Viologen embedded zeolites

Reactions between molecules leading to new materials are complex processes. In an effort to understand these complex systems chemists have understandably attempted to minimize complexity. This has resulted in a distinct preference for study of reactions in homogenous, rather than in heterogeneous media, despite the fact that heterogeneous reactions in real world situations are ubiquitous. Nevertheless, the advantages of heterogeneous systems in terms of environmental friendliness and in the ability to control reaction outcome are widely recognized and as a result are attracting increased attention. Zeolites are excellent examples. The early use of zeolites focused entirely on their use as acid catalysts in petroleum processing and only recently has attention turned to their use in fine chemical synthesis. In this review we present recent results in the design and use of the very interesting heterogeneous host-guest viologen/zeolite complexes. (C) 2004 Elsevier B.V. All rights reserved.