X-Ray Charge Densities and Chemical Bonding

Abstract

This book deals with the electron density distribution in molecules and solids as obtained experimentally by X-ray diffraction. It is a comprehensive treatment of the methods involved, and the interpretation of the experimental results in terms of chemical bonding and intermolecular interactions. Inorganic and organic solids, as well as metals, are covered in the chapters dealing with specific systems. As a whole, this monograph is especially appealing because of its broad interface with numerous disciplines. Accurate X-ray diffraction intensities contain fundamental information on the charge distribution in crystals, which can be compared directly with theoretical results, and used to derive other physical properties, such as electrostatic moments, the electrostatic potential and lattice energies, which are accessible by spectroscopic and thermodynamic measurements. Consequently, the work will be of great interest to a broad range of crystallographers and physical scientists.

Unravelling the Mysteries of the [3+2] Cycloaddition Reactions

“…Although several theoretical models based on the analysis of separated MOs, such as the FMO theory, are widely used to explain chemical reactivity in organic chemistry, MOs are only mathematical constructs defined in 1930 to assemble the molecular wavefunction, that cannot be determined by experiment . In contrast, the electron density distribution in a molecule or crystal can be experimentally determined by electron diffraction and X‐ray crystallography; and it can also, and often more readily, be obtained from ab initio or DFT calculations …”

Curly arrows meet electron density transfers in chemical reaction mechanisms: from electron localization function (ELF) analysis to valence-shell electron-pair repulsion (VSEPR) inspired interpretation

“…[59][60][61][62][63][64][65][66][67] A number of excellent works in the subject have been published to remark the importance of charge density analysis applied to chemical and biological systems and solids. 47,48,56,[68][69][70][71][72][73][74] Probing the electron density distribution during a chemical reaction can provide important insights, but this aim has required extension of the relationships between the traditional chemical concepts and the quantum mechanical ones. In this context, the catastrophe theory has been used to study the evolution along a reaction path of the topologies of the electron density, 75,76 the laplacian of the electron density 77 3 and of the electron localization function (ELF), 78 i.e.…”

Insight into trifluoromethylation – experimental electron density for Togni reagent I

“… 21,22 An experimental approach to the electron density may complement theoretical calculations: low temperature X-ray diffraction data of sufficient resolution allow to obtain the experimental charge density and associate it with intra- and inter-molecular interactions. 23–25 Such advanced structure models based on aspherical scattering factors have also been applied in the study of halogen bonds. 26–30 In this contribution, we provide direct experimental information for the electronic situation in Togni reagent I, 1; in particular, we analyze the charge distribution around the hypervalent iodine atom.…”