Chemical binding

About: Chemical binding is a research topic. Over the lifetime, 1822 publications have been published within this topic receiving 52516 citations.

The interaction of inert gases

Abstract: The following paper studies from a quantum mechanical point of view a special kind of chemical reaction, namely, the inertness of the inert gases. In the development of the quantum theory of homopolar binding this chapter has hitherto been omitted for the following reason: not only is the charge distribution of an inert gas atom spherically symmetrical, but the whole ψ-function, which depends in the case of n electrons on 3 n space co-ordinated and n spin co-ordinates, is invariant under a simultaneous orthogonal transformation of all co-ordinates. This means that there is no space degeneracy. If now this atom is brought near to another similar one, the disappearance of direction symmetry is not followed by a disappearance of degeneracy—the stationary state does not split up into several states as in most cases of chemical binding, but remains single and seems to correspond, under ordinary conditions, to repulsion. On the other hand, Heitler and London in their well-known treatment of the H2-problem, found that it was just the removal of a degeneracy, which they called “exchange degeneracy,” which gave rise to large resonance forces and thus led to binding in one of the resultant states and repulsion in the other. This induced subsequent workers to suppose that the antiparallel copuling of two electron spins in different atoms always entails a binding force. This was supported from the theorectical side by the fact that the interaction energy could actually be worked out as a sum of terms each belonging to such as coupling. Such a theory could not fail to fit the experiments as it established the rules Lewis’ theory of electron pairs—a theory already proved to have wide validity.

Single-Molecule Imaging of Activated Nitrogen Adsorption on Individual Manganese Phthalocyanine

Abstract: An atomic-scale understanding of gas adsorption mechanisms on metal-porphyrins or metal-phthalocyanines is essential for their practical application in biological processes, gas sensing, and catalysis. Intensive research efforts have been devoted to the study of coordinative bonding with relatively active small molecules such as CO, NO, NH3, O2, and H2. However, the binding of single nitrogen atoms has never been addressed, which is both of fundamental interest and indeed essential for revealing the elementary chemical binding mechanism in nitrogen reduction processes. Here, we present a simple model system to investigate, at the single-molecule level, the binding of activated nitrogen species on the single Mn atom contained within the manganese phthalocyanine (MnPc) molecule supported on an inert graphite surface. Through the combination of in situ low-temperature scanning tunneling microscopy, scanning tunneling spectroscopy, ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations, the active site and the binding configuration between the activated nitrogen species (neutral nitrogen atom) and the Mn center of MnPc are investigated at the atomic scale.

SERS investigation on the adsorption and photoreaction of 4‐nitroanisole in Ag hydrosols

Abstract: The adsorption of 4-nitroanisole on silver colloidal nanoparticles was investigated by surface-enhanced Raman spectroscopy (SERS). Actually, the chemical binding with a metal substrate may play a role in changing the electronic structure of this molecule, which can be considered a push–pull chromophore, because an internal charge-transfer occurs between methoxy and nitrogroup. A SERS signal could be detected only in chloride-activated silver colloids, but the spectrum recorded with green-light excitation was not related to adsorbed 4-nitroanisole, but to its azoderivative, formed by photoreduction of the nitrogroup on the surface of the silver substrate. Copyright © 2013 John Wiley & Sons, Ltd.