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.
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.
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.
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.
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.