pinecone/core-2020-05-10-deduplication huggingface dataset:
How does aromaticity rule the thermodynamic stability of hydroporphyrins?

Several measures of aromaticity including energetic, magnetic, and electron density criteria are employed to show how aromatic stabilization can explain the stability sequence of hydroporphyrins, ranging from porphin to octahydroporphin, and their preferred hydrogenation paths. The methods employed involve topological resonance energies and their circuit energy effects, bond resonance energies, multicenter delocalization indices, ring current maps, magnetic susceptibilities, and nuclear-independent chemical shifts. To compare the information obtained by the different methods, the results have been put in the same scale by using recently proposed approaches. It is found that all of them provide essentially the same information and lead to similar conclusions. Also, hydrogenation energies along different hydrogenation paths connecting porphin with octahydroporphin have been calculated with density functional theory. It is shown by using the methods mentioned above that the relative stability of different hydroporphyrin isomers and the observed inaccessibility of octahydroporphin both synthetically and in nature can be perfectly rationalized in terms of aromaticity
Diastereoselective Synthesis of cycloSaligenyl-Nucleosyl-Phosphotriesters

A diastereoselective synthesis of cycloSal-phosphotriesters (cycloSal=cycloSaligenyl) based on chiral auxiliaries has been developed that allows the synthesis of single diastereomers of the cycloSal-pronucleotides. In previously described synthesis routes, the cycloSal-compounds were always obtained as 1:1 diastereomeric mixtures that could be separated in only rare cases. However, it was shown that the diastereomers have different antiviral activity, toxicity, and hydrolysis stabilities. Here, first a chiral thiazoline derivative was used to prepare nonsubstituted and 5-methyl-cycloSal-phosphotriesters in 48 and ≥95 % de (de=diastereomeric excess). However, this approach failed to give the important group of 3-substituted cycloSal-nucleotides. Therefore, two other chiral groups were discovered that allowed the synthesis of (R(P) )- and (S(P) )-3-methyl-cycloSal-phosphotriesters as well. The antiviral activity was found to be five- to 20-fold different between the two individual diastereomers, which proved the importance of this approach.status: publishe
Immobilization of DNA on Magnetic Microparticles for Mercury Enrichment and Detection with Flow Cytometry

This is the peer reviewed version of the following article: Huang, P.-J. J., & Liu, J. (2011). Immobilization of DNA on Magnetic Microparticles for Mercury Enrichment and Detection with Flow Cytometry. Chemistry - A European Journal, 17(18), 5004–5010, which has been published in final form at https://doi.org/10.1002/chem.201002934. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Mercury detection in water has attracted a lot of research interest due to its highly toxic nature and adverse environmental impact. In particular, the recent discovery of specific binding of HgII to thymine-rich (T-rich) DNA resulting in T-HgII-T base pairs has led to the development of a number of sensors with different signaling mechanisms. However, the majority of such sensors were non-immobilized. Immobilization, on the other hand, allows active mercury adsorption, signal amplification, and sensor regeneration. In this work, we immobilized a thymine-rich DNA on a magnetic microparticle (MMP) surface through biotin–streptavidin interactions. In the presence of HgII, the DNA changes from a random coil structure into a hairpin, upon which SYBR Green I binds to emit green fluorescence. Detection was carried out by using flow cytometry where the fluorescence intensity increased ≈9-fold in the presence of mercury and the binding of mercury reached equilibrium in less than 2 min. The sensor showed a unique sample-volume-dependent fluorescence signal change where a higher fluorescence was obtained with a larger sample volume, suggesting that the particles can actively adsorb HgII. Detection limits of 5 nM (1 ppb) and 14 nM (2.8 ppb) were achieved in pure buffer and in mercury-spiked Lake Ontario water samples, respectively.University of Waterloo  ||
Natural Sciences and Engineering Research Council |
Hydride mobility in trinuclear sulfido clusters with the core [Rh 3(μ-H)(μ3-S)2]: Molecular models for hydrogen migration on metal sulfide hydrotreating catalysts

The treatment of [{Rh(μ-SH){P(OPh)3}2} 2] with [{M(μ-Cl)(diolef)}2] (diolef=diolefin) in the presence of NEt3 affords the hydrido-sulfido clusters [Rh 3(μ-H)(μ3-S)2(diolef){P(OPh) 3}4] (diolef=1,5-cyclooctadiene (cod) for 1, 2,5-norbornadiene (nbd) for 2, and tetrafluorobenzo[5,6]bicyclo[2.2.2]octa-2,5, 7-triene (tfb) for 3) and [Rh2Ir(μ-H)(μ3-S) 2(cod){P(OPh)3}4] (4). Cluster 1 can be also obtained by treating [{Rh(μ-SH){P(OPh)3}2}2] with [{Rh(μ-OMe)(cod)}2], although the main product of the reaction with [{Ir(μ-OMe)(cod)}2] was [RhIr2(μ-H) (μ3-S)2(cod)2{P(OPh)3} 2] (5). The molecular structures of clusters 1 and 4 have been determined by X-ray diffraction methods. The deprotonation of a hydrosulfido ligand in [{Rh(μ-SH)(CO)(PPh3)}2] by [M(acac)(diolef)] (acac=acetylacetonate) results in the formation of hydrido-sulfido clusters [Rh3(μ-H)(μ3-S)2(CO)2(diolef) (PPh3)2] (diolef=cod for 6, nbd for 7) and [Rh 2Ir(μ-H)(μ3-S)2(CO)2(cod) (PPh3)2] (8). Clusters 1-3 and 5 exist in solution as two interconverting isomers with the bridging hydride ligand at different edges. Cluster 8 exists as three isomers that arise from the disposition of the PPh3 ligands in the cluster (cis and trans) and the location of the hydride ligand. The dynamic behaviour of clusters with bulky triphenylphosphite ligands, which involves hydrogen migration from rhodium to sulfur with a switch from hydride to proton character, is significant to understand hydrogen diffusion on the surface of metal sulfide hydrotreating catalysts.Financial support from Ministerio de Ciencia e Innovación (MICINN/ FEDER) is gratefully acknowledged (Projects: CTQ2006-03973 and CTQ2009-08089).Peer Reviewe
The Doping Effect of Fluorinated Aromatic Solvent on the Rate of Ruthenium Catalysed Olefin Metathesis

A study concerning the effect of using a fluorinated aromatic solvent as the medium for olefin metathesis reactions catalysed by ruthenium complexes bearing N-heterocyclic carbene ligands is presented. The use of\ud
fluorinated aromatic hydrocarbons (FAH) as solvents for olefin metathesis reactions catalysed by standard commercially available ruthenium pre-catalysts allows substantially higher yields of the desired products to be obtained,especially in the case of demanding polyfunctional molecules, including natural and biologically active compounds. Interactions between the FAH and the second-generation ruthenium catalysts, which apparently improve the\ud
efficiency of the olefin metathesis transformation, have been studied by X-ray structure analysis and computations,\ud
as well as by carrying out a number of metathesis experiments. The optimisation of reaction conditions by\ud
using an FAH can be regarded as a complementary approach for the design of new improved ruthenium catalysts.\ud
Fluorinated aromatic solvents are an attractive alternative medium for promoting challenging olefin metathesis reactions
Click Assembly of Dye-Functionalized Octasilsesquioxanes for Highly Efficient and Photostable Photonic Systems

New hybrid organic–inorganic\ud
dyes based on an azide-functionalized\ud
cubic octasilsesquioxane (POSS)\ud
as the inorganic part and a 4,4-difluoro-\ud
4-bora-3a,4a-diaza-s-indacene\ud
(BDP) chromophore as the organic\ud
component have been synthesized by\ud
copper(I)-catalyzed 1,3-dipolar cycloaddition\ud
of azides to alkynes. We have\ud
studied the effects of the linkage group\ud
of BDP to the POSS unit and the\ud
degree of functionalization of this inorganic\ud
core on the ensuing optical properties\ud
by comparison with model dyes.\ud
The high fluorescence of the BDP dye\ud
is preserved in spite of the linked chain\ud
at its meso position, even after attaching\ud
one BDP moiety to the POSS core.\ud
The laser action of the new dyes has\ud
been analyzed under transversal pumping\ud
at 532 nm in both the liquid phase\ud
and when incorporated into solid polymeric\ud
matrices. The monosubstituted\ud
new hybrid dye exhibits high lasing efficiency\ud
of up to 56% with high photostability,\ud
with its laser output remaining\ud
at the initial value after 4 105 pump\ud
pulses in the same position of the\ud
sample at a repetition rate of 30 Hz.\ud
However, functionalization of the\ud
POSS core with eight fluorophores\ud
leads to dye aggregation, as quantum\ud
mechanical simulation has revealed,\ud
worsening the optical properties and\ud
extinguishing the laser action. The new\ud
hybrid systems based on dye-linked\ud
POSS nanoparticles open up the possibility\ud
of using these new photonic materials\ud
as alternative sources for optoelectronic\ud
devices, competing with\ud
dendronized or grafted polymersWe thank the Spanish Ministerio de Ciencia e Innovaci n (projects\ud
MAT2007-65778-C02-01, MAT2007-65778-C02–02, TRACE2009-0144,\ud
CTQ-2006-15515-C02, CTQ2009-14551-C02-02, MAT2010-20646-C04-01,\ud
MAT2010-20646-C04-03, and MAT2010-20646-C04-04), the Comunidad\ud
de Madrid (project S2009/PPQ-1634 “AVANCAT”), and Gobierno Vasco\ud
(IT339-10) for financial support. We also thank the Ministerio de Ciencia\ud
e Innovaci n for an FPU predoctoral fellowship to B.T. and the C.S.I.C.\ud
for a JAE-PREDOC fellowship to M.E.P.-O. The SGI/IZO-SGIker UPV/\ud
EHU is gratefully thanked for allocation of computational resources.Peer reviewe
Sonochemical coating of cotton and polyester fabrics with “Antibacterial” BSA and casein spheres

A novel antibacterial coating for cotton and polyester fabrics has been developed by using drug-loaded proteinaceous microspheres made of bovine serum albumin and casein proteins. The microbubbles were created and anchored
onto the fabrics (see figure) in a one-step reaction that lasts 3 min. The sonochemically
produced “antibacterial fabrics” have been characterized. The efficiency of
the sonochemical process in converting the native proteins into microspheres, encapsulating the drug, and coating the fabric has also been studied.This research was carried out as part of the activities of the LIDWINE Consortium, Contract No. NMP2-CT-2006-026741. LIDWINE is an IP Project of the 6th European Customers (EC) Program
One-Pot Functionalization of Graphene with Porphyrin through Cycloaddition Reactions

Two types of graphene-based hybrid materials, graphene-TPP (TPP=tetraphenylporphyrin) and graphene-PdTPP (PdTPP=palladium tetraphenylporphyrin), were prepared directly from pristine graphene through one-pot cycloaddition reactions. The hybrid materials were characterized by thermogravimetric analysis (TGA), by TEM, by UV/Vis, FTIR, Raman, and luminescence spectroscopy, and by fluorescence/phosphorescence lifetime measurements. The presence of the covalent linkages between graphene and porphyrin was confirmed by FTIR and Raman spectroscopy and further supported by control experiments. The presence of TPP (or PdTPP) in the hybrid material was demonstrated by UV/Vis spectroscopy, with TGA results indicating that the graphene-TPP and graphene-PdTPP hybrid materials contained approximately 18% TPP and 20% PdTPP. The quenching of fluorescence (or phosphorescence) and reduced lifetimes suggest excited state energy/electron transfer between graphene and the covalently attached TPP (or PdTPP) molecules.
Click Chemistry for the Assembly of Gold Nanorods and Silver Nanoparticles

The synthesis of compact nanostructures with highly integratedfunctionalities through the controlled assembly ofnanoparticles (NPs) is potentially of broad interest in researchfields such as drug delivery, multimodal imaging, andelectronic devices. This concept seems to be particularlyimportant in view of the emerging concept of theranostic,according to which both therapeutic and diagnostic capabilitiescan be present in two nanostructures. A key step, however,is how to combine individual nanostructures withoutloosing the original properties
Spectroscopic, Morphological and Mechanistic Investigation of the Solvent.Promoted Aggregation of Porphyrins Modified in meso-positions by Glucosylated steroids

Solvent-driven aggregation\ud
of a series of porphyrin derivatives was\ud
studied by UV/Vis and circular dichroism\ud
spectroscopy. The porphyrins are\ud
characterised by the presence in the\ud
meso positions of steroidal moieties\ud
further conjugated with glucosyl\ud
groups. The presence of these groups\ud
makes the investigated macrocycles\ud
amphiphilic and soluble in aqueous solvent,\ud
namely, dimethyl acetamide/\ud
water. Aggregation of the macrocycles\ud
is triggered by a change in bulk solvent\ud
composition leading to formation of\ud
large architectures that express supramolecular\ud
chirality, steered by the presence\ud
of the stereogenic centres on the\ud
periphery of the macrocycles. The aggregation\ud
behaviour and chiroptical\ud
features of the aggregates are strongly\ud
dependent on the number of moieties\ud
decorating the periphery of the porphyrin\ud
framework. In particular, experimental\ud
evidence indicates that the\ud
structure of the steroid linker dictates\ud
the overall chirality of the supramolecular\ud
architectures. Moreover, the porphyrin\ud
concentration strongly affects\ud
the aggregation mechanism and the\ud
CD intensities of the spectra. Notably,\ud
AFM investigations reveal strong differences\ud
in aggregate morphology that\ud
are dependent on the nature of the appended\ud
functional groups, and closely\ud
in line with the changes in aggregation\ud
mechanism. The suprastructures\ud
formed at lower concentration show a\ud
network of long fibrous structures\ud
spanning over tens of micrometres,\ud
whereas the aggregates formed at\ud
higher concentration have smaller rodshaped\ud
structures that can be recognised\ud
as the result of coalescence of\ud
smaller globular structures. The fully\ud
steroid substituted derivative forms\ud
globular structures over the whole concentration\ud
range explored. Finally, a rationale\ud
for the aggregation phenomena\ud
was given by semiempirical calculations\ud
at the PM6 level
Rapid synthesis of porous honeycomb Cu/Pd through a hydrogen-bubble templating method

A rapid electrochemical method based on using a clean hydrogen-bubble template to form a bimetallic porous honeycomb Cu/Pd structure has been investigated. The addition of palladium salt to a copper-plating bath under conditions of vigorous hydrogen evolution was found to influence the pore size and bulk concentration of copper and palladium in the honeycomb bimetallic structure. The surface was characterised by X-ray photoelectron spectroscopy, which revealed that the surface of honeycomb Cu/Pd was found to be rich with a Cu/Pd alloy. The inclusion of palladium in the bimetallic structure not only influenced the pore size, but also modified the dendritic nature of the internal wall structure of the parent copper material into small nanometre-sized crystallites. The chemical composition of the bimetallic structure and substantial morphology changes were found to significantly influence the surface-enhanced Raman spectroscopic response for immobilised rhodamine B and the hydrogen-evolution reaction. The ability to create free-standing films of this honeycomb material may also have many advantages in the areas of gas- and liquid-phase heterogeneous catalysis
Imidazole to NHC rearrangements at molybdenum centers. An experimental and theoretical study

El pdf del artículo es la versión de autor.-- et al.Both manganese and rhenium complexes of the type [M(bipy)(CO)3(N-RIm)]+ (bipy=2,2’-bipyridine) undergo deprotonation of the central CH group of the N-alkylimidazole (N-RIm) ligand when treated with a strong base. However, the outcome of the reaction is very different for either metal. For Mn, the addition of the equimolar amount of an acid to the product of the deprotonation affords an N-heterocyclic carbene (NHC) complex, whereas for Re, once the deprotonation of the central imidazole CH group has occurred, the bipy ligand undergoes a nucleophilic attack on an ortho carbon, affording the C--C coupling product. The extension of these studies to pseudo-octahedral [Mo(η3-allyl)(bipy)(CO)2(N-RIm)]+complexes has allowed us to isolate cationic NHC complexes (MnI-type behavior), as well as their neutral imidazol-2-yl precursors. Theoretical studies of the reaction mechanisms using DFT computations were carried out on the deprotonation of [Mn(bipy)(CO)3(N-PhIm)]+, [Re(bipy)(CO)3(N-MesIm)]+, and [Mo(η3-C4H7)(bipy)(CO)2(N-MesIm)]+ complexes (Mes=mesityl) at the B3LYP/6-31G(d) (LANL2DZ for Mn, Re, and Mo) level of theory. Our results explain why different products have been found experimentally for Mn, Mo, and Re complexes. For Re, the process leading to a C_C coupling product is clearly more favored than those forming an imidazol-2-yl product. In contrast, for Mn and Mo complexes, the lower stabilizing interaction between the central imidazole and ortho bipy C atoms, along with the higher lability of the ligands, make the formation of an NHC-type product kinetically more accessible, in good agreement with experimental findings.Financial support from the Ministerio de Ciencia e Innovación (MICINN, project number CTQ2009–12366) and Principado de Asturias (project number IB08–104) is gratefully acknowledged.Peer Reviewe
A Self-Assembled Complex with a Titanium(IV) Catecholate Core as a Potential Bimodal Contrast Agent

A ditopic chelating ligand (H64) that bears catechol and diethylenetriamine-N,N,N′,N′′,N′′-pentaacetate (DTPA) has been designed and shown to specifically bind lanthanide(III) ions at the DTPA core ([Ln(H24)(H2O)]−) and further self-assemble with titanium(IV), thereby giving rise to the formation of a supramolecular metallostar complex with a lanthanide(III)-to-titanium(IV) ratio of 3:1, [(Ln4)3Ti(H2O)3]5− (Ln=La, Eu, Gd). The efficacy of the metallostar complex as a potential bimodal optical/magnetic resonance imaging (MRI) agent has been evaluated. Nuclear magnetic relaxation dispersion (NMRD) measurements for the [(Gd4)3Ti(H2O)3]5− complex have demonstrated an enhanced r1 relaxivity that corresponds to 36.9 s−1 mM−1 per metallostar molecule at 20 MHz and 310 K, which is a result of a decreased tumbling rate. The ability of the complex to bind to human serum albumin (HSA) was also examined by relaxometric measurements. In addition, upon UV irradiation the [(Gd4)3Ti(H2O)3]5− complex exhibits broad-band green emission in the range 400–750 nm with a maximum at 490 nm. Taking into account the high relaxivity and luminescence properties, the [(Gd4)3Ti(H2O)3]5− complex is a good lead compound for the development of efficient bimodal contrast agents.status: publishe
Binap-gold (I) versus Binap-silver trifluoroacetate complexes as catalysts in 1,3-dipolar cycloadditions of axomethine ylides

The 1,3-dipolar cycloaddition between azomethine ylides and alkenes is efficiently catalysed by [{(Sa)-Binap-Au(tfa)}2] (Binap=2,2′-bis(diphenylphosphino)-1,1′-binaphthyl; tfa=trifluoroacetyl). Maleimides, 1,2-bis(phenylsulfonyl)ethylene, chalcone and nitrostyrene were suitable dipolarophiles even when using sterically hindered 1,3-dipole precursors. The results obtained in these transformations improve the analogous ones obtained in the same reactions catalysed by [Binap–Ag(tfa)]. In addition, computational studies have also been carried out to demonstrate both the high enantioselectivity exhibited by the chiral gold(I) complex, and the non-linear effect observed in this transformation.This work has been supported by the DGES of the Spanish Ministerio de Ciencia e Innovación (MICINN) (Consolider Ingenio 2010 CSD2007-00006, FEDER-CTQ2007-62771/BQU, CTQ2007/67528, CTQ2010-20387 and by the Hispano-Brazilian project PHB2008-0037-PC), Generalitat Valenciana (PROMETEO/2009/039), the Basque government (grant IT-324-07) and by the University of Alicante
Synthesis of Chondramide A Analogues with Modified β‐Tyrosine and Their Biological Evaluation

Starting from cinnamates  9 , obtained by Wittig reaction or Heck coupling, the diols  17  were prepared by asymmetric dihydroxylation. This was followed by a regioselective substitution of the 3‐OH group with hydrazoic acid under Mitsunobu conditions. Methylation of the 2‐OH group and reduction of the azide group led to the β‐tyrosine derivatives  8 . Condensation with the dipeptide acid  6  furnished the tripeptide part of the chondramides. The derived acids  21  were combined with the hydroxy ester  7  to the esters  22 . Cleavage of the  tert ‐butyl groups and intramolecular lactam formation gave rise to the chondramide A analogues  2 b – k . Growth inhibition assays showed most of the analogues to be biologically active. Some of them even reach the activity of jasplakinolide. It can be concluded that the 4‐position of the aryl ring in the β‐tyrosine of chondramide A tolerates structural modifications quite well.     SUB ‐ units : Ten different chondramide A analogues were prepared with different substituents at the 3‐amino‐2‐methoxy‐propanoate subunit. The modified β‐tyrosines were obtained from the corresponding cinnamates. From Mitsunobu esterification, acyclic depsipeptides were obtained that were cyclized by macrolactam formation. Almost all analogues were at least as active as chondramide A itself. However, an amide group reduced the cytotoxicity significantly
Rhodium-catalyzed asymmetric hydrogenation of olefins with PhthalaPhos, a new class of chiral supramolecular ligands

A library of 19 binol-derived chiral monophosphites that contain a phthalic acid diamide group (Phthala- Phos) has been designed and synthesized in four steps. These new ligands were screened in the rhodium-catalyzed enantioselective hydrogenation of prochiral dehydroamino esters and enamides. Several members of the library showed excellent enantioselectivity with methyl 2-acetamido acrylate (6 ligands gave >97% ee), methyl (Z)-2- acetamido cinnamate (6 ligands gave >94% ee), and N-(1-phenylvinyl)acetamide (9 ligands gave >95% ee), whilst only a few representatives afforded high enantioselectivities for challenging and industrially relevant substrates N-(3,4-dihydronaphthalen-1- yl)-acetamide (96% ee in one case) and methyl (E)-2-(acetamidomethyl)-3- phenylacrylate (99% ee in one case). In most cases, the new ligands were more active and more stereoselective than their structurally related monodentate phosphites (which are devoid of functional groups that are capable of hydrogen-bonding interactions). Control experiments and kinetic studies were carried out that allowed us to demonstrate that hydrogen-bonding interactions involving the diamide group of the PhthalaPhos ligands strongly contribute to their outstanding catalytic properties. Computational studies carried out on a rhodium precatalyst and on a conceivable intermediate in the hydrogenation catalytic cycle shed some light on the role played by hydrogen bonding, which is likely to act in a substrate-orientation effect. © 2012 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim