Catalysis, molecular imprinting

Keywords Catalysis Molecular imprinting Self-assembly Sensor Separation... 

In conclusion, molecularly imprinted polymers and related materials have every potential to become popular tools in analytical chemistry, catalysis, and sensor technology. Obviously this will require further research, especially in the problem areas of MI mentioned above. Nevertheless, the author of this contribution fully expects that in the near future MIP will become real competitors for biological enzymes or antibodies, and thus will have a major impact on the whole area of biotechnology. 

Andersson LI, Ekberg B, Mosbach K (1993) Bioseparation and catalysis in molecularly imprinted polymers. In Ngo TT (ed) Molecular interactions in bioseparations. Plenum Press, New York, p 383... 

This chapter focuses on several recent topics of novel catalyst design with metal complexes on oxide surfaces for selective catalysis, such as stQbene epoxidation, asymmetric BINOL synthesis, shape-selective aUcene hydrogenation and selective benzene-to-phenol synthesis, which have been achieved by novel strategies for the creation of active structures at oxide surfaces such as surface isolation and creation of unsaturated Ru complexes, chiral self-dimerization of supported V complexes, molecular imprinting of supported Rh complexes, and in situ synthesis of Re clusters in zeolite pores (Figure 10.1). 

In addition to imprinted acid-base catalysts [49-55], attempts to imprint metal complexes have been reported and constitute the current state of the art [46, 47]. In most cases of metal-complex imprinting, ligands of the complexes are used as template molecules, which aims to create a cavity near the metal site. Molecular imprinting of metal complexes exhibits several notable features (i) attachment of metal complex on robust supports (ii) surrounding of the metal complex by polymer matrix and (iii) production of a shape selective cavity on the metal site. Metal complexes thus imprinted have been appHed to molecular recognition [56, 57], reactive complex stabilization [58, 59], Hgand exchange reaction [60] and catalysis [61-70]. 

Wulff G. Enzyme-Uke catalysis by molecularly imprinted polymers. Chem Rev 2002 102 ... 

Antibody Catalysis. Recent advances in biocatalysis have led to the generation of catalytic antibodies exhibiting aldolase activity by Lemer and Barbas. The antibody-catalyzed aldol addition reactions display remarkable enantioselectivity and substrate scope [18]. The requisite antibodies were produced through the process of reactive immunization wherein antibodies were raised against a [Tdiketone hapten. During the selection process, the presence of a suitably oriented lysine leads to the condensation of the -amine with the hapten. The formation of enaminone at the active site results in a molecular imprint that leads to the production of antibodies that function as aldol catalysts via a lysine-dependent class I aldolase mechanism (Eq. 8B2.12). 

The aim of this chapter is to give a brief overview of the molecularly imprinted catalysts reported up to approximately the turn of the millennium, followed by a more concise review of the literature thereafter. In addition to catalysis, that is cases in which a reaction TSA or intermediate are used as the template, imprinted polymers capable of aiding chemical transformations will also be discussed. In these cases the reaction substrate or product are often used as the template in order to control the regio- or stereochemistry of the reaction. 

RAMSTROM o and mosbach K (1999), Synthesis and catalysis by molecularly imprinted materials , Curr Opin Chem Biol, 3, 759-764. 

Molecular imprinting has recently attracted considerable attention as an approach to the preparation of polymers containing recognition sites with predetermined selectivity. The history and specifics of the imprinting technique pioneered by Wulff in the 1970s have been detailed in brilliant review article [40]. These materials, if successfully prepared, are expected to find applications in numerous areas such as the resolution of racemates, chromatography, substrate selective catalysis, and the production of "artificial antibodies". Imprinted monoliths have also recently received... 

Tada, M., Sasaki, T. and Iwasawa, Y. Design of a novel molecular-imprinted Rh-amine complex on Si02 and its shape-selective catalysis for alpha-methylstyrene hydrogenation, J. Phys. Chem. B, 2004, 108, 2918-2930. 

Visnjevski A et al (2005) Catalysis of a Diels-Alder cycloaddition with differently fabricated molecularly imprinted polymers. Cat Commun 6 601-606... 

Li, W. andii, S. Molecular Imprinting A Versatile Tool for Separation, Sensors and Catalysis. Vol. 206, pp. 191-210... 

However, also in this case enantio-selectivities never exceeded the values obtained with the oxazaborolidine in solution, probably because of diffusional limitations within the polymer support, which enhanced the contribution of the non-selective, direct borane reduction of the ketone. In spite of the rather low imprinting effects obtained in these initial attempts, we feel that this approach still represents a most interesting application of molecularly imprinted polymers in catalysis and deserves further attention in the near future. 

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