Electronic Spectra of Transition-metal Complexes

Abstract

We have, to a very limited extent, already discussed the magnetic and spectral properties of complexes in chapter 5. We now look at these topics in greater detail. The theory behind this material is difficult; in order that some progress can be made towards understanding the spectra and magnetism of complexes, it will be assumed that the student has some elenlentary knowledge of spectroscopic term symbols. Some of the more theoretical aspects of electronic spectra and a discussion of term symbols are to be found in the references cited in the bibliography. The study of the spectral and magnetic properties of complexes provides us with much information that we have seen can shed considerable light on bonding theories. Spectral properties are concerned with differences between the ground state and the excited states of molecules, whereas the magnetic properties are concerned with the nature of states very close in energy to the ground state. Since electronic spectra can be measured directly in a few minutes, information is often quickly forthcoming from this technique. Because these electronic spectral bands are usually very broad, the spectra are not often used as ‘fingerprints’ or in looking for functional groups as is done in infrared spectroscopy. However, a combination of spectral and magnetic studies often enables the stereochemistry of a complex to be determined, and may also indicate something about the extent of distortion therein.