Bipyridine Ruthenium Complex Research Articles

Single walled carbon nanotubes covalently functionalized by a ruthenium complex for photocatalytic oxidations

The covalent bonding of a ruthenium bipyridine complex derivative with the aromatic network of single walled carbon nanotubes (SWNT) through a stepwise protocol is presented, thus yielding the sample SWNT-Ru. To do that, an-amino decorated phenanthroline is bonded to the nanotube by means of the diazonium chemistry protocol, providing anchoring points for discrete organometallic units as depicted by the solid characterization techniques employed. The hybrid material, able to emit upon excitation, is active in the visible light-driven photocatalytic oxidation of organic sulfides to sulfoxides. SWNT-Ru presents a wide scope being able to convert more than 10 substrates with different characteristics, including added-value chemicals, with a stable performance over more than 6 cycles without metal leaching and enhanced activity compared to related homogeneous complexes. A versatile character is also demonstrated since this hybrid catalyst follows both possible photooxidation mechanisms.

Artificial receptor-mediated phototransduction toward protocellular subcompartmentalization and signaling-encoded logic gates.

Engineering artificial cellular systems capable of perceiving and transmitting external signals across membranes to activate downstream targets and coordinate protocellular responses is key to build cell-cell communications and protolife. Here, we report a synthetic photoreceptor-mediated signaling pathway with the integration of light harvesting, photo-to-chemical energy conversion, signal transmission, and amplification in synthetic cells, which ultimately resulted in protocell subcompartmentalization. Key to our design is a ruthenium-bipyridine complex that acts as a membrane-anchored photoreceptor to convert visible light into chemical information and transduce signals across the lipid membrane via flip-flop motion. By coupling receptor-mediated phototransduction with biological recognition and enzymatic cascade reactions, we further develop protocell signaling-encoded Boolean logic gates. Our results illustrate a minimal cell model to mimic the photoreceptor cells that can transduce the energy of light into intracellular responses and pave the way to modular control over the flow of information for complex metabolic and signaling pathways.

A novel comparative study for simultaneous determination of Cd (II) and Pb (II) based on ruthenium complex-nanoparticles-nafion modified screen-printed gold electrode

A novel and effective method for immobilization of active ruthenium (II) bipyridine complex on screen printed gold electrode surface was developed for simultaneous determination of Cd (II) and Pb (II) in an environmental water sample. The electrostatic interaction between negatively charged graphene oxide (GO) or citrate-capped gold nanoparticles (AuNPs) and positively charged ruthenium (II) bipyridine complex ([Ru(bpy)3]2+) was studied with the incorporation of cation exchanging Nafion polymer, which enhanced electron transfer rate, reduced the interference caused by active compounds and results in long term stability. The comparison between the hybrid Ru-GO/Nafion and Ru-Au/Nafion nanocomposites’ behavior was electrochemically investigated in this paper through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and square wave anodic stripping voltammetry (SWASV). Additionally, the surface morphologies of the screen-printed electrode were evaluated using energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). The proposed Ru-GO/Nafion sensor exhibited a higher sensitivity towards cadmium ion with a detection limit of 4.2 ppb compared to the Ru-Au/Nafion assay, which reveals low sensitivity with a limit of detection of 12.01 ppb. The developed assays show excellent electrochemical performance towards lead ions with a detection limit of 5.3 ppb and 2.5 ppb for Ru-GO/Nafion and Ru-Au/Nafion, respectively, indicating that the lead ions can be accumulated more on the surface of Ru-Au/Nafion SPGE. The hybrid nanocomposite assays were successfully employed in river and tap water samples and validated using Atomic Absorption Spectroscopy (AAS).

(Electro)chemical and antimicrobial characterization of novel Ru(II) bipyridine complexes with acetylpyridine analogs

Three ruthenium-bipyridine complexes (1–3) carrying acetylpyridine ligand unit were synthesized in methanol via the reaction of [RuCl2(bpy)2] with corresponding acetylpyridine (2-, 3-, and 4-acpy). Obtained complexes were characterized by (1H and 13C) NMR and IR spectroscopy, MS spectrometry, UV‒vis spectrophotometry, and cyclic voltammetry. Their structural characterization revealed bidentate coordination mode for 2-acpy while 3- and 4-acpy acted as monodentate ligands. The electrochemical profile of newly synthesized compounds was investigated by cyclic voltammetry which confirmed their electrochemical activity. Voltammetric responses within the −1.20 < Ep < 1.50 V range of potentials were summarized in two major events: Ru(II)→Ru(III) oxidation spotted at app. ΔEp = 0.65 V and successive reductions of bpy units located from ‒0.79 V to 0.47 V (vs. Ag/AgCl (3 M) electrode). The DNA-binding activity of the complexes was evaluated by both UV‒vis spectrophotometry and cyclic voltammetry indicating DNA-intercalation with a slight contribution of electrostatic interactions. Furthermore, antimicrobial activity was tested against bacterial and fungal strains, for which moderate activity was observed. Assessment of in vitro toxicity against freshly hatched nauplii of Artemia salina as well as radical scavenging capacity was evaluated. The test compounds showed neither toxicity nor antioxidant activity.

Phosphate Group-Derivated Bipyridine-Ruthenium Complex and Titanium Dioxide Nanoparticles for Electrochemical Sensing of Protein Kinase Activity.

Monitoring of protein kinase activity is of significance for fundamentals of biochemistry, biomedical diagnose, and drug screening. To reduce the usage of a relatively complicated bio-labeled signal probe, the phosphate group-derivated bipyridine-ruthenium (Pbpy-Ru) complex and titanium dioxide nanoparticles (TiO2 NPs) were employed as signal probes to develop an electrochemical sensor for evaluating the protein kinase A (PKA) activity. Through the specific interaction between the phosphate groups and TiO2 NPs, the preparation of a Pbpy-Ru-TiO2 NP signal probe and its linkage with the phosphorylated PKA substrate peptides could be performed in a simple and effective way. The tethering of Pbpy-Ru onto the TiO2 NP surface does not degrade the electrochemical property of the complex. The Pbpy-Ru-TiO2 NP probe exhibits well-defined redox signals at about 1.0 V versus Ag/AgCl reference and notably has about fivefold current response than that of the TiO2 NPs with physically adsorbed tris-(bipyridine)-Ru. The PKA activity evaluation was realized by measuring the electrochemical response of the Pbpy-Ru-TiO2 NPs at the phosphorylated peptide-assembled electrode. Operating at optimal conditions, the cathodic signals at the potential of 1.03 V exhibit a good linearity with the PKA concentrations of 0.5-40 U mL-1. The electrochemical sensor shows good selectivity, low detection limit (0.2 U mL-1, signal/noise = 3), qualified reproducibility, and satisfactory applicability for PKA determination in the cell lysate. The Pbpy-Ru-TiO2 NPs/electrode system would be an excellent electrochemical platform for protein phosphorylation monitoring and sensing.

Improving Cytotoxicity against Breast Cancer Cells by Using Mixed-Ligand Ruthenium(II) Complexes of 2,2'-Bipyridine, Amino Acid, and Nitric Oxide Derivatives as Potential Anticancer Agents.

Several metal-based molecules that display cytotoxicity against multiple cell lines have been pursued in an attempt to fight against cancer and to overcome the typical side effects of drugs like cisplatin. In this scenario, ruthenium complexes have been extensively studied due to their activity in both in vitro and in vivo biological systems, including various cancer cell strains. We aimed to develop a method to synthesize novel [Ru(NO)(bpy)2L2]2+ complexes containing amino acid ligands by using an alternative Click Chemistry approach, namely the copper azide-alkyne cycloaddition reaction (CuAAC reaction), to construct nitrosyl/nitrite complexes bearing a modified lysine residue. We synthesized a new ligand by Click Chemistry approach and new compounds bearing the unprecedented ligand. Cytotoxicity was assessed by the classical MTT colorimetric assay. MCF-7 and MDAMB- 231 cells were used as breast cancer cell models. MCF-10 was used as a model of healthy cells. Amino acid ligands related to N3-Lys(Fmoc) and the new pyLys were successfully synthesized by the diazotransfer reaction and the CuAAC reaction, respectively. The latter reaction involves coupling between N3-Lys(Fmoc) and 3ethynylpyridine. Both N3-Lys(Fmoc) and the new pyLys were introduced into the ruthenium bipyridine complex I, or cis-[RuII(NO)(NO2)(bpy)2]2+, to generate the common nitro-based complex III, which was further converted to the final complex IV. Results of the MTT assay proved the cytotoxic effect of cis- [RuII(NO)(pyLysO-)(bpy)2](PF6)2 against the mammalian breast cancer cells MCF-7 and MDA-MB231. The viability assays revealed that complex IV, bearing a NO group and a modified lysine residue, was able to release NO and cross tumor cell membranes. In this work, Complex IV was observed to be the most active ruthenium bipyridine complex against the mammalian breast cancer cells MCF-7 and MDA-MB231: it was approximately twice as active as cisplatin, whilst complexes I-III proved to be less cytotoxic than complex IV. Additional tests using healthy MCF 10A cells showed that complexes II-IV were three- to sixfold less toxic than cisplatin, which suggested that complex IV was selective against cancer cells.

Ruthenium bipyridine complexes as electrochemiluminescent transducers for ionophore-based ion-selective detection.

We report here a method to determine target ion concentrations (with Na+ as a model) based on ionophores and electrochemiluminescence (ECL). Ruthenium bipyridine complexes were released from thin polymeric films (plasticized poly(vinyl chloride) also containing a sodium ionophore) into the sample solution following an explicit ion-exchange process (between Na+ and the ruthenium complex). Two signal transducers, tris(2,2'-(pCF3)bipyridine)ruthenium(II) (Ru(p-CF3-bpy)32+) and tris(2,2'-bipyridyl)dichlororuthenium(II) (Ru(bpy)32+), were examined using the sensing film, with the latter providing a more sensitive detection range (ca. 1 to 100 μM) than that of the more hydrophobic one (0.01 to 1 mM). While the ionophore (Na+ ionophore X) offered excellent selectivity to the method, the ruthenium complexes made the measurements independent of the sample pH. Furthermore for complex biological samples such as blood serum, an indirect approach of measuring the ECL of the remaining ruthenium complexes helps avoid background matrix interference to the ECL production at the working electrode, making the ECL method more attractive for real complex samples.

Autocatalytic photodegradation of [Ru(II)(2,2'-bipyridine)2DAD]+ (DADH = 1,2-dihydroxyanthracene-9,10-dione) by hydrogen peroxide under acidic aqueous conditions.

As part of a continuing effort to identify ruthenium agents capable of the photorelease of anthraquinone-based ligands the complexes Δ/Λ-[Ru(bpy)2DAD]+ (bpy = 2,2'-bipyridine) were produced by the reaction of 1,2-dihydroxyanthracene-9,10-dione (DADH) with chirally pure Δ/Λ-[Ru(bpy)2(py)2][(+)-O,O'-dibenzoyl-d-tartrate]·12H2O (py = pyridine). A very subtle difference in the chemical shift of the hydroxyl proton in their high-field 1H NMR spectra was observed, supporting that the OH proton is susceptible to a small change in environment at the metal centre. The excited state lifetime of the complexes, as measured by femtosecond pump-probe spectroscopy, was 7.1 (±0.8) ps in water (pH 2) and 13 (±1) ps in MeCN. Illumination of a sample of Λ-[Ru(bpy)2DAD]+ in water (pH 2) in the presence of hydrogen peroxide resulted in decomposition of the complex. The decay profile, as monitored at several wavelengths, was sigmoidal indicating the reaction was autocatalytic, in which the product formed catalysed decomposition of the starting complex. A mechanism is proposed that relies on participation of the uncoordinated hydroxyl group on the anthraquinone ligand in promoting water loss and radical formation in the excited state. The radical is oxidised by peroxide to generate the ruthenium(iii) complex, which behaves as an oxidant in the autocatalytic process.

Electrochemical properties of Rubpy-reduced graphene oxide synergized by ultrasonication for label-free quercetin sensing

Tuning the interfacial properties of oxygenated graphene and reduced graphene oxide (rGO) with optical/electrochemically active molecules are highly useful for sensor studies. Herein, we demonstrate the ultrasonochemical mediated simultaneous reduction of oxygenated graphene and adsorption of ruthenium bipyridine complex (Rubpy) on the planes of rGO nanosheets. Different weight percentage ratio of Rubpy was decorated on the planes of rGO by simple alteration in the sonication parameters. Intercalation of Rubpy complex influences the electron cloud of inherent graphitic carbon network and intermolecular oxygenated functional moieties on the rGO matrix. Activation of CN network derived from bipyridine ligands of organometallic coordination compound, Rubpy, on the rGO planes enable an amplified electron mobility at the interface of electrode beneficial for electrocatalytic analysis. rGO-Rubpy modified electrode enabled direct electrochemical redox reaction of quercetin, exhibiting a linear detection range of 0.05–50 µM, with a lowest detection limit of 0.002 µM. Demonstrated label-free sensor platform display selectivity toward quercetin even in the presence of interferents and sensitivity in the real sample, promising for complementary analytical application.

Reduced polyoxometalates and bipyridine ruthenium complex forming a tunable photocatalytic system for high efficient CO2 reduction

Photocatalytic CO2 reduction (CO2RR) into value-added chemicals is a promising approach to address global warming and develop sustainable energy, but the key challenge is seeking efficient photocatalytic systems with high performance and straightforward mechanism as well. Herein, we present three new reduced polyoxometalate-based hybrid compounds, Na6[Co(H2O)2(H2tib)]2{Co[Mo6O15(HPO4)4]2}·5H2O (1), Na3[Co(H2O)3][Co2(bib)] (H2bib)2.5{HCo[Mo6O14(OH)(HPO4)4]2}·4H2O (2) and (H2bpp)3 {HNa[Mo6O12(OH)3(HPO4)3(H2PO4)]2}·6H2O (3) (bib = 1,4-bis(1-H-imidazol-4-yl)benzene, tib = 1,3,5-tris(1-imidazolyl)benzene, bpp = 1,3-bi(4-pyridyl)propane), which can combine with [Ru(bpy)3]Cl2 complex to form a new tunable photocatalytic system (abbr. {P4Mo6}/Ru(bpy)) for CO2RR. 1/Ru(bpy) and 2/Ru(bpy) exhibit promising photocatalytic CO2RR performance into CO with the yield of 322.7 and 281.81 nmol and the selectivity of 96.3% and 96.4%, respectively. Conversely, 3/Ru(bpy) shows poor photocatalytic CO2RR activity. The photocatalytic mechanism of the {P4Mo6}/Ru(bpy) photocatalytic system was investigated by a series of control experiments and transient photovoltage measurements, which suggested that {P4Mo6}-based POMs act as the sites of oxidizing TEOA and Ru(bpy) served as the center of reducing CO2. The modified cobalt cation on {P4Mo6} polyoxoanions can optimize the energy band structure of parent {P4Mo6}, which regulates the electron transfer pathway of the {P4Mo6}/Ru(bpy) photocatalytic systems, thus achieving highly efficient photocatalytic CO2RR. This work shows a specific mechanism of photocatalytic reduction of CO2 and provides a guidance for the design of new tunable photocatalytic systems for high efficient CO2RR.

1,3,4-Oxadiazole based ruthenium amphiphile for Langmuir-Blodgett films and photo-responsive logic gate construction

Amphiphilic ruthenium bipyridine complexes based on 1,3,4-oxadiazole-pyridine ligands (L1, L2) were synthesized and characterized by 1H NMR, UV–Vis spectroscopy, electrochemistry and UV–Vis spectroelectrochemistry. The free ligands and the respective ruthenium(II) complexes exhibit an intraligand π−π∗ absorption band in the UV region that overlaps with the MLCT bands. The [Ru(bpy)2(L2)](PF6)2 complex with a bidentated L2 ligand did not form a stable monolayer in water-air interface demonstrating the relevance of coordination geometry on the molecular packing properties. In contrast, stable Langmuir-Blodgett films of the [Ru(bpy)2(L1)Cl]PF6 complex (RuL1) exhibiting reversible and fast spectroelectrochemical properties associated with the Ru(III/II) redox couple were obtained, where redox site inactivation become relevant above 20 monolayers where the current leveled up. Thin LB films were deposited on poly(bithiophene) to enhance its photoelectrochemical properties and realize photoresponsive AND and OR logic gate devices.

Minimizing Side Product Formation in Alkyne Functionalization of Ruthenium Complexes by Introduction of Protecting Groups

The synthesis of alkyne functionalized bipyridine ruthenium complexes are reported. The improved synthetic approach through application of stable protecting groups prevents formation of possible side products while facilitating purification. By applying copper‐catalysed azide‐alkyne cycloaddition reactions (CuAAC) pyrene units with flexible alkyl linkers are introduced at the periphery of the complex, opening up various applications including surface immobilization and DNA intercalation. All complexes are characterized structurally as well as photophysically, especially regarding the influence of the introduced alkyne and triazolyl substituents on their photophysical behavior.

Syntheses, crystal structures and electrochemical properties of a series of ruthenium(II) bipyridine complexes with ferrocene carboxylate ligands

The reaction of Ru(bpy)2(PPh3)(CF3SO3), Ru(bpy)(PPh3)2(CF3SO3)2 or Ru(bpy)2(CF3SO3)2 with mono- or di-carboxylate ligands in the presence of triethylamine afforded the heterometallic Ru(II) and Fe(II) complexes [Ru(bpy)(PPh3)2(η2-O2CFc)](CF3SO3) (1), [Ru(bpy)2(PPh3)(O2CFc)](CF3SO3) (2), [Ru(bpy)2(η2-O2CFc)](CF3SO3) (3) and [{Ru(bpy)2(PPh3)}2{O2CFcCO2}](CF3SO3)2 (4). The molecular structures of complexes 1 and 2 have been determined by single-crystal X-ray diffraction analysis and show that the ruthenium units are coordinated by the ferrocene carboxylate ligand in a monodentate mode or a bidentate-chelating mode. Electrochemical studies reveal that complexes 1, 2, 3 and 4 contain reversible or quasi-reversible Ru and Fe oxidation waves. The redox potentials have been well ascribed. By comparing the coordination environment of the central ruthenium atoms, we found that the RuII/RuIII redox potential shifted to the negative direction along with the increase of electron-deficient bpy ligands. The redox potentials for the ferrocenecarboxylate ligand ranged from +0.5 to +0.6 V.

Opto-electrochemical functionality of Ru(II)-reinforced graphene oxide nanosheets for immunosensing of dengue virus non-structural 1 protein

Transforming the structural and functional properties of carbon nanostructures are highly beneficial for healthcare diagnostics. This research demonstrates the functionalization of opto-electrochemically active ruthenium bipyridine complex (Ru(II)) on the surface of graphene oxide (GO), enabling a dual-functional immunoprobe for the detection of non-structural 1 (NS1) protein, a dengue biomarker. Structural investigations reveals that Ru(II) has intermolecular bonding with functional groups of GO. Ultraviolet photoelectron spectral readouts display the changes in the work function and ionization energy of GO, supporting the functionalization of Ru(II). Bio-affinity layers of protein-G (Pro-G) at GO-Ru(II) electrode interface promotes the localization of monoclonal antibodies (mAb) selective for binding the epitopes of NS1 antigen. The chronoamperometric and fluorescence quenching-based immunoassays showed a linear response with a lowest detection limit of 0.38 and 0.48 ng/mL, respectively. Under optimal condition, the developed immunosensor studied to have retained stability/sensitivity toward NS1 without impact from interferents. The dual functional immuno-bioprobe translated from GO-Ru(II) conjugated nanostructures offers new insights for further studies in on-site diagnosis.

Dynamic Supramolecular Ruthenium-Based Gels Responsive to Visible/NIR Light and Heat.

A simple supramolecular crosslinked gel is reported with a photosensitive ruthenium bipyridine complex functioning as a crosslinker and poly(4‐vinylpyridine) (P4VP) as a macromolecular ligand. Irradiation of the organogels in H2O/MeOH with visible and NIR light (in a multiphoton process) leads to cleavage of pyridine moieties from the ruthenium complex breaking the cross‐links and causing degelation and hence solubilization of the P4VP chains. Real‐time (RT) photorheology experiments of thin films showed a rapid degelation in several seconds, whereas larger bulk samples could also be photocleaved. Furthermore, the gels could be reformed or healed by simple heating of the system and restoration of the metal–ligand crosslinks. The relatively simple dynamic system with a high sensitivity towards light in the visible and NIR region make them interesting positive photoresists for nano/micropatterning applications, as was demonstrated by writing, erasing, and rewriting of the gels by single‐ and multiphoton lithography.

Heterogeneous Rate Constants of the Electron-Transfer of Iron- and Ruthenium-bipyridine Complexes in Imidazolium-Based Ionic Liquids

The heterogeneous rate constants (ks) for the oxidation of iron- and ruthenium-bipyridine complexes, [Fe(bpy)3]²⁺/³⁺ and [Ru(bpy)3]²⁺/³⁺ have been determined using Nicholson's method in imidazolium-based ionic liquids with five different types of cation/anion over a range of temperature from 298–318 K. The heterogeneous rate constants of these redox reactions range from 10⁻⁴ to 10⁻³ cm s⁻¹, depending on the dynamic viscosity and type of cation/anion of the ILs. Marcus-Hush theory is used to explain the activation energies, Ea. Similar activation energies are found for the Fe-bipyridine and Ru-bipyridine complexes indicating that inner-sphere reorganization energy has only a small influence. For the calculation of the solvent-dependent outer sphere reorganization energy a dipole-free expression is used, adopted to the different dielectric properties of ionic liquids compared to organic solvents. i-Ru drops have been compensated using the corresponding experimental uncompensated Ru-values obtained from temperature dependent Bode-plots.

Robust hollow nanocomposites with ruthenium-bipyridine complexes for heterogeneous catalysis of logic-controlled RAFT polymerization.

Photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization has become a powerful and eco-friendly toolkit to create well-defined macromolecular buildups while exhibiting composition, sequence and spatiotemporal control. Although PET-RAFT polymerization is generally much more convenient than living ionic polymerization, it is still a great challenge to regulate the polymerization upon multiple external stimuli and to simplify the procedures of post-polymerization purification. In this contribution, hHPGE-PFPPNRu nanocomposites were engineered as catalyst supports to firmly accommodate ruthenium-bipyridine complexes for heterogeneous catalysis of PET-RAFT polymerization. The manipulation of reaction temperature modulated the performance of the nanocatalysts, with a pronounced acceleration of the polymerization kinetics being identified at a temperature above the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAM) brushes compared to that below it. Consequently, the control of RAFT polymerization can be achieved upon the dual-stimuli of light and heat. Moreover, these nanocatalysts conferred radical polymerizations with myriad attractive features such as the adaptability of diverse monomer formulations and reaction media, exquisite control over the molecular variables, oxygen tolerance, and catalyst doses in the ppm range. Owing to the robust mechanical nature of nanocomposites, the separation and reuse of the nanocatalysts were readily realized by rapid centrifugation, and they showed inappreciable catalyst leakage along with consistent catalytic performance even after multiple polymerization runs.

Energy Transfer in Dendritic Systems Having Pyrene Peripheral Groups as Donors and Different Acceptor Groups.

In this feature article, a specific overview of resonance energy transfer (FRET) in dendritic molecules was performed. We focused mainly on constructs bearing peripheral pyrene groups as donor moieties using different acceptor groups, such as porphyrin, fullerene C60, ruthenium-bipyridine complexes, and cyclen-core. We have studied the effect of all the different donor-acceptor pairs in the energy transfer efficiency (FRET). In all cases, high FRET efficiency values were observed.

Ruthenium-bipyridine complex catalyzed C–H alkenylation of arylpyrazole derivatives

Direct dehydrogenative alkenylation of N-arylpyrazoles by acrylates has proven to be efficient under Ru(II) carboxylate complexes SPS-BPY and SPS-DB-BPY catalyst along with $$\hbox {Cu(OAc)}_{2}{\cdot }\hbox {H}_{2}\hbox {O}$$ as an oxidant. The reaction was found to be atom-economical and was characterized by a number of substituted N-arylpyrazoles with excellent chemoselectivity. The reaction allowed a direct alkenylation to be performed under the eco-friendly solvent system. The diverse functional group tolerance of this protocol opened up a new insight to the use of ruthenium(II) bipyridine complexes as a productive method for the oxidative heterocoupling of N-arylpyrazole. Synopsis Ruthenium(II)-Bipyridine catalyst was used for directive C–C alkenylation of arylpyrazoles and aryloxazolines under additive- and co-catalyst-free mild conditions. The comprehensive substrate scope and high chemoselectivity make the protocol versatile. The method prevents the formation of homo-coupled byproducts thereby challenging the traditional alkenylation reactions and opens up a new genre in ruthenium catalysis.

New ruthenium(II) bipyridine complex bearing 2-aminophenylbenzimidazole: Synthesis, spectral characterization and optical properties

The new bipyridine-based ruthenium(II) complex [Ru(bpy)2(Hapbim)]2+ (bpy being 2,2′-bipyridine, and Hapbim is 2-aminophenylbenzimidazole) was synthesized and characterized. On the basis of elemental analysis, spectroscopic techniques (FTIR, 1H NMR, UV-Visible), magnetic, conductivity and thermal analysis measurements, it was found that the Hapbim ligand coordinates to Ru(II) kernel in a neutral bidentate fashion through cyclic azomethine N of benzimidazole moiety along with the terminal nitrogen of the amino group forming six-membered chelate ring. Thin films of the Ru(II)-complex were prepared using thermal evaporation technique. The thin film structure was characterized using FTIR and X-Ray diffraction techniques. FTIR analysis revealed that the complex is chemically stable under both thermal evaporation and thermal annealing. The optical properties were studied by spectrophotometric measurements. The optical constants of the complex were calculated and it is found to have 1.5 eV band gap. Also, the effect of thermal annealing on the optical properties of the complex is studied. Annealing of the complex thin films increased the values of the dispersion parameters and decreased the value of the band gap.