Getting Physical - Methods and Outcomes

A surprisingly large array of physical methods has been applied to metal complexes in order to provide information on molecular structure, stereochemistry, properties and reactivity. While characterization may be tackled by first isolating a complex in the solid state, this approach is complicated by differences that sometimes exist between the character of a species in solution and the solid state. In fact, it may be inappropriate to assume that the isolated solid state species even persists in solution. Thus, it may be necessary to define species in different environments. Fortunately, the vast array of chemical and instrumental methods now available makes the task of defining structure achievable, but what to choose and how a method assists definition is not always obvious. 

It is not the task of an introductory text to pursue this issue to exhaustion, but it seems essential to at least acquaint you with the basic and advanced techniques and what they can achieve. This has been produced in summary form in Tables 7.1-7.4. 

Of course, the first task in any study is acquisition of a pure compound. For coordination chemistry, this is often a non-trivial task, as several stable compounds may form during a synthesis. Separation, by chromatography and/or crystallization, is often required (Table 7.1). Crystal growth through slow solvent evaporation, dilution with another solvent, lowering temperature or addition of other counter-ions is a common task in coordination chemistry, although it is now possible to define compounds reasonably well in solution. 

Ion chromatography columns packed with appropriate cationic or anionic polymer resin. 

Commercial HPLC instrument with appropriate packed columns. 

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