Synthesis, DNA-binding, Cytotoxicity, Photo Cleavage, Antimicrobial and Docking Studies of Ru(II) Polypyridyl Complexes

Three Ruthenium(II) polypyridine complexes, [Ru(phen)₂(mipc)]²⁺(1), [Ru(bpy)₂(mipc)]²⁺ (2) and [Ru(dmb)₂(mipc)]²⁺(3) [mipc?=?2-(6-methyl-3-(1H-imidazo[4, 5-f][1,10]-phenanthroline-2-yl)-4H-chromene-4-one, phen?=?1,10-phenanthroline,bpy?=?2, 2′bipyridine,dmb?=?4, 4′-dimethyl-2, 2′-bipyridine] have been synthesized and characterized by elemental analysis, IR, UV–Vis, ¹H& ¹³C NMR and mass spectra. The DNA-binding properties of the Ruthenium(II) complexes were investigated by spectrophotometric methods, viscosity measurements and light switch studies. These three complexes have been focused on photo activated cleavage studies with pBR-322 and antimicrobial studies. Experimental results indicate that the three complexes intercalate into DNA base pairs and follows the order of 1?>?2?>?3 respectively. Molecular docking studies also support the DNA interactions with complexes through hydrogen bonding and vander Waal’s interactions. Cytotoxicity studies with Hela cell lines has been revealing about anti tumor activity of these complexes.     

Mononuclear Co(III) and Ni(II) Complexes with Polypyridyl Ligands, [Co(phen)2(taptp)]3+ and [Ni(phen)2(taptp)]2+: Synthesis, Photocleavage and DNA-binding

Two novel, mixed ligand complexes of cobalt(III) and nickel(II), [Co(phen)₂(taptp)]³⁺ (1) and [Ni(phen)₂(taptp)]²⁺ (2) (phen = 1,10-phenanthroline and taptp = 4,5,9,18-tetraazaphenanthreno [9,10-b]triphenylene), were synthesized and characterized by elemental analyses, UV-visible and NMR spectroscopies. The binding interactions of the two complexes with DNA have been investigated using absorption and emission spectroscopy methods and electrophoresis measurement mode. The intrinsic binding constants for these complexes to DNA are in the order of 10⁵. In Tris buffer, the Co(III) complex shows a moderate luminescence which was enhanced after binding to DNA. However for complex Ni(II), no emission was observed in Tris buffer. The [Co(phen)₂(taptp)]³⁺ and [Ni(phen)₂(taptp)]²⁺ can cause the photocleavage of DNA supercoiled pBR322 upon irradiation by 360 nm light. Based on the data, an intercalative mode of DNA binding is suggested for the two complexes.     

Influence of Co(III) Polypyridyl Complexes on Luminescence Behavior,DNA Binding,Photocleavage, Antimicrobial Activity and Molecular Docking Studies

A new ligand FIPB?=?5-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)furan-2-yl-2-boronic acid, having three cobalt(III) polypyridyl complexes [Co(phen)₂(FIPB)]³⁺(1) {FIPB?=?5-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)furan-2-yl-2-boronic acid}, (phen?=?1,10-Phenanthroline), [Co(bpy)₂(FIPB)]³⁺(2) (bpy?=?2,2’bipyridyl), [Co(dmb)₂(FIPB)]³⁺(3) (dmb?=?4, 4′-dimethyl 2, 2′-bipyridine) have been synthesized and characterized by elemental analysis, ES-MS,¹H-NMR, ¹³C-NMR, UV-Vis and FTIR. Their DNA binding behavior has been explored by various spectroscopic titrations and viscosity measurements, which indicated that all the complexes bind to calf thymus DNA by means of intercalation with different binding strengths. The binding properties of these all three complexes towards calf-thymus DNA (CT-DNA) have been investigated by UV-visible, emission spectroscopy and viscosity measurements.The experimental results suggested that three Co(III) complexes can intercalate into DNA base pairs,but with different binding affinities. Photo induced DNA cleavage studies have been performed and results indicate that three complexes efficiently cleave the pBR322-DNA in different forms. The three synthesized compounds were tested for antimicrobial activity by using Staphylococcus aureus and Bacillus subtilis organisms, these results indicated that complex 1 was more activity compared to other two complexes against both tested microbial strains. The in vitro cytotoxicity of these complexes was evaluatedby MTT assay, and complex 1 shows higher cytotoxicity than complex 2 and 3 on HeLa cells.

     

Study of DNA Light Switch Ru(II) Complexes : Synthesis,Characterization, Photocleavage and Antimicrobial Activity

The three Ru(II) complexes of [Ru(phen)₂dppca]²⁺ (1) [Ru(bpy)₂dppca]²⁺ (2) and [Ru(dmb)₂dppca]²⁺ (3) (where phen = 1,10 phenanthroline, bpy = 2,2-bipyridine, dmb = 2 ,2-dimethyl 2′,2′-bipyridine and polypyridyl ligand containing a single carboxylate functionality dppca ligand (dipyridophenazine-11-carboxylic acid) have been synthesized and characterized. These complexes have been shown to act as promising calf thymus DNA intercalators and a new class of DNA light switches, as evidenced by UV-visible and luminescence titrations with Co²⁺ and EDTA, steady-state emission quenching by [Fe(CN)₆]⁴⁻ and KI, DNA competitive binding with ethidium bromide, viscosity measurements, and DNA melting experiments. The results suggest that 1, 2, and 3 complexes bind to CT-DNA through intercalation and follows the order 1 > 2 > 3. Under irradiation at 365 nm, the three complexes have also been found to promote the photocleavage of plasmid pBR322 DNA.     

The key Cl− ligand for metal‐to‐ligand charge transfer in mononuclear terpyridine ruthenium(II) and binuclear ruthenium(II) tetrapyridylpyrazine complexes

Electronic structures of binuclear ruthenium complexes [Ru₂(terpy)₂(tppz)]⁴⁺ ( 1A ) and [Ru₂Cl₂(L)₂(tppz)]²⁺ {L = bpy ( 2A ), phen ( 3A ), and dpphen ( 4A )} were studied by density functional theory calculations. Abbreviations of the ligands (Ls) are bpy = 2,2′‐bipyridine, phen = 1,10‐phenanthroline, dpphen = 4,7‐diphenyl‐1,10‐phenanthroline, terpy = 2,2′:6′,2″‐terpyridine, and tppz = tetrakis(2‐pyridyl)pyrazine. Their mononuclear reference complexes [Ru(terpy)₂]²⁺ ( 1B ) and [RuClL(terpy)]⁺ {L = bpy ( 2B ), phen ( 3B ), and dpphen ( 4B )} were also examined. Geometries of these mononuclear and binuclear Ru(II) complexes were fully optimized. Their geometric parameters are in good agreement with the experimental data. The binuclear complexes were characterized by electrospray ionization mass spectrometry, UV–Vis spectroscopy, and cyclic voltammograms. Hexafluorophosphate salts of binuclear ruthenium complexes of 3A and 4A were newly prepared. The crystal structure of binuclear complex 1A (PF₆)₄ was also determined. Orbital interactions were analyzed to characterize the metal‐to‐ligand charge‐transfer (MLCT) states in these complexes. The Cl^? ligand works to raise the orbital energy of the metal lone pair, which leads to the low MLCT state. Copyright © 2011 John Wiley & Sons, Ltd.     

Optical oxygen sensing materials based on trinuclear starburst ruthenium(II) complexes assembled in mesoporous silica

The preparation and oxygen sensing properties of optical materials based on two trinuclear starburst ruthenium(II) complexes: [Ru₃(bpy)₆(TMMB)]⁶⁺ (1) and [Ru₃(phen)₆(TMMB)]⁶⁺ (2) (bpy=2,2′-bpyridine, phen=1,10-phenathroline, TMMB=1,3,5-tris[2-(2′-pyridyl)benzimidazoyl]methylbenzene) assembled in two mesoporous silicate (MS) are described in this paper. The luminescence of Ru complexes/silicate assemble materials can be quenched by molecular oxygen with good sensitivity (I₀/I₁>5 for 2/MS and I₀/I₁>3 for 1/MS), indicating that trinuclear starburst Ru(II) complexes/MS systems are sensitive to oxygen molecules.     

Synthesis,Characterization, DNA Binding,Light Switch “On and Off”, Docking Studies and Cytotoxicity,of Ruthenium(II) and Cobalt(III) Polypyridyl Complexes

The novel ligand (dmbip) 2-(4-N, N-dimethylbenzenamine)1H-imidazo[4, 5-f][1, 10]phenanthroline and its complexes [Ru(phen)₂dmbip]²⁺ (1), [Ru(bpy)₂dmbip]²⁺ (2), [Co(phen)₂dmbip]³⁺ (3) and [Co(bpy)₂dmbip]³⁺ (4) [where phen?=?1, 10-phenanthroline, bpy?=?2, 2^′-bipyridine], have been synthesized and characterized by elemental analysis, IR, UV-Vis, ¹H NMR, ¹³C NMR and Mass spectra. The DNA binding properties of the complexes were investigated by absorption, emission, quenching studies, light switch “on and off”, salt dependent, sensor (cation and anion) studies, viscosity measurements, cyclic voltammetry, molecular modeling and docking studies. The four complexes were screened for Photo cleavage of pBR322 DNA, antimicrobial activity and cytotoxicity. The experimental results indicate that the four complexes can intercalate into DNA base pairs. The DNA-binding affinities of these complexes follow the order [Ru(phen)₂dmbip]²⁺ > [Co(phen)₂dmbip]³⁺ > [Ru(bpy)₂dmbip]²⁺ > [Co(bpy)₂dmbip]³⁺.     

Study of transient luminescence of three kinds of Ru complexes bound to DNA

The transient luminescence of three kinds of ruthenium complexes [Ru(bpy)₂(7-CH₃-dppz)]²⁺, [Ru(bpy)₂(7-F-dppz)]²⁺ and [Ru(phen)₂(7-F-dppz)]²⁺ bound to calf thymus DNA (ctDNA) has been studied by using the time-resolved spectroscopy. The results show that the luminescence is due to the radiative decay from the charge-transfer states to the ground state. By the interaction with DNA, the radiativeless rate of the photoexcited Ru complex molecules decreases, which results in the increase of luminescence lifetime and efficiency. The structure of the Ru complex has an important impact on the interaction with DNA. The [Ru(bpy)₂(7-CH₃-dppz)]²⁺ shows the longest luminescence lifetime (about 382 ns), while the [Ru(bpy)₂(7-F-dppz)]²⁺ shows the shortest lifetime (about 65 ns). The possible origin of the luminescence dynamics is discussed. Supported by the National Natural Science Foundation of China (Grant Nos. 60478013 and 20571089), the Key Program of Natural Science Foundation of Guangdong Province of China (Grant No. 05101819), the Doctoral Program Foundation of Institutions of Higher Education of China (Grant No. 20040558031) and the Scientific Research Foundation of Maoming College (Grant No. 203346)     

Synthesis,Characterization and Luminescence Sensitivity with Variance in pH,DNA and BSA Binding Studies of Ru(II) Polypyridyl Complexes

Three ruthenium(II) polypyridyl complexes, [Ru(phen)₂(mip)](ClO₄)₂ (1) (phen =1,10-Phenanthroline), [Ru(bpy)₂(mip)](ClO₄)₂ (2) (bpy = 2,2’bipyridyl) and [Ru(dmb)₂(mip)](ClO₄)₂ (3) (dmb = 4, 4′-dimethyl 2, 2′-bipyridine), were synthesized with an intercalative ligand mip (2-morpholino-1H-imidazo[4,5-f][1, 10]phenanthroline) and characterized by ¹H, ¹³C–NMR, IR, UV-vis, mass spectra and elemental analysis. pH effect, ion selectivity (cations, anions) and solvent sensitivity of complexes were studied. The interaction of these complexes with DNA was performed using absorption, emission spectroscopy and viscosity measurements. The experimental results indicated that the two complexes interacted with calf thymus DNA (CT-DNA) by intercalative mode. BSA (Bovine Serum Albumin) protein binding of these complexes was studied by UV-visible and fluorescence techniques. The binding capacity of these complexes was explained theoretically by molecular docking method.     

Synthesis,Characterization, DNA Binding Studies,Photocleavage, Cytotoxicity and Docking Studies of Ruthenium(II) Light Switch Complexes

A new ligand 3-(1H-imidazo[4,5-f][1,10]phenanthrolin-2yl)phenylboronic acid and its (IPPBA) three ruthenium(II) complexes [Ru(phen)₂(IPPBA)](ClO₄)₂ (1), [Ru(bpy)₂(IPPBA)](ClO₄)₂ (2) and [Ru(dmb)₂(IPPBA)](ClO₄)₂ (3) have been synthesized and characterized by elemental analysis, UV/VIS, IR, ¹H-NMR,¹³C-NMR and mass spectra. The binding behaviors of the three complexes to calf thymus DNA were investigated by absorption spectra, emission spectroscopy, viscosity measurements, thermal denaturation and photoactivated cleavage. The DNA-binding constants for complexes 1, 2 and 3 have been determined to be 7.9?×?10⁵ M^?1, 6.7?×?10⁵ M^?1 and 2.9?×?10⁵ M^?1. The results suggest that these complexes bound to double-stranded DNA in an intercalation mode. Upon irradiation at 365 nm, three ruthenium complexes were found to promote the cleavage of plasmid pBR322 DNA from super coiled form ? to nicked form ??. Further in the presence of Co²⁺, the emission of DNA–Ru(ΙΙ) complexes can be quenched. And when EDTA was added, the emission was recovered. The experimental results show that all three complexes exhibited the “on–off–on” properties of molecular “light switch”. The highest Cytotoxicity potential of the complex1 was observed on the Human alveolar adenocarcinoma (A549) cell line. Good agreement was generally found between the spectroscopic techniques and molecular docked model which provides further evidence of groove binding.     

Photoluminescence, optical absorption and hypersensitivity in mono- and dinuclear lanthanide (Tb and Ho) β-diketonate complexes with diimines and bis-diimine bridging ligand

The photoluminescence properties of three Tb(III) complexes of the form [Tb₂(fod)₆(μ-bpm)], [Tb(fod)₃(phen)] and [Tb(fod)₃(bpy)] and optical absorption properties of their Ho(III) analogues (fod=anion of 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione, bpm=2,2′-bipyrimidine, phen=1,10-phenanthroline and bpy=2,2′-bipyridyl) in a series of solvents are presented. The luminescence of the complexes is sensitive to changes in environment (ligand/solvent) around Tb(III) and co-sensitization of the ancillary ligands. The enhancement of the luminescence intensity in coordinating solvents is attributed to the transformation of eight-coordination into less symmetric nine-coordination structure around Tb(III). Among phen and bpy, the phen is better co-sensitizer while bpm has been observed as poor co-sensitizer. The enhancement of the oscillator strength of ⁵G₆←⁵I₈ hypersensitive transition in the 4f-4f absorption in some coordinating solvents is attributed to decrease in the symmetry of the field around Ho(III) ion. The [Ho(fod)₃(phen)] is inert towards the solvents and retains its bulk structure and composition in solution. The transformation of the holmium complexes in DMSO into [Ho(fod)₃(DMSO)₂] species is found. The results reveal that the luminescence and 4f-4f absorption properties of lanthanide complexes in solution can be modulated by tuning the coordination structure through ancillary ligands and donor solvents.     

Dynamics of tRNAtyr Probed with Long-Lifetime Metal-Ligand Complexes

The metal-ligand complexes, [Ru(bpy)₂(dppz)]²⁺ (bpy = 2,2??-bipyridine, dppz = dipyrido[3,2-a:2??,3??-c]phenazine) (RuBD) and [Ru(phen)₂(dppz)]²⁺ (phen = 1,10-phenanthroline) (RuPD), display favorable photophysical properties including long lifetime, polarized emission, and very little background fluorescence. To check if RuBD and RuPD reflect the overall rotational mobility of small nucleic acid, we measured the intensity and anisotropy decays of RuBD and RuPD when intercalated into tRNA^tyr using pBC SK(+) phagemid as a control. We used frequency-domain fluorometry with a blue light-emitting diode (LED) as the modulated light source. We observed shorter lifetimes for tRNA^tyr than those for the pBC SK(+) phagemid for both probes, however, RuPD showed much larger decrease in the mean lifetime values (64%). The slow rotational correlation time of RuBD (31.3 ns) and the fast rotational correlation time of RuPD (26.0 ns) reflected the overall rotational mobility of tRNA^tyr. In addition, the steady-state anisotropy and time-resolved anisotropy decay data showed a clear difference between tRNA^tyr and pBC SK(+) phagemid. This suggests the possibility of a homogeneous assay for identifying target nucleic acids and/or nucleic acid binding proteins.     

钌(Ⅱ)配合物与DNA相互作用的瞬态发光特性

以三种新合成的钌配合物[Ru(bpy)₂(7-CH₃-dppz)]²⁺、[Ru(bpy)₂(7-F-dppz)]²⁺、[Ru(phen)₂(7-F-dppz)]²⁺为研究对象,采用时间分辨的荧光光谱技术分别测量了这三种钌配合物与小牛胸腺DNA相互作用时的瞬态荧光动力学过程。结果表明:[Ru(bpy)₂(7-CH₃-dppz)]²⁺的发光寿命最长(约382 ns),而[Ru(bpy)₂(7-F-dppz)]²⁺的发光寿命最短(约65 ns)。分析表明:钌配合物的发光来源于配合物分子中的电荷转移态到基态的辐射跃迁。通过钌配合物与DNA的相互作用,使得配合物激发态分子的无辐射弛豫几率减小,从而导致发光寿命的增加。配合物的分子与DNA相互作用越强,激发态分子的无辐射弛豫几率越小,发光寿命也越长,最终导致高的发光效率。配合物的分子结构对配合物的分子与DNA的相互作用具有重要的影响。     

Long-lifetime metal-ligand complexes as luminescent probes for DNA

We examined the intensity and anisotropy decays of DNA labeled with two ruthenium metalligand complexes, [Ru(bpy)₂(dppz)]²⁺ and [Ru(phe)₂(dppz)]²⁺. Both complexes display high emission anisotropies in the absence of rotational diffusion, making them suitable probes for rotational motions. When bound to DNA, these complexes display decay times as long as 294 ns, providing long-lived probes of DNA dynamics. The decay times of both complexes were rather insensitive to dissolved oxygen. We examined anisotropy decays of these complexes bound to B-form DNA. The anisotropy decays revealed correlation times near 10, 50, and several hundred nanoseconds, suggesting that these probes are sensitive to a wide range of DNA motions. The use of metalligand complexes should allow resolution of both the torsional and bending motions of DNA, the latter of which has been mostly inaccessible using shorter-lived fluorescent probes bound to DNA. Dedicated to Professor Robert F. Steiner upon his retirement     

Synthesis and luminescence of Eu(III) complexes with macrocyclic azacrown ethers and 1,10-phenanthroline

Complexes of Eu(III) with mixed macrocyclic azacrown ethers and 1,10-phenanthroline (phen) were synthesized and their luminescence properties measured. The specific azacrown ethers used were 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetate (TETA) and 1,4,8,12-tetraazacyclopentadecane ([15]aneN₄). The phen-coordinated complexes excited by UV light produced a very bright red emission via an intra-molecular energy transfer from phen to Eu(III). For [Eu(TETA)·(phen)·(H₂O)]⁻ and [Eu([15]aneN₄)·(phen)₂]³⁺, the quantum yields of sensitized luminescence were 8.4% and 7.8%, respectively, and were much greater than those from non-sensitized luminescence of 1.2% and 4.4%, respectively. The decay times of the corresponding phen-coordinated complexes, as measured at room temperature, were 1.6 and 0.6 ms, respectively, and were much longer than those of the phen-uncoordinated complexes of 0.3 and 0.2 ms, respectively.     

A Study on the Spectra Characterization of Ruthenium(Ii) Complexes

Abstract

A series of Ru(II) complexes have been synthesized, and their electronic spectra and NMR spectroscopy properties were characterized. the chemical shifts of aromatic protons of [Ru(bpy)₃] (PF₆)₂, [Ru(phen)₃](ClO₄)₂ and [Ru(bqdi)₃](PF₆) move downfield, but the resonance peaks of cis-Ru(bpy)₂Cl₂ shift upfield. Within the visible spectra of the ruthenium(II) complexes appear a relatively high oscillator strength which is referred to as the π(Ru)→? (ligands) transition.     

Spectroscopic and quantum-chemical investigations of chloro-bis-bipyridyl complexes of ruthenium(II) with 4-substituted pyridine ligands

The luminescence spectra of cis-[Ru(bpy)₂(L)Cl]⁺ (bpy is 2,2′-bipyridyl; L is pyrazine, pyridine, 4-amino-pyridine, 4-picolin, isonicotinamide, 4-cyanopyridine, or 4,4′bipyridyl) complexes are studied in alcoholic (4: 1 EtOH-MeOH) solutions at 77 K. A linear correlation is found between the energy of the lowest electronically excited metal-to-ligand charge transfer (³MLCT) state d _π(Ru) → π* (bpy) and the parameter pK _a of the free 4-substituted pyridines and pyrazine used as ligands L. The [B3LYP/6-31G + LanL2DZ(Ru)] hybrid method of the density functional theory is used to optimize the geometry of complexes and calculate their electronic structure and the charge distribution on the atoms of the nearest environment of the ruthenium ion. It is shown that there exists a linear unambiguous correlation between the negative charge on the nitrogen atom (qN ^L) of ligands L coordinated in the complex and the parameters pK _a of free ligands. The calculated energies of ³MLCT excited states almost linearly (correlation coefficient 0.958) depend on the charge qN ^L, which completely agrees with experimental data.     

Hypersensitivity in the Luminescence and 4f?C4f Absorption Properties of Mono- and Dinuclear EuIII and ErIII Complexes Based on Fluorinated ??-Diketone and Diimine/ Bis-Diimine Ligands

The results of our investigation on the sensitized luminescence properties of three Eu(III) ??-diketonate complexes of the form [Eu₂(fod)₆(??-bpm)], [Eu(fod)₃(phen)] and [Eu(fod)₃(bpy)] and 4f?C4f absorption properties of their Er(III) analogues ( fod = anion of 6,6,7,7,8,8,8- heptafluoro-2,2-dimethyl-3,5-octanedione, bpm = 2,2??-bipyrimidine, phen = 1,10-phenanthroline and bpy = 2,2??-bipyridyl) in a series of non-aqueous solvents are presented. The Eu(III) complexes are highly luminescent and their luminescence properties (intensity and band shape) are sensitive to the changes in the inner coordination sphere of the Eu(III) ion. The luminescence intensity of the mononuclear complexes in pyridine is drastically decreased. The coordination structure of the complexes in pyridine is transformed into a more symmetrical one which results into a slow radiative rate of the emission from the complexes. The ancillary ligands, phen and bpy are found better co-sensitizers as compared to the bpm to sensitize Eu(III)-luminescence. The 4f?C4f absorption properties (oscillator strength and band shape) of the Er(III) complexes demonstrate that ⁴G_11/2 ?? ⁴I_11/2 and ²H_11/2 ?? ⁴I_15/2 hypersensitive transitions of Er(III) are very sensitive in some coordinating solvents which reflects complex?Csolvent interaction in solution. The hypersensitive transitions of [Er(fod)₃(phen)] remain unaffected in any of the solvents and this complex retains its bulk composition in solution. The erbium complexes as well as the Er(fod)₃ chelate are invaded by DMSO. This solvent enters the inner coordination sphere by replacing heterocyclic ligand and the complexes acquire similar structure [Er(fod)₃(DMSO)₂] in this solvent. The results reveal that the luminescence and absorption properties of lanthanide complexes in solution can be controlled by tuning the coordination structure through ancillary ligands and donor solvents. This work shall prove useful in designing new biological applications with such probes.     

Spectroscopy and photophysics of chloro-bis-bipyridyl complexes of ruthenium(II) with pyridine ligands

The absorption, luminescence, and luminescence excitation spectra of ruthenium(II) complexes cis-[Ru(bpy)₂(L)Cl]⁺[bpy=2,2′-bipyridyl; L=NH₃, pyrazine, pyridine, 4-aminopyridine, 4-picoline, isonicotinamide, 4-cyanopyridine, 4,4′-bipyridyl, or trans-1,2-bis(4-pyridyl)ethylene] in alcoholic (4: 1 EtOH-MeOH) solutions are studied. At 77 K, the quantum yields and decay times of the luminescence of the complexes are measured and the deactivation rate constants of the lowest electronically excited metal-to-ligand charge transfer state (³MLCT) are determined. The linear correlation between the energy of the lowest state ³MLCT d _π(Ru)>π*(bpy) of the cis-[Ru(bpy)₂(L)Cl]⁺ complexes and the parameter pK_a of the free 4-substituted pyridines and pyrazine used as ligands is established.     

Fabrication of Ru(bpy)3-titanate nanotube nanocomposite and its application as sensitive solid-state electrochemiluminescence sensor material

A novel and facile method for effective immobilization of Ru(bpy)₃²⁺ within titanate nanotubes (TiNTs) and its application as a sensitive solid-state electrochemiluminescence (ECL) sensor material was studied. The process involved the formation of Ru(bpy)₃²⁺-titanate nanotube nanocomposite (Ru-TiNTs) via electrostatic interactions by mixing TiNTs and Ru(bpy)₃(ClO₄)₂ in aqueous medium. Then Ru-TiNTs were attached to the surface of a Pt electrode to form an ECL sensor. Characterization of Ru(bpy)₃²⁺-titanate nanotube nanocomposite was accomplished by transmission electron microscopy, X-ray photoelectron spectrum, and field emission scanning electron microscope. The electrochemistry and ECL behavior of Ru(bpy)₃²⁺ immobilized on TiNTs were studied with tripropylamine as a coreactant. As-prepared Ru-TiNTs exhibited very good stability and Ru(bpy)₃²⁺ species contained showed excellent ECL behavior. Therefore, the as-prepared Ru(bpy)₃²⁺-titanate nanotube nanocomposite exhibited great promise as new luminescent materials for solid-state ECL detection.