pinecone/core-2020-05-10-deduplication huggingface dataset:
Towards a rational design of ruthenium CO2 hydrogenation catalysts by Ab initio metadynamics

Complete reaction pathways relevant to CO2 hydrogenation by using a homogeneous ruthenium dihydride catalyst ({[}Ru(dmpe)(2)H-2], drape = Me2PCH2CH2PMe2) have been investigated by ab initio metadynamics. This approach has allowed reaction intermediates to be identified and free-energy profiles to be calculated, which provide new insights into the experimentally observed reaction pathway. Our simulations indicate that CO2 insertion, which leads to the formation of formate complexes, proceeds by a concerted insertion mechanism. It is a rapid and direct process with a relative-low activation barrier, which is in agreement with experimental observations. Subsequent H, insertion into the formate-Ru complex, which leads to the formation of formic acid, instead occurs via an intermediate {[}Ru(eta(2)-H-2)] complex in which the molecular hydrogen coordinates to the ruthenium center and interacts weakly with the formate group. This step has been identified as the rate-limiting step. The reaction completes by hydrogen transfer from the {[}Ru(eta(2)-H-2)] complex to the formate oxygen atom, which forms a dihydrogen-bonded Ru-H center dot center dot center dot HO(CHO) complex. The activation energy for the H, insertion step is lower for the trans isomer than for the cis isomer. A simple measure of the catalytic activity was proposed based on the structure of the transition state of the identified rate-limiting step. From this measure, the relationship between catalysts with different ligands and their experimental catalytic activities can be explained
A Wheel-Shaped Single-Molecule Magnet of [MnII3MnIII4]: Quantum Tunneling of Magnetization under Static and Pulse Magnetic Fields

The reaction of N-(2-hydroxy-5-nitrobenzyl)iminodiethanol (=H3(5-NO2-hbide)) with Mn(OAc)2·4H2O in methanol, followed byrecrystallization from 1,2-dichloroethane, yielded a wheel singlemolecule magenet (SMM) of [MnII3MnIII4(5-NO2-hbide)6]·5C2H4Cl2 (1).In 1, seven manganese ions are linked by six tri-anionic ligandsand compose the wheel in which the two manganese ions on the rimand the one in the center are MnII and the other four manganese ionsare MnIII ions. Powder magnetic susceptibility measurements showeda gradual increase with χmT values as the temperature was lowered,reaching a maximum value of 53.9 emu mol-1 K. Analyses of magneticsusceptibility data suggested a spin ground state of S = 19/2. Thezero-field splitting parameters of D and B40 were estimated to-0.283(1) K and -1.64(1) × 10-5 K, respectively, by high-field eprmeasurements (HF-EPR). The anisotropic parameters agreed with theones estimated from magnetization and inelastic neutron scatteringexperiments. AC magnetic susceptibility measurements showedfrequency dependent in- and out-of-phase signals, characteristicof an SMM, and an Arrhenius plot of the relaxation time gave are-orientation energy barrier (ΔE) of 18.1 K and a pre-exponentialfactor of 1.63 × 10-7 s. Magnetization experiments on aligned singlecrystals below 0.7 K showed a stepped hysteresis loop, confirming4the occurrence of quantum tunneling of the magnetization (QTM).QTM was, on the other hand, suppressed by rapid sweeps of themagnetic field even at 0.5 K. The sweep-rate dependence of the spinflips can be understood by considering theLandau-Zener-Stückelberg (LZS) model
Fe2 and Fe4 Clusters Encapsulated in Vacant Polyoxotungstates: Hydrothermal Synthesis, Magnetic, Electrochemical Properties, and DFT calculations

While the reaction of [PW11O39]7- towards first row transition metal ions Mn+ under usual bench conditions only leads to monosubstituted {PW11O39M(H2O)} anions, we show that the use of this precursor under hydrothermal conditions allows to isolate a family of novel polynuclear molecular magnetic polyoxometalates (POMs). The hybrid asymmetric [FeII(bpy)3][PW11O39Fe2III(OH)(bpy)2]·12H2O complex (1) contains the dinuclear {Fe(μ-O(W))(μ-OH)Fe} core where one iron atom is coordinated to a monovacant POM while the other is coordinated to two bipyridine ligands. Magnetic measurements indicate that in 1 the FeIII centers are weakly antiferromagnetically coupled (J = -11.2 cm-1, Ĥ = -JŜ1Ŝ2) compared to {Fe(μ-O)(μ-OH)Fe} systems. This is due to the long distance between the iron center embedded in the POM and the oxygen atom of the POM bridging the two magnetic centers but also, as shown by DFT calculations, to the important mixing of bridging oxygen orbitals with orbitals of the POM tungsten atoms. (Hdmbpy)2[FeII(dmbpy)3]2[(PW11O39)2Fe4IIIO2(dmbpy)4]·14H2O (2) (dmby = 5,5’-dimethyl-2,2’-bpy) and H2[FeII(dmbpy)3]2[(PW11O39)2Fe4IIIO2(dmbpy)4]·10H2O (3) represent the first butterfly-like POM complexes. In these species, a tetranuclear FeIII complex is sandwiched between two lacunary polyoxotungstates which are pentacoordinated to two FeIII cations, the remaining paramagnetic centers being each coordinated to two dmbpy ligands. The best fit of the χMT = f(T) curve leads to Jwb = -59.6 cm-1 and Jbb = -10.2 cm-1 (Ĥ = -Jwb(Ŝ1Ŝ2 + Ŝ1Ŝ2* + Ŝ1*Ŝ2 + Ŝ1*Ŝ2*) – Jbb(Ŝ2Ŝ2*)). While the Jbb value is within the range of related exchange parameter previously reported for non-POM butterfly systems, the Jwb constant is significantly lower. As for complex 1, this can be justified considering Few-O distances. Finally, in absence of coordinating ligand, the dimeric complex [N(CH3)4]10[(PW11O39FeIII)2O]·12H2O (4) has been isolated. In this complex, the two single oxo-bridged FeIII centers are ver
Metal ion-dependent biological properties of a chelator-derivatised somatostatin analogue for tumour targeting

A publicar na Revista Chemistry a European JournalSomatostatin-based
radioligands were shown to have
sensitive imaging properties for
neuroendocrine tumours and their
metastases. The potential of
[55Co]DOTATOC (DOTATOC = 4,7,
10-tricarboxymethyl-1,4,7,10-
tetraazacyclododecane-1-yl-acetyl-DPhe-
Lys-Tyr-D-Trp-Lys-Thr-Lys-1-
threoninol (disulfide bond) as a new
radiopharmaceutical agent for PET was
evaluated. 57Co was used as a surrogate
of the positron emitter 55Co and the
pharmacokinetics of [57Co]DOTATOC
was investigated using two nude mouse
models. The somatostatin receptor
subtype (sst1-5) affinity profile of [natCo]DOTA-TOC was assessed using
autoradiographic methods on
membranes transfected with human
somatostatin receptor subtypes. These
studies revealed that [57Co]DOTATOC
is an sst2-specific radiopeptide
presenting the highest affinity ever
found for the sst2 receptor subtype.
The rate of internalisation into the
AR4-2J cell line also was the highest
found for any somatostatin-based
radiopeptide.
Biodistribution studies, performed in
nude mice bearing the AR4-2J tumour
or a transfected HEK-sst2 cell-based
tumour, showed high and specific
uptake in the tumour and in other sst receptor-expressing tissues reflecting
the high receptor binding affinity and
the high rate of internalisation.
The pharmacologic differences between
[57Co]DOTATOC and [67Ga]DOTATOC
were discussed in terms of the
structural parameters found for the
chelate models CoII(DOTA)2- and
GaIII(DOTA)-, whose X-ray structures
were determined. Both chelates show
sixfold coordination in
pseudooctahedral arrangements
Experimental Measurement of Carbohydrate–Aromatic Stacking in Water by Using a Dangling-Ended DNA Model System

8 páginas, 3 figuras, 2 tablas, 2 esquemasProtein–carbohydrate recognition is of fundamental importance for a large number of biological processes; carbohydrate–aromatic stacking is a widespread, but poorly understood, structural motif in this recognition. We describe, for the first time, the measurement of carbohydrate–aromatic interactions from their contribution to the stability of a dangling-ended DNA model system. We observe clear differences in the energetics of the interactions of several monosaccharides with a benzene moiety depending on the number of hydroxy groups, the stereochemistry, and the presence of a methyl group in the pyranose ring. A fucose–benzene pair is the most stabilizing of the studied series (−0.4 Kcal mol−1) and this interaction can be placed in the same range as other more studied interactions with aromatic residues of proteins, such as Phe–Phe, Phe–Met, or Phe–His. The noncovalent forces involved seem to be dispersion forces and nonconventional hydrogen bonds, whereas hydrophobic effects do not seem to drive the interaction.We thank the Ministry of Science and Education for funding (grant no.: CTQ-2006-01123/BQU) and for a Ramón y Cajal contract (J.C.M.).Peer reviewe
Fragmentation of carbohydrate anomeric alkoxyl radicals: new synthesis of chiral 1-fluoro-1-halo-1-iodoalditols

9 pages, 1 figure, 1 table, 3 schemes.-- PMID: 18576400 [PubMed].Supporting information (30 pages) available at: http://www.wiley-vch.de/contents/jc_2111/2008/f800734_s.pdf2 Errata to this paper (1 page) published in: [1] Chemistry - A European Journal 14(33): 10179 (2008), http://dx.doi.org/10.1002/chem.200890136, and [2] Chemistry - A European Journal 14(35): 10871 (2008), http://dx.doi.org/10.1002/chem.200890145A new general methodology for the synthesis of 1,1,1-trihaloalditols by starting from 1,5-anhydro-2-deoxy-hex-1-enitol derivatives (glycals) is described. The halogens are introduced sequentially in each of the three different steps of the process. The fluorine is introduced in the first step by electrophilic fluorination of the starting glycal; next, hydroxyhalogenation of the resulting vinyl fluoride allows the addition of any halogen (F, Cl, Br or I) at will, and finally, an iodine atom is inserted through an alkoxyl radical fragmentation reaction. This methodology allows the preparation of diverse types of 1,1,1-trihalogenated compounds (R--CF(2)I, R--CFI(2), R--CFClI and R--CFBrI) under mild conditions compatible with sensitive substituents. In some cases, the diastereomeric mixtures generated from R--CFClI and R--CFBrI can be chromatographically separated, and their configuration determined by X-ray crystallographic analysis. The synthetic usefulness of these compounds has been preliminarily assessed by examining the reactivity of the fluorinated radical generated by rupture of the C--I bond.This work was supported by the Investigation programs nos. CTQ2004–06381/BQU, CTQ2004–02367/BQU and CTQ2007–67492/BQU of the Ministerio de Educación y Ciencia (Spain) cofinanced with the Fondo Europeo de Desarrollo Regional (FEDER). N.R.P. thanks the I3P-CSIC\ud
Program for a fellowship
Speciation of Rare-Earth Metal Complexes in Ionic Liquids: A Multiple-Technique Approach

The dissolution process of metal complexes in ionic liquids was investigated by a multiple-technique approach to reveal the solvate species of the metal in solution. The task-specific ionic liquid betainium bis(trifluoromethylsulfonyl)imide([Hbet][Tf2N])
is able to dissolve stoichiometric amounts of the oxides of the rare-earth elements. The crystal structures of the
compounds [Eu2(bet)8(H2O)4]Tf2N]6, [Eu2(bet)8(H2O)2][Tf2N]6·2H2O, and [Y2(bet)6(H2O)4][Tf2N]6 were found to
consist of dimers. These rare-earth complexes are well soluble in the ionic liquids [Hbet][Tf2N] and [C4mim][Tf2N] (C4mim = 1-butyl-3-methylimidazolium). The speciation of the metal complexes after dissolution in these ionic liquids was investigated by luminescence spectroscopy, 1H, 13C, and 89Y NMR spectroscopy, and by the synchrotron
techniques EXAFS (extended X-ray absorption fine structure) and HEXS (high-energy X-ray scattering). The combination of these complementary analytical techniques reveals that
the cationic dimers decompose into monomers after dissolution of the complexes in the ionic liquids. Deeper insight into the solution processes of metal compounds is desirable for applications of ionic liquids in the field of
electrochemistry, catalysis, and materials chemistry.status: publishe
Pyrrolidinium Ionic Liquid Crystals

N-Alkyl-N-methylpyrrolidinium cations have been used for the design of ionic liquid crystals, including a new type of uranium-containing metallomesogen. Pyrrolidinium salts with bromide, bis(trifluoromethylsulfonyl)-imide, tetrafluoroborate, hexafluorophosphate, thiocyanate, tetrakis(2-thenoyltrifluoroacetonato)europate(III) and tetrabromouranyl] counteranions were prepared. For the bromide salts and tetrabromouranyl compounds, the chain length of the alkyl group CnH2n+1 was varied from eight to twenty carbon atoms (n =8. 10-20). The compounds show rich mesomorphic behaviour: highly ordered smectic phases (the crystal smectic E phase and the uncommon crystal smectic T phase), smectic A phases, and hexagonal. columnar phases were observed, depending on chain length and anion. This work gives better insight into the nature and formation of the crystal smectic T phase, and the Molecular requirements for the appearance of this highly ordered phase. This uncommon tetragonal mesophase is thoroughly discussed on the basis of detailed powder X-ray diffraction experiments and in relation to the existing literature. Structural models are proposed for self-assembly of the molecules within the smectic layers. In addition, the photophysical properties of the compounds containing a metal complex anion were investigated. For the uranium-containing mesogens, luminescence can be induced by dissolving them in an ionic: liquid matrix. The europium-containing compound shows intense red photoluminescence with high colour Purity.status: publishe
The Synthesis and One- and Two-Photon Optical Properties of Dipolar, Quadrupolar and Octupolar Donor-Acceptor Molecules Containing Dimesitylboryl Groups

C. Katan present address: CNRS UMR6082 FOTON, INSA de Rennes, 20 avenue des Buttes de Coësmes, CS 70839, 35708 RENNES cedex 7, FranceInternational audienceTwo series of related donor-acceptor conjugated dipolar, pseudo-quadrupolar (V-shaped) and octupolar molecular systems based on the p-dimesitylborylphenylethynylaniline, namely 4-(4-dimesitylborylphenylethynyl)-N,N-dimethylaniline, 4-[4-(4-dimesitylboryl-phenylethynyl)phenylethynyl]-N,N-dimethylaniline, 4,4'-bis(4-dimesitylborylphenyl-ethynyl)-N-n-butylcarbazole and tris[4-(4-dimesitylborylphenylethynyl)phenyl]amine, and on the E-p-dimesitylborylethenylaniline motif, namely E-4-dimesitylborylethenyl-N,N-di(4-tolyl)aniline, 4,4'-bis(E-dimesitylborylethenyl)-N-n-butylcarbazole and tris(E-4-dimesitylborylethenylphenyl)amine have been synthesized, by palladium catalyzed cross-coupling and hydroboration routes respectively. Their absorption and emission maxima, fluorescence lifetimes and quantum yields have been obtained and their two-photon absorption spectra and two-photon absorption (TPA) cross-sections have been examined. Of these systems, the octupolar compound tris-(E-4-dimesitylborylethenylphenyl)amine has been shown to exhibit by far the largest two-photon absorption cross-section among the two series and amount to about 1000 GM at 740 nm. Its TPA performance is comparable to those of other triphenylamine based octupoles of similar size
Mono- and Bis(tetrathiafulvalene)-1,3,5-Triazines as Covalently Linked Donor-Acceptor Systems: Structural, Spectroscopic, and Theoretical Investigations

International audienceReaction of 2,4,6-trichloro-1,3,5-triazine with lithiated tetrathiafulvalene (TTF) in stoichiometric conditions, followed by treatment with sodium methanolate, provides mono- and bis(TTF)–triazines as new covalently linked (multi)donor–acceptor systems. Single-crystal X-ray analyses reveal planar structures for both compounds, with formation of peculiar segregated donor and acceptor stacks for the mono(TTF)–triazine compound, while mixed TTF–triazine stacks establish in the case of the bis(TTF) derivative. Cyclic voltammetry measurements show reversible oxidation of the TTF units, at rather low potential, with no splitting of the oxidation waves in the case of the dimeric TTF, whereas irreversible reduction of the triazine core is observed. Intramolecular charge transfer is experimentally evidenced through solution electronic absorption spectroscopy. Time-dependent DFT calculations allow the assignment of the charge transfer band to singlet transitions from the HOMO of the donor(s) to the LUMO of the acceptor. Solution EPR measurements correlated with theoretical calculations were performed in order to characterize the oxidized species. In both cases the spectra show very stable radical species and contain a triplet of doublet pattern, in agreement with the coupling of the unpaired electron with the three TTF protons. The dication of the bis(TTF)–triazine is paramagnetic, but no spin–spin exchange interaction could be detected
Discovery of New Natural Products by Intact-Cell Mass Spectrometry and LC-SPE-NMR: Malbranpyrroles, Novel Polyketides from Thermophilic Fungus Malbranchea sulfurea

Six photosensitive polyketides, malbranpyrroles A-F, were discovered from the thermophilic fungus Malbranchea sulfurea by using intact-cell desorption/ionization on silicon mass (ICD-MS) and LC-SPE-NMR. These two strategies facilitate the searching and structural determination of unstable natural products. The ICD-MS indicated that only brown hyphae of M. sulfurea can produce malbranpyrroles. The biosynthetic pathway of malbranpyrroles was evidenced by (13)C isotope precursors and amino acid feeding experiments. The cytotoxicity data revealed that the conformation of the conjugated system in malbranpyrroles does not affect cytotoxic potency against cancer cell lines. In addition, the chlorine atom was shown to be the pharmacophore for cytotoxicity
Solvent-resistant nanofiltration for product purification and catalyst recovery in Click chemistry reactions

The quickly developing field of "click" chemistry Would undoubtedly benefit from the availability of an easy and efficient technology for product purification to reduce the potential health risks associated with the presence of copper in the final product. Therefore. solvent-resistant nanofiltration (SRNF) membranes have been developed to selectively separate "clicked" polymers from the copper catalyst and solvent. By using these solvent-stable cross-linked polyimide membranes in diafiltration, up to 98% of the initially present copper could be removed through the membrane together with the DMF solvent, the polymer product being almost completely retained. This paper also presents the first SRNF application in which the catalyst permeates through the membrane and the reaction product is retained
Cobalt(II) complexes of nitrile-functionalized ionic liquids

A series of nitrile-functionalized ionic liquids were found to exhibit temperature-dependent miscibility (thermomorphism) with the lower alcohols. Their coordinating abilities toward cobalt(II) ions were investigated through the dissolution process of cobalt(II) bis(trinfluoromethylsulfonyl)-imide and were found to depend on the donor abilities of the nitrile group. The crystal structures of the cobalt(II) solvates [Co(C(1)C(1CN)Pyr)(2)(Tf2N)(4)] and [Co(C(1)C(2CN)Pyr)(6)][Tf2N](s). which were isolated from ionic-liquid solutions. gave in insight into the coordination chemistry of functionalized ionic liquids. Smooth layers of cobalt metal could be obtained by electrodeposition of the cobalt-containing ionic liquids.status: publishe
The solution structure and self-association properties of the cyclic lipodepsipeptide pseudodesmin A support its pore-forming potential

Pseudodesmin A is a cyclic lipodepsipeptide (CLP) of the viscosin group with a moderate in vitro biological activity. For several CLPs, including members of this group, this activity has been related to the ability to form ion pores in cellular membranes. As their size does not allow individual CLPs to span the membrane bilayer, individual monomers must somehow assemble into a larger structure. NMR spectroscopy has been used to demonstrate that in chloroform and other apolar organic solvents, pseudodesmin A monomers assemble into a supramolecular structure. These self-assembled structures can become sufficiently large to span the membrane bilayer as demonstrated with translational diffusion NMR spectroscopic measurements. With the aim to obtain more insight into the structural nature of this assembly, the solution conformation of pseudodesmin A was first determined by using ROESY (rOe) restraints measured in acetonitrile, in which no selfassociation occurs. The structure, which is found to be mostly similar to the previously described crystal structure, is shown to be retained within the supramolecular complex. Intermolecular rOe contacts obtained in chloroform together with chemical shift perturbation data provides structural insight into the organization of the selfassociated complex. Based upon this analysis, a model for the organization of pseudodesmin A monomers in the supramolecular assembly is proposed, which is in agreement with the formation of bilayer spanning hydrophilic pores and provides the basis for a structure–function relationship for this type of CLPs. Finally, it is demonstrated that the differences previously reported between the crystal and solution conformation of the white line inducing principle (WLIP), a close analogue of pseudodesmin A, are the result of the use of dimethyl sulfoxide as solvent, whose strong hydrogen-bonding capacity induces conformational exchange
Guanidiniocarbonyl-pyrrole-aryl derivatives : structure tuning for spectrophotometric recognition of specific DNA and RNA sequences and antiproliferative activity

We present here a systematic study of different guanidiniocarbonyl-pyrrole-aryl derivatives designed to interact with DNA or RNA both by intercalation of an aromatic moiety into the base stack of the nucleotide as well as groove binding of a guanidinio-carbonyl pyrrole cation. We varied 1.) the size of the aromatic ring (benzene, naphthalene, pyrene and acridine), 2.) the length and flexibility of the linker connecting the two binding groups, as well as 3.) the total number of positive charges present at different pH values. The compounds and their interaction with DNA and RNA were studied by UV/Vis-, fluorescence and CD spectroscopy. Also the antiproliferative activity against human tumour cell lines was determined. Our studies show that efficient interaction with e.g. DNA requires a significantly large aromatic ring (pyrene) connected via a flexible linker to the pyrrole moiety. However, a positive charge as in 12 is also needed. Compound 12 allows for a base pair selective recognition of ds-DNA at physiological pH. The antiproliferative activity correlates with the binding affinity of these compounds towards DNA suggesting that the biological effect is most likely due to DNA binding
Microspheres of mixed proteins

This paper describes the synthesis of mixed proteinaceous microspheres (MPMs) by the sonochemical method. The current fundamental research follows the research of Suslick and co-workers who have developed a method by which high-intensity ultrasound is used to make aqueous suspensions of proteinaceous microcapsules filled with water-insoluble liquids.1 By using high-intensity ultrasound, we have synthesized microspheres made of a few different proteins. The three proteins used in the current experiments are bovine serum albumin (BSA), green fluorescent protein (GFP), and cyan fluorescent protein–glucose binding protein–yellow fluorescent fused protein (CFP-GBP-YFP). The two synthesized microspheres made of mixed proteins are BSA-GFP and BSA-(CFP-GBP-YFP). This paper presents the characterization of the sonochemically produced microspheres of mixed proteins. It also provides an estimate of the efficiency of the sonochemical process in converting the native proteins to microspheres