Littérature scientifique sur le sujet « Bader’s topological analysis »

In partitioning space in the analysis of a continuous charge distribution, the requirement of locality, formulated by Kurki-Suonio (Kurki-Suonio 1968, 1971; Kurki-Suonio and Salmo 1971), should be preserved. It states that density at a point should be assigned to a center in the proximity of that point. In discrete boundary partitioning schemes, the density at each point is assigned to a specific basin, while in fuzzy boundary partitioning, the density at the point may be assigned to overlapping functions centered at different locations. The least-squares formalisms described in chapter 3 implicitly define a space partitioning scheme, based on the density functions used in the refinement that are each centered on a specific nucleus. Since the density functions are continuous, they overlap, so the fragments interpenetrate rather than meet at a discrete boundary. Such fuzzy boundaries correspond to smoothly varying functions, both in real and reciprocal space, and therefore to well-behaved fragment scattering factors, and reasonable fragment electrostatic moments. The interpenetratingfragment partitioning schemes are related to the Mulliken and Løwdin population analyses of theoretical chemistry. The topological analysis of the total density, developed by Bader and coworkers, leads to a scheme of natural partitioning into atomic basins which each obey the virial theorem. The sum of the energies of the individual atoms defined in this way equals the total energy of the system. While the Bader partitioning was initially developed for the analysis of theoretical densities, it is equally applicable to model densities based on the experimental data. The density obtained from the Fourier transform of the structure factors is generally not suitable for this purpose, because of experimental noise, truncation effects, and thermal smearing. The topological analysis of the density leads to a powerful classification of bonding based on the electron density. It is discussed in the final sections of this chapter. The stockholder partitioning concept is one of the important contributions to charge density analysis made by Hirshfeld (1977b). It defines a continuous sampling function wi(r), which assigns the density among the constituent atoms. The sampling function is based on the spherical-atom promolecule density—the sum of the spherically averaged ground-state atom densities.

In this chapter, the influence of non-covalent interactions on the complexes formed by the various biomolecules (mesalazine, para-aminosalicylic acid, acetaminophen, psoralen, and methyl salicylate) with the Cu2+ cation is investigated using the density functional theory (DFT) method. Since the interactions involving aromatic rings are crucial binding forces in chemical systems, this is exciting research trying to understand and control the effect of non-covalent interactions responsible for complicated functions in nature. Herein, the calculations are performed in the gas phase and water solvent. The results show that the absolute amounts of energy are reduced by going from the gas phase to the solution. The topological properties of the electron density and the values of charge transfer are evaluated by the Bader theory of atoms in molecules (AIM) and the natural bond orbital (NBO) analysis, respectively. These results are useful for understanding the role of the drug-receptor interactions in the complexes. The electronic descriptors are also important factors in forming a charge-transfer complex between cation and biological target. The results of this study that are ubiquitous in biological systems may be useful for the design and synthesis of a variety of supramolecular complexes with the desired properties.