Intramolecular Bonding and Charge Distributions in XO₄(X = Si, P, S, Cl and Ge, As, Se, Br) Oxyanions from Topological Analyses of the Electron Density

Abstract

Intramolecular X−O bonds and charge distributions in XO4 (X = Si, P, S, Cl, and Ge, As, Se, Br) oxyanions were investigated with topological analyses of the electron density in the frameworks of the theories of atoms in molecules (AIM) and of the electron localization function (ELF). The optimized geometries and wave functions of all oxyanions were obtained at the B3LYP/6-311+G(3df) level. AIM analyses recover a significant concentration of electrons at (3,−1) bond critical points increasing from SiO4 4- (0.12 au) to ClO4 - (0.37 au) and from GeO4 4- (0.14 au) to BrO4 1- (0.27 au). Perchlorate is the only oxyanion exhibiting true shared interactions in the sense of AIM with a large and negative Laplacian of the electron density at the bond critical point. All other oxyanions are intermediate to shared and closed-shell interactions with positive values of the Laplacian of the electron density. ELF analyses tend to support the conclusions of AIM by localizing disynaptic basins between 3rd row X atoms and O with electron populations ranging from 1.56e (SiO4 4-) to 1.84e (ClO4 1-). The X−O bonds are also shown to be of donor−acceptor type. Fourth row oxyanions have highly delocalized and small disynaptic basin populations ranging from 0.27e (AsO4 3-) to 0.30e (BrO4 1-) with GeO4 4- as the only oxyanion without any formally defined disynaptic basin. The attractive forces in these oxyanions are thus mostly of electrostatic nature. All ELF disynaptic basins have strong cross-contributions with the lone pair monosynaptic valence basins of O. These latter basins contain about three electron pairs (6.12e) for ClO4 1- to about four (7.99e) for GeO4 4-. Finally, the Merz−Kollman scheme was used to determine point charges that can reproduce the electrostatic potential of the oxyanions. Their values are however notably different than those obtained by AIM.

Charge density distribution of 3-(1-aminoethylidene)-2-methoxy-2-oxo-2,3-dihydro-2λ5-benzo[e][1,2]oxaphosphinin-4-one

“…However, positive Laplacians are reproducible for the experiment, as mentioned above. On the other hand, many examples exist of theoretical values of Laplacians which are comparable to those we have found here (Lopez et al, 1996;Mõ & Yá ň ez, 1996;Boily, 2002). A thorough investigation of r 2 (BCP) values of oxaphosphinane derivatives optimized previously has revealed comparable values.…”

Counterion Effects in Metal Hybrid Biopolymer Materials for Sulfate Adsorption: An Experimental and Computational Study

“…The zeta potential provides insights on the surface charge of the material, which is influenced by the acid–base and coordination properties of the anion. In addition, shielding the Al 3+ centers via coordination will change the zeta potential and the PZC in conjunction with the possible effect of charge density of the counterion species. , The hydration properties were inferred from the FWHM Raman spectral results (cf. Figure ).…”

The Joint Use of Catastrophe Theory and Electron Localization Function to Characterize Molecular Mechanisms. A Density Functional Study of the Diels−Alder Reaction between Ethylene and 1,3-Butadiene

“…ELF basins are defined quantities, although based on strong physical arguments regarding the Fermi hole , that can be interpreted consistently on the simple ideas of chemical bonding associated to the Pauli exclusion principle. A wide range of applications of the ELF method for the treatment of chemical reactivity has also appeared. − …”