Person:
Filippone, Salvatore

First Name

Salvatore

Last Name

Filippone

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Químicas

Department

Química Orgánica

Area

Química Orgánica

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Now showing 1 - 10 of 13

Effect of Incarcerated HF on the Exohedral Chemical Reactivity of HF@C60
(RSC, 2017-10-14) Vidal, Sara; Izquierdo, Marta; Alom, Shamim; García-Borrás, Marc; Filippone, Salvatore; Osuna, Silvia; Solà, Miquel; Whitby, Richard J.; Martin León, Nazario
The first chemical modification on the brand new endohedral HF@C60 is reported. In particular, the isomerization from optically pure (2S,5S)-cis-pyrrolidino[3,4:1,2][60]fullerene 2b to (2S,5R)-trans-pyrrolidino[3,4:1,2][60]fullerene 2b has been studied and compared with empty C60 (2a) and endohedral H2O@C60 (3). The comparative study shows a kinetic order for the isomerization process of H2O@C60 ˃ HF@C60 ˃ C60, thus confirming the effect of the incarcerated species on the zwitterionic intermediate stability.
Chiral Fullerenes from Asymmetric Catalysis
(ACS, 2014-08) Maroto, Enrique; Izquierdo Barroso, Marta; Reboredo Angulo, Silvia; Marco Martínez, Juan; Filippone, Salvatore; Martín, Nazario
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 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 paid 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 2 chiral fullerenes at will in an efficient manner by using asymmetric catalysis had never been previously addressed in fullerenes science. Thus, despite fullerenes chirality 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 been usually obtained just 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 that have allowed synthesizing, in a highly efficient way, enantiomerically pure derivatives with a total control of the stereochemical result using either metallic catalysts and/or organocatalysts under very mild conditions. Theoretical DFT 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 2 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 non-coordinating 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 non-expensive asymmetric catalysts should open the access to chiral fullerenes and their further application to a variety of different fields. In this regard, in addition to the bio-medical applications, chiral fullerenes are of interest in less-studied areas such as materials science, organic electronics and nanoscience where the control of the order and morphology at the nanometer scale are critical issues for achieving better devices efficiencies.
Chiral Fullerenes from Asymmetric Catalysis
(ACS, 2014) Maroto, Enrique E.; Izquierdo, Marta; Reboredo, Silvia; Marco-Martínez, Juan; Filippone, Salvatore; Martín, Nazario
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.
Synthesis of modified fullerenes for oxygen reduction reactions
(RSC, 2016-08-15) Girón, Rosa María; Martínez, Juan Marco; Bellani, Sabastiano; Insuasty, Alberto; Comas Rojas, Hansel; Antognazza, María Rosa; Filippone, Salvatore; Martín, Nazario
In the search for carbon based catalysts for Oxygen Reduction Reactions (ORR), two different classes of fullerene hybrids and metal free fullerene derivatives have been prepared by highly selective metal- and organo-catalyzed synthetic methods. They were included as both electron acceptors and catalysts in polymer-based photo-electrochemical cell,fully demonstrating electrocatalytic activity. Remarkably, the activity of the metal free fullerenes proved to be as high as that observed for metallofullerenes based on noble metals, and up to ten-fold higher than by using PCBM.
Cyclobuteno[60]fullerenes as efficient n-type organic semiconductors
(Wiley, 2016-09) Reboredo, Silvia; Girón, Rosa M.; Filippone, Salvatore; Mikie, Tsubasa; Sakurai, Tsuneaki; Seki, Shu; Martín, Nazario
Cyclobuteno[3,4:1,2][60]fullerenes have been prepared in a straightforward manner by a simple reaction between [60]fullerene and readily available allenoates or alkynoates as organic reagents under basic and mild conditions. The chemical structure of the new modified fullerenes has been determined by standard spectroscopic techniques and confirmed by X-Ray diffraction analysis. Some of these new fullerene derivatives exhibit a remarkable intrinsic electron mobility – determined by using flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurements – which surpasses that of the well-known PCBM, thus behavi ng as promising n-type organic semiconductors.
Catalytic Stereodivergent Synthesis of Steroid–Fulleropyrrolidine Hybrids
(ACS, 2017-04-13) Suarez, Margarita; Ruiz, Alberto; Almagro, Luis; Coro, Julieta; Maroto, Enrique E.; Filippone, Salvatore; Molero, Dolores; Martínez-Alvarez, Roberto; Martín León, Nazario
The diastereoselective synthesis of cis and trans steroid-fulleropyrrolidines hybrids by reaction of N-metalated azomethine ylides [Cu(II) or Ag(I)] with the appropriate chiral ligand and C60 is described. The experimental findings reveal that the azomethine ylide stabilized by an allylic group cycloadds to [60]fullerene in an efficient manner and with a good diastereomeric excess. Furthermore, the new generated stereocenters are fully controlled by the catalytic systems used without being influenced by the chirality of the steroid. Interestingly, by this synthetic methodology the each one of the four possible stereoisomers have efficiently been obtained and characterized by CD spectra.
Chiral Molecular Carbon Nanostructures
(American Chemical Society, 2019-06) Fernández García, Jesús M.; Evans, Paul J.; Filippone, Salvatore; Herranz, M.Angeles; Martín, Nazario
Chirality is a fascinating property present in naturally occurring and artificial molecules and materials, observable as chiroptical behavior. The emerging area of carbon nanostructures has undergone tremendous development, with a wide variety of carbon nanoforms reported over the last two decades. However, despite interest in merging chirality and nanocarbons, this has been successfully achieved only in empty fullerenes, whereas in other kinds of fullerenes or carbon nanostructures such as carbon nanotubes, graphene, and graphene quantum dots (GQDs), to name the most popular systems, it is almost unknown. Therefore, controlling chirality in carbon nanostructures currently represents a major challenge for the chemical community. In this Account, we show our progress in the synthesis of chiral molecular carbon nanostructures, namely, metallofullerenes, endohedral fullerenes, GQDs, and curved molecular nanographenes, by using asymmetric catalysis and both topdown and bottom-up chemical approaches. Furthermore, we bring in a new family of lesser-known molecular chiral bilayer nanographenes, where chirality is introduced from the starting helicene moiety and a single enantiomer of the nanographene is synthesized. Some important landmarks in the development of chiral molecular carbon nanostructures shown in this Account are the application of synthesis-tailored, enantiomerically pure metallofullerenes as catalysts for hydrogen transfer reactions and the use of endohedral fullerenes to determine the effect of the incarcerated molecule in the carbon cage on the cis−trans stereoisomerization of optically active pendent moieties. Furthermore, the first top-down synthesis of chiral GQDs by functionalization with chiral alcohols is also presented. An emerging alternative to GQDs, when the desire for purity and atomistic control outweighs the cost of multistep synthesis, is the bottom-up approach, in which molecular nanographenes are formed in precise sizes and shapes and enantiomeric control is feasible. In this regard, a singular and amazing example is given by our synthesis of a single enantiomer of the first chiral bilayer nanographene, which formally represents a new family of molecular nanographenes with chirality controlled and maintained throughout their syntheses. The aforementioned synthetic chiral nanostructures represent groundbreaking nanocarbon systems where chirality is a further dimension of structural control, paving the way to a new scenario for carbon nanoforms in which chirality selection determines the properties of these novel carbon-based materials. Fine-tuning of such properties is envisioned to impact biomedical and materials science applications.
Enantiospecific cis−trans Isomerization in Chiral Fulleropyrrolidines:Hydrogen-Bonding Assistance in the Carbanion Stabilization in H2O@C60
(ACS, 2015-01) Maroto, Enrique; Mateos, Jaime; García Borràs, Marc; Osuna, Silvia; Filippone, Salvatore; Herranz, M.Angeles; Murata, Yasujiro; Solà, Miquel; Martín, Nazario
The stereochemical outcome of cis−trans isomerization of optically pure [60], [70], and endohedral H2O@C60 fulleropyrrolidines reveals that the electronic nature of substituents, fullerene size, and surprisingly the incarcerated water molecule plays a crucial role in this rearrangement process. Theoretical DFT calculations are in very good agreement with the experimental findings. On the basis of the experimental results and computational calculations, a plausible reaction mechanism involving the hydrogen-bonding assistance of the inner water molecule in the carbanion stabilization of endofullerene is proposed.
Stereodivergent-at-Metal Synthesis of [60]Fullerene Hybrids
(Wiley Online Library, 2017-02-13) Marco Martínez, Juan; Vidal, Sara; Fernández, Israel; Filippone, Salvatore; Martín, Nazario
Chiral fullerene–metal hybrids with complete control over the four stereogenic centers, including the absolute configuration of the metal atom, have been synthesized for the first time. The stereochemistry of the four chiral centers formed during [60]fullerene functionalization is the result of both the chiral catalysts employed and the diastereoselective addition of the metal complexes used (iridium, rhodium, or ruthenium).DFT calculations underpin the observed configurational stability at the metal center, which does not undergo an epimerization process.
Fullerenes for Catalysis: Metallofullerenes in Hydrogen Transfer Reactions
(RSC, 2017-04-17) Vidal, Sara; Marco Martínez, Juan; Filippone, Salvatore; Martín León, Nazario
[60]Fullerene hybrids have succesfully been used as catalysts in hydrogen transfer reactions, namely ketones reduction and Nalkylation with alcoholes. Due to the poor solubility in polar solvent, these hybrids behave as homogeneous/heterogeneous catalysts that can be mechanically separated and reused for several times while the final products do not need chromatographic separation.