pinecone/core-2020-05-10-deduplication huggingface dataset:
A p-stacked porphyrin-fullerene electron donor-acceptor conjugate that features a surprising frozen geometry

A “frozen” electron donor–\ud
acceptor array that bears porphyrin\ud
and fullerene units covalently linked\ud
through the ortho position of a phenyl\ud
ring and the nitrogen of a pyrrolidine\ud
ring, respectively, is reported. Electrochemical\ud
and photophysical features\ud
suggest that the chosen linkage supports\ud
both through-space and throughbond\ud
interactions. In particular, it has\ud
been found that the porphyrin singlet\ud
excited state decays within a few picoseconds\ud
by means of a photoinduced\ud
electron transfer to give the rapid formation\ud
of a long-lived charge-separated\ud
state. Density functional theory\ud
(DFT) calculations show HOMO and\ud
LUMO to be localized on the electrondonating\ud
porphyrin and the electronaccepting\ud
fullerene moiety, respectively,\ud
at this level of theory. More specifically,\ud
semiempirical molecular orbital\ud
(MO) configuration interaction (CI)\ud
and unrestricted natural orbital\ud
(UNO)-CI methods shed light on the\ud
nature of the charge-transfer states and\ud
emphasize the importance of the close\ud
proximity of donor and acceptor for effective\ud
electron transfer
Synthesis of 2-Azulenyl-1,1,4,4-tetracyano-3-ferrocenyl-1,3-butadienes by [2+2] Cycloaddition of (Ferrocenylethynyl)azulenes with Tetracyanoethylene

1-, 2-, and 6-(Ferrocenylethynyl)azulene derivatives 1016 have been prepared by palladium-catalyzed alkynylation of ethynylferrocene with the corresponding haloazulenes under SonogashiraHagihara conditions. Compounds 1016 reacted with tetracyanoethylene (TCNE) in a [2+2] cycloadditioncycloreversion reaction to afford the corresponding 2-azulenyl-1,1,4,4,-tetracyano-3-ferrocenyl-1,3-butadiene chromophores 1723 in excellent yields. The redox behavior of the novel azulene chromophores 1723 was examined by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their multistep electrochemical reduction properties. Moreover, a significant color change was observed by visible spectroscopy under electrochemical reduction conditions
Total Synthesis of (+)-trans-Trikentrin A

Several syntheses have already been reported for cis-trikentrins and herbindoles, which are indole alkaloids unsubstituted at the C2 and C3 positions that bear a trans-1,3-dimethylcyclopentyl unit. Herein, we describe the first asymmetric and stereoselective synthesis of the more challenging trans-trikentrin A as its naturally occurring isomer. Different approaches were investigated and the strategy of choice was a combination of an enzymatic kinetic resolution and a thallium(III)-mediated ring contraction. The antiproliferative activities of the natural product and related intermediates have been tested against human tumor cell lines, leading to the discovery of new compounds with potent antitumor activity.CNPqFAPESPCAPE
Enhancing photoactivity of TiO2(B)/anatase core-shell nanofibers by selectively doping cerium ions into the TiO2(B) Core

Cerium ions (Ce3+) can beselectively doped into the TiO2(B) core of TiO2(B)/anatase core–shell nanofibers by means of a simple one-pot hydrothermal treatment of a starting material of hydrogen trititanate (H2Ti3O7) nanofibers. These Ce3+ ions (≈0.202 nm) are located on the (110) lattice planes of the TiO2(B) core in tunnels (width≈0.297 nm). The introduction of Ce3+ ions reduces the defects of the TiO2(B) core by inhibiting the faster growth of (110) lattice planes. More importantly, the redox potential of the Ce3+/Ce4+ couple (E0(Ce3+/Ce4+)=1.715 V versus the normal hydrogen electrode) is more negative than the valence band of TiO2(B). Therefore, once the Ce3+-doped nanofibers are irradiated by UV light, the doped Ce3+ ions in close vicinity to the interface between the TiO2(B) core and anatase nanoshell can efficiently trap the photogenerated holes. This facilitates the migration of holes from the anatase shell and leaves more photogenerated electrons in the anatase nanoshell, which results in a highly efficient separation of photogenerated charges in the anatase nanoshell. Hence, this enhanced charge-separation mechanism accelerates dye degradation and alcohol oxidation processes. The one-pot treatment doping strategy is also used to selectively dope other metal ions with variable oxidation states such as Co2+/3+ and Cu+/2+ ions. The doping substantially improves the photocatalytic activity of the mixed-phase nanofibers. In contrast, the doping of ions with an invariable oxidation state, such as Zn2+, Ca2+, or Mg2+, does not enhance the photoactivity of the mixed-phase nanofibers as the ions could not trap the photogenerated holes
Aerobic Oxidation of Carbon Monoxide in a Tetrametallic Complex

Seminaked extended metal-atom chains (EMACs) are suitable for the aerobic oxidation of CO to CO 2. One molecule of carbon dioxide remains attached to the metallic chain as a doubly deprotonated formate group (see figure), whereas the other is released. The reaction involves the activation and cleavage of a molecule of dioxygen with transfer of the atoms to two CO ligands. Copyright Â© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.The generous financial support from MICINN/FEDER (Project CTQ2011-22516), Gobierno de Aragón (GA)/FSE (E70) and GA-La Caixa (2012/GA LC 057) is gratefully acknowledged. S.S. thanks GA for a fellowship.Peer Reviewe
Controlling the structural and electrical properties of Diacid Oligo(Phenylene Ethynylene)Langmuir-Blodgett films.

The preparation, characterization and electrical properties of Langmuir–Blodgett (LB) films composed of a symmetrically substituted oligomeric phenylene ethynylene derivative, namely, 4,4′-[1,4-phenylenebis(ethyne-2,1-diyl)]dibenzoic acid (OPE2A), are described. Analysis of the surface pressure versus area per molecule isotherms and Brewster angle microscopy reveal that good-quality Langmuir (L) films can be formed both on pure water and a basic subphase. Monolayer L films were transferred onto solid substrates with a transfer ratio of unity to obtain LB films. Both L and LB films prepared on or from a pure water subphase show a red shift in the UV/Vis spectrum of about 14 nm, in contrast to L and LB films prepared from a basic subphase, which show a hypsochromic shift of 15 nm. This result, together with X-ray photoelectron spectroscopic and quartz crystal microbalance experiments, conclusively demonstrate formation of one-layer LB films in which OPE2A molecules are chemisorbed onto gold substrates and consequently COOAu junctions are formed. In LB films prepared on a basic subphase the other terminal acid group is also deprotonated and associates with an Na+ counterion. In contrast, LB films prepared from a pure water subphase preserve the protonated acid group, and lateral H-bonds with neighbouring molecules give rise to a supramolecular structure. STM-based conductance studies revealed that films prepared from a basic subphase are more conductive than the analogous films prepared from pure water, and the electrical conductance of the deprotonated films also coincides more closely with single-molecule conductance measurements. This result was interpreted not only in terms of better electron transmission in COOAu molecular junctions, but also in terms of the presence of lateral H-bonds in the films formed from pure water, which lead to reduced conductance of the molecular junctions
Escherichia coli β-Galactosidase Inhibitors through Modifications at the Aglyconic Moiety: Experimental Evidence of Conformational Distortion in the Molecular Recognition Process

Herein, we describe the use of thioglycosides as glycosidase inhibitors by employing novel modifications at the reducing end of these glycomimetics. The inhibitors display a basic galactopyranosyl unit (1-4)-bonded to a 3-deoxy-4-thiopentopyranose moiety. The molecular basis of the observed inhibition has been studied by using a combination of NMR spectroscopy and molecular modeling techniques. It is demonstrated that these molecules are not recognized by Escherichia coli bgalactosidase in their ground-state conformation, with a conformational selection process taking place. In fact, the observed conformational distortion depends on the chemical nature of the compounds and results from the rotation around the glycosidic linkage (variation of F or Y) or from the deformation of the six-membered ring of the pentopyranose. The bound conformations of the ligand are adapted in the enzymatic pocket with a variety of hydrogen-bond, van der Waals, and stacking interactions.Fil: Calle, Luis. Consejo Superior de Investigaciones Cientificas. Centro de Investigaciones Biologicas; España;Fil: Roldós, Virginia. Consejo Superior de Investigaciones Cientificas. Centro de Investigaciones Biologicas; España;Fil: Cañada, Javier F.. Consejo Superior de Investigaciones Cientificas. Centro de Investigaciones Biologicas; España;Fil: Uhrig, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono; Argentina;Fil: Cagnoni, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono; Argentina;Fil: Manzano, Veronica Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono; Argentina;Fil: Varela, Oscar Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono; Argentina;Fil: Jiménez Barbero, Jesús. Consejo Superior de Investigaciones Cientificas. Centro de Investigaciones Biologicas; España
Room‐Temperature Columnar Mesophases in Triazine–Gold Thiolate Metal–Organic Supramolecular Aggregates

Producción CientíficaSupramolecular mono‐ and dinuclear liquid‐crystalline gold(I) aggregates have been synthesized by means of hydrogen bond interactions of 2,4,6‐triarylamino‐1,3,5‐triazine with thiolate moities of gold metalloacids [Au(PR3)(SC6H4COOH)] or [μ‐(binap){Au(SC6H4COOH)}2], in 1:1 and 2:1 molar ratio, respectively. All of the supramolecular aggregates display a stable columnar hexagonal mesophase (Colh) at room‐temperature. The supramolecular arrangement within the columns consists of the one‐dimensional stacking of triazine units, with the core of the attached metallic thioacid fragments acting as the fourth branch. The phosphine‐containing moieties of the metallic thioacid protrude out in the aliphatic continuum. These complexes do not show metallophilic interactions, but this strategy appears very promising for the future design of room‐temperature LC mesophases containing interacting metallic fragments.Ministerio de Ciencia e Innovación (Proyect CTQ2011–25137)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA248 A11‐2
Synthesis and properties of isobicyclo-DNA

We present the synthesis of the isobicyclo-DNA building blocks with the nucleobases A, C, G and T, as well as biophysical and biological properties of oligonucleotides derived thereof. The synthesis of the sugar part was achieved in 5 steps starting from a known intermediate of the tricyclo-DNA synthesis. Dodecamers containing single isobicyclo-thymidine incorporations, fully modified A- and T-containing sequences, and fully modified oligonucleotides containing all four bases were synthesized and characterized. Isobicyclo-DNA forms stable duplexes with natural nucleic acids with a pronounced preference for DNA over RNA as complements. The most stable duplexes, however, arise by self-pairing. Isobicyclo-DNA forms preferentially B-DNA-like duplexes with DNA and A-like duplexes with complementary RNA as determined by circular dichroism (CD) spectroscopy. Self-paired duplexes show a yet unknown structure, as judged from CD spectroscopy. Biochemical tests revealed that isobicyclo-DNA is stable in fetal bovine serum and does not elicit RNaseH activity
Bispidine Platform Grants Full Control over Magnetic State of Ferrous Chelates in Water

International audienceA bicyclic ligand platform for iron(II), which allows total control over the complex’s magnetic properties in aqueous solution simply by varying one of the six coordination sites of the bispidine ligand, is reported. To achieve this, an efficient synthetic route to an N5 bispidine framework (ligand L4) that features an unsubstituted N-7 site is established. Then, by choosing appropriate N-7-coordinating substituents, the spin state of choice can be imposed on the corresponding ferrous complexes under environmentally relevant conditions in water and near-room temperature. Importantly, the first low-spin and diamagnetic iron(II) chelates in the bispidine series, both in the solid state and in aqueous solution, are reported. The eradication of head-on steric clashes between pendent coordinating arms is at the origin of this success. A new pair of constitutionally similar ferrous coordination compounds of a multidentate ligand system is obtained, which exhibits a distinctly binary (off–on) magnetic relationship. The new synthetic intermediate L4 may be substituted in just one step by any desired pendent arm, thus allowing access to complexes with finely tuned magnetic properties
Multinuclear Solid-State Magnetic Resonance as a Sensitive Probe of Structural Changes upon the Occurrence of Halogen Bonding in Co-crystals

Although the understanding of intermolecular interactions, such as hydrogen bonding, is relatively well-developed, many additional weak interactions work both in tandem and competitively to stabilize a given crystal structure. Due to a wide array of potential applications, a substantial effort has been invested in understanding the halogen bond. Here, we explore the utility of multinuclear (13C, 14/15N, 19F, and 127I) solid-state magnetic resonance experiments in characterizing the electronic and structural changes which take place upon the formation of five halogen-bonded co-crystalline product materials. Single-crystal X-ray diffraction (XRD) structures of three novel co-crystals which exhibit a 1:1 stoichiometry between decamethonium diiodide (i.e., [(CH3)3N+(CH 2)10N+(CH3)3][2 I -]) and different para-dihalogen-substituted benzene moieties (i.e., p-C6X2Y4, X=Br, I; Y=H, F) are presented. 13C and 15N NMR experiments carried out on these and related systems validate sample purity, but also serve as indirect probes of the formation of a halogen bond in the co-crystal complexes in the solid state. Long-range changes in the electronic environment, which manifest through changes in the electric field gradient (EFG) tensor, are quantitatively measured using 14N NMR spectroscopy, with a systematic decrease in the 14N quadrupolar coupling constant (CQ) observed upon halogen bond formation. Attempts at 127I solid-state NMR spectroscopy experiments are presented and variable-temperature 19F NMR experiments are used to distinguish between dynamic and static disorder in selected product materials, which could not be conclusively established using solely XRD. Quantum chemical calculations using the gauge-including projector augmented-wave (GIPAW) or relativistic zeroth-order regular approximation (ZORA) density functional theory (DFT) approaches complement the experimental NMR measurements and provide theoretical corroboration for the changes in NMR parameters observed upon the formation of a halogen bond
A Dioxane Template for Highly Selective Epoxy Alcohol Cyclizations

Ladder polyether natural products are a class of natural products denoted by their high functional-group density and large number of well-defined stereocenters. They comprise the toxic component of harmful algal blooms (HABs), having significant negative economic and environmental ramifications. However, their mode of action, namely blocking various cellular ion channels, also denotes their promise as potential anticancer agents. Understanding their potential mode of biosynthesis will not only help with developing ways to limit the damage of HABs, but would also facilitate the synthesis of a range of analogs with interesting biological activity. 1,3-Dioxan-5-ol substrates display remarkable ‘enhanced template effects’ in water-promoted epoxide cyclization processes en route to the synthesis of these ladder polyether natural products. In many cases, they provide near complete endo-to-exo selectivity in the cyclization of epoxy alcohols, thereby strongly favoring the formation of tetrahydropyran (THP) over tetrahydrofuran (THF) rings. The effects of various Brønsted and Lewis acidic and basic conditions are explored to demonstrate the superior selectivity of the template over the previously reported THP-based epoxy alcohols. In addition, the consideration of other synthetic routes are also considered with the goal of gaining rapid access to a plethora of potential starting materials applicable towards the synthesis of ladder polyethers. Finally, cascade sequences with polyepoxides are investigated, further demonstrating the versatility of this new reaction template.National Institute of General Medical Sciences (U.S.) (Grant GM72566)Natural Sciences and Engineering Research Council of CanadaFonds québécois de la recherche sur la nature et les technologie
Evaluating cis-2,6-dimethylpiperidide (cis-DMP) as a base component in lithium-mediated zincation chemistry

Most recent advances in metallation chemistry have centred on the bulky secondary amide 2,2,6,6-tetramethylpiperidide (TMP) within mixed metal, often ate, compositions. However, the precursor amine TMP(H) is rather expensive so a cheaper substitute would be welcome. Thus this study was aimed towards developing cheaper non-TMP based mixed-metal bases and, as cis-2,6- dimethylpiperidide (cis-DMP) was chosen as the alternative amide, developing cis-DMP zincate chemistry which has received meagre attention compared to that of its methyl-rich counterpart TMP. A new lithium diethylzincate, [(TMEDA)LiZn(cis-DMP)Et] (TMEDA=N,N,N′,N′- tetramethylethylenediamine) has been synthesised by co-complexation of Li(cis-DMP), EtZn and TMEDA, and characterised by NMR (including DOSY) spectroscopy and X-ray crystallography, which revealed a dinuclear contact ion pair arrangement. By using N,N-diisopropylbenzamide as a test aromatic substrate, the deprotonative reactivity of [(TMEDA)LiZn(cis-DMP)Et] has been probed and contrasted with that of the known but previously uninvestigated di-tert-butylzincate, [(TMEDA)LiZn(cis-DMP)tBu]. The former was found to be the superior base (for example, producing the ortho-deuteriated product in respective yields of 78 % and 48 % following D O quenching of zincated benzamide intermediates). An 88 % yield of 2-iodo-N,N-diisopropylbenzamide was obtained on reaction of two equivalents of the diethylzincate with the benzamide followed by iodination. Comparisons are also drawn using 1,1,1,3,3,3-hexamethyldisilazide (HMDS), diisopropylamide and TMP as the amide component in the lithium amide, EtZn and TMEDA system. Under certain conditions, the cis-DMP base system was found to give improved results in comparison to HMDS and diisopropylamide (DA), and comparable results to a TMP system. Two novel complexes isolated from reactions of the di-tert-butylzincate and crystallographically characterised, namely the pre-metallation complex [{(iPr)N(Ph)Ci'O}LiZn(cis-DMP)tBu ] and the post-metallation complex [(TMEDA)Li(cis-DMP){2-[1-C(=O) N(iPr)]CH}Zn(tBu)], shed valuable light on the structures and mechanisms involved in these alkali-metal-mediated zincation reactions. Aspects of these reactions are also modelled by DFT calculations. Amide austerity: Lithium amidozincate bases replacing expensive TMP (2,2,6,6-tetramethylpiperidide) by inexpensive cis-DMP (cis-2,6- dimethylpiperidide) have been synthesised (see scheme) and utilised for the ortho-deprotonation of a benzamide substrate for comparision with their TMP and other common amido analogues
A molecular toolkit for the functionalization of titanium-based biomaterials that selectively control integrin-mediated cell adhesion

We present a click chemistry-\ud
based molecular toolkit for the bio-\ud
functionalization of materials to selec-\ud
tively control integrin-mediated cell ad-\ud
hesion. To this end,\ud
a\ud
5\ud
b\ud
1-selective\ud
RGD peptidomimetics were covalently\ud
immobilized on Ti-based materials, and\ud
the capacity to promote the selective\ud
binding of\ud
a\ud
5\ud
b\ud
1 was evaluated using a\ud
solid-phase integrin binding assay. This\ud
functionalization strategy yielded surfa-\ud
ces with a nine-fold increased affinity\ud
for\ud
a\ud
5\ud
b\ud
1, in comparison to control\ud
samples, and total selectivity against\ud
the binding of the closely related integ-\ud
rin\ud
a\ud
v\ud
b\ud
3. Moreover, our methodology\ud
allowed the screening of several phos-\ud
phonic acid containing anchoring units\ud
to find the best spacer–anchor moiety\ud
required for establishing an efficient\ud
binding to titanium and to promote se-\ud
lective integrin binding. The integrin\ud
subtype specificity of these biofunc-\ud
tionalized surfaces was further exam-\ud
ined in vitro by inducing selective ad-\ud
hesion of genetically modified fibro-\ud
blasts, which express exclusively the\ud
a\ud
5\ud
b\ud
1 integrin. The versatility of our\ud
molecular toolkit was proven by shift-\ud
ing the cellular specificity of the mate-\ud
rials from\ud
a\ud
5\ud
b\ud
1- to\ud
a\ud
v\ud
b\ud
3-expressing fi-\ud
broblasts by using an\ud
a\ud
v\ud
b\ud
3-selective\ud
peptidomimetic as coating molecule.\ud
The results shown here represent the\ud
first functionalization of Ti-based mate-\ud
rials with\ud
a\ud
5\ud
b\ud
1- or\ud
a\ud
v\ud
b\ud
3-selective pep-\ud
tidomimetics that allow an unprece-\ud
dented control to discriminate between\ud
a\ud
5\ud
b\ud
1- and\ud
a\ud
v\ud
b\ud
3-mediated adhesions.\ud
The role of these two integrins in dif-\ud
ferent biological events is still a matter\ud
of debate and is frequently discussed in\ud
literature. Thus, such bioactive titanium\ud
surfaces will be of great relevance for\ud
the study of integrin-mediated cell ad-\ud
hesion and the development of new bi-\ud
omaterials targeting specific cell typesPeer ReviewedPostprint (published version