Molecular structure of uranium carbides: Isomers of UC3

In this article, the most relevant isomers of uranium tricarbide are studied through quantum chemical methods. It is found that the most stable isomer has a fan geometry in which the uranium atom is bonded to a quasilinear C3 unit. Both, a rhombic and a ring CU(C2) structures are found about 104–125 kJ/mol higher in energy. Other possible isomers including linear geometries are located even higher. For each structure, we provide predictions for those molecular properties (vibrational frequencies, IR intensities, dipole moments) that could eventually help in their experimental detection. We also discuss the possible routes for the formation of the different UC3 isomers as well as the bonding situation by means of a topological analysis of the electron densityFil: Zalazar, Maria Fernanda. Universidad Nacional del Nordeste. Facultad de Cs.exactas Naturales y Agrimensura. Departamento de Quimica. Laboratorio de Estructura Molecular y Propiedades; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rayon, Victor M.. Universidad de Valladolid. Facultad de Ciencias; EspañaFil: Largo, Antonio. Universidad de Valladolid. Facultad de Ciencias; Españ

Molecular Structure and Bonding in Plutonium Carbides: A Theoretical Study of PuC3

8 págs.; 4 figs.; 4 tabs.The most relevant species of plutonium tricarbide were characterized using theoretical methods. The global minimum is predicted to be a fan structure where the plutonium atom is bonded to a quasi-linear C unit. A rhombic isomer, shown to be a bicyclic species with transannular C-C bonding, lies about 39 kJ/mol above the fan isomer. A linear PuCCC isomer and a three-membered ring CPuC isomer were found to be higher in energy (150 and 195 kJ/mol, respectively, above the predicted global minimum). The possible processes for the formation of these species are discussed, and the IR spectra were predicted to help in possible experimental detection. The nature of the Pu-C interaction has been analyzed in terms of a topological analysis of the electronic density, showing that Pu-C bonding is essentially ionic with a certain degree of covalent character. Copyright © 2016 American Chemical SocietyFinancial support from the Junta de Castilla y León (Grant VA077U13) is gratefully acknowledgedPeer Reviewe

Iodine and Bromine Redox Systems Induce the Formation of Nitrogen Centered Radicals. Searching for a possible Role of Iodine, Bromine and Sulfamates in Biological Radical Processes.

Trabajo presentado en el WG4/WG1 Meeting COST Action CM1201: Biomimetic Radical Chemistry, celebrado en el Puerto de la Cruz (Tenerife) del 1 al 3 de octubre de 2014.In the last years, we have been focused in the development of new synthetic strategies to perform the selective functionalization of unactivated aliphatic C(sp3)–H bond mainly employing nitrogen centered radicals as activating specie.1 For this purpose, various N‐halo sulfamates have been used as N‐radicals precursors and therewith, promote selective transformations of C–H bonds into new C–Halogen, C–N, and C–O bonds. Within the mechanistic studies involved in such processes, we have faced a very complex reactive medium characterized by the interaction of halogenated species in different oxidation states with sulfamates. This complex medium is extremely reactive but however, remarkably selective and moldable due to its high sensitivity to modifications in the reaction conditions. Iodine and bromine are trace elements that exist in natural water, earth, atmosphere and most of living organisms, being biologically essential nutrients for all mammals including humans, and, indeed, most organisms seem to have the ability to produce halogenated organic compounds.2 In general, it is accepted that halogenated alkanes are formed either by mediated nucleophilic attack of corresponding halides (Br‐ or I‐) (equation a), or by reactions of I+ and Br+ species (e.g. HOX, X2, X3+,etc.), generated by haloperoxidases (HPO), with electron‐rich substrates (equation b); however no radical processes induced by X+ species appear in the literature.3 Herein, we will discuss about the possibility to perform apparently direct transformations of alkyl C–H bonds into C–N or C–O bonds via a transient C–X bond formation (X = Br or I) using an initial radical pathway followed by an oxidative dehalogenation step. Is it not a possible metabolic pathway to perform selective oxidation in biological systems?, Is it possible to export our mechanistic findings (in vitro) into possible biological radical processes?... These and other questions will be posed to the audience.Peer Reviewe

N-Halo Sulfonamides, Sulfamates and Sulfamides as Nitrogen-Centered Radicals Precursors and its Applications in the Selective Functionalizations of Unactivated Methyl Groups and Oxidations

Trabajo presentado en el WG4/WG1 Meeting COST Action CM1201: Biomimetic Radical Chemistry, celebrado en el Puerto de la Cruz (Tenerife) del 1 al 3 de octubre de 2014.Among all the functionalizations of unactivated C(sp3)¿H bonds described in the literature to date, the functionalization of methyl groups in conformational non-restricted molecules remains challenging. In this communication, we focused on the reactivity of these methyl groups, to convert a C¿H bond in a C¿N or C¿X (X = Halogen) bond with high chemoselectivity. These functionalizations are achieved in an intramolecular way, with Nitrogen-centered radicals generated from different precursors using the redox systems [I0¿I+¿I3+] and [Br0¿Br+]. The key for the chemoselectivity between mono- and polyoxidation of the methyl moiety, via Single Hydrogen Atom Transference (SHAT) or Multiple Hydrogen Atom Transferences (MHAT), respectively, is also discussed.3 In addition, the use of sulfamates and sulfamides as N-radical precursors also allows the oxidation to synthetically versatile aldi- or ketimines.Peer Reviewe