A bis(bipyridyl)pyrazolate ((Me)bbp(-)) has recently been introduced as a rugged dinucleating, bi... more A bis(bipyridyl)pyrazolate ((Me)bbp(-)) has recently been introduced as a rugged dinucleating, bis(tridentate) ligand for the formation of efficient diruthenium water oxidation catalysts (J. Am. Chem. Soc. 2014, 136, 24-27). Now, detailed protocols for the synthesis of a whole family of such dinuclear ruthenium complexes [{Ru(pyR(2))2}2(μ-(R1)bbp)(X,Y)](2+) based on the bis(bipyridyl)pyrazolate scaffold are reported. The isolation of a synthetic key intermediate allowed the straightforward introduction of different pyridines as axial ligands. Thereby, a set of complexes with different substituents at the pyrazolate backbone (R(1) = Br, H, Me), different pyridines as axial ligand (R(2) = H, NMe2, SO3), and different (non)bridging units in the in,in-position (X,Y = Cl, H2O, OAc) has been prepared and thoroughly characterized. Complexes of the type [{Ru(pyR(2))2}2(μ-(R1)bbp)(μ-OAc)](2+), with an exogenous acetato bridge, have been used as catalyst precursors in catalytic water oxidatio...
The synthetic intermediate cis(out),cis-[Ru(Cl)2(HL)(DMSO)2], 1 (DMSO = dimethyl sulfoxide), and ... more The synthetic intermediate cis(out),cis-[Ru(Cl)2(HL)(DMSO)2], 1 (DMSO = dimethyl sulfoxide), and four new mononuclear ruthenium complexes with general formula out/in-[Ru(HL)(trpy)(X)](m+) (trpy = 4-tert-butylpyridine; X = Cl(-), m = 1, 2a(+) and 2b(+); X = H2O, m = 2, 3a(2+) and 3b(2+)) based on the ligand 1H-pyrazole-3-carboxylic acid, 5-(2-pyridinil)-, ethyl ester (HL), are synthesized and characterized by analytical, spectroscopic, and electrochemical methods. A linkage isomerism is observed for a DMSO moiety of 1, and relevant thermodynamics and kinetics values are obtained through electrochemical experiments and compared to literature. Different synthetic routes are developed to obtain isomeric 2a(+) and 2b(+), with different relative yields. Water oxidation activity of 3a(2+) and 3b(2+) is analyzed by means of electrochemical methods, through foot of the wave analysis, yielding kobs values of 1.00 and 2.23 s(-1), respectively. Chemically driven water oxidation activity is tested using [(NH4)2Ce(NO3)6] as sacrificial electron acceptor, and turnover number (TON) and turnover frequency (TOF) values of TON = 10.8 and TOFi = 58.2 × 10(-3) s(-1) for 3a(2+) and TON = 4.2 and TOFi = 15.4 × 10(-3) s(-1) for 3b(2+) are obtained.
One main difficulty for the technological development of photoelectrochemical (PEC) water splitti... more One main difficulty for the technological development of photoelectrochemical (PEC) water splitting (WS) devices is the fabrication of active, stable and cost-effective photoelectrodes that ensure high performance. Here, we report the development of a CuO/Silicon based photoanode, which shows an onset potential for the water oxidation of 0.53 V vs SCE at pH 9, that is, an overpotential of 75 mV, and high stability above 10 h. These values account for a photovoltage of 420 mV due to the absorbed photons by silicon, as proven by comparing with analogous CuO/FTO electrodes that are not photoactive. The photoanodes have been fabricated by sputtering a thin film of Cu(0) on commercially available n-type Si wafers, followed by a photoelectrochemical treatment in basic pH conditions. The resulting CuO/Cu layer acts as (1) protective layer to avoid the corrosion of nSi, (2) p-type hole conducting layer for efficient charge separation and transportation, and (3) electrocatalyst to reduce the overpotential of the water oxidation reaction. The low cost, low toxicity, and good performance of CuO-based coatings can be an attractive solution to functionalize unstable materials for solar energy conversion.
Under the appropriate reaction conditions and stoichiometries the combination of a Cu (I) complex... more Under the appropriate reaction conditions and stoichiometries the combination of a Cu (I) complex, t-BuOOH and molecular oxygen generates a catalyst that is capable of oxidizing alkanes, alkenes, alcohols and triphenyl phosphine under one atmosphere oxygen ...
... In the absence of 02, (a) the Fenton systems yield R(py) or ROH [KIE = 1.1-1.7 (HOOH) and 4.6... more ... In the absence of 02, (a) the Fenton systems yield R(py) or ROH [KIE = 1.1-1.7 (HOOH) and 4.6 (r-BuOOH)] with reaction efficiencies up to 80% [product per HOOH(Bu-t)], and for FeI'(PA)2/HOOH the relative reactivity of c-CgH12/ PhCH2CH3 is 2.0 ... (17) Sohal, R. S.; Allen, R. 0 ...
Several iron complexes [FeII(bpy)22+, FeII(OPPh3)42+, and FeII(PA)2] in combination with hydrogen... more Several iron complexes [FeII(bpy)22+, FeII(OPPh3)42+, and FeII(PA)2] in combination with hydrogen peroxide (HOOH) catalytically hydroxylate aromatic substrates (ArH). The base-induced nucleophilic addition of HOOH to the electrophilic iron center yields the reactive intermediate of Fenton reagents . The latter includes a ‘stabilized’ hydroxyl radical that is able to replace an aromatic hydrogen (H) with a hydroxyl group (HO) via an initial addition reaction. With PhCH3 and PhCH2CH3 as substrates free HO· (from the radiolysis of H2O) reacts via aryl addition (97 and 85%, respectively) to give Ar-Ar as the predominant product, whereas 1 favors H-atom abstraction from the alkyl group (50 and 80%, respectively) and the only detectable products from aryl addition are the respective substituted phenols (o:p-ArOH). Other substituted benzenes (PhX) undergo addition by free HO at the ortho and para aryl carbons (o:p ratio, 2), followed by dimerization and elimination of two H2O molecules to yield substituted biphenyls. In contrast, 1 reacts with PhX to yield substituted phenol (ArOH; o:p ratio, 0.5 – 1.1). With phenol (PhOH) as the substrate, reaction with 1 yields mainly catechol (o-Ar(OH)2; o:p ratio, 20). In a solvent matrix of MeCN:H2O (3:1 mol:mol ratio) the reaction efficiencies with FeII(bpy)22+ and FeII(OPPh3)42+ for the hydroxylation of benzene to phenol are 36 and 42%, respectively (product per HOOH).Iron(II) complexes [FeIILx2+; FEII(bpy)22+, FeII(OPPh3)42+, FeII(PA)2 (PAH = picolinic acid)] catalytically activate hydrogen peroxide via Fenton chemistry for the hydroxylation of aromatic molecules (PhX).
The present study provides mechanistic details of a mild aromatic C-H activation effected by a co... more The present study provides mechanistic details of a mild aromatic C-H activation effected by a copper(II) center ligated in a triazamacrocylic ligand, affording equimolar amounts of a Cu III -aryl species and Cu I species as reaction products. At low temperatures the Cu II complex 1 forms a three-center, threeelectron C-H · · · Cu II interaction, identified by pulse electron paramagnetic resonance spectroscopy and supported by density functional theory calculations. C-H bond cleavage is coupled with copper oxidation, as a Cu III -aryl product 2 is formed. This reaction proceeds to completion at 273 K within minutes through either a copper disproportionation reaction or, alternatively, even faster with 1 equiv of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), quantitatively yielding 2. Kinetic studies of both reactions strongly implicate a rate-limiting proton-coupled electron transfer as the key C-H activation step, a mechanism that does not conform to the C-H activation mechanism in a Ni II analogue or to any previously proposed C-H activation mechanisms. Figure 3. X-band HYSCORE spectra taken at the observer positions (A) and (B) as indicated in the top figure. First row: 1 formed with H33m. Second row: 1 formed with D-H33m. Third row: HYSCORE simulation of the C-H a interaction of interest. The features that disappear upon monodeuteration of the ligand are indicated with arrows.
New coordination compounds of formulae: [Ru(trpy)(bpy)(4,4′-azpy)]2+, 1, [Ru(tpm)(bpy)(4,4′-azpy)... more New coordination compounds of formulae: [Ru(trpy)(bpy)(4,4′-azpy)]2+, 1, [Ru(tpm)(bpy)(4,4′-azpy)]2+, 2, [(trpy)(bpy)Ru(4,4′-azpy)Ru(NH3)5]4+, 3, and [(trpy)(bpy)Ru(4,4′-azpy)Ru(bpy)(trpy)]4+, 5, with trpy = 2,2′:6′,2″-terpyridine, tpm = tris(1-pyrazolyl)methane), bpy = 2,2′-bipyridine and 4,4′-azpy = 4,4′-azobis(pyridine), have been synthesized as PF6- salts and characterized by spectroscopic and electrochemical techniques. The structure of the cation [Ru(trpy)(bpy)(4,4′-azpy)]2+ has been determined by X-ray diffraction analysis, which reveals a trans-configuration of coordinated 4,4′-azpy and a packing structure that is based on extensive π-interactions within neighboring molecules. Upon controlled potential electrolysis of the dinuclear [RuII,RuII] complex 3, a stable [RuII, RuIII] mixed-valent species, 4, was detected. From spectral data and Gaussian deconvolution analysis of the intervalence transition in 4, a strong electronic interaction between both ruthenium centers is disclosed (HAB = 550 cm−1), pointing to possible applications of 4,4′-azpy as a conducting bridge in “molecular wires”.New mononuclear and dinuclear polypyridyl ruthenium(II) complexes containing 4,4′- azpy have been synthesized and characterized by spectroscopic, X-ray diffraction and electrochemical techniques. In the mixed-valent asymmetric complex with pentaammineruthenium(III) as an electron acceptor, a relatively strong metal–metal coupling is disclosed, pointing to possible applications of 4,4′-azpy in “molecular wires”.
A new decadentate dinucleating ligand containing a pyridazine bridging group and pyridylic arms h... more A new decadentate dinucleating ligand containing a pyridazine bridging group and pyridylic arms has been synthesized and characterized by analytical and spectroscopic techniques. Four new dinuclear cobalt complexes featuring this ligand have been prepared and thoroughly characterized both in the solid state (X-ray diffraction) and in solution (1D and 2D NMR spectroscopy, ESI-MS, and electrochemical techniques). The flexible but stable coordination environment provided by the ligand scaffold when coordinating Co in different oxidation states is shown to play a crucial role in the performance of the set of complexes when tested as catalysts for the photochemical hydrogen evolution reaction (HER) and chemical oxygen reduction reaction (ORR).
Page 1. Synthesis, Structure, and Magnetic Properties of [Dithiazolylium] x [M(tdas) 2 ] Salts Sa... more Page 1. Synthesis, Structure, and Magnetic Properties of [Dithiazolylium] x [M(tdas) 2 ] Salts Sarah S. Staniland School of Chemistry, University of Edinburgh, Edinburgh, UK Wataru Fujita Yoshikatsu Umezono Kunio Awaga Department ...
Mastering the light-induced four-electron oxidation of water to molecular oxygen is a key step to... more Mastering the light-induced four-electron oxidation of water to molecular oxygen is a key step towards the achievement of overall water splitting to produce alternative solar fuels. In this work, we report two rugged molecular pyrazolate-based diruthenium complexes that efficiently catalyze visible-light-driven water oxidation. These complexes were fully characterized both in the solid state (by X-ray diffraction analysis) and in solution (spectroscopically and electrochemically). Benchmark performances for homogeneous oxygen production have been obtained for both catalysts in the presence of a photosensitizer and a sacrificial electron acceptor at pH 7, and a turnover frequency of up to 11.1 s(-1) and a turnover number of 5300 were obtained after three successive catalytic runs. Under the same experimental conditions with the same setup, the pyrazolate-based diruthenium complexes outperform other well-known water oxidation catalysts owing to both electrochemical and mechanistic asp...
The upper critical field of heavy fermion superconductor CeCoIn5 much exceeds the Pauli limit. Th... more The upper critical field of heavy fermion superconductor CeCoIn5 much exceeds the Pauli limit. This raises the possibility of a first-order transition to the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) inhomogeneous superconducting state at high field, which coexists with ferromagnetism. A first-order metamagnetic transition has been reported using bulk magnetization measurement. However, result from this type of measurements includes effect due to flux pinning/depinning. We report here magnetization result using neutron diffraction technique, which couples directly to magnetic moments. A smooth change in magnetization is observed.
The computation of good viewpoints is important in several fields: computer graphics, removal of ... more The computation of good viewpoints is important in several fields: computer graphics, removal of degeneracies in computational geometry, robotics, graph drawing, etc. However, in areas such as computer graphics there is no consensus on what a good viewpoint means and, consequently, each author uses his or her own definition according to the requirements of the application. In this paper we present a formal measure strongly based on Information Theory, viewpoint entropy, that can be applied to certain problems of Computer Graphics such as automatic exploration of objects or scenes and Scene Understanding. We also define a new measure, the orthogonal frustum entropy, in order to fulfill the requirements needed to visualize molecules. We design an algorithm that makes use of graphics hardware to accelerate computation, and whose complexity depends mainly on the number of views we want to analyze. Computation of good views of molecules is useful for molecular scientists, a field which includes practitioners from Crystallography, Chemistry, and Biology.
A bis(bipyridyl)pyrazolate ((Me)bbp(-)) has recently been introduced as a rugged dinucleating, bi... more A bis(bipyridyl)pyrazolate ((Me)bbp(-)) has recently been introduced as a rugged dinucleating, bis(tridentate) ligand for the formation of efficient diruthenium water oxidation catalysts (J. Am. Chem. Soc. 2014, 136, 24-27). Now, detailed protocols for the synthesis of a whole family of such dinuclear ruthenium complexes [{Ru(pyR(2))2}2(μ-(R1)bbp)(X,Y)](2+) based on the bis(bipyridyl)pyrazolate scaffold are reported. The isolation of a synthetic key intermediate allowed the straightforward introduction of different pyridines as axial ligands. Thereby, a set of complexes with different substituents at the pyrazolate backbone (R(1) = Br, H, Me), different pyridines as axial ligand (R(2) = H, NMe2, SO3), and different (non)bridging units in the in,in-position (X,Y = Cl, H2O, OAc) has been prepared and thoroughly characterized. Complexes of the type [{Ru(pyR(2))2}2(μ-(R1)bbp)(μ-OAc)](2+), with an exogenous acetato bridge, have been used as catalyst precursors in catalytic water oxidatio...
The synthetic intermediate cis(out),cis-[Ru(Cl)2(HL)(DMSO)2], 1 (DMSO = dimethyl sulfoxide), and ... more The synthetic intermediate cis(out),cis-[Ru(Cl)2(HL)(DMSO)2], 1 (DMSO = dimethyl sulfoxide), and four new mononuclear ruthenium complexes with general formula out/in-[Ru(HL)(trpy)(X)](m+) (trpy = 4-tert-butylpyridine; X = Cl(-), m = 1, 2a(+) and 2b(+); X = H2O, m = 2, 3a(2+) and 3b(2+)) based on the ligand 1H-pyrazole-3-carboxylic acid, 5-(2-pyridinil)-, ethyl ester (HL), are synthesized and characterized by analytical, spectroscopic, and electrochemical methods. A linkage isomerism is observed for a DMSO moiety of 1, and relevant thermodynamics and kinetics values are obtained through electrochemical experiments and compared to literature. Different synthetic routes are developed to obtain isomeric 2a(+) and 2b(+), with different relative yields. Water oxidation activity of 3a(2+) and 3b(2+) is analyzed by means of electrochemical methods, through foot of the wave analysis, yielding kobs values of 1.00 and 2.23 s(-1), respectively. Chemically driven water oxidation activity is tested using [(NH4)2Ce(NO3)6] as sacrificial electron acceptor, and turnover number (TON) and turnover frequency (TOF) values of TON = 10.8 and TOFi = 58.2 × 10(-3) s(-1) for 3a(2+) and TON = 4.2 and TOFi = 15.4 × 10(-3) s(-1) for 3b(2+) are obtained.
One main difficulty for the technological development of photoelectrochemical (PEC) water splitti... more One main difficulty for the technological development of photoelectrochemical (PEC) water splitting (WS) devices is the fabrication of active, stable and cost-effective photoelectrodes that ensure high performance. Here, we report the development of a CuO/Silicon based photoanode, which shows an onset potential for the water oxidation of 0.53 V vs SCE at pH 9, that is, an overpotential of 75 mV, and high stability above 10 h. These values account for a photovoltage of 420 mV due to the absorbed photons by silicon, as proven by comparing with analogous CuO/FTO electrodes that are not photoactive. The photoanodes have been fabricated by sputtering a thin film of Cu(0) on commercially available n-type Si wafers, followed by a photoelectrochemical treatment in basic pH conditions. The resulting CuO/Cu layer acts as (1) protective layer to avoid the corrosion of nSi, (2) p-type hole conducting layer for efficient charge separation and transportation, and (3) electrocatalyst to reduce the overpotential of the water oxidation reaction. The low cost, low toxicity, and good performance of CuO-based coatings can be an attractive solution to functionalize unstable materials for solar energy conversion.
Under the appropriate reaction conditions and stoichiometries the combination of a Cu (I) complex... more Under the appropriate reaction conditions and stoichiometries the combination of a Cu (I) complex, t-BuOOH and molecular oxygen generates a catalyst that is capable of oxidizing alkanes, alkenes, alcohols and triphenyl phosphine under one atmosphere oxygen ...
... In the absence of 02, (a) the Fenton systems yield R(py) or ROH [KIE = 1.1-1.7 (HOOH) and 4.6... more ... In the absence of 02, (a) the Fenton systems yield R(py) or ROH [KIE = 1.1-1.7 (HOOH) and 4.6 (r-BuOOH)] with reaction efficiencies up to 80% [product per HOOH(Bu-t)], and for FeI'(PA)2/HOOH the relative reactivity of c-CgH12/ PhCH2CH3 is 2.0 ... (17) Sohal, R. S.; Allen, R. 0 ...
Several iron complexes [FeII(bpy)22+, FeII(OPPh3)42+, and FeII(PA)2] in combination with hydrogen... more Several iron complexes [FeII(bpy)22+, FeII(OPPh3)42+, and FeII(PA)2] in combination with hydrogen peroxide (HOOH) catalytically hydroxylate aromatic substrates (ArH). The base-induced nucleophilic addition of HOOH to the electrophilic iron center yields the reactive intermediate of Fenton reagents . The latter includes a ‘stabilized’ hydroxyl radical that is able to replace an aromatic hydrogen (H) with a hydroxyl group (HO) via an initial addition reaction. With PhCH3 and PhCH2CH3 as substrates free HO· (from the radiolysis of H2O) reacts via aryl addition (97 and 85%, respectively) to give Ar-Ar as the predominant product, whereas 1 favors H-atom abstraction from the alkyl group (50 and 80%, respectively) and the only detectable products from aryl addition are the respective substituted phenols (o:p-ArOH). Other substituted benzenes (PhX) undergo addition by free HO at the ortho and para aryl carbons (o:p ratio, 2), followed by dimerization and elimination of two H2O molecules to yield substituted biphenyls. In contrast, 1 reacts with PhX to yield substituted phenol (ArOH; o:p ratio, 0.5 – 1.1). With phenol (PhOH) as the substrate, reaction with 1 yields mainly catechol (o-Ar(OH)2; o:p ratio, 20). In a solvent matrix of MeCN:H2O (3:1 mol:mol ratio) the reaction efficiencies with FeII(bpy)22+ and FeII(OPPh3)42+ for the hydroxylation of benzene to phenol are 36 and 42%, respectively (product per HOOH).Iron(II) complexes [FeIILx2+; FEII(bpy)22+, FeII(OPPh3)42+, FeII(PA)2 (PAH = picolinic acid)] catalytically activate hydrogen peroxide via Fenton chemistry for the hydroxylation of aromatic molecules (PhX).
The present study provides mechanistic details of a mild aromatic C-H activation effected by a co... more The present study provides mechanistic details of a mild aromatic C-H activation effected by a copper(II) center ligated in a triazamacrocylic ligand, affording equimolar amounts of a Cu III -aryl species and Cu I species as reaction products. At low temperatures the Cu II complex 1 forms a three-center, threeelectron C-H · · · Cu II interaction, identified by pulse electron paramagnetic resonance spectroscopy and supported by density functional theory calculations. C-H bond cleavage is coupled with copper oxidation, as a Cu III -aryl product 2 is formed. This reaction proceeds to completion at 273 K within minutes through either a copper disproportionation reaction or, alternatively, even faster with 1 equiv of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), quantitatively yielding 2. Kinetic studies of both reactions strongly implicate a rate-limiting proton-coupled electron transfer as the key C-H activation step, a mechanism that does not conform to the C-H activation mechanism in a Ni II analogue or to any previously proposed C-H activation mechanisms. Figure 3. X-band HYSCORE spectra taken at the observer positions (A) and (B) as indicated in the top figure. First row: 1 formed with H33m. Second row: 1 formed with D-H33m. Third row: HYSCORE simulation of the C-H a interaction of interest. The features that disappear upon monodeuteration of the ligand are indicated with arrows.
New coordination compounds of formulae: [Ru(trpy)(bpy)(4,4′-azpy)]2+, 1, [Ru(tpm)(bpy)(4,4′-azpy)... more New coordination compounds of formulae: [Ru(trpy)(bpy)(4,4′-azpy)]2+, 1, [Ru(tpm)(bpy)(4,4′-azpy)]2+, 2, [(trpy)(bpy)Ru(4,4′-azpy)Ru(NH3)5]4+, 3, and [(trpy)(bpy)Ru(4,4′-azpy)Ru(bpy)(trpy)]4+, 5, with trpy = 2,2′:6′,2″-terpyridine, tpm = tris(1-pyrazolyl)methane), bpy = 2,2′-bipyridine and 4,4′-azpy = 4,4′-azobis(pyridine), have been synthesized as PF6- salts and characterized by spectroscopic and electrochemical techniques. The structure of the cation [Ru(trpy)(bpy)(4,4′-azpy)]2+ has been determined by X-ray diffraction analysis, which reveals a trans-configuration of coordinated 4,4′-azpy and a packing structure that is based on extensive π-interactions within neighboring molecules. Upon controlled potential electrolysis of the dinuclear [RuII,RuII] complex 3, a stable [RuII, RuIII] mixed-valent species, 4, was detected. From spectral data and Gaussian deconvolution analysis of the intervalence transition in 4, a strong electronic interaction between both ruthenium centers is disclosed (HAB = 550 cm−1), pointing to possible applications of 4,4′-azpy as a conducting bridge in “molecular wires”.New mononuclear and dinuclear polypyridyl ruthenium(II) complexes containing 4,4′- azpy have been synthesized and characterized by spectroscopic, X-ray diffraction and electrochemical techniques. In the mixed-valent asymmetric complex with pentaammineruthenium(III) as an electron acceptor, a relatively strong metal–metal coupling is disclosed, pointing to possible applications of 4,4′-azpy in “molecular wires”.
A new decadentate dinucleating ligand containing a pyridazine bridging group and pyridylic arms h... more A new decadentate dinucleating ligand containing a pyridazine bridging group and pyridylic arms has been synthesized and characterized by analytical and spectroscopic techniques. Four new dinuclear cobalt complexes featuring this ligand have been prepared and thoroughly characterized both in the solid state (X-ray diffraction) and in solution (1D and 2D NMR spectroscopy, ESI-MS, and electrochemical techniques). The flexible but stable coordination environment provided by the ligand scaffold when coordinating Co in different oxidation states is shown to play a crucial role in the performance of the set of complexes when tested as catalysts for the photochemical hydrogen evolution reaction (HER) and chemical oxygen reduction reaction (ORR).
Page 1. Synthesis, Structure, and Magnetic Properties of [Dithiazolylium] x [M(tdas) 2 ] Salts Sa... more Page 1. Synthesis, Structure, and Magnetic Properties of [Dithiazolylium] x [M(tdas) 2 ] Salts Sarah S. Staniland School of Chemistry, University of Edinburgh, Edinburgh, UK Wataru Fujita Yoshikatsu Umezono Kunio Awaga Department ...
Mastering the light-induced four-electron oxidation of water to molecular oxygen is a key step to... more Mastering the light-induced four-electron oxidation of water to molecular oxygen is a key step towards the achievement of overall water splitting to produce alternative solar fuels. In this work, we report two rugged molecular pyrazolate-based diruthenium complexes that efficiently catalyze visible-light-driven water oxidation. These complexes were fully characterized both in the solid state (by X-ray diffraction analysis) and in solution (spectroscopically and electrochemically). Benchmark performances for homogeneous oxygen production have been obtained for both catalysts in the presence of a photosensitizer and a sacrificial electron acceptor at pH 7, and a turnover frequency of up to 11.1 s(-1) and a turnover number of 5300 were obtained after three successive catalytic runs. Under the same experimental conditions with the same setup, the pyrazolate-based diruthenium complexes outperform other well-known water oxidation catalysts owing to both electrochemical and mechanistic asp...
The upper critical field of heavy fermion superconductor CeCoIn5 much exceeds the Pauli limit. Th... more The upper critical field of heavy fermion superconductor CeCoIn5 much exceeds the Pauli limit. This raises the possibility of a first-order transition to the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) inhomogeneous superconducting state at high field, which coexists with ferromagnetism. A first-order metamagnetic transition has been reported using bulk magnetization measurement. However, result from this type of measurements includes effect due to flux pinning/depinning. We report here magnetization result using neutron diffraction technique, which couples directly to magnetic moments. A smooth change in magnetization is observed.
The computation of good viewpoints is important in several fields: computer graphics, removal of ... more The computation of good viewpoints is important in several fields: computer graphics, removal of degeneracies in computational geometry, robotics, graph drawing, etc. However, in areas such as computer graphics there is no consensus on what a good viewpoint means and, consequently, each author uses his or her own definition according to the requirements of the application. In this paper we present a formal measure strongly based on Information Theory, viewpoint entropy, that can be applied to certain problems of Computer Graphics such as automatic exploration of objects or scenes and Scene Understanding. We also define a new measure, the orthogonal frustum entropy, in order to fulfill the requirements needed to visualize molecules. We design an algorithm that makes use of graphics hardware to accelerate computation, and whose complexity depends mainly on the number of views we want to analyze. Computation of good views of molecules is useful for molecular scientists, a field which includes practitioners from Crystallography, Chemistry, and Biology.
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Papers by Antoni Llobet