Decomposition of Molecular Integrals into Atomic Contributions via Becke Partitioning Scheme: a Caveat

Decomposition of molecular integrals into physically meaningful atomic contributions by means of the Becke integration scheme requires some care with respect to the choice of suitable atomic size adjustments. Using a simple illustrative example, it is shown that the adjustment of cell boundaries, as originally proposed by considering Bragg-Slater atomic radii, does not provide reliable results. Alternatively, the positions of the bond critical points of the electron density can be adopted to define heteronuclear cutoff profiles which allow for a more reasonable atomic partition of the molecular electron density. This work is licensed under a Creative Commons Attribution 4.0 International License

Synthesis and Stereochemical Characterization of a Novel Chiral α-Tetrazole Binaphthylazepine Organocatalyst

A novel α-tetrazole-substituted 1,1'-binaphthylazepine chiral catalyst has been synthesized and its absolute configuration has been determined by DFT computational analysis of the vibrational circular dichroism (VCD) spectrum of its precursor. The VCD analysis, carried out through the model averaging method, allowed to assign the absolute configuration of a benzylic stereocenter in the presence of a chiral binaphthyl moiety. The 1,1'-binaphthylazepine tetrazole and the nitrile its immediate synthetic precursor, have been preliminarily tested as chiral organocatalysts in the asymmetric intramolecular oxa-Michael cyclization of 2-hydroxy chalcones for the synthesis of chiral flavanones obtaining low enantioselectivity

Coupled Hartree-Fock calculations of molecular magnetic properties annihilating the transverse paramagnetic current density

The reliability of the continuous transformations of origin of the current density method, which makes the transverse paramagnetic current vanish (CTOCD-PZ), for the prediction of nearly gauge-origin independent molecular magnetic susceptibility and gauge-origin independent nuclear magnetic shielding, is proved on the basis of a fairly large number of calculations, It is shown that, within the computational scheme provided by the coupled Hartree-Fock perturbation theory (CHF), convergence towards the presumed Hartree-Fock limit, for magnetic susceptibility and proton magnetic shielding, is systematically reached using basis sets which are smaller than those required by conventional common origin and CTOCD-DZ techniques. For second-row nuclear magnetic shieldings a variant of the CTOCD-PZ method, which shifts the origin of the current towards the nearest nucleus for points close to nuclei, as suggested originally by Keith and Bader with the CSDGT method [T. A. Keith and R. F. W. Bader, Chem. Phys. Lett. 210, 223 (1993)], gives likewise good results with affordable basis sets. (C) 1996 American Institute of Physics