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Ferraccioli R.,CNR Institute of Molecular Science and Technologies
Synthesis (Germany) | Year: 2013

Direct aromatic functionalization based on the use of a palladium catalyst and norbornene is a useful method to achieve straightforward synthesis of carbo- and heterocyclic compounds. New ring formation occurs through a cascade process triggered by ortho C-H alkylation (inter- and intramolecular) or arylation (homo- and heterocoupling) of aryl iodides. Up to four new carbon-carbon bonds are generated under palladium control in a single operation. 1 Introduction 2 ortho C-H Alkylation 2.1 Intermolecular ortho C-H Alkylation 2.1.1 Heck Reaction 2.1.2 C-N Coupling 2.1.3 C-H Arylation 2.2 Intramolecular ortho C-H Alkylation 2.2.1 Heck Reaction 2.2.2 Cyanation Coupling 2.3 Coupling Inter- and Intramolecular ortho C-H Alkylation 3 ortho C-H Arylation 3.1 Homocoupling 3.2 Heterocoupling 3.2.1 α-Arylation/CO Addition 3.2.2 Heck Reaction 3.2.3 C-N Coupling 4 Conclusion. © Georg Thieme Verlag Stuttgart New York.

Mercuri F.,CNR Institute of Molecular Science and Technologies
Journal of Physical Chemistry C | Year: 2010

The outstanding properties of single-walled carbon nanotubes (CNTs) are often impaired by the presence of structural defects, such as vacancies, as consequence of peculiar growth techniques or electron irradiation. However, the changes in the electronic structure due to the presence of defects can also induce the formation of sites at the sidewall exhibiting unusual reactive properties. In particular, monovacancies constitute active reaction sites toward the addition of different kinds of adsorbates, which can potentially cure the defects and restore the properties of pristine nanotubes. In this work, the interaction of carbon monoxide with monovacancies on single-walled CNTs is investigated by means of an integrated approach, based on density functional theory, consisting of both static and molecular dynamics calculations for the evaluation of potential-energy minima and free-energy barriers. Our simulations suggest viable reaction routes for the healing of single vacancies on the sidewall by subsequent interaction with two CO molecules, leading to the restoration of a perfect hexagonal carbon-atom network. The outlined results clarify the role of CO as precursor for the growth of nanotubes both as carbon source and as active chemical species for the formation of a defect-free sidewall. © 2010 American Chemical Society.

Pastore M.,CNR Institute of Molecular Science and Technologies | De Angelis F.,CNR Institute of Molecular Science and Technologies
Topics in Current Chemistry | Year: 2014

We present a review of recent first-principles computational modeling studies on dye-sensitized solar cells (DSCs), focusing on the materials and processes modeling aspects which are key to the functioning of this promising class of photovoltaic devices. Crucial to the DSCs functioning is the photoinduced charge separation occurring at the heterointerface(s) between a dye-sensitized nanocrystalline, mesoporous metal oxide electrode and a redox shuttle. Theoretical and computational modeling of isolated cell components (e.g., dye, semiconductor nanoparticles, redox shuttle, etc⋯) as well as of combined dye/semiconductor/redox shuttle systems can successfully assist the experimental research by providing basic design rules of new sensitizers and a deeper comprehension of the fundamental chemical and physical processes governing the cell functioning and its performances. A computational approach to DSCs modeling can essentially be cast into a stepwise problem, whereby one first needs to simulate accurately the individual DSCs components to move to relevant pair (or higher order) interactions characterizing the device functioning. This information can contribute to enhancing further the target DSCs characteristics, such as temporal stability and optimization of device components. After presenting selected results for isolated dyes, including the computational design of new dyes, and model semiconductors, including realistic nanostructure models, we focus in the remainder of this review on the interaction between dye-sensitizers and semiconductor oxides, covering organic as well as metallorganic dyes. © 2013 Springer-Verlag Berlin Heidelberg.

Maia A.,CNR Institute of Molecular Science and Technologies
Mini-Reviews in Organic Chemistry | Year: 2011

Ionic liquids (ILs) are attracting increasing interest as a potential ecosustainable alternative to traditional volatile organic solvents (VOCs), generally used in large amounts. About the "greenness" of ILs a certain controversy still exists because their toxicity and biodegradability need to be fully assessed. Moreover, the real advantages of using this novel class of solvents should be more deeply studied in comparison with traditional media. This article presents some of the most recent findings in this field by reviewing selected examples of applications of ILs in organic synthesis and catalysis. In addition, anionic reactivity data for some organic reactions will be discussed and compared with those previously found for the same reactions in molecular solvents. Finally, updated results concerning toxicity, ecotoxicity and biodegradation of the most common ILs will be reported. © 2011 Bentham Science Publishers Ltd.

Pina C.D.,CNR Institute of Molecular Science and Technologies | Falletta E.,CNR Institute of Molecular Science and Technologies | Rossi M.,CNR Institute of Molecular Science and Technologies
Chemical Society Reviews | Year: 2012

This critical review aims to update the recent development in the selective oxidation of organic compounds by gold catalysis, highlighting the progress in the last three years. Following the impressive developments in the last decades, several protocols for catalytic oxidation are today available, which are based on the extraordinary properties of gold in terms of catalytic activity, selectivity, reusability and resistance to poisons. Beside many other applications, gold can be recommended for green processes dedicated to fine chemicals, pharmaceuticals and the food industry owing to its recognized bio-compatibility. The collected literature is focused on experiments concerning the oxidation of different chemical groups and could be of interest, in the wide area of organic chemistry, for improving previous processes or for exploring new catalytic pathways (174 references).

Ferraccioli R.,CNR Institute of Molecular Science and Technologies
Current Organic Synthesis | Year: 2012

This Review reports recent developments in the synthesis of benzo-fused heterocycles through Pd-catalyzed carbon-carbon and carbon-heteroatom bond forming reactions via direct C-H activation. Nitrogen-, oxygen- and sulfur-containing heterocyclic rings can be rapidly assembled starting from precursors with minimal preactivation. Compared to classical coupling reactions (i.e. Suzuki, Stille, Buchwald-Hartwig), these methods provide a more straightforward and economical route to various heterocyclic scaffolds, which is of practical importance considering their role in biology and pharmaceutical industry. © 2012 Bentham Science Publishers.

De Angelis F.,CNR Institute of Molecular Science and Technologies
Accounts of Chemical Research | Year: 2014

Over the last 2 decades, researchers have invested enormous research effort into hybrid/organic photovoltaics, leading to the recent launch of the first commercial products that use this technology. Dye-sensitized solar cells (DSCs) have shown clear advantages over competing technologies. The top certified efficiency of DSCs exceeds 11%, and the laboratory-cell efficiency is greater than 13%. In 2012, the first reports of high efficiency solid-state DSCs based on organohalide lead perovskites completely revolutionized the field. These materials are used as light absorbers in DSCs and as light-harvesting materials and electron conductors in meso-superstructured and flat heterojunction solar cells and show certified efficiencies that exceed 17%.To effectively compete with conventional photovoltaics, emerging technologies such as DSCs need to achieve higher efficiency and stability, while maintaining low production costs. Many of the advances in the DSC field have relied on the computational design and screening of new materials, with researchers examining material characteristics that can improve device performance or stability. Suitable modeling strategies allow researchers to observe the otherwise inaccessible but crucial heterointerfaces that control the operation of DSCs, offering the opportunity to develop new and more efficient materials and optimize processes. In this Account, we present a unified view of recent computational modeling research examining DSCs, illustrating how the principles and simulation tools used for these systems can also be adapted to study the emerging field of perovskite solar cells.Researchers have widely applied first-principles modeling to the DSC field and, more recently, to perovskite-based solar cells. DFT/TDDFT methods provide the basic framework to describe most of the desired materials and interfacial properties, and Car-Parrinello molecular dynamics allow researchers the further ability to sample local minima and dynamical fluctuations at finite temperatures. However, conventional DFT/TDDFT has some limitations, which can be overcome in part by tailored solutions or using many body perturbation theory within the GW approach, which is however more computationally intensive. Relativistic effects, such as spin-orbit coupling, are also included in simulations since they are fundamental for addressing systems that contain heavy atoms. We illustrate the performance of the proposed simulation toolbox along with the fundamental modeling strategies using selected examples of relevant isolated device constituents, including dye and perovskite absorbers, metal-oxide surfaces and nanoparticles, and hole transporters. We critically assess the accuracy of various computational approaches against the related experimental data. We analyze the representative interfaces that control the operational mechanism of the devices, including dye-sensitized TiO2/hole transporter and organohalide lead perovskite/TiO2, and the results reveal fundamental aspects of the device's operational mechanism. Although the modeling of DSCs is relatively mature, the recent "perovskite storm" has presented new problems and new modeling challenges, such as understanding exciton formation and dissociation at interfaces and carrier recombination in these materials. © 2014 American Chemical Society.

Pastore M.,CNR Institute of Molecular Science and Technologies | De Angelis F.,CNR Institute of Molecular Science and Technologies
Journal of Physical Chemistry Letters | Year: 2013

We present a unified overview of our recent activity on the modeling of relevant intermolecular interactions occurring in dye-sensitized solar cells (DSCs). The DSC is an inherent complex system, whose efficiency is essentially determined by the interrelated phenomena occurring at the multiple molecular-semiconductor-electrolyte heterointerfaces. In this Perspective, we illustrate the basic methodology and selected applications of computational modeling of dye-dye and dye-coadsorbent intermolecular interactions taking place at the dye-sensitized interface. We show that the proposed methodology offers a realistic picture of aggregation phenomena among surface-adsorbed dyes and nicely describes semiconductor surfaces cosensitized by different dyes. The information acquired from this type of studies might constitute the basis for an integrated multiscale computational description of the device functioning, including all of the possible interdependencies among the device constituents, which may further boost the DSCs efficiency. We believe that this direction should be the target of future computational research in the DSC field. © 2013 American Chemical Society.

Pastore M.,CNR Institute of Molecular Science and Technologies | Angelis F.D.,CNR Institute of Molecular Science and Technologies
Journal of Physical Chemistry Letters | Year: 2012

TiO 2 cosensitization by different dyes having complementary absorption represents an appealing strategy to obtain panchromatic sensitization in dye-sensitized solar cells. Fluorescence (Föster) resonance energy transfer (FRET) from an energy relay dye to a sensitizing dye, both grafted onto TiO 2, was effectively shown to produce additional photocurrent (Hardin et al. J. Am. Chem. Soc.2011, 133, 10662). Here we develop a realistic cosensitization model to provide a precise estimate of the geometrical parameters, which govern the FRET rate. The reliability of our model is fully confirmed by the quantitative reproduction of the experimental spectral shift in the naphtalocyanine absorption band and by the excellent agreement between the experimentally reported FRET rates. Our model provides a realistic picture of the cosensitized TiO 2 interface and is capable, at the same time, of predicting the cosensitization mechanism and the associated FRET kinetics based on the sole photophysical characterization of the isolated donor/acceptor partners © 2012 American Chemical Society.

Gatti C.,CNR Institute of Molecular Science and Technologies
Physica Scripta | Year: 2013

Narrating my scientific career, I show in this paper how, starting as a computational and theoretical chemist, I got naturally involved with x-ray crystallographers because of the common interest in charge density and in the study of chemical bonds based on such an observable. The tools I devised and the conceptual developments I made to facilitate a profitable encounter between x-ray charge density and computational chemistry researchers are illustrated, with a special focus on the proposal and applications of the Source Function concept. © 2013 The Royal Swedish Academy of Sciences.

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