Electronic Mechanisms of Intra and Intermolecular J Couplings in Systems with C-H···O Interactions

Computational chemistry in drug lead discovery and design

“…[]. Our early work in the field of theoretical quantum chemistry, both in the calculation of NMR parameters, (together with Ruben H. Contreras†, Martín Ruiz de Azúa†, and Claudia Giribet at the Department of Physics, University of Buenos Aires, City of Buenos Aires, Argentina), in the field of the polarization propagator, and studies of glucose diffusivity in nano‐confinement will not be further analyzed in detail in this review.…”

IPPP-CLOPPA Analysis of the Influence of the Methylation on the Potential Energy and the Molecular Polarizability of the Hydrogen Bonds in the Cytosine–Guanine Base Pair

“…The IPPP-CLOPPA (Inner Projections of the Polarization Propagator-Contributions from Localized Orbitals within the Polarization Propagator Approach) technique − has proven to be a convenient method to deal with these issues, as it was intended to identify the electronic mechanisms operating in a given phenomenon in terms of localized molecular orbitals (LMOs). Although it was implemented for the theoretical analysis of NMR spin–spin couplings − and the static molecular polarizability tensor, − the same scheme can be used for any second-order molecular property. Additionally, more recently, the same idea of defining a molecular fragment with LMOs was applied for calculating first-order properties; in particular, the energy associated with a molecular fragment …”

CLOPPA Analysis of the Molecular Polarizability and the Energy of Strong Intramolecular Hydrogen Bonds: Resonance Assisted?

“…In the early times, HBs had been characterized as a proton shared by two electronegative atoms (i.e., by two electron pairs), thus suggesting an electrostatic nature. However, this kind of description does not stand for the great variety of moieties, which nowadays have been recognized as HBs, − and therefore, this pure electrostatic picture has been replaced by a combination of both electrostatic and covalent contributions . On the basis of experimental grounds, Gilli and co-workers have proposed a qualitative electrostatic-covalent HB model (ECHBM), − which relates the HB strength with the main character of the bond, such that a weak HB is mainly electrostatic in nature, and its covalent character increases with increasing strength.…”

“…The contributions from localized orbitals within the polarization propagator approach (CLOPPA) technique − appears as a convenient method to deal with these issues, as it is a useful tool to identify the electronic mechanisms operating in a given phenomenon in terms of localized molecular orbitals (LMOs). It was implemented at the ab initio level for the theoretical analysis of NMR spin–spin couplings ,− and the static molecular polarizability tensor, , although the same scheme can be used for any second-order molecular property. It is noteworthy that the very idea of defining a molecular fragment with LMOs could also be applied for calculating first-order properties; in particular, the energy associated to a molecular fragment could be evaluated in this way.…”