Bpy Ligands Research Articles

Synthesis, characterization, and binding assessment with human serum albumin of three bipyridine lanthanide(III) complexes

In this work, the terbium(III), dysprosium(III), and ytterbium(III) complexes containing 2, 2′-bipyridine (bpy) ligand have been synthesized and characterized using CHN elemental analysis, FT-IR, UV–Vis and 1H-NMR techniques and their binding behavior with human serum albumin (HSA) was studied by UV–Vis, fluorescence and molecular docking examinations. The experimental data indicated that all three lanthanide complexes have high binding affinity to HSA with effective quenching of HSA fluorescence via static mechanism. The binding parameters, the type of interaction, the value of resonance energy transfer, and the binding distance between complexes and HSA were estimated from the analysis of fluorescence measurements and Förster theory. The thermodynamic parameters suggested that van der Waals interactions and hydrogen bonds play an important role in the binding mechanism. While, the energy transfer from HSA molecules to all these complexes occurs with high probability, the order of binding constants (BpyTb > BpyDy > BpyYb) represents the importance of radius of Ln3+ ion in the complex-HSA interaction. The results of molecular docking calculation and competitive experiments assessed site 3 of HSA, located in subdomain IB, as the most probable binding site for these ligands and also indicated the microenvironment residues around the bound mentioned complexes. The computational results kept in good agreement with experimental data.

Role of Seroalbumin in the Cytotoxicity of cis-Dichloro Pt(II) Complexes with (N^N)-Donor Ligands Bearing Functionalized Tails.

Given the potent anticancer properties of cis-diamminedichloroplatinum(II) and knowing its mode of action, we synthesized four new cis-[PtCl2(N^N)] organoplatinum complexes, two with N-substituted pbi ligands (pbiR = 1-R-2-(2-pyridyl)benzimidazole) (namely, 1 and 2) and two more with 4,4'-disubstituted bpy ligands (bpy = 2,2'-bipyridine) (namely, 3 and 4). We explored their cytotoxicity and ability to bind to deoxyguanosine monophosphate (dGMP), DNA, and albumin models. By 1H NMR and UV-vis spectroscopies, circular dichroism, agarose gel electrophoresis, differential scanning calorimetry measurements, and density functional theory calculations, we verified that only 3 can form aquacomplex species after dimethyl sulfoxide solvation; surprisingly, 1, 2, and 3 can bind covalently to DNA, whereas 4 can form a noncovalent complex. Interestingly, only complexes 1 and 4 exhibit good cytotoxicity against human ovarian carcinoma (HeLa) cell line, whereas 2 and 3 are inactive. Although lung carcinoma (A549) cells are more resistant to the four platinum complexes than HeLa cells, when the protein concentration in the extracellular media is lower, the cytotoxicity becomes substantially enhanced. By native electrophoresis of bovine seroalbumin (BSA) and inductively coupled plasma mass spectrometry uptake studies we bear out, on one hand, that 2 and 3 can interact strongly with BSA and its cellular uptake is negligible and, on the other hand, that 1 and 4 can interact with BSA only weakly, its cellular uptake being higher by several orders. These results point up the important role of the protein binding features on their biological activity and cellular uptake of cis-"PtCl2" derivatives. Our results are valuable in the future rational design of new platinum complexes with improved biological properties, as they expose the importance not only of their DNA binding abilities but also of additional factors such as protein binding.

Semi-Integral Electroanalysis of the Electrochemistry of Tris(2,2`-bipyridine) Complexes

The 2,2`-bipyridine (bpy) ligand is one of the most widely used in coordination chemistry. It was first synthesized at the end of the 19th century, with the iron(II) tris(bpy) being the first complex of this ligand ever observed1. Over the years a diversity of metals complexed with bpy have been synthesized and extensively studied, and recently some applications of these complexes have been proposed, e.g. the use of iron (II) and nickel (II) tris(bpy) complexes for non-aqueous electrolytes of batteries2 and the use of cobalt (II) tris(bpy) for thermo electrochemical cells3. Also, currently there is a growing interest in using ionic liquids (ILs) for electrochemical applications, because these compounds, broadly defined as salts that are liquid at or close to room temperature, usually present some interesting properties, such as low volatility, non-flammability and intrinsic ionic conductivity. The semi-integral electroanalysis is a powerful method for investigating the kinetics of redox reactions and determining the diffusion coefficients4 and was used to aid the interpretation of the electrochemical behaviour of tris(bpy) complexes. The purpose of this work was to study the electrochemistry of the tris(bpy) complexes of cobalt (II)5, nickel (II) and iron (II)6 in ILs and organic solvents, thus contributing to the understanding of how these compounds behave in these media. Four ILs (two having the imidazolium cation and two the pyrrolidinium cation) and three organic solvents were used and the basic electrochemical properties of these complexes were investigated, including the redox potentials and the chemical and electrochemical reversibility of the redox reactions, as well as the kinetics of the oxidation reactions. The semi-integral electroanalysis was used for determining diffusion coefficients and for a qualitative analysis of the reversibility of the redox reactions. E. C. Constable, in Adv. Inorg. Chem., ed. A. G. Sykes, Academic Press, 1989, vol. Volume 34, pp. 1-63.J. Mun, M.-J. Lee, J.-W. Park, D.-J. Oh, D.-Y. Lee and S.-G. Doo, Electrochem. Solid-State Lett., 2012, 15, A80-A82.M. A. Lazar, D. Al-Masri, D. R. MacFarlane and J. M. Pringle, PCCP, 2016, 18, 1404-1410.K. B. Oldham, Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1976, 72, 371-378.D. Cabral, P. C. Howlett, J. M. Pringle, X. Zhang and D. MacFarlane, Electrochim. Acta, 2015, 180, 419-426.D. M. Cabral, P. C. Howlett and D. R. MacFarlane, Electrochim. Acta, 2016, 220, 347-353.

Effects of Introducing Methoxy Groups into the Ancillary Ligands in Bis(diimine) Copper(I) Dyes for Dye-Sensitized Solar Cells

A systematic investigation of four heteroleptic bis(diimine) copper(I) dyes in n-type Dye-Sensitized Solar Cells (DSSCs) is presented. The dyes are assembled using a stepwise, on-surface assembly. The dyes contain a phosphonic acid-functionalized 2,2′-bipyridine (bpy) anchoring domain (5) and ancillary bpy ligands that bear peripheral phenyl (1), 4-methoxyphenyl (2), 3,5-dimethoxyphenyl (3), or 3,4,5-trimethoxyphenyl (4) substituents. In masked DSSCs, the best overall photoconversion efficiency was obtained with the dye [Cu(5)(4)]+ (1.96% versus 5.79% for N719). Values of JSC for both [Cu(5)(2)]+ (in which the 4-MeO group is electron releasing) and [Cu(5)(4)]+ (which combines electron-releasing and electron-withdrawing effects of the 4- and 3,5-substituents) and are enhanced with respect to [Cu(5)(1)]+. DSSCs with [Cu(5)(3)]+ show the lowest JSC. Solid-state absorption spectra and external quantum efficiency spectra reveal that [Cu(5)(4)]+ benefits from an extended spectral range at higher energies. Values of VOC are in the order [Cu(5)(4)]+ > [Cu(5)(1)]+ > [Cu(5)(2)]+ > [Cu(5)(3)]+. Density functional theory calculations suggest that methoxyphenyl character in MOs within the HOMO manifold in [Cu(5)(2)]+ and [Cu(5)(4)]+ may contribute to the enhanced performances of these dyes with respect to [Cu(5)(1)]+.

Exploration of Uncharted 3PES Territory for [Ru(bpy)3]2+: A New 3MC Minimum Prone to Ligand Loss Photochemistry.

We have identified a new 3MC state bearing two elongated Ru-N bonds to the same ligand in [Ru(bpy)3]2+. This DFT-optimized structure is a local minimum on the 3PES. This distal MC state (3MCcis) is destabilized by less than 2 kcal/mol with respect to the classical MC state (3MCtrans), and energy barriers to populate 3MCcis and 3MCtrans from the 3MLCT state are similar according to nudged elastic band minimum energy path calculations. Distortions in the classical 3MCtrans, that is, elongation of two Ru-N bonds toward two different bpy ligands, are not expected to favor the formation of ligand-loss photoproducts. On the contrary, the new 3MCcis could be particularly relevant in the photodegradation of Ru(II) polypyridine complexes.

Synthesis, characterisation and DNA intercalation studies of regioisomers of ruthenium (II) polypyridyl complexes

Regioisomers of the functional group of the main ligand (L) on a series of [Ru(phen)2L]2+and [Ru(bpy)2L]2+ complexes, where phen is 1,10 phenanthroline and bpy is 2,2′-bipyridine, were synthesised to investigate the interaction with deoxyribonucleic acid (DNA) as potential therapeutics. UV–Vis binding titrations, thermal denaturation and circular dichroism were used to evaluate their interaction with DNA. The conclusions indicated the significance of the auxiliary ligand; especially 1,10-phenanthroline has on the binding constants (Kb). The systematic variation of auxiliary ligand(phen or bpy), and polypyridyl ligand (4-(1H-Imidazo[4,5-f][1,10]phenanthrolin-2-yl)benzonitrile (CPIP), 2-(4-formylphenyl)imidazo[4,5-f] [1,10] phenanthroline (FPIP), 2-(4-bromophenyl)imidazo[4,5-f][1,10]phenanthroline (BPIP) and 2-(4-nitrophenyl)imidazo[4,5-f] [1,10] phenanthroline (NPIP), split in terms of functional group change were investigated for DNA interaction. The CPIP analogues in particular were investigated for the regioisomerism (ortho, meta, para) effect of the nitrile group on the ligand. It was found that both the DNA interaction could be tailored through the systematic variation of the electronic nature of the individual auxiliary ligand and to a lesser extent the functional group and regioisomeric change. Preliminary cell line studies have been carried out to determine the selectivity of the complexes against cell lines such as A375 (Skin Cancer), HeLa (Cervical Cancer), A549 (Lung Cancer), Beas2B (Lung Normal Cell) and MCF-7 (Breast Cancer). Complexes which had strong DNA interactions in the binding studies have proven to be the most efficacious against certain cell lines. Establishing well-defined structure property relationships when looking at trends in spectroscopic properties and DNA binding will aid in the intelligent design of potential therapeutic complexes.

Kinetic and Mechanistic Effects of Bipyridine (bpy) Substituent, Labile Ligand, and Brønsted Acid on Electrocatalytic CO2 Reduction by Re(bpy) Complexes

In order to help develop robust and deployable molecular electrocatalysts for the reduction of CO2 to CO, we must understand the effects of tuning their structure and catalytic conditions. To this end, we quantify how modifications to the catalyst fac-Re(4,4′-R-bpy)(CO)3X (bpy = 2,2′-bipyridine, R = OCH3, CH3, tBu, H, CN, CF3; X = Cl, Br, py(OTf), or CH3CN(OTf)) with and without an added proton source (phenol, acetic acid, 2,2,2-trifluoroethanol) affect the catalyst stability, activity, and overpotential. Through cyclic voltammetry experiments, we found that the substituents and proton source had a large effect on both overpotential and activity. Substituents with moderate electron-donating ability (tBu and CH3) increased activity and overpotential in comparison to the unsubstituted complex Re(bpy)(CO)3Cl. In contrast, substituents resulting in too much electron density distributed over the bpy ligand, either from too-strong electron-donating ability (OCH3) or from the requirement of a third reduction to ...

Synthesis, spectroscopic, DFT studies and biological activity of some ruthenium carbonyl derivatives of bis-(salicylaldehyde)phenylenediimine Schiff base ligand

Bis-(salicylaldehyde)phenylenediimine Schiff base (H2salphen) reacted oxidatively with the triruthenium dodecacarbonyl complex, [Ru3(CO)12] to give the dicarbonyl derivative [Ru(CO)2(salphen)], 1. In presence of a secondary ligand L (L = pyridine, triphenyl phosphine, 2-aminobenzimidazole or thiourea), the monocarbonyl derivatives [Ru(CO)(salphen)L], 2–5, were isolated. When the bipyridine (bpy) ligand was used as a secondary ligand, the dicarbonyl complex [Ru(CO)2(Hsalphen)(bpy)], 6, was obtained. In complexes 1–5, the Schiff base ligand acted as a tetradentate, while it coordinated as a bidentate in complex 6. The structure and stoichiometry of the complexes were investigated by the conventional analytical and spectroscopic techniques, which revealed that they have several structural arrangements. The structures of ligand and complexes were verified by theoretical calculations based on accurate DFT approximations. The relative reactivities were estimated using chemical descriptors analysis. Biological activities of the complexes against the Escherchia coli and Staphylococcus aureus bacteria were screened.

Phosphonate‐Mediated Immobilization of Rhodium/Bipyridine Hydrogenation Catalysts

RhL2 complexes of phosphonate-derivatized 2,2'-bipyridine (bpy) ligands L were immobilized on titanium oxide particles generated in situ. Depending on the structure of the bipy ligand-number of tethers (1 or 2) to which the phosphonate end groups are attached and their location on the 2,2'-bipyridine backbone (4,4'-, 5,5'-, or 6,6'-positions)-the resulting supported catalysts showed comparable chemoselectivity but different kinetics for the hydrogenation of 6-methyl-5-hepten-2-one under hydrogen pressure. Characterization of the six supported catalysts suggested that the intrinsic geometry of each of the phosphonate-derivatized 2,2'-bipyridines leads to supported catalysts with different microstructures and different arrangements of the RhL2 species at the surface of the solid, which thereby affect their reactivity.

Tailoring the Fluorescence of AIE-Active Metal-Organic Frameworks for Aqueous Sensing of Metal Ions.

A hydroxyl-functionalized ligand was designed for the construction of metal-organic framework (MOF) materials with the aggregation-induced emission (AIE) feature, in which the fluorescence can be deliberately tailored: quenching the fluorescence to an "off" state by the decoration with heterocyclic auxiliary ligand 4,4'-bypyridine (Bpy) in the framework as a quenching agent and triggering the enhanced fluorescence to an "on" state by removal of Bpy through the metal competitive coordination substitution strategy. Our study shows that the occurrence of exciton migration between the AIE linker and conjugated auxiliary ligand Bpy causes fluorescence quenching. Time-dependent density functional theory was employed to understand the photoinduced electron transfer process and explain the origins of fluorescence quenching. Using this strategy, the prepared MOF material can perform as a fluorescence "off-on" probe for highly sensitive detection of Al3+ in aqueous media. The hydroxyl group plays a crucial role in sensing as it can selectively chelate Al3+, which is directly related to the dissociation of nonfluorescent MOF and consequent activation of the AIE process.

Judicious Design of Cationic, Cyclometalated Ir(III) Complexes for Photochemical Energy Conversion and Optoelectronics

The exponential growth in published studies on phosphorescent metal complexes has been triggered by their utilization in optoelectronics, solar energy conversion, and biological labeling applications. Very recent breakthroughs in organic photoredox transformations have further increased the research efforts dedicated to discerning the inner workings and structure-property relationships of these chromophores. Initially, the principal focus was on the Ru(II)-tris-diimine complex family. However, the limited photostability and lack of luminescence tunability discovered in these complexes prompted a broadening of the research to include 5d transition metal ions. The resulting increase in ligand field splitting prevents the population of antibonding eg* orbitals and widens the energy range available for color tuning. Particular attention was given to Ir(III), and its cyclometalated, cationic complexes have now replaced Ru(II) in the vast majority of applications. At the start, this Account documents the initial efforts dedicated to the color tuning of these complexes for their application in light emitting electrochemical cells, an easy to fabricate single-layer organic light emitting device (OLED). Systematic modifications of the ligand sphere of [Ir(ppy)2bpy]+ (ppy: 2-phenylpyridine, bpy: 2,2'-bipyridine) with electron withdrawing and donating substituents allowed access to complexes with luminescence emission maxima throughout the visible spectrum exhibiting room temperature excited state lifetimes ranging from nanoseconds to dozens of microseconds and quantum yields up to 15 times that of [Ru(bpy)3]2+. The diverse photophysical properties were also beneficial when using these Ir(III) complexes for driving solar fuel-producing reactions. For instance, photocatalytic water-reduction systems were explored to gain access to efficient water splitting systems. For this purpose, a variety of water reduction catalysts were paired with libraries of Ir(III) photosensitizers in high-throughput photoreactors. This parallelized approach allowed exploration of the interplay between the diverse photophysical properties of the Ir compounds and the electron-accepting catalysts. Further work enhanced and simplified the critical electron transfer processes between these two species through the use of bridging functional groups installed on the photosensitizer. Later, a novel approach summarized in this Account explores the possibility of using Zn metal as a solar fuel. Structure-activity relationships of the light-driven reduction of Zn2+ to Zn metal are described. DFT calculations along with cyclic voltammetry were utilized to gain clear insights into the complexes' electronic structures responsible for the effective photochemical properties observed in these dyes. While [Ir(ppy)2bpy]+ and its derivatives were found to be much more photostable than the Ru(II)-tris-diimine complex family, mass spectrometry indicated that the bpy ligand still photodissociated under extensive illumination. An interesting new approach involved the substitution of the bidentate 2,2'-bipyridine with a stronger chelating terpyridine ligand. This approach leaves room for one 2-phenylpyridine ligand and a third, anionic ligand, either Cl- or CN-. This Account reviews the effect of structural modifications on the photophysical properties of these [Ir(tpy)(ppy)X]+ complexes and corroborates the findings with the results obtained through DFT modeling. These complexes found application in photocatalytic CO2 reductions as well as a solvent tolerant light-absorber for the photogeneration of hydrogen. It was also documented that the robustness of these dyes in photoredox processes supersedes those of the commercially available [Ir(ppy)2(dtbbpy)]PF6 and [Ir(dF(CF3)ppy)2(dtbbpy)]PF6 complexes pioneered in the Bernhard laboratory.

Bicapped Keggin polyoxomolybdates: discrete species and experimental and theoretical investigations on the electronic delocalization in a chain compound.

Three monomeric polyoxometalates [M(C10H8N2)3][α-PMoMoO40Zn2(C10H8N2)2]·2H2O (M-PMo12Zn2, M = Fe, Co, Ru) with {Zn(bpy)2}2+ units capped on reduced α-Keggin polyanions and [M(bpy)3]2+ counter-ions were synthesized under hydrothermal conditions. The 1D polymer [N(C4H9)4][Ru(C10H8N2)3][α-PMoMoO43] (Ru-PMo14) was prepared by a similar strategy, in the absence of 2,2'-bpy ligands. In this chain capped reduced Keggin anions are linked via Mo-O-Mo bridges and are surrounded by both tetrabutylammonium cations and [Ru(bpy)3]2+ counter-ions. The compounds were characterized in the solid state by single crystal and powder X-ray diffraction and IR spectroscopy and in solution by 31P NMR spectroscopy. 31P diffusion ordered NMR spectroscopy (DOSY) indicates that the diffusion coefficient of the dissolved species of Ru-PMo14 corresponds to a dimeric structure. Magnetic susceptibility measurements performed on Ru-PMo14 show the existence of antiferromagnetic interactions between the d1 electrons of the six MoV centers, with a singlet spin ground state. However, attempts to fit the data in the 2-300 K temperature range with Heisenberg Hamiltonians adapted for 0 or 1D systems suggest that these electrons are delocalized. Density Functional Theory (DFT) and Wave Function Theory (WFT) calculations indicate a migration of the electrons of the capping MoV centers into the PMo12 units at high temperature, allowing the rationalization of the experimental observations.

Correction: Magnetic properties of the seven-coordinated nanoporous framework material Co(bpy)1.5(NO3)2 (bpy = 4,4'-bipyridine).

Correction for 'Magnetic properties of the seven-coordinated nanoporous framework material Co(bpy)1.5(NO3)2 (bpy = 4,4'-bipyridine)' by Elena Bartolomé et al., Dalton Trans., 2012, 41, 10382-10389.

Self-assembly of heteroleptic dinuclear silver(i) complexes bridged by bis(diphenylphosphino)ethyne.

We present a study of the self-assembling behaviour in solution of Ag[PF6] with one equivalent of an N^N ligand (N^N = 6,6'-dimethyl-2,2'-bipyridine (6,6'-Me2bpy) or 2,2':6',2''-terpyridine (tpy)), together with either 0.5 or one equivalent of the bridging ligand bis(diphenylphosphino)ethyne (dppa). Each product contains a dinuclear cation, with one or two dppa ligands bridging the two Ag+ centres; 6,6'-Me2bpy and tpy, respectively, act as chelating ligands. The compounds have been analysed in solution using NMR spectroscopic methods (1H, 1H{31P}, COSY, NOESY, 13C, HMQC and HMBC), including room and low temperature measurements. 31P{1H} NMR spectra recorded at different temperatures allow a deeper insight into the dynamic equilibrium processes. In addition, solution 31P-109Ag HSQC spectroscopic measurements were performed and show, inter alia, the ratio of the splitting in the F1 dimension and the 1J31P-109Ag coupling constant in the fully coupled HSQC. Single crystal X-ray diffraction yielded two pseudo-polymorphic structures for the doubly-bridged [Ag2(dppa)2(tpy)2][PF6]2 and one for the singly-bridged [Ag2(dppa)(6,6'-Me2bpy)2][PF6]2.

Highly active, separable and recyclable bipyridine iridium catalysts for C–H borylation reactions

Iridium complexes generated from Ir(i) precursors and PIB oligomer functionalized bpy ligands efficiently catalyzed the reaction of arenes with bis(pinacolato)diboron under mild conditions to produce a variety of arylboronate compounds.

Luminescent copper(i) complexes with bisphosphane and halogen-substituted 2,2'-bipyridine ligands.

Heteroleptic [Cu(P^P)(N^N)][PF6] complexes, where N^N is a halo-substituted 2,2'-bipyridine (bpy) and P^P is either bis(2-(diphenylphosphino)phenyl)ether (POP) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos) have been synthesized and investigated. To stabilize the tetrahedral geometry of the copper(i) complexes, the steric demands of the bpy ligands have been increased by introducing 6- or 6,6'-halo-substituents in 6,6'-dichloro-2,2'-bipyridine (6,6'-Cl2bpy), 6-bromo-2,2'-bipyridine (6-Brbpy) and 6,6'-dibromo-2,2'-bipyridine (6,6'-Br2bpy). The solid-state structures of [Cu(POP)(6,6'-Cl2bpy)][PF6], [Cu(xantphos)(6,6'-Cl2bpy)][PF6]·CH2Cl2, [Cu(POP)(6-Brbpy)][PF6] and [Cu(xantphos)(6-Brbpy)][PF6]·0.7Et2O obtained from single crystal X-ray diffraction are described including the pressure dependence of the structure of [Cu(POP)(6-Brbpy)][PF6]. The copper(i) complexes with either POP or xantphos and 6,6'-Cl2bpy, 6-Brbpy and 6,6'-Br2bpy are orange-to-red emitters in solution and yellow-to-orange emitters in the solid state, and their electrochemical and photophysical properties have been evaluated with the help of density functional theory (DFT) calculations. The emission properties are strongly influenced by the substitution pattern that largely affects the geometry of the emitting triplet state. [Cu(POP)(6,6'-Cl2bpy)][PF6] and [Cu(xantphos)(6,6'-Cl2bpy)][PF6] show photoluminescence quantum yields of 15 and 17%, respectively, in the solid state, and these compounds were tested as luminophores in light-emitting electrochemical cells (LECs). The devices exhibit orange electroluminescence and very short turn-on times (<5 to 12 s). Maximum luminance values of 121 and 259 cd m-2 for [Cu(POP)(6,6'-Cl2bpy)][PF6] and [Cu(xantphos)(6,6'-Cl2bpy)][PF6], respectively, were achieved at an average current density of 100 A m-2. External quantum efficiencies of 1.2% were recorded for both complexes.

RuII Photosensitizer‐Functionalized Two‐Dimensional MoS2 for Light‐Driven Hydrogen Evolution

Metallic-phase molybdenum disulfide (1T-MoS2 ) nanosheets have proven to be highly active in the hydrogen evolution reaction (HER). We describe construction of photosensitizer functionalized 1T-MoS2 by covalently tethering the molecular photosensitizer [RuII (bpy)3 ]2+ (bpy=2,2'-bipyridine) on 1T-MoS2 nanosheets. This was achieved by covalently tethering the bpy ligand to 1T-MoS2 nanosheets, and subsequent complexation with [RuII (bpy)2 Cl2 ] to yield [RuII (bpy)3 ]-MoS2 . The obtained [RuII (bpy)3 ]-MoS2 nanosheets were characterized using infra-red, electronic absorption, X-ray photoelectron, and Raman spectroscopies, X-ray powder diffraction and electron microscopy. The fabricated material exhibited a significant improvement of photocurrent and HER performance, demonstrating the potential of such two-dimensional [RuII (bpy)3 ]-MoS2 constructs in photosensitized HER.

A robust ruthenium complex with nonyl-substituted bpy ligand for dye-sensitized photoelectrochemical cell application

Stability, electrochemical and photoelectrochemical studies of a new ruthenium polypyridyl complex [Ru(nbipy)2(bipydipa)]2+ (P2), where nbipy = 4,4′-dinonyl-2,2′-bipyridine and bipydipa = 2,2′-bipyridine-4,4′-diphosphonic acid, immobilised as FTO/TiO2/P2 electrode were investigated and compared with the parent complex [Ru(bipy)2(bipydipa)]2+ (P1), where bipy = 2,2′-bipyridine. Upon immersion in pH 5.9 and pH 8.1 solutions, P2 absorbed in TiO2 proved to be less prone to desorption from the surface in comparison with P1. The immobilised P2 in FTO/TiO2/P2 electrode displays higher RuIII/RuII oxidation potential (1.47 V vs. NHE) than that of the P1 counterpart (1.33 V vs. NHE). The DSPEC assembled with FTO/TiO2/P2 electrode shows greater photocurrent densities, higher amount of hydrogen gas, better Faradaic efficiency and greater photostability during the photolysis experiments at 0.2 V NHE.

Effect of the ortho-Hydroxyl Groups on a Bipyridine Ligand of Iridium Complexes for the High-Pressure Gas Generation from the Catalytic Decomposition of Formic Acid.

The hydroxyl groups of a 2,2'-bipyridine (bpy) ligand near the metal center activated the catalytic performance of the Ir complex for the dehydrogenation of formic acid at high pressure. The position of the hydroxyl groups on the ligand affected the catalytic durability for the high-pressure H2 generation through the decomposition of formic acid. The Ir complex with a bipyridine ligand functionalized with para-hydroxyl groups shows a good durability with a constant catalytic activity during the reaction even under high-pressure conditions, whereas deactivation was observed for an Ir complex with a bipyridine ligand with ortho-hydroxyl groups (2). In the presence of high-pressure H2 , complex 2 decomposed into the ligand and an Ir trihydride complex through the isomerization of the bpy ligand. This work provides the development of a durable catalyst for the high-pressure H2 production from formic acid.

Slow magnetic relaxation in a carboxylate-bridged CoII complex

A new Co(II) complex, {[Co(MPA)(4,4′-bpy)(H2O)]·2H2O}n (1) (H2MPA = 4-methylphthalic acid, 4,4′-bpy = 4,4′-bipyridine), has been prepared under solvothermal condition and fully characterized. The X-ray crystallography test demonstrates that 1 exhibits two-dimensional (2D) layer structure in which the helical Co(II) chains linked by syn-anti carboxylate bridges are connected by 4,4′-bpy ligands. Weak ferromagnetism was observed on direct-current (dc) susceptibility due to the collective effects of the helical chain structure and antiferromagnetic couplings between Co(II) ions transmitted by μ2-1,3-carboxylate groups. Interestingly, slow magnetic relaxation was observed in 1 at liquid helium temperatures without an external dc field.