pinecone/core-2020-05-10-deduplication huggingface dataset:
Binding of Scandium Ions to Metalloporphyrin–Flavin Complexes for Long-Lived Charge Separation

A porphyrin–flavin-linked dyad and its zinc and palladium complexes (MPor[BOND]Fl: 2[BOND]Fl: 2[BONDM, M=2 H, Zn, and Pd) were newly synthesized and the X-ray crystal structure of 2[BOND]Pd was determined. The photodynamics of 2[BOND]M were examined by femto- and nanosecond laser flash photolysis measurements. Photoinduced electron transfer (ET) in 2[BOND]H2 occurred from the singlet excited state of the porphyrin moiety (H2Por) to the flavin (Fl) moiety to produce the singlet charge-separated (CS) state 1(H2Por.+[BOND]Fl.−), which decayed through back ET (BET) to form 3[H2Por]*[BOND]Fl with rate constants of 1.2×1010 and 1.2×109 s−1, respectively. Similarly, photoinduced ET in 2[BOND]Pd afforded the singlet CS state, which decayed through BET to form 3[PdPor]*[BOND]Fl with rate constants of 2.1×1011 and 6.0×1010 s−1, respectively. The rate constant of photoinduced ET and BET of 2[BOND]M were related to the ET and BET driving forces by using the Marcus theory of ET. One and two Sc3+ ions bind to the flavin moiety to form the Fl[BOND]Sc3+ and Fl[BOND](Sc3+)2 complexes with binding constants of K1=2.2×105 M−1 and K2=1.8×103 M−1, respectively. Other metal ions, such as Y3+, Zn2+, and Mg2+, form only 1:1 complexes with flavin. In contrast to 2[BOND]M and the 1:1 complexes with metal ions, which afforded the short-lived singlet CS state, photoinduced ET in 2[BOND]Pd⋅⋅⋅Sc3+ complexes afforded the triplet CS state (3[PdPor.+[BOND]Fl.−[BOND](Sc3+)2]), which exhibited a remarkably long lifetime of τ=110 ms (kBET=9.1 s−1)
Mechanism of alkyne alkoxycarbonylation at a Pd catalyst with P,N hemilabile ligands : a density functional study

The authors thank the School of Chemistry and EaStCHEM for supportA detailed mechanism for alkyne alkoxycarbonylation mediated by a palladium catalyst has been characterised at the B3PW91-D3/PCM level of density functional theory (including bulk solvation and dispersion corrections). This transformation, investigated via the methoxycarbonylation of propyne, involves a uniquely dual role for the P, N hemilabile ligand acting co-catalytically as both an in situ base and proton relay coupled with a Pd0 centre, allowing for surmountable barriers (highest ΔG≠ of 22.9 kcal mol-1 for alcoholysis). This proton-shuffle between methanol and coordinated propyne accounts for experimental requirements (high acid concentration) and reproduces observed regioselectivities as a function of ligand structure. A simple ligand modification is proposed, which is predicted to improve catalytic turnover by three orders of magnitude.PostprintPeer reviewe
Preparation of chemically modified RNA origami nanostructures.

In nucleic acid nanotechnology, designed RNA molecules are widely explored because of their usability originating from RNA's structural and functional diversity. Herein, a method to design and prepare RNA nanostructures by employing DNA origami strategy was developed. A single-stranded RNA scaffold and staple RNA strands were used for the formation of RNA nanostructures. After the annealing of the mixtures, 7-helix bundled RNA tile and 6-helix bundled RNA tube structures were observed as predesigned shapes. These nanostructures were easily functionalized by introducing chemical modification to the RNA scaffolds. The DNA origami method is extended and utilized to construct RNA nanostructures
A combined "electrochemical-frustrated Lewis pair" approach to hydrogen activation: surface catalytic effects at platinum electrodes

Herein, we extend our “combined electrochemical–frustrated Lewis pair” approach to include Pt electrode surfaces for the first time. We found that the voltammetric response of an electrochemical–frustrated Lewis pair (FLP) system involving the B(C6F5)3/[HB(C6F5)3]− redox couple exhibits a strong surface electrocatalytic effect at Pt electrodes. Using a combination of kinetic competition studies in the presence of a H atom scavenger, 6-bromohexene, and by changing the steric bulk of the Lewis acid borane catalyst from B(C6F5)3 to B(C6Cl5)3, the mechanism of electrochemical–FLP reactions on Pt surfaces was shown to be dominated by hydrogen-atom transfer (HAT) between Pt, [Pt[BOND]H] adatoms and transient [HB(C6F5)3]⋅ electrooxidation intermediates. These findings provide further insight into this new area of combining electrochemical and FLP reactions, and proffers additional avenues for exploration beyond energy generation, such as in electrosynthesis
Mixed-metal MIL-100(Sc,M) (M=Al, Cr, Fe) for Lewis acid catalysis and tandem C -C bond formation and alcohol oxidation

The authors thank Johnson Matthey and the EPSRC for an Industrial CASE award to L.M. We gratefully acknowledge the IAESTE UK for a scholarship to B.E. They also thank the Leverhulme Trust (F/00 268/BJ), EPSRC (EP/J501542/1), and the EaStCHEM Research Computing Facility.The trivalent metal cations Al3+, Cr3+, and Fe3+ were each introduced, together with Sc3+, into MIL-100(Sc,M) solid solutions (M=Al, Cr, Fe) by direct synthesis. The substitution has been confirmed by powder X-ray diffraction (PXRD) and solid-state NMR, UV/Vis, and X-ray absorption (XAS) spectroscopy. Mixed Sc/Fe MIL-100 samples were prepared in which part of the Fe is present as α-Fe2O3 nanoparticles within the mesoporous cages of the MOF, as shown by XAS, TGA, and PXRD. The catalytic activity of the mixed-metal catalysts in Lewis acid catalysed Friedel–Crafts additions increases with the amount of Sc present, with the attenuating effect of the second metal decreasing in the order Al>Fe>Cr. Mixed-metal Sc,Fe materials give acceptable activity: 40 % Fe incorporation only results in a 20 % decrease in activity over the same reaction time and pure product can still be obtained and filtered off after extended reaction times. Supported α-Fe2O3 nanoparticles were also active Lewis acid species, although less active than Sc3+ in trimer sites. The incorporation of Fe3+ into MIL-100(Sc) imparts activity for oxidation catalysis and tandem catalytic processes (Lewis acid+oxidation) that make use of both catalytically active framework Sc3+ and Fe3+. A procedure for using these mixed-metal heterogeneous catalysts has been developed for making ketones from (hetero)aromatics and a hemiacetal.PostprintPeer reviewe
Palladium-catalyzed cross-coupling of unactivated aryl sulfides with arylzinc reagents under mild conditions.

Cross-coupling of general aryl alkyl sulfides with arylzinc reagents proceeds smoothly, even at room temperature or below, with a palladium-N-heterocyclic carbene (NHC) catalyst. When combined with reactions that are unique to organosulfurs, that is, the SNAr sulfanylation or Pummerer reaction, the cross-coupling offers interesting transformations that are otherwise difficult to achieve. An alkylsulfanyl group is preferentially converted whilst leaving the tosyloxy and chloro intact, which expands the variety of orthogonal cross-coupling
Electronic properties of mono-substituted tetraferrocenyl porphyrins in solution and on a gold surface: Assessment of the influencing factors for photoelectrochemical applications

Two unsymmetric meso-tetraferrocenyl-containing porphyrins of general formula Fc3(FcCOR)Por (Fc=ferrocenyl, R=CH3 or (CH2)5Br, Por=porphyrin) were prepared and characterized by a variety of spectroscopic methods, whereas their redox properties were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) approaches. The mixed-valence [Fc3(FcCOR)Por]n+ (n=1,3) were investigated using spectroelectrochemical as well as chemical oxidation methods and corroborated with density functional theory (DFT) calculations. Inter-valence charge-transfer (IVCT) transitions in [Fc3(FcCOR)Por]+ were analyzed, and the resulting data matched closely previously reported complexes and were assigned as Robin–Day class II mixed-valence compounds. Self-assembled monolayers (SAMs) of a thioacetyl derivative (Fc3(FcCO(CH2)5SCOCH3)Por) were also prepared and characterized. Photoelectrochemical properties of SAMs in different electrolyte systems were investigated by electrochemical techniques and photocurrent generation experiments, showing that the choice of electrolyte is critical for efficiency of redox-active SAMs
High ionic conductivity in a LiFeO2-LiAlO2 composite under H2/air fuel cell conditions

New ionic conducting materials for electrolytes for electrochemical devices have been attracting the interest of researchers in energy materials. Here, for the first time, we report a conductive composite with high ionic conductivity derived from an electronic conductor α-LiFeO2 and an insulator γ-LiAlO2. High conductivity was observed in the α-LiFeO2-γ-LiAlO2 composite when prepared by a solid state reaction method. However, the conductivity enhancement in α-LiFeO2-γ-LiAlO2 composite was not observed when the two oxides were mechanically mixed. The α-LiFeO2-γ-LiAlO2 composite also exhibits O2- or/and H+ ionic conduction which was confirmed through H2/air fuel cell measurements. An exceptionally high conductivity of 0.50 S cm-1 at 650°C was observed under H2/air fuel cell conditions. This provides a new approach to discover novel ionic conductors from composite materials derived from electronic conductors
High relaxivity Mn2+-based MRI contrast agents

[Abstract] Stable Mn2+ mono- and binuclear complexes containing pentadentate 6,6′-((methylazanediyl)bis(methylene)) dipicolinic acid coordinating units give remarkably high relaxivities due to the presence of two inner-sphere water molecules. The mononuclear derivative binds human serum albumin (HSA) with an association constant of 3372 M−1, which results in the replacement of the coordinated water molecules by donor atoms of protein residues. The dinuclear analogue also binds HSA while leaving one of the Mn2+ centres exposed to the solvent with two coordinated water molecules. Thus, this complex shows remarkably high relaxivities upon protein binding (39.0 mM−1 s−1 per Mn, at 20 MHz and 37 °C).Xunta de Galicia; EM 2012/088Xunta de Galicia; CN 2012/01
Insights into the crystallisation process from anhydrous, hydrated and solvated crystal forms of diatrizoic acid.

Diatrizoic acid (DTA), a clinically used X-ray contrast agent, crystallises in two hydrated, three anhydrous and nine solvated solid forms, all of which have been characterised by X-ray crystallography. Single-crystal neutron structures of DTA dihydrate and monosodium DTA tetrahydrate have been determined. All of the solid-state structures have been analysed using partial atomic charges and hardness algorithm (PACHA) calculations. Even though in general all DTA crystal forms reveal similar intermolecular interactions, the overall crystal packing differs considerably from form to form. The water of the dihydrate is encapsulated between a pair of host molecules, which calculations reveal to be an extraordinarily stable motif. DTA presents functionalities that enable hydrogen and halogen bonding, and whilst an extended hydrogen-bonding network is realised in all crystal forms, halogen bonding is not present in the hydrated crystal forms. This is due to the formation of a hydrogen-bonding network based on individual enclosed water squares, which is not amenable to the concomitant formation of halogen bonds. The main interaction in the solvates involves the carboxylic acid, which corroborates the hypothesis that this strong interaction is the last one to be broken during the crystal desolvation and nucleation process
Molecular Recognition and Scavenging of Arsenate from Aqueous Solution Using Dimetallic Receptors

A series of copper(II), nickel(II) and zinc(II) dimetallic complexes were prepared and their affinities towards arsenate investigated. Indicator displacement assays (IDAs) were carried out to establish the complexes with best affinities towards arsenate. A di-zinc complex (3) was selected and its arsenate-binding abilities investigated by isothermal titration calorimetry (ITC). The X-ray crystal structure of this metallo-receptor bound to arsenate is also reported, which allowed us to establish the binding mode between 3 and this oxyanion. Immobilising 3 onto HypoGel resin yielded a novel adsorbent (Zn–HypoGel) with high affinity for arsenate. Adsorption of arsenate from competitive solutions and natural groundwater was greater than that of the commercially used iron oxide Bayoxide E33. Zn–HypoGel could be efficiently and simply regenerated by washing with sodium acetate solution
Photoresponsive DNA nanocapsule having an open/close system for capture and release of nanomaterials.

A photofunctionalized square bipyramidal DNA nanocapsule (NC) was designed and prepared for the creation of a nanomaterial carrier. Photocontrollable open/close system and toehold system were introduced into the NC for the inclusion and release of a gold nanoparticle (AuNP) by photoirradiation and strand displacement. The reversible open and closed states were examined by gel electrophoresis and atomic force microscopy (AFM), and the open behavior was directly observed by high-speed AFM. The encapsulation of the DNA-modified AuNP within the NC was carried out by hybridization of a specific DNA strand (capture strand), and the release of the AuNP was examined by addition of toehold-containing complementary DNA strand (release strand). The release of the AuNP from the NC was achieved by the opening of the NC and subsequent strand displacement
N-Heterocyclic Carbene Formation Induced Fluorescent and Colorimetric Sensing of Fluoride Using Perimidinium Derivatives

International audienceIn this study, two perimidinium derivatives (1 and 2) were designed, synthesized, and developed as efficient fluorescent and colorimetric chemodosisensors for F− in DMSO or more competitive media (DMSO containing 10 % water). In the presence of F−, the yellow and non-fluorescent solution of 1/2 became colourless and exhibited strong blue fluorescence. This unique spectroscopic behaviour of 1/2 towards F− was attributed to the formation of N-heterocyclic carbene deprotonated by F−, which immediately reacted with water to give a colourless and fluorescent carbinol. Interestingly, it was found that this carbinol intermediate was unstable and further underwent a redox disproportionation to generate two other optically changed compounds. All the proposed mechanisms for the sensing process have been carefully confirmed by experiments
Palladium-catalyzed α-arylation of arylketones at low catalyst loadings

The authors thank the ERC (Advanced Researcher award-FUNCAT), 7th Framework Program NMP2-LA-2010–246461 (SYNFLOW) and King Saud University for funding.A general catalytic protocol for the a-arylation of aryl ketones has been developed. It involves the use of a preformed, bench-stable Pd–N-heterocyclic carbene precatalyst bearing IHept as an ancillary ligand, and allows the coupling of various functionalized coupling partners at very low catalyst loading. Careful choice of the solvent/base system was crucial to obtain optimum catalyst performance. The pre-catalyst was also successfully tested in the synthesis of an industrially relevant compound.PostprintPeer reviewe
Synthesis, Properties, and Redox Behavior of 1,1,4,4-Tetracyano-2-ferrocenyl-1,3-butadienes Connected by Aryl, Biaryl, and Teraryl Spacers

Aryl-substituted 1,1,4,4-tetracyano-1,3-butadienes (FcTCBDs) and bis(1,1,4,4-tetracyanobutadiene)s (bisFcTCBDs), possessing a ferrocenyl group on each terminal, were prepared by the reaction of a variety of alkynes with tetracyanoethylene (TCNE) in a [2+2] cycloaddition reaction, followed by retro-electrocyclization of the initially formed [2+2] cycloadducts (i.e., cyclobutene derivatives). The characteristic intramolecular charge transfer (ICT) between the donor (ferrocene) and acceptor (TCBD) moieties were investigated by using UV/ Vis spectroscopy. The redox behaviors of FcTCBDs and bis-FcTCBDs were examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their properties of multi-electron transfer depending on the number of ferrocene and TCBD moieties. Moreover, significant color changes were observed by visible spectroscopy under the electrochemical reduction conditions
Improving the photocatalytic reduction of CO2 to CO through immobilization of a molecular Re catalyst on TiO2

The photocatalytic activity of phosphonated Re complexes, [Re(2,2’-
bipyridine-4,4’-bisphosphonic acid)(CO)3(L)] (ReP) with L = 3-picoline, or L =
bromide, immobilized on TiO2 nanoparticles is reported. The heterogenized Re
catalyst on the semiconductor, ReP-TiO2 hybrid, displays an improvement in CO2
reduction photocatalysis. A high turnover number (TON) of 48 mol CO (mol Re)–1
was observed in DMF with the electron donor triethanolamine at λ > 420 nm, which
compares favourably to previously reported homogeneous systems and is the highest
TON observed with a CO2 reducing Re catalyst under visible light in the absence of
an additional molecular dye. Photocatalytic CO2 reduction could even be observed
with ReP-TiO2 using wavelengths λ > 495 nm. Infrared and X-ray photoelectron
spectroscopies confirmed that an intact ReP catalyst is present on the TiO2 surface
before and during catalysis. Transient absorption spectroscopy suggests that the high
activity upon heterogenization is due to an increase in the lifetime of the immobilized
anionic Re intermediate (t50% > 1 s for ReP-TiO2 compared with t50% = 60 ms for ReP
in solution) and immobilization might also reduce the formation of inactive Re dimers.
This study demonstrates that the activity of a homogenous photocatalyst can be
improved through immobilization on a metal oxide surface by favorably modifying its
photochemical kinetics.Financial support from the EPSRC (EP/H00338X/2 to E.R.; studentship and Doctoral
Prize to C.D.W.; DTP scholarship to E.P.), the Christian Doppler Research
Association (Austrian Federal Ministry of Science, Research and Economy and the 
28
National Foundation for Research, Technology and Development) and the OMV
Group (to E.R.), the ERC (project Intersolar to J.D.) and the European Commission
Marie Curie CIG (PCIG10-GA-2011-303650 to A.R.) is gratefully acknowledged.This is the final published version. It first appeared in Chemistry - a European Journal, 2015, 21, 3746 – 3754, DOI: 10.1002/chem.20140504
Iridium(I)-catalyzed regioselective C[BOND]H activation and hydrogen-isotope exchange of non-aromatic unsaturated functionality

Isotopic labelling is a key technology of increasing importance for the investigation of new CH activation and functionalization techniques, as well as in the construction of labelled molecules for use within both organic synthesis and drug discovery. Herein, we report for the first time selective iridium-catalyzed CH activation and hydrogen-isotope exchange at the b-position of unsaturated organic compounds. The use of our highly active [Ir(cod)(IMes)(PPh3)][PF6] (cod=1,5-cyclooctadiene) catalyst, under mild reaction conditions, allows the regioselective b-activation and labelling of a range of a,b-unsaturated compounds with differing steric and electronic properties. This new process delivers high levels of isotope incorporation over short reaction times by using low levels of catalyst loading
Multicomponent Self-Assembly with a Shape-Persistent N-Heterotriangulene Macrocycle on Au(111)

Multicomponent network formation by using a shape-persistent macrocycle (MC6) at the interface between an organic liquid and Au(111) surface is demonstrated. MC6 serves as a versatile building block that can be coadsorbed with a variety of organic molecules based on different types of noncovalent interactions at the liquid–solid interface. Scanning tunneling microscopy (STM) reveals the formation of crystalline bicomponent networks upon codeposition of MC6 with aromatic molecules, such as fullerene (C60) and coronene. Tetracyanoquinodimethane, on the other hand, was found to induce disorder into the MC6 networks by adsorbing on the rim of the macrocycle. Immobilization of MC6 itself was studied in two different noncovalently assembled host networks. MC6 assumed a rather passive role as a guest and simply occupied the host cavities in one network, whereas it induced a structural transition in the other. Finally, the central cavity of MC6 was used to capture C60 in a complex three-component system. Precise immobilization of organic molecules at discrete locations within multicomponent networks, as demonstrated here, constitutes an important step towards bottom-up fabrication of functional surface-based nanostructures.status: publishe
Combined Experimental and Computational Investigations of Rhodium Catalysed C—H Functionalisation of Pyrazoles with Alkenes

Detailed experimental and computational studies have been carried out on the oxidative coupling of the alkenes C2H3Y (Y=CO2Me (a), Ph (b), C(O)Me (c)) with 3-aryl-5-R-pyrazoles (R=Me (1 a), Ph (1 b), CF3 (1 c)) using a [Rh(MeCN)3Cp*][PF6]2/Cu(OAc)2⋅H2O catalyst system. In the reaction of methyl acrylate with 1 a, up to five products (2 aa–6 aa) were formed, including the trans monovinyl product, either complexed within a novel CuI dimer (2 aa) or as the free species (3 aa), and a divinyl species (6 aa); both 3 aa and 6 aa underwent cyclisation by an aza-Michael reaction to give fused heterocycles 4 aa and 5 aa, respectively. With styrene, only trans mono- and divinylation products were observed, whereas with methyl vinyl ketone, a stronger Michael acceptor, only cyclised oxidative coupling products were formed. Density functional theory calculations were performed to characterise the different migratory insertion and β-H transfer steps implicated in the reactions of 1 a with methyl acrylate and styrene. The calculations showed a clear kinetic preference for 2,1-insertion and the formation of trans vinyl products, consistent with the experimental results.Peer-reviewedPublisher Versio
Conformational dependence of through-space tellurium-tellurium spin-spin coupling in peri-substituted bis(tellurides)

The work in this project was supported by the Engineering and Physical Sciences Research Council (EPSRC). M.B. wishes to thank EaStCHEM and the University of St Andrews for support.Three related series of peri-substituted bis(tellurides) bearing naphthalene, acenaphthene and acenaphthylene backbones [Nap/Acenap/Aceyl(TeY)2 (Nap = naphthalene-1,8-diyl N; Acenap = acenaphthene-5,6-diyl A; Aceyl = acenaphthylene-5,6-diyl Ay; Y = Ph 1; Fp 2; Tol 3; An-p 4; An-o 5; Tp 6; Mes 7; Tip 8] have been synthesised and their solid-state structures determined by X-ray crystallography. Molecular conformations were classified as a function of the two C9-C-Te-C(Y) dihedral angles (θ); in the solid all members adopt AB or CCt configurations, with larger Te(aryl) moieties exclusively imposing the CCt variant. Exceptionally large J(125Te,125Te) spin-spin coupling constants between 3289-3848 Hz were obtained for compounds substituted by bulky Te(aryl) groups, implying these species are locked in a CCt type conformation. In contrast, compounds incorporating smaller Te(aryl) moieties are predicted to be rather dynamic in solution and afford much smaller J values (2050-2676 Hz), characteristic of greater populations of AB conformers with lower couplings. This conformational dependence of through-space coupling is supported by DFT calculations.PostprintPeer reviewe