the formation of the aggregates containing [Ru(bpy)₃]²⁺, dihexadecyl phosphate (DHP) and guanine. The electrocatalysis of [Ru(bpy)₃]²⁺ toward guanine oxidation was promoted by anionic surfactant DHP and, however, hindered by an excess amount of hexadecyl trismethyl ammonium chloride (HTAC) or SWCNTs added to solutions. The electrocatalytic mechanism of [Ru(bpy)₃]²⁺ for guanine oxidation becomes evident, strongly depending on the presence of anionic or cationic surfactants and SWCNTs.     

Preparation and chemical properties of π-conjugated poly(1,10-phenanthroline-3,8-diyl)s with crown ether subunits

π-Conjugated polymers consisting of 1,10-phenanthroline units and crown ether subunits (Poly-1, Poly-2, and Poly-3) were prepared by dehalogenation polycondensation of the corresponding dibromo monomers using a zero-valent nickel complex as a condensing agent. They were characterized by elemental analysis, ¹H NMR and UV–Vis spectroscopies, and cyclic voltammetry (CV). They were partly soluble in CHCl₃, and the number average molecular weight of the soluble part of Poly-2, which had 15-crown-5 subunits, was estimated to be 5300. The polymers exhibited UV–Vis peaks at approximately λ_max = 360 nm, which was reasonable. Complexation with [Ru(bpy)₂]²⁺ and alkaline metal ions made the polymer soluble in organic solvents. The complexation of [Ru(bpy)₂]²⁺ to the 1,10-phenanthroline unit proceeded quantitatively, and the [Ru(bpy)₂]²⁺ complexes exhibited CV curves characteristic of [Ru(N-N)₃]²⁺ complexes.