pinecone/core-2020-05-10-deduplication huggingface dataset:
Dinuclear Ru-Cu complexes : electronic characterisation and application to dye-sensitised solar cells

Dye-sensitised solar cells have emerged as an important developing technology for low-cost solar energy conversion and a crucial element of these is the dye, responsible for light harvesting and control of interfacial electron-transfer processes.[1] A number of examples of dye exist in the literature which link a ruthenium polypyridyl complex to another platinum group metal complex such as Ru (II), Os (II), Re (I) or Rh (III) via a bridging ligand.[2-6]  These systems are often referred to as heterosupramolecular triads when adsorbed on the surface of TiO2 as the semiconductor becomes an active component in the system.  A number of problems can arise with these types of sensitisers, for example if a flexible linker, e.g. bis-pyridylethane, is used to couple the two complexes it can be hard to control the orientation of the whole dye.  This may lead to the resultant dye cation hole being closer to the surface than desired, and hence the long-lived charge-separated state is not achieved.  In addition the size of these dyes may be much larger than that of a mononuclear complex and can lead to poor pore filling on the TiO2 and lower dye coverage, leading to a lower efficiency cell.[7] Despite these issues, efficient charge-separation has been achieved with polynuclear complexes and a long-lived state on the millisecond timescale has been observed for a trinuclear ruthenium complex.[8
Nickel-iron-selenium hydrogenases - An overview

[NiFeSe] hydrogenases are a subgroup of the large family of [NiFe] hydrogenases in which a selenocysteine ligand coordinates the Ni atom at the active site. As observed for other selenoproteins, the [NiFeSe] hydrogenases display much higher catalytic activities than their Cys-containing homologues. Here, we review the biochemical, catalytic, spectroscopic and structural properties of known [NiFeSe] hydrogenases, namely from the Hys (group 1 [NiFeSe] hydrogenase), Fru (F420-reducing [NiFeSe] hydrogenases) and Vhu families (F420-non-reducing [NiFeSe] hydrogenases). A survey of new [NiFeSe] hydrogenases present in the databases showed that all enzymes belong to either group 1 periplasmic uptake hydrogenases (Hys) or to group 3 cytoplasmic hydrogenases (Fru and Vhu) and are present in either sulfate-re-ducing or methanogenic microorganisms. In both kinds of organisms, the [NiFeSe] hydrogenases are preferred over their Cys-containing homologues if selenium is available. Since no structural information is available for the Vhu and Fru enzymes, we have modelled the large subunit of these enzymes and analyzed the area surrounding the active site. Three [NiFeSe] hydrogenases of the Hys and Vhu types were identified in which the selenocysteine residue is found in a different location in the sequence, which could result in a different coordination to the Ni atom. The high activity and fast reactivation, together with a degree of oxygen tolerance for the H2-production activity, make the Hys hydrogenases attractive catalysts for technological applications. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA.This work was supported by research grants PTDC/BIAPRO/70429/2006 funded by Fundação para a Ciência e Tecnologia (FCT, MCES, Portugal) and European Union FEDER program, and CTQ2006-12097 funded by the Ministerio de Ciencia e Innovacion (Spain).Peer Reviewe
Proton conductivity versus acidic strength of one-pot synthesized acidic functionalized SBA-15 Mesoporous silica

International audienceThis paper reports the one-pot synthesis and characterization of functionalized mesoporous SBA-15 silica, containing two loadings of different acid groups (-CO2H, -PO(OH)2 and -SO3H). The thermodynamic features of the water confined in these porous silicas is investigated by Differential Scanning Calorimetry (DSC). The results show that the melting behaviour of the confined water is mainly governed by the pore diameter and, as a consequence, indicate that the chemical "decoration" of the porous surface does not play any key role on water thermodynamics in that case. On the contrary, the proton conductivity of the hydrated mesoporous materials, examined in a wide range of temperatures (-100 to 70°C), turns out to be strongly dependent on both the physical state of the confined water and the acidity of the functions located at the porous surface. The proton conductivity is shown to be directly related to the pKa and the density of the functional groups attached to the mesopore surface. The high conductivity values obtained at low temperature when the confined water is frozen, let us think that the -SO3H functionalized SBA-15 investigated here could be promising candidates for electrolyte solids applications in fuel cells
Atom Transfer Radical Reactions as a Tool for Olefin Functionalization : On the Way to Practical Applications

Transition-metal-catalyzed atom transfer radical reactions of halogenated compounds with olefins constitute a versatile tool in organic synthesis within the area of C–C bond forming transformations. The inter- or intramolecular versions, atom transfer radical addition (ATRA) or cyclization (ATRC), respectively, lead to the atom-economic, useful synthesis of compounds that can be further functionalized. This contribution summarizes the recent developments in this area in terms of catalyst design as well as the applicability of this methodology in sequential, domino, or tandem reactions.We thank the Ministerio de Ciencia e Innovacion (grants CTQ2008-00042BQU and CTQ2008-06866-CO2-02/BQU), Consolider Ingenio 2010 (CSD2006-0003), and the Junta de Andalucia (Grant P07-FQM-02794) for financial support
A modular approach towards the synthesis of target-specific MRI contrast agents

In this paper, a modular pathway towards the synthesis of new specific MRI contrast agents and their luminescent analogues is described. Using two azide bearing probes: 
3β-deoxycholic acid and cRGDfK(N3), we performed a “click” reaction with an alkyne bearing DOTA analogue, yielding a possible blood-pool contrast agent, as well as a contrast agent with a high affinity for αvβ3 integrin expressing cells. The NMRD profiles and HSA titration of the deoxycholic acid bearing contrast agent show that this contrast agent interacts with HSA. T1 measurements of Jurkat T cells in the presence of the contrast agent, proved the retention of integrin binding of the RGD bearing contrast agent.status: publishe
Ligand redox non-innocence in transition-metal sigma-alkynyl and related complexes.

Transition-metal σ-alkynyl complexes are valuable functional materials that have found application as sructural units in the assembly of polymetallic arrays and large molecular structures, reagents for the transfer, oligomerisation or functionalisation of alkynes, magnetic or optical materials and putative components for use in a future molecular-based electronics platform. Many σ-alkynyl complexes are redox-active, undergoing facile oxidation (reduction) at moderate potentials to generate radical cations (anions) in which the charge and spin density can be tuned from being largely metal-centred to alkynyl ligand-centred by variation of the nature of the metal, supporting ligands and alkynyl substituents. This review summarises the diverse chemical behaviour of metal-supported σ-alkynyl radicals, and some selected closely related systems, which can often be rationalised in terms of the distribution of electron-spin density over the metal–alkynyl scaffold.\u
Coordination chemistry of α-ω-di(pyridyl-imine) ligands containing flexible linkers with copper(I)

Copper(I) complexes of a series of six potentially tetradentate bis(pyridylimine) ligands were prepared, where the pyridylimine groups were separated by different linking units [in L1, CH2CH2CH2(SiMe2O)20SiMe2CH2CH2CH2; in L2, CH2CH2CH2SiMe2OSiMe2CH2CH2CH2; in L3, CH2CH2; in L4, CH2(CH2)4CH2; in L5, CH2(CH2)7CH2; in L6, CH2CH2CH2OCH2CH2OCH2CH2OCH2CH2CH2]. The solubilities of L1, L2 and [Cu(L2)](PF6) in supercritical carbon dioxide were determined. The coordination chemistry of L1–L2 with CuI was studied by UV/Vis, multinuclear NMR and IR spectroscopy, MALDI-TOF and ESI mass spectrometries and elemental analysis. These data suggested that [1+1] complexes had formed. Dicopper complexes of L3–L6 were prepared for comparison, and [Cu2(L5)2](PF6)2 characterized by single-crystal X-ray diffraction analysis. Close methylene C–H···π interactions are observed within the structure. PGSE NMR spectroscopy was used to determine the hydrodynamic radii of the species in solution and comparison of these data with computational models for the complexes was made. Freezing point depression measurements afforded molecular weights for solution-state species in agreement with the formulations proposed via NMR and mass spectrometric data. There is no evidence to support linear metallopolymer formation but data suggest that [2+2] and [1+1] metallomacrocyles were formed, with siloxane linking groups encouraging the formation of [1+1] species. Solid-state NMR spectroscopic data on [Cu(L1)](PF6) indicate the presence of two different environments for the PF6– anions
New insights on the thermal decomposition of lanthanide(III) and actinide(III) oxalates: from neodymium and cerium to plutonium

International audienceLanthanides are often used as surrogates to study the properties of actinide compounds. Their behaviour is considered to be quite similar as they both possess f valence electrons and are close in size and chemical properties. This study examines the potential of using two lanthanides (neodymium and cerium) as surrogates for plutonium during the thermal decomposition of isomorphic oxalate compounds, in the trivalent oxidation state, into oxides. Thus, the thermal decomposition of neodymium, cerium and plutonium (III) oxalates are investigated by several coupled thermal analyses (TG-DTA/DSC-MS/FT-IR) and complementary characterisation techniques (XRD, UV-vis, FT-IR, SEM, carbon analyser) under both oxidizing and inert atmosphere. The thermal decomposition mechanisms determined in this study confirmed some previous results reported in the literature, among diverging propositions, while also elucidating some original mechanisms not previously considered. Calculated thermodynamic and kinetic parameters for the studied systems under both atmospheres are reported and compared with available literature data. Similarities and differences between the thermal behaviour of plutonium(III) and lanthanide(III) oxalates are outlined
Platinum complexes of 5,6-Dihydroacenaphtho[5,6-cd]-1,2-dichalcogenoles

Six bis(phosphane) platinum complexes bearing dichalcogen acenaphthene ligands have been prepared by metathesis from cis-[PtCl2(PR3)(2)] (R-3 = Ph-3, Ph2Me, PhMe2) and the dilithium salts of the parent 5,6-dihydroacenaphtho[5,6-cd]-1,2-dichalcogenoles (AcenapE(2), L1 E = S, L2 E = Se). For their synthesis, the appropriate disulfide or diselenide species was treated with super hydride [LiBEt3H] to afford the dilithium salt by in situ reduction of the AcenapE(2) E-E bond. Further reaction, by metathetical addition to the cis-platinum precursor afforded the respective platinum(II) complexes [Pt(5,6-AcenapE(2))(PR3)(2)] (R-3 = Ph-3: E = S 1, Se 2; R-3 = Ph2Me: E = S 3, Se 4; R-3 = PhMe2: E = S 5, Se 6). All six complexes have been fully characterised, principally by multinuclear magnetic resonance spectroscopy, IR spectroscopy and MS. The selenium complexes 4 and 6 provide examples of AA'X spin systems, as displayed by their P-31{H-1} NMR spectra. The X-ray structures of L1, L2, 1, 2, 5 and 6 were determined and, where appropriate, the platinum metal geometry, peri-atom displacement, splay angle magnitude, acenaphthene ring torsion angles and E center dot center dot center dot E interactions were analysed. The platinum atoms were found to adopt a distorted square-planar geometry in all four complexes, and the nature of the AcenapE(2) ligand plays little part in the conformation of the substituents bound to the trivalent phosphorus atoms.PostprintPeer reviewe
Luminescent Pt-Ag clusters based on neutral benzoquinolate cyclometalated platinum complexes

Complexes of the type [Pt(C6F5)(bzq)L] {bzq = 7,8-benzoquinolinate; L = PPh3 (2), 2,6-diphenylpyridine (pyPh 2, 3), tetrahydrothiophene (tht, 4), MeCN (5)} were prepared by replacing the acetone ligand in [Pt(C6F5)(bzq)(Me 2CO)] (1) with the corresponding L ligand. The structures of complexes 2-4 were established by X-ray diffraction. Despite their neutral nature, complexes 1-5 react with AgClO4 in a 2:1 molar ratio to give the corresponding trinuclear complexes [{Pt(C6F5)(bzq)L} 2Ag]ClO4 {L = Me2CO (6), PPh3 (7), pyPh2 (8), tht (9), MeCN (10)}, which contain Pt → Ag dative bonds. The structures of complexes 7, 9, and 10 were established by X-ray diffraction, which confirmed the existence of Pt-Ag bonds (ca. 2.8 Å) and short η1 bonding Ag-C interactions with the Cipso atom of bzq (ca. 2.4 Å). Moreover, complexes 3, 4, 7, 9, and 10 show intermolecular π⋯π interactions between the aromatic rings of the bzq ligands (separations of ca. 3.5 Å). The reactions of 1-5 with [Ag(PPh3)(OClO3)] in a 1:1 molar ratio proceed with interchange of the ligands between the metals and the formation of [{Pt(bzq)(C6F5)(PPh3)}2Ag]ClO 4 (7) and [AgL2]ClO4 (X-ray). Only in the case of L = pyPh2 (3) was the dinuclear complex [(C6F 5)(bzq)(PPh3)PtAg(pyPh2)]ClO4 (11) identified, and its structure was determined by X-ray diffraction. Complex 11 contains a Pt → Ag [2.8147(1) Å] bond and a η1-Ag- Cipso(bzq) interaction [2.293(1) Å]. The electronic absorption and luminescence behaviors of 1-11 were investigated. The lower-lying absorption bands of the mononuclear complexes are ascribed to ligand-centered [ 1IL, π-π* (bzq)] character mixed with some metal-to-ligand charge transfer [1MLCT 5d(Pt) → π*(bzq)]. For the trinuclear complexes, these bands are assigned to 1ILCT/1MM′LCT [π-π*(bzq)]/{d/s(Pt,Ag)} → π*(bzq)] transitions and to mixed 1MLCT/ 1L′LCT [MLCT 5d(Pt) → π*(bzq)]/[L′LCT, Arf → bzq] for dinuclear complex 11 on the basis of time-dependent TD (DFT) calculations carried out on 2, 4, 5, 9, 10, and 11Me in CH2Cl2. Only 2 and the heteronuclear compounds are emissive in the solid state at room temperature; however, all of the complexes are emissive at 77 K (solids and glasses). In each case, the main phosphorescent emission seems to be due to a transition similar in character to the lowest-energy electronic absorption. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.This work was supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) (DGPTC/FEDER) (project number CTQ2008-06669-C02-01/BQU). We thank CESGA (Supercomputing Centre of Galicia, Santiago de Compostela, Spain) for the supercomputing facilities.Peer Reviewe
Connecting [4Fe–4S] Clusters and Hemes – Towards Modeling the Active Site of Sulfite Reductase

In this paper, we present a new design for biologically  inspired  models for the active site of assimilatory sulfite and nitrite reductases (aSIR and aNIR), which consists of a siroheme that is directly linked to a [4Fe–4S] cubane cluster. The individual components used here to construct this model are a site‐differentiated [4Fe–4S] cluster, a bifunctional bridging ligand, and a metalloporphyrin. We have prepared two new site‐differentiated clusters, [Fe 4 S 4 (TriS)(SPy)] and [Fe 4 S 4 (TriS)(SEtIm)], which contain pyridine and imidazole linkers for the binding to a metalloporphyrin, and characterized these compounds, using  UV/Vis , IR, and  1 H‐NMR spectroscopy, cyclic voltammetry (CV), and mass spectrometry. Titration experiments where then performed by using [Zn(TPP)] (TPP 2–  =  meso ‐tetraphenylporphyrin dianion) and corresponding fluorinated derivatives to find the best [4Fe–4S]–heme combination for an optimal binding of the two components in solution.  Excitingly, our results demonstrate the formation of the desired [4Fe–4S]–heme catalytic arrays in solution with high specificity . The best combination of cubane cluster and metalloporphyrin for future catalyst development corresponds to the complex (Bu 4 N) 2 [M(T o ‐F 2 PP)–{Fe 4 S 4 (TriS)(SEtIm)}] {T o ‐F 2 PP 2–  =  meso ‐tetra( ortho ‐difluorophenyl)porphyrin dianion}. The binding between these components with M = Zn 2+  was further confirmed by CV. Thus, we have created a new type of biologically inspired model system for the aSIR and aNIR active site that leads to a robust attachment of the individual components in solution.    The binding between fluorinated zinc porphyrins and site‐differentiated [4Fe–4S] clusters through pyridyl‐ and imidazolylthiolate bifunctional bridging ligands generates catalytic arrays inspired by the active site of sulfite reductase. The properties of the unique [4Fe–4S] clusters applied here are described, and binding constants are reported for the two components of the resulting macromolecular scaffold
Unveiling the Interaction of Vanadium Compounds with Human Serum Albumin by Using 1H STD NMR and Computational Docking Studies

The binding of the VV oxidation products of two vanadium(
IV) compounds, [VO(dmpp)2] and [VO(maltolato)2],
which have shown promising anti-diabetic properties, to human
serum albumin (HSA) in aqueous aerobic solution has
been studied by 1H saturation transfer difference (STD) NMR
spectroscopy and computational docking studies. Group epitope
mapping and docking simulations indicate a preference
of HSA binding to the 1:1 [VO2(dmpp)(OH)(H2O)]– and 1:2
[VO2(maltol)2]– vanadium(V) species. By using known HSA
binders, competition NMR experiments revealed that both complexes preferentially bind to drug site I. Docking simulations
carried out with HADDOCK together with restraints derived
from the STD results led to three-dimensional models
that are in agreement with the NMR spectroscopic data, providing
useful information on molecular interaction modes.
These results indicate that the combination of STD NMR and
data-driven docking is a good tool for elucidating the interactions
in protein–vanadium compounds and thus for clarifying
the mechanism of drug delivery as vanadium compounds
have shown potential therapeutic properties.Financial support by the Portuguese Fundação para a Ciência e
Tecnologia (FCT) within the Programa Nacional de Reequipamento
Científico Varian (contract number REDE/1517/
RMN/2005) as part of the Portuguese-NMR network (Rede Nacional
de RMN) is acknowledged. D. M. D. thanks the The European
NMR Large Scale Facility Utrecht for the contact with
SONNMRLSF (project number BIO-NMR-00041). A. M. J. J. B.
and J. R. acknowledge funding from the Dutch Foundation for Scientific
Research (NWO) (VICI grant number 700.56.442) and
Utrecht University (Focus and Massa grant)
Copper(II)imida-salen complexes encapsulated into NaY zeolite for oxidations reactions

Oxidation of phenol, cychohexanol and hydroquinone has been screened in the presence of copper(II) complexes with Schiff base Salen ligand, 1,5-bis{[(1E)-(2-hydroxyphenyl)methylene]amino}-1H-imidazole-4-carbonitrile, and encapsulated in the zeolite NaY using two different methods (A and B). The new heterogeneous catalysts were characterized by SEM, XRD, FTIR, EPR, Raman and chemical analysis. The structure of the copper(II) complexes were 	proposed by theoretical studies (DFT). The catalytic activities of the encapsulated copper(II) complexes in NaY were compared with the homogeneous counterpart. The results show higher or similar substrate conversion when compared with the free complex in all the reactions tested. After their use in catalytic reaction, these catalysts were found to be reusable without loss of activity.I. K. B. thanks the Fundacao para Ciencia e Tecnologia (FCT) for a contract under the program Ciencia 2007. The authors are grateful to Dr. A. S. Azevedo for collecting the powder diffraction data. The authors thank the FCT and the European Fund for Regional Development (FEDER, COMPETE-QREN-EU) for financial support to the Research Centre (CQ/UM PEst-C/QUI/UI0686/2011, FCOMP-01-0124-FEDER-022716) and to the financial support from the NMR Portuguese Network (PT NMR, Bruker Avance III 400, Univ. of Minho)
Mechanistic Approaches to Molecular Catalysts for Water Oxidation

Water oxidation, in which two water molecules undergo the coupled loss of four electrons and four protons to form an O–O bond, is one of the most appealing target reactions for molecular catalysts in view of hydrogen production by electrolytic or photolytic water splitting to cope with urgent energy and environmental problems. Inspired by a natural oxygen-evolving multinuclear manganese cluster, a number of water oxidation catalysts based on multinuclear transition-metal complexes have been developed over the last three decades. In recent years, in parallel with the discovery of mononuclear oxygen-evolving complexes, both experimental and theoretical studies have yielded important insight into O–O bond-formation pathways in these water-oxidizing complexes. In this microreview, we will present an updated view of selected current literature focusing on the working mechanism of ruthenium-based water oxidation catalysts and on the development of rationally designed ruthenium complexes that activate water at mild potentials
Isolation and Characterization of Single and Sulfide‐Bridged Double [4Fe–4S] Cubane Clusters with 4‐Pyridinethiolato Ligands

Cuboidal iron–sulfur clusters, [4Fe–4S], are important electron‐transfer (ET) sites in biology. In addition, more complex structures, usually consisting of modified or fused cubane clusters, are used as active sites in many important enzymes. For example, the Fe–Mo cofactor (FeMoco) of nitrogenase contains two fused cubanes. Here, we report the synthesis of three new  para ‐pyridylthiolate ligated iron–sulfur cubane clusters, two single clusters (Bu 4 N) 2 [Fe 4 S 4 (SMePy) 4 ] and (Bu 4 N) 2 [Fe 4 S 4 (SPy) 4 ], and the sulfide‐bridged double cubane (Bu 4 N) 4 [{Fe 4 S 4 (SPy) 3 } 2 S] with 4‐pyridinethiolato exogenous ligands. The properties of these clusters were then explored by  1 H NMR, IR, and UV/Vis spectroscopy, cyclic voltammetry (CV), and X‐ray crystallography. Importantly, (Bu 4 N) 4 [{Fe 4 S 4 (SPy) 3 } 2 S] is the first example of a crystallographically characterized sulfide‐bridged double cubane with all‐thiolato exogenous ligands that is not supported by a large encapsulating ligand. This cluster shows a bridging Fe–S–Fe angle of 104°, its other structural parameters are in close agreement with those of the single‐cluster analog (Bu 4 N) 2 [Fe 4 S 4 (SPy) 4 ]. Finally, the one‐electron‐reduced forms of (Bu 4 N) 2 [Fe 4 S 4 (SPy) 4 ] and (Bu 4 N) 4 [{Fe 4 S 4 (SPy) 3 } 2 S] were studied by low‐temperature electron paramagnetic resonance (EPR) spectroscopy. Both clusters exhibit reversible one‐electron reductions at –401 and –528 mV [vs. the normal hydrogen electrode (NHE)], respectively. The one‐electron‐reduced forms of both clusters show  S  = 1/2 ground states as evident from EPR spectroscopy at liquid‐helium temperature. The temperature‐dependent data for the double cubane further indicate that the extra electron is trapped in one of the clusters of the dimer and that a low‐lying excited state is likely present in this complex, close in energy to the ground state.    The syntheses of unique  para ‐pyridylthiolate‐ligated cuboidal clusters, including two single [4Fe–4S] clusters and a sulfide‐bridged double [4Fe–4S] cubane, are described. The properties of these clusters are characterized by  1 H NMR, IR and UV/Vis spectroscopy, cyclic voltammetry, and X‐ray crystallography