On the transferability of QTAIMC descriptors derived from X-ray diffraction data and DFT calculations: substituted hydropyrimidine derivatives

Abstract

The combined study of electron-density features in three substituted hydropyrimidines of the Biginelli compound family has been fulfilled. Results of the low-temperature X-ray diffraction measurements and density functional theory (DFT) B3LYP/6-311++G** calculations of these compounds are described. The experimentally derived atomic and bonding characteristics determined within the quantum-topological theory of atoms in molecules and crystals (QTAIMC) were demonstrated to be fully transferable within chemically similar structures such as the Biginelli compounds. However, for certain covalent bonds they differ significantly from the theoretical results because of insufficient flexibility of the atom-centered multipole electron density model. It was concluded that currently analysis of the theoretical electron density provides a more reliable basis for the determination of the transferability of QTAIMC descriptors for molecular structures. Empirical corrections making the experimentally derived QTAIMC bond descriptors more transferable are proposed.

Should environmental effects be included when performing QTAIM calculations on actinide systems? A comparison of QTAIM metrics for Cs2UO2Cl4, U(Se2PPh2)4 and Np(Se2PPh2)4 in gas phase, COSMO and PEECM

“…[28,29,47] In these studies experimental values of the Laplacian were up to 1.3 a.u. higher than theory for C=O bonds and 0.…”

“…Other studies on organic molecules also found only small differences between molecular and periodic boundary condition DFT calculations. [28,29] Parenthetically, we note that Vallet et al have previously studied the effect of environment on the electronic spectrum of the uranyl dication (UO 2…”

Cl···Cl Interactions in Molecular Crystals: Insights from the Theoretical Charge Density Analysis

“…For example, we did not locate the critical point corresponding to the Cl•••Cl intermolecular interaction in the chlorokojic acid crystal; the Cl•••Cl contact in this crystal is characterized by D = 4.366 Å and ρ b < 0.003 au. 62 This value of the electron density is at the limit of the experimental accuracy that may be reached nowadays in experimental charge density analysis 119 or evaluated from the theoretical electron density of molecular crystals. 58 1 and S2) are approximately described by a single curve.…”

Density functional theory is straying from the path toward the exact functional

“…The HCTH407 (8) and B97-2 (9) functionals were fitted to reproduce the profile of nearly exact exchange-correlation potentials (and thereby densities) of some atomic and molecular systems. Electron densities produced by several DFT functionals have already been tested in various studies [ (10)(11)(12)(13)(14)(15) and references therein], but modern highly parameterized functionals were not included.…”