Incorporation of Metal-Schiff Base Complexes

Imines are C=NH group-containing compounds formed through reaction of ammonia with an aldehyde or a ketone. However, this type of imine is very unstable, and it is easy for these compounds to hydrolyse to compounds containing a carbonyl group. However, the substituted imines synthesized from condensation of a primary amine and an aldehyde or ketone are much more stable [Equation (9.14)]  

These substituted imines are the so-called Schiff bases. Although substituted imines are more stable than imines, they still undergo reversible hydrolysis or polymerization. Nevertheless, if the substituting alkyl groups on the C and N atoms are replaced by 

Bessel and Rolison reported the electrochemical behavior of [Co(SALEN)]2 1 and Fe(bpy)3]2+ in zeolite Y.[1571 They prepared an electrode using the complex-zeolite composite and carbon powder, and tested the electrochemical behaviors of the electrode and the composite dispersed in a solution. It was found that the electrochemical behaviors of these two materials differ to a great extent. After several cycles, the former loses all the electrochemical signals, whereas the latter continuously shows the signals. They believed that the electrochemical signals arise from the complex attached onto the zeolite external surface (defects or external supercages), whereas the complex inside the zeolite channel does not participate in electron transfer of the electrochemical process. In fact, there has been dispute on whether the electrochemical signals arise from electron transfer in zeolite channels or from those complexes on the zeolite external surface. Both views can find experimental support.1158 1591 

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