Neutral water splitting catalysis with a high FF triple junction polymer cell

This document is the Accepted Manuscript version of a Published Work that appeared in final form in CS catalysis, copyright © American Chemical Society, after peer review and technical editing by the publisher and may be found at http://dx.doi.org/10.1021/acscatal.6b01036We report a photovoltaics-electrochemical (PV-EC) assembly based on a compact and easily processable triple homojunction polymer cell with high fill factor (76%), optimized conversion efficiencies up to 8.7%, and enough potential for the energetically demanding water splitting reaction (V-oc = 2.1 V). A platinum-free cathode made of abundant materials is coupled to a ruthenium oxide on glassy carbon anode (GC-RuO2) to perform the reaction at optimum potential (Delta E = 1.70-1.78 V, overpotential = 470-550 mV). The GC-RuO2 anode contains a single monolayer of catalyst corresponding to a superficial concentration (Gamma) of 0.15 nmol cm(-2) and is highly active at pH 7. The PV-EC cell achieves solar to hydrogen conversion efficiencies (STH) ranging from 5.6 to 6.0%. As a result of the solar cell's high fill factor, the optimal photovoltaic response is found at 1.70 V, the minimum potential at which the electrodes used perform the water splitting reaction. This allows generating hydrogen at efficiencies that would be very similar (96%) to those obtained as if the system were to be operating at 1.23 V, the thermodynamic potential threshold for the water splitting reaction.Peer ReviewedPostprint (author's final draft

Oxygen−Oxygen Bond Formation by the Ru-Hbpp Water Oxidation Catalyst Occurs Solely via an Intramolecular Reaction Pathway

Oxygen−Oxygen Bond Formation by the Ru-Hbpp Water Oxidation Catalyst Occurs Solely via an Intramolecular Reaction Pathwa

New Dinuclear Ruthenium Complexes: Structure and Oxidative Catalysis

The synthesis of new dinuclear complexes of the general formula {[Ru^II(trpy)]₂(μ-pdz-dc)­(μ-(L)}⁺ [pdz-dc is the pyridazine-3,6-dicarboxylate dianion; trpy is 2,2′:6′,2″-terpyridine; L = Cl (<b>1</b>^<b>+</b>) or OH (<b>2⁺</b>)] is described. These complexes are characterized by the usual analytical and spectroscopic techniques and by X-ray diffraction analysis. Their redox properties are characterized by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Complex <b>2⁺</b> is used as the starting material to prepare the corresponding Ru-aqua complex {[Ru^II(trpy)­(H₂O)]₂(μ-pdz-dc)}²⁺ (<b>3²⁺</b>), whose electrochemistry is also investigated by means of CV and DPV. Complex <b>3²⁺</b> is able to catalytically and electrocatalytically oxidize water to dioxygen with moderate efficiencies. In sharp contrast, <b>3²⁺</b> is a superb catalyst for the epoxidation of alkenes. For the particular case of <i>cis</i>-β-methylstyrene, the catalyst is capable of carrying out 1320 turnovers with a turnover frequency of 11.0 cycles min^–1, generating <i>cis</i>-β-methylstyrene oxide stereospecifically

New Dinuclear Ruthenium Complexes: Structure and Oxidative Catalysis

The synthesis of new dinuclear complexes of the general formula {[Ru^II(trpy)]₂(μ-pdz-dc)­(μ-(L)}⁺ [pdz-dc is the pyridazine-3,6-dicarboxylate dianion; trpy is 2,2′:6′,2″-terpyridine; L = Cl (<b>1</b>^<b>+</b>) or OH (<b>2⁺</b>)] is described. These complexes are characterized by the usual analytical and spectroscopic techniques and by X-ray diffraction analysis. Their redox properties are characterized by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Complex <b>2⁺</b> is used as the starting material to prepare the corresponding Ru-aqua complex {[Ru^II(trpy)­(H₂O)]₂(μ-pdz-dc)}²⁺ (<b>3²⁺</b>), whose electrochemistry is also investigated by means of CV and DPV. Complex <b>3²⁺</b> is able to catalytically and electrocatalytically oxidize water to dioxygen with moderate efficiencies. In sharp contrast, <b>3²⁺</b> is a superb catalyst for the epoxidation of alkenes. For the particular case of <i>cis</i>-β-methylstyrene, the catalyst is capable of carrying out 1320 turnovers with a turnover frequency of 11.0 cycles min^–1, generating <i>cis</i>-β-methylstyrene oxide stereospecifically

Synthesis, Structure, and Reactivity of New Tetranuclear Ru-Hbpp-Based Water-Oxidation Catalysts

The preparation of three new octadentate tetranucleating ligands made out of two Ru-Hbpp-based units [where Hbpp is 3,5(bispyridyl)pyrazole], linked by a xylyl group attached at the pyrazolate moiety, of general formula (Hbpp)2-u-xyl (u = p, m, or o) is reported, together with its dinucleating counterpart substituted at the same position with a benzyl group, Hbpp-bz. All of these ligands have been characterized with the usual analytical and spectroscopic techniques. The corresponding tetranuclear ruthenium complexes of general formula {[Ru2(trpy)2(L)]2(μ-(bpp)2-u-xyl)}n+ [L = Cl or OAc, n = 4; L = (H2O)2, n = 6] and their dinuclear homologues {[Ru2(trpy)2(L)](μ-bpp-bz)}n+ [L = Cl or OAc, n = 2; L = (H2O)2, n = 3] have also been prepared and thoroughly characterized both in solution and in the solid state. In solution, all of the complexes have been characterized spectroscopically by UV−vis and NMR and their redox properties investigated by means of cyclic voltammetry techniques. In the solid state, monocrystal X-ray diffraction analysis has been carried out for two dinuclear complexes {[Ru2(trpy)2(L)](μ-bpp-bz)}2+ (L = Cl and OAc) and for the tetranuclear complex {[Ru2(trpy)2(μ-OAc)]2(μ-(bpp)2-m-xyl)}4+. The capacity of the tetranuclear aqua complexes {[Ru2(trpy)2(H2O)2]2(μ-(bpp)2-u-xyl)}6+ and the dinuclear homologue {[Ru2(trpy)2(H2O)2](μ-bpp-bz)}3+ to act as water-oxidation catalysts has been evaluated using cerium(IV) as the chemical oxidant in pH = 1.0 triflic acid solutions. It is found that these complexes, besides generating significant amounts of dioxygen, also generate carbon dioxide. The relative ratio of [O2]/[CO2] is dependent not only on para, meta, or ortho substitution of the xylylic group but also on the concentration of the starting materials. With regard to the tetranuclear complexes, the one that contains the more sterically constrained ortho-substituted ligand generates the highest [O2]/[CO2] ratio

Synthesis, Structure, and Reactivity of New Tetranuclear Ru-Hbpp-Based Water-Oxidation Catalysts

The preparation of three new octadentate tetranucleating ligands made out of two Ru-Hbpp-based units [where Hbpp is 3,5(bispyridyl)pyrazole], linked by a xylyl group attached at the pyrazolate moiety, of general formula (Hbpp)2-u-xyl (u = p, m, or o) is reported, together with its dinucleating counterpart substituted at the same position with a benzyl group, Hbpp-bz. All of these ligands have been characterized with the usual analytical and spectroscopic techniques. The corresponding tetranuclear ruthenium complexes of general formula {[Ru2(trpy)2(L)]2(μ-(bpp)2-u-xyl)}n+ [L = Cl or OAc, n = 4; L = (H2O)2, n = 6] and their dinuclear homologues {[Ru2(trpy)2(L)](μ-bpp-bz)}n+ [L = Cl or OAc, n = 2; L = (H2O)2, n = 3] have also been prepared and thoroughly characterized both in solution and in the solid state. In solution, all of the complexes have been characterized spectroscopically by UV−vis and NMR and their redox properties investigated by means of cyclic voltammetry techniques. In the solid state, monocrystal X-ray diffraction analysis has been carried out for two dinuclear complexes {[Ru2(trpy)2(L)](μ-bpp-bz)}2+ (L = Cl and OAc) and for the tetranuclear complex {[Ru2(trpy)2(μ-OAc)]2(μ-(bpp)2-m-xyl)}4+. The capacity of the tetranuclear aqua complexes {[Ru2(trpy)2(H2O)2]2(μ-(bpp)2-u-xyl)}6+ and the dinuclear homologue {[Ru2(trpy)2(H2O)2](μ-bpp-bz)}3+ to act as water-oxidation catalysts has been evaluated using cerium(IV) as the chemical oxidant in pH = 1.0 triflic acid solutions. It is found that these complexes, besides generating significant amounts of dioxygen, also generate carbon dioxide. The relative ratio of [O2]/[CO2] is dependent not only on para, meta, or ortho substitution of the xylylic group but also on the concentration of the starting materials. With regard to the tetranuclear complexes, the one that contains the more sterically constrained ortho-substituted ligand generates the highest [O2]/[CO2] ratio

Synthesis, Structure, and Reactivity of New Tetranuclear Ru-Hbpp-Based Water-Oxidation Catalysts

The preparation of three new octadentate tetranucleating ligands made out of two Ru-Hbpp-based units [where Hbpp is 3,5(bispyridyl)pyrazole], linked by a xylyl group attached at the pyrazolate moiety, of general formula (Hbpp)2-u-xyl (u = p, m, or o) is reported, together with its dinucleating counterpart substituted at the same position with a benzyl group, Hbpp-bz. All of these ligands have been characterized with the usual analytical and spectroscopic techniques. The corresponding tetranuclear ruthenium complexes of general formula {[Ru2(trpy)2(L)]2(μ-(bpp)2-u-xyl)}n+ [L = Cl or OAc, n = 4; L = (H2O)2, n = 6] and their dinuclear homologues {[Ru2(trpy)2(L)](μ-bpp-bz)}n+ [L = Cl or OAc, n = 2; L = (H2O)2, n = 3] have also been prepared and thoroughly characterized both in solution and in the solid state. In solution, all of the complexes have been characterized spectroscopically by UV−vis and NMR and their redox properties investigated by means of cyclic voltammetry techniques. In the solid state, monocrystal X-ray diffraction analysis has been carried out for two dinuclear complexes {[Ru2(trpy)2(L)](μ-bpp-bz)}2+ (L = Cl and OAc) and for the tetranuclear complex {[Ru2(trpy)2(μ-OAc)]2(μ-(bpp)2-m-xyl)}4+. The capacity of the tetranuclear aqua complexes {[Ru2(trpy)2(H2O)2]2(μ-(bpp)2-u-xyl)}6+ and the dinuclear homologue {[Ru2(trpy)2(H2O)2](μ-bpp-bz)}3+ to act as water-oxidation catalysts has been evaluated using cerium(IV) as the chemical oxidant in pH = 1.0 triflic acid solutions. It is found that these complexes, besides generating significant amounts of dioxygen, also generate carbon dioxide. The relative ratio of [O2]/[CO2] is dependent not only on para, meta, or ortho substitution of the xylylic group but also on the concentration of the starting materials. With regard to the tetranuclear complexes, the one that contains the more sterically constrained ortho-substituted ligand generates the highest [O2]/[CO2] ratio

Synthesis, Structure, and Reactivity of New Tetranuclear Ru-Hbpp-Based Water-Oxidation Catalysts

The preparation of three new octadentate tetranucleating ligands made out of two Ru-Hbpp-based units [where Hbpp is 3,5(bispyridyl)pyrazole], linked by a xylyl group attached at the pyrazolate moiety, of general formula (Hbpp)2-u-xyl (u = p, m, or o) is reported, together with its dinucleating counterpart substituted at the same position with a benzyl group, Hbpp-bz. All of these ligands have been characterized with the usual analytical and spectroscopic techniques. The corresponding tetranuclear ruthenium complexes of general formula {[Ru2(trpy)2(L)]2(μ-(bpp)2-u-xyl)}n+ [L = Cl or OAc, n = 4; L = (H2O)2, n = 6] and their dinuclear homologues {[Ru2(trpy)2(L)](μ-bpp-bz)}n+ [L = Cl or OAc, n = 2; L = (H2O)2, n = 3] have also been prepared and thoroughly characterized both in solution and in the solid state. In solution, all of the complexes have been characterized spectroscopically by UV−vis and NMR and their redox properties investigated by means of cyclic voltammetry techniques. In the solid state, monocrystal X-ray diffraction analysis has been carried out for two dinuclear complexes {[Ru2(trpy)2(L)](μ-bpp-bz)}2+ (L = Cl and OAc) and for the tetranuclear complex {[Ru2(trpy)2(μ-OAc)]2(μ-(bpp)2-m-xyl)}4+. The capacity of the tetranuclear aqua complexes {[Ru2(trpy)2(H2O)2]2(μ-(bpp)2-u-xyl)}6+ and the dinuclear homologue {[Ru2(trpy)2(H2O)2](μ-bpp-bz)}3+ to act as water-oxidation catalysts has been evaluated using cerium(IV) as the chemical oxidant in pH = 1.0 triflic acid solutions. It is found that these complexes, besides generating significant amounts of dioxygen, also generate carbon dioxide. The relative ratio of [O2]/[CO2] is dependent not only on para, meta, or ortho substitution of the xylylic group but also on the concentration of the starting materials. With regard to the tetranuclear complexes, the one that contains the more sterically constrained ortho-substituted ligand generates the highest [O2]/[CO2] ratio

DNA-Cleavage Induced by New Macrocyclic Schiff base Dinuclear Cu(I) Complexes Containing Pyridyl Pendant Arms

A new series of dinuclear Cu(I) complexes with hexaazamacrocyclic Schiff base ligand containing pyridyl pendant arms has been synthesized and characterized. The solid-state structures of [Cu2I(bsp3py)](CF3SO3)2 (1(CF3SO3)2), [Cu2I(bsm3py)](SbF6)2 (2(SbF6)2), and [Cu2I(bsp2py)](CF3SO3)2 (3(CF3SO3)2) have been established by single-crystal X-ray diffraction analysis. The geometries of the copper centers in all three cases are almost identical showing a distorted tetrahedral coordination, very close to a trigonal pyramidal arrangement. Interactions of complexes with calf thymus DNA have been investigated by circular dichroism spectroscopy (CD) which suggests that the interaction for each complex is a nonintercalative mode with regard to DNA. The electrophoretic mobility study and the atomic force microscopy (AFM) in the presence of H2O2 reveal a cleavage of pBR322 supercoiled DNA that depends on the nature of the Cu(I) complex used. The most efficient reactivity is observed for complexes 1(CF3SO3)2 and 2(CF3SO3)2 whereas complex 3(CF3SO3)2 displays a lesser reactivity. The different DNA-cleavage activity of complexes 1−3 is due the different electronic factors and complex topology induced by the natures of the different ligands. This work constitutes an example of how small modifications introduced in the macrocyclic backbone of the metal complexes lead to dramatic changes in the nuclease activity

Synthesis, Structure, and Substitution Mechanism of New Ru(II) Complexes Containing 1,4,7-Trithiacyclononane and 1,10-Phenanthroline Ligands

Two new Ru complexes containing the 1,10-phenanthroline (phen) and 1,4,7-trithiacyclononane ([9]aneS3, ligands of general formula [Ru(phen)(L)([9]aneS3)]2+ (L = MeCN, 3; L = pyridine (py), 4) have been prepared and thoroughly characterized. Structural characterization in the solid state has been performed by means of X-ray diffraction analyses, which show a distorted octahedral environment for a diamagnetic d6 Ru(II), as expected. 1H NMR spectroscopy provides evidence that the same structural arrangement is maintained in solution. Further spectroscopic characterization has been carried out by UV−vis spectroscopy where the higher π acceptor capability of MeCN versus the py ligand is manifested in a 9−15-nm blue shift in its MLCT bands. The E1/2 redox potential of the Ru(III)/Ru(II) couple for 3 is anodically shifted with respect to its Ru−py analogue, 4, by 60 mV, which is also in agreement with a higher electron-withdrawing capacity of the former. The mechanism for the reaction Ru−py + MeCN → Ru−MeCN + py has also been investigated at different temperatures with and without irradiation. In the absence of irradiation at 326 K, the thermal process gives kinetic constants of k2 = 1.4 × 10-5 s-1 (ΔH⧧ = 108 ± 3 kJ mol-1, ΔS⧧ = −8 ± 9 J K-1 mol-1) and k-2 = 2.9 × 10-6 s-1 (ΔH⧧ = 121 ± 1 kJ mol-1, ΔS⧧ = 18 ± 3 J K-1 mol-1). The phototriggered process is faster and consists of preequilibrium formation of an intermediate that thermally decays to the final Ru−MeCN complex with an apparent rate constant of (k1Khν)app = 1.8 × 10-4 s-1 at 304 K, under the continuous irradiation experimental conditions used