Francesco Giacalone

New Concepts and Applications in the Macromolecular Chemistry of Fullerenes

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 C(60)-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 C(60)-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 C(60)-polymer systems and in the self-assembly of C(60)-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.

New ionic liquid-modified silica gels as recyclable materials for L-proline- or H–Pro–Pro–Asp–NH2-catalyzed aldol reaction

L-proline and the tripeptide H–Pro–Pro–Asp–NH2 (1) have been supported, by adsorption, onto the surface of modified silica gels functionalized with a monolayer of covalently attached 1,2-dimethyl-imidazolium chloride, tetrafluoroborate or hexafluorophosphate ionic moieties, respectively. Three different linkers were used to attach the ionic liquid moiety to the surface of these supports. The resulting materials have been used as catalysts for the aldol reaction between acetone and several substituted benzaldehydes. Good yields and enantioselectivities, comparable to or better than those obtained under homogeneous conditions, were obtained. These materials are easily recovered by filtration, and studies regarding their re-use have been carried out. Studies performed using L-proline-supported materials have shown that the re-use of these materials is dependent on the nature of the linker. The supported tripeptide H–Pro–Pro–Asp–NH2 gave higher enantioselectivities than those obtained with supported-proline. Recycling investigations using tripeptide-supported materials showed continued good selectivities but diminishing conversions over consecutive runs. L-proline-supported materials however, can be used at least nine times without loss of either conversion or selectivity.

Multilayered supported ionic liquids as catalysts for chemical fixation of carbon dioxide: a high-throughput study in supercritical conditions

Multilayered, covalently supported ionic liquid phase (mlc-SILP) materials were synthesized by using a new approach based on the grafting of bis-vinylimidazolium salts on different types of silica or polymeric supports. The obtained materials were characterized and tested as catalysts in the reaction of supercritical carbon dioxide with various epoxides to produce cyclic carbonates. The material prepared by supporting a bromide bis-imidazolium salt on the ordered mesoporous silica SBA-15 was identified as the most active catalyst for the synthesis of cyclic carbonates and displayed improved productivity compared with known supported ionic liquid catalysts. The catalyst retained its high activity upon reuse in consecutive catalytic runs. This is the first report of the application of mlc-SILP materials as catalysts in a reaction for the fixation of carbon dioxide. Rapid, parallel screening and comparison of the catalysts was performed by means of high-throughput experimentation.

“Release and catch” catalytic systems

In this perspective article the “release and catch” catalytic system concept is discussed. A “release and catch” catalytic system is prepared by non-covalent immobilization of the catalytic moiety on a suitable support, but differently from the usual non-covalently supported catalyst, the catalytic moiety is released in solution over the course of the reaction and it is recaptured at the end of the reaction. Such a “catalyst-sponge like” or “boomerang” system allows one to combine the benefits of homogeneous and heterogeneous catalysis and can be applied to organometallic-based catalysts, organocatalysts and metal-based catalysts.

Covalently Supported Ionic Liquid Phases: An Advanced Class of Recyclable Catalytic Systems

In this review, the most recent advances in the synthesis and catalytic applications of covalently supported ionic liquid (IL) phases will be discussed. This class of recyclable catalytic materials is based on the covalent attachment of several types of ammonium salts, usually imidazolium, but also thiazolium, triazolium, and pyrrolidinium salts, on the surface of different supports, for example, silica, periodic mesoporous organosilica, polystyrene, magnetic‐based materials, carbon nanotubes (NTs), halloysite NTs, polyhedral oligomeric silsesquioxane (POSS), and fullerenes. Moreover, poly(ionic liquid) materials, in which the IL‐based structure also acts as a support, will be considered. The synthetic applications of these materials will be presented, with special emphasis on their roles as catalysts, without added organocatalysts or metal‐based catalysts, as supports for organocatalysts, and as supports for metal‐based catalysts.

Highly selective detection of Epinephrine at oxidized Single-Wall Carbon Nanohorns modified Screen Printed Electrodes (SPEs).

Oxidized Single-Wall Carbon Nanohorns (o-SWCNHs) were used, for the first time, to assemble chemically modified Screen Printed Electrodes (SPEs) selective towards the electrochemical detection of Epinephrine (Ep), in the presence of Serotonine-5-HT (S-5HT), Dopamine (DA), Nor-Epineprhine (Nor-Ep), Ascorbic Acid (AA), Acetaminophen (Ac) and Uric Acid (UA). The Ep neurotransmitter was detected by using Differential Pulse Voltammetry (DPV), in a wide linear range of concentration (2-2500 μM) with high sensitivity (55.77 A M(-1) cm(-2)), very good reproducibility (RSD% ranging from 2 to 10 for different SPEs), short response time for each measurement (only 2s) and low detection of limit (LOD=0.1 μM). o-SWCNHs resulted in higher analytical performances when compared with other nanomaterials used in literature for electrochemical sensors assembly.

A Liquid–Liquid Biphasic Homogeneous Organocatalytic Aldol Protocol Based on the Use of a Silica Gel Bound Multilayered Ionic Liquid Phase

An innovative two stage liquid–liquid biphasic homogeneous protocol for the asymmetric organocatalytic aldol reaction is proposed, based on the use of the cis‐ion‐tagged proline 8 dissolved in the liquid film of a multilayered ionic liquid covalently bonded to silica gel 4. The resulting catalytically active material 9 is first soaked with cyclohexanone in the presence of water, resulting in a semi‐transparent gel, then the aldehyde is added and the mixture stirred at RT. In the first stage, 4 acts as a catalyst reservoir that delivers 8 to the cyclohexanone phase allowing the reaction to take place homogeneously. In the second stage, cyclohexanone is removed under vacuum and the resulting slurry is extracted with anhydrous diethylether. Now 4 acts as a catalyst sponge, redissolving 8. Product extraction is extremely selective; no trace of catalyst is detected in the product‐containing phase, and 9 can be easily reused several times with high cumulative productivity values (up to 523).

Fullerene-ionic-liquid conjugates: a new class of hybrid materials with unprecedented properties.

A modular approach has been followed for the synthesis of a series of fullerene-ionic-liquid (IL) hybrids in which the number of IL moieties (two or twelve), anion, and cation have been varied. The combination of C60 and IL give rise to new unique properties in the conjugates such as solubility in water, which was higher than 800 mg mL(-1) in several cases. In addition, one of the C60 -IL hybrids has been employed for the immobilization of palladium nanoparticles through ion exchange followed by reduction with sodium borohydride. Surprisingly, during the reduction several carbon nanostructures were formed that comprised nano-onions and nanocages with few-layer graphene sidewalls, which have been characterized by means of thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy/energy-dispersive X-ray analysis (SEM-EDAX), and high-resolution transmission electron microscopy (HRTEM). Finally, the material thus obtained was successfully applied as catalyst in Suzuki and Mizoroki-Heck reactions in a concentration of just 0.2 mol %. In the former process it was recyclable for five runs with no loss in activity.

A polyhedral oligomeric silsesquioxane-based catalyst for the efficient synthesis of cyclic carbonates

Polyhedral oligomeric silsesquioxane functionalized with imidazolium chloride peripheries (POSS-Imi) was successfully synthesized through a novel synthesis protocol. The solid was extensively characterized via1H NMR, 13C NMR and IR spectroscopy as well as combustion chemical analysis, mass spectrometry and transmission electron microscopy. Moreover, an in-depth investigation through 29Si NMR was performed. POSS-Imi was used for the first time as a catalyst for the conversion of CO2 and epoxides into cyclic carbonates with excellent results in terms of both yield and selectivity. The catalyst displayed improved catalytic performance with respect to unsupported 1-butyl-3-methylimidazolium chloride. The enhanced activity was ascribed to the proximity effect generated by the increased local concentration of imidazolium species surrounding the inorganic silsesquioxane core.

Donor–acceptor polythiophene copolymers with tunable acceptor content for photoelectric conversion devices

The synthesis and characterization of a new series of substituted polythiophenes containing an electron acceptor anthraquinone moiety in the side chain are reported. The acceptor molar content was varied by the co-polymerization of both alkylthiophene and thiophene bearing anthraquinone monomers in different ratios. NMR analysis shows a good correlation between the monomer feed composition at the beginning of the polymerization and the actual unit composition of the backbone. The conjugation length and the chemical composition of the copolymers as a function of the molecular weight have been studied by size exclusion chromatography. Small angle X-ray scattering and UV-Vis absorption spectra have been used to monitor the degree of order and chain organization in the solid state. The materials exhibit a lamellar organization, in which the anthraquinone units of neighboring side chains are also organized to some degree in layered structures parallel to the polythiophene main chains. The photoluminescence measurements in solution suggest that, upon photoexcitation of the polythiophene backbone, the anthraquinone moieties act as electron acceptors and the conjugated backbone as electron donor. The tunability of the donor–acceptor ratio and the morphology in the solid state make these photoactive copolymers interesting candidates for organic photoelectric conversion devices.