The infection of humans by lethal pathogens such as Ebola and other related viruses has not been properly addressed so far. In this context, a relevant question arises: What can chemistry do in the ...search for new strategies and approaches to solve this emergent problem? Although initially a variety of known chemical compoundsfor other purposesproved disappointing in tests against Ebola virus (EBOV) infection, more recently, specific molecules have been prepared. In this Perspective, we present new approaches directed at the design of efficient entry inhibitors to minimize the development of resistance by viral mutations. In particular, we focus on dendrimers as well as fullerene C60with a unique symmetrical and 3D globular structureas biocompatible carbon platforms for the multivalent presentation of carbohydrates. The antiviral activity of these compounds in an Ebola pseudotyped infection model was in the low micromolar range for fullerenes with 12 and 36 mannoses. However, new tridecafullerenesin which the central alkyne scaffold of 60fullerene is connected to 12 sugar-containing 60fullerene units (total 120 mannoses)exhibit an outstanding antiviral activity with IC50 in the sub-nanomolar range! The multivalent presentation of specific carbohydrates by using 3D fullerenes as controlled biocompatible carbon scaffolds represents a real advance, being currently the most efficient molecules in vitro against EBOV infection. However, additional studies are needed to determine the optimized fullerene-based leads for practical applications.
A new classification on the different types of fullerene‐containing polymers is presented according to their different properties and applications they exhibit in a variety of fields. Because of ...their interest and novelty, water‐soluble and biodegradable C60‐polymers are discussed first, followed by polyfullerene‐based membranes where unprecedented supramolecular structures are presented. Next are compounds that involve hybrid materials formed from fullerenes and other components such as silica, DNA, and carbon nanotubes (CNTs) where the most recent advances have been achieved. A most relevant topic is still that of C60‐based donor‐acceptor (D–A) polymers. Since their application in photovoltaics D–A polymers are among the most realistic applications of fullerenes in the so‐called molecular electronics. The most relevant aspects in these covalently connected fullerene/polymer hybrids as well as new concepts to improve energy conversion efficiencies are presented.
The last topics disccused relate to supramolecular aspects that are in involved in C60‐polymer systems and in the self‐assembly of C60‐macromolecular structures, which open a new scenario for organizing, by means of non‐covalent interactions, new supramolecular structures at the nano‐ and micrometric scale, in which the combination of the hydrofobicity of fullerenes with the versatility of the noncovalent chemistry afford new and spectacular superstructures.
Polymers are everywhere in our world! A new and fantastic scenario in terms of future possibilities is envisaged by combining polymers with the spherical fullerene molecules. This unprecedented hybrid fullerene world, using fullerenes covalently or supramolecularly mixed with other materials such as silica, DNA, carbon nanotubes, or semiconducting polymers, paves the way to new possibilities in materials science.
After the last epidemic of the Zika virus (ZIKV) in Brazil that peaked in 2016, growing evidence has been demonstrated of the link between this teratogenic flavivirus and microcephaly cases. However, ...no vaccine or antiviral drug has been approved yet. ZIKV and Dengue viruses (DENV) entry to the host cell takes place through several receptors, including dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN), so that the blockade of this receptor through multivalent glycoconjugates supposes a promising biological target to inhibit the infection process. In order to get enhanced multivalency in biocompatible systems, tridecafullerenes appended with up to 360 1,2-mannobiosides have been synthesized using a strain-promoted cycloaddition of azides to alkynes (SPAAC) strategy. These systems have been tested against ZIKV and DENV infection, showing an outstanding activity in the picomolar range.
Two novel homo and hetero three-dimensional nanographenes, NG1 and NG2, featuring a cyclooctatetraene core are designed, synthesized, and characterized. A concise and efficient bottom-up methodology ...was employed during which 24 new carbon–carbon bonds were formed. By means of a Scholl reaction nanographenes with 53 fused rings are realized, which exhibited good solubility in common organic solvents. The resulting saddle-like structures of NG1 and NG2 are electron-rich and show good chemical and electrochemical stability. Their molecular structures are fully elucidated by single-crystal X-ray crystallography. From their crystal structure analysis is concluded that both nanographenes are chiral and crystallize as a racemic mixture. Our work was rounded-off by excited state investigations such as electron and energy transfer with electron-acceptors and -donors.
Chiral Fullerenes from Asymmetric Catalysis Maroto, Enrique E; Izquierdo, Marta; Reboredo, Silvia ...
Accounts of chemical research,
08/2014, Letnik:
47, Številka:
8
Journal Article
Recenzirano
Conspectus Fullerenes are among the most studied molecules during the last three decades, and therefore, a huge number of chemical reactions have been tested on these new carbon allotropes. However, ...the aim of most of the reactions carried out on fullerenes has been to afford chemically modified fullerenes that are soluble in organic solvents or even water in the search for different mechanical, optical, or electronic properties. Therefore, although a lot of effort has been devoted to the chemical functionalization of these molecular allotropes of carbon, important aspects in the chemistry of fullerenes have not been properly addressed. In particular, the synthesis of chiral fullerenes at will in an efficient manner using asymmetric catalysis has not been previously addressed in fullerene science. Thus, despite the fact that the chirality of fullerenes has always been considered a fundamental issue, the lack of a general stereoselective synthetic methodology has restricted the use of enantiopure fullerene derivatives, which have usually been obtained only after highly expensive HPLC isolation on specific chiral columns or prepared from a pool of chiral starting materials. In this Account, we describe the first stereodivergent catalytic enantioselective syntheses in fullerene science, which have allowed the highly efficient synthesis of enantiomerically pure derivatives with total control of the stereochemical result using metallic catalysts and/or organocatalysts under very mild conditions. Density functional theory calculations strongly support the experimental findings for the assignment of the absolute configuration of the new stereocenters, which has also been ascertained by application of the sector rule and single-crystal X-ray diffraction. The use of the curved double bond of fullerene cages as a two-π-electron component in a variety of stereoselective cycloaddition reactions represents a challenging goal considering that, in contrast to most of the substituted olefins used in these reactions, pristine fullerene is a noncoordinating dipolarophile. The aforementioned features make the study of stereoselective 1,3-dipolar cycloadditions onto fullerenes a unique scenario to shed light onto important mechanistic aspects. On the other hand, the availability of achiral starting materials as well as the use of nonexpensive asymmetric catalysts should provide access to chiral fullerenes and their further application in a variety of different fields. In this regard, in addition to biomedical applications, chiral fullerenes are of interest in less-studied areas such as materials science, organic electronics, and nanoscience, where control of the order and morphology at the nanometer scale are critical issues for achieving better device efficiencies.
Fused oligothiophene-based π-conjugated organic derivatives have been widely used in electronic devices. In particular, two-dimensional (2D) heteroarenes offer the possibility of broadening the scope ...by extending the π-conjugated framework, which endows enhanced charge transport properties due to the potential intermolecular π–π stacking. Here, the synthesis and characterization of two new small-molecule hole-transporting materials (HTMs) for perovskite solar cells (PSCs) are reported. The newly custom-made compounds are based on dibenzoquinquethiophene (DBQT) and dibenzosexithiophene (DBST) cores, which are covalently linked to triphenylamine moieties to successfully afford the four-armed tetrakistriphenylamine (TTPA) derivatives TTPA–DBQT and TTPA–DBST. The combination of these novel central scaffolds with the electron-donor TTPA units bestow the resulting HTMs with the appropriate energy levels and, therefore, good electronic contact with the perovskite for extracting the hole efficiently. TTPA–DBQT surpasses TTPA–DBST not only in terms of conductivity but also in light-to-energy conversion efficiency using conventional mesoscopic n–i–p perovskite devices, 18.1% and 14.3%, respectively. These results were systematically compared with the benchmark HTM, 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). Additionally, scanning electron microscopy (SEM) hints that TTPA–DBQT forms high quality and fully homogeneous films, whereas TTPA–DBST leads to the formation of thinner films with pinholes, which explains its lower fill factor despite its better hole-extraction properties owing to its more planar π-extended scaffold.
A geometrically selective bottom-up synthesis of curved nanographenes is described. The synthetic methodology used involves the extension of the π-system of positively curved corannulene by a 4+2 ...cycloaddition reaction followed by cyclodehydrogenation (Scholl oxidation). By selecting the conditions for the Scholl oxidation, the formation of a seven-membered ring that also confers negative curvature to the resulting nanographene can be activated, offering two topologically distinct, curved nanographenes from a common precursor. Additionally, the structure–property relationship in these new nanographenes is explored via theoretical, electrochemical, photophysical, Raman, and X-ray crystallographic studies.
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