X-ray absorption spectroscopy in coordination chemistry

X-ray absorption spectroscopy (XAS) is one of the premier tools for investigating the local structural environment of metal ions. XAS can be divided into X-ray absorption near edge structure (XANES), which provides information primarily about geometry and oxidation state, and extended X-ray absorption fine structure (EXAFS) which provides information about metal site ligation. One of the key attractions of XAS is that it can be used regardless of the physical form of the sample, and in particular it can be used to study non-crystalline materials. Consequently, XAS has come to be widely utilized by the biochemistry and materials science communities. Recently, however, it has become clear that there are numerous questions of interest to coordination chemists that can be addressed using XAS. In this contribution, the physical basis of XAS is reviewed, the advantages and limitations of the technique are discussed, and several examples of the applications of XAS to coordination chemistry are presented. The prospects for future applications of XAS are summarized.