Experimental and Theoretical Evidence for Nitrogen-Fluorine Halogen Bonding in Silver-Initiated Radical Fluorinations

We report experimental and computational evidence for nitrogen–fluorine halogen bonding in Ag­(I)-initiated radical C–H fluorinations. Simple pyridines form [N–F–N]+ halogen bonds with Selectfluor to facilitate single-electron reduction by catalytic Ag­(I). Pyridine electronics affect the extent of halogen bonding, leading to significant differences in selectivity between mono- and difluorinated products. Electronic structure calculations show that halogen bonding to various pyridines alters the single-electron reduction potential of Selectfluor, which is consistent with experimental electrochemical analysis. Multinuclear correlation NMR also provides spectroscopic evidence for pyridine halogen bonding to Selectfluor under ambient conditions

MODELING ELECTRON DETACHMENT FROM METAL OXIDE CLUSTERS WITH EFFICIENT ELECTRONIC STRUCTURE METHODS

Photoelectron spectroscopy is a powerful technique for investigating the structure and reactivity of metal oxide clusters, which can serve as models of surface defect sites. Assigning photoelectron spectra typically requires corroborating computational simulations. Motivated by the complicated electronic structure often exhibited by these species that can challenge the quality of computational results using widely available quantum chemistry methods, our group has explored the development of efficient electronic structure models to describe photodetachment. This talk will describe these efforts and our lab’s recent applications of such models in investigations of various metal oxide clusters

Modeling emission features of salicylidene aniline molecular crystals: A QM/QM' approach

A new computational protocol relying on the use of electrostatic embedding, derived from QM/QM' ONIOM calculations, to simulate the effect of the crystalline environment on the emission spectra of molecular crystals is here applied to the beta-form of salicylidene aniline (SA). The first singlet excited states (S-1) of the SA cis-keto and trans-keto conformers, surrounded by a cluster of other molecules representing the crystalline structure, were optimized by using a QM/QM' ONIOM approach with and without electronic embedding. The model system consisting of the central salicylidene aniline molecule was treated at the DFT level by using either the B3LYP, PBE0, or the CAM-B3LYP functional, whereas the real system was treated at the HF level. The CAM-B3LYP/HF level of theory provides emission energies in good agreement with experiment with differences of 220/232 nm (cis-keto form) and 28/214 nm (trans-keto form), respectively, whereas notably larger differences are obtained using global hybrids. Though such differences on the optical properties arise from the density functional choice, the contribution of the electronic embedding is rather independent of the functional used. This plays in favor of a more general applicability of the present protocol to other crystalline molecular systems

Uncovering the mechanism leading to the synthesis of symmetric and asymmetric Tröger's bases

Tröger´s bases have been attracting great interest due to their potential applications in nanoelectronics, supramolecular chemistry, molecular recognition, biological activity and auxiliaries for asymmetric synthesis. However, a detailed step by step proposal for the mechanism leading to the production of these compounds is still uncovered. A set of five model syntheses of symmetric and asymmetric Tröger´s base derivatives starting from substituted anilines and formaldehyde was done and envisaged as representative for understanding the underlying mechanism. All reasonable pathways were thoroughly scanned by means of DFT calculations. The highest energy TS was associated with the entrance of the first formaldehyde which produces the first out of three key carbocations. The last step, the closure of the methylene-bridged diazocyne heterocycle was also found of kinetic relevance and as a source of stable intermediates or byproducts. The whole mechanistic picture would provide keys for the rational planning of the synthesis of these compounds.Fil: Lanza, Priscila Ailín. Universidad Nacional de Mar del Plata; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones En Biodiversidad y Biotecnologia. Grupo de Investigacion En Quimica Analitica y Modelado Molecular.; ArgentinaFil: Dusso, Diego. Departamento de Química; ArgentinaFil: Ramirez, Cristina Lujan. Universidad Nacional de Mar del Plata; ArgentinaFil: Parise, Alejandro Ruben. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones En Biodiversidad y Biotecnologia. Grupo de Investigacion En Quimica Analitica y Modelado Molecular.; Argentina. Universidad Nacional de Mar del Plata; ArgentinaFil: Chesta, Carlos Alberto. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; ArgentinaFil: Moyano, Elizabeth Laura. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; ArgentinaFil: Vera, Domingo Mariano Adolfo. Universidad Nacional de Mar del Plata; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones En Biodiversidad y Biotecnologia. Grupo de Investigacion En Quimica Analitica y Modelado Molecular.; Argentin

A mathematical and computational review of Hartree-Fock SCF methods in Quantum Chemistry

We present here a review of the fundamental topics of Hartree-Fock theory in Quantum Chemistry. From the molecular Hamiltonian, using and discussing the Born-Oppenheimer approximation, we arrive to the Hartree and Hartree-Fock equations for the electronic problem. Special emphasis is placed in the most relevant mathematical aspects of the theoretical derivation of the final equations, as well as in the results regarding the existence and uniqueness of their solutions. All Hartree-Fock versions with different spin restrictions are systematically extracted from the general case, thus providing a unifying framework. Then, the discretization of the one-electron orbitals space is reviewed and the Roothaan-Hall formalism introduced. This leads to a exposition of the basic underlying concepts related to the construction and selection of Gaussian basis sets, focusing in algorithmic efficiency issues. Finally, we close the review with a section in which the most relevant modern developments (specially those related to the design of linear-scaling methods) are commented and linked to the issues discussed. The whole work is intentionally introductory and rather self-contained, so that it may be useful for non experts that aim to use quantum chemical methods in interdisciplinary applications. Moreover, much material that is found scattered in the literature has been put together here to facilitate comprehension and to serve as a handy reference.Comment: 64 pages, 3 figures, tMPH2e.cls style file, doublesp, mathbbol and subeqn package

Regioselective Nickel-Catalyzed Reductive Couplings of Enones and Allenes

No AbstractPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78305/1/anie_201004740_sm_miscellaneous_information.pd

Synthesis, Structure-Activity, and Structure-Stability Relationships of 2-Substituted- N

N-Acylethanolamine acid amidase (NAAA) is a cysteine amidase that preferentially hydrolyzes saturated or monounsaturated fatty acid ethanolamides (FAEs), such as palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), which are endogenous agonists of nuclear peroxisome proliferator-activated receptor-α (PPAR-α). Compounds that feature an α-amino-β-lactone ring have been identified as potent and selective NAAA inhibitors and have been shown to exert marked anti-inflammatory effects that are mediated through FAE-dependent activation of PPAR-α. We synthesized and tested a series of racemic, diastereomerically pure β-substituted α-amino-β-lactones, as either carbamate or amide derivatives, investigating the structure-activity and structure-stability relationships (SAR and SSR) following changes in β-substituent size, relative stereochemistry at the α- and β-positions, and α-amino functionality. Substituted carbamate derivatives emerged as more active and stable than amide analogues, with the cis configuration being generally preferred for stability. Increased steric bulk at the β-position negatively affected NAAA inhibitory potency, while improving both chemical and plasma stability