Four-dimensional chemistry catalysis

Asymmetric catalysis is four-dimensional chemistry as stated by Noyori,6 because high efficiency can only be achieved through the coordination of both an ideal three-dimensional structure x, y, z) and suitable kinetics (/). Recently developed metal-ligand difunctional catalysts really provide a new basis for developing efficient catalytic reactions. 

Zinc usually binds to proteins via residues of cysteine and histidine. Sometimes zinc is bound to residues of glutamate or aspartate. The zinc ion sometimes plays a catalytic role and sornetimes a structural role. In the latter case, it helps maintain the three-dimensional structure or conformation of the protein. For example carboxypeptidase A contains twr> atoms of zinc. One is required for catalytic activity and is bound to cysteine and histidine. The other, which plays a structural role, is bound only hr cysteine. Cytoplasmic supeioxide dismutase is a dimer, ft contains one atom of Cu and one of Zn + per subunit. The zinc is bound via three residues of histidine and one residue of aspartate. It is buried deep within the enzyme and serves a structural role. The copper atom is bound via four residues of histidine. It resides dose to the surface of the protein and participates in the chemistry of catalysis. 

Microporous materials with regular pore architectures comprise wonderfully complex structures and compositions. Their fascinating properties, such as ion-exchange, separation, and catalysis, and their roles as hosts in nanocomposite materials, are essentially determined by their unique structural characters, such as the size of the pore window, the accessible void space, the dimensionality of the channel system, and the numbers and sites of cations, etc. Traditionally, the term zeolite refers to a crystalline aluminosilicate or silica polymorph based on comer-sharing TO4 (T = Si and Al) tetrahedra forming a three-dimensional four-connected framework with uniformly sized pores of molecular dimensions. Nowadays, a diverse range of zeolite-related microporous materials with novel open-framework stmctures have been discovered. The framework atoms of microporous materials have expanded to cover most of the elements in the periodic table. For the structural chemistry aspect of our discussions, the second key component of the book, we have a chapter (Chapter 2) to introduce the structural characteristics of zeolites and related microporous materials. 

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