Chemical bonds electronic structure changes

We shall use the hydrogen molecule to illustrate how the electronic structure changes during the formation of a chemical bond. 

In a carbon-supported metal electrocatalyst, the electronic interaction between metal and carbon support has a significant effect on its electrochemical performance [4], For carbon-supported Pt electrocatalyst, carbon could accelerate the electron transfer at the electrode-electrolyte interface, leading to an accelerated electrode process. Typically, the electrons are transferred from platinum clusters to the oxygen species on the surfece of a carbon support material and the chemical bond formation or the charge transfer process occurs at the contacting phase, which is considered to be beneficial to the enhancement of the catalytic properties in terms of activity and stability of the electrocatalysts. Experimentally, the investigation into the electron interaction between metal catalyst and support materials could be realized by various physical, spectroscopic, and electrochemical approaches. The electron donation behavior of Pt to carbon support materials has been demonstrated by the electron spin resonance (ESR) X-ray photoelectron spectroscopy (XPS) studies, with the conclusion that the electron interaction between Pt and carbon support depends on their Fermi level of electrons. It is considered that the electronic structure change of Pt on carbon support induced by the electron interaction has positive effect toward the enhancement of the catalytic properties and the improvement of the stability of the electrocatalyst system. However, the exact quantitative relationship between electronic interaction of carbon-supported catalyst and its electrocatalytic performance is still not yet fully established [4]. 

Of course the structural changes represented in Table 1 are much more complex than the simple bond angle plus electronic effect analysis reveals. For example, solvation of the carbene may depend on the details of its structure, and solvation undoubtedly influences chemical and physical properties (Langan et al., 1984). Nonetheless, it is possible to develop a good grasp of the most important properties of aromatic carbenes from the simple considerations described above. Before we proceed to examine these relationships in more detail, the carbene properties of interest must be identified, and the experimental procedures available for measurement of these properties must be critically considered. 

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