page_title: Supramolecular catalysis
section_title: Nolte's successive epoxidation catalyst for alkene polymer
hierarchical_section_title: Supramolecular catalysis / Prominent examples of supramolecular catalysts / Nolte's successive epoxidation catalyst for alkene polymer
caption_attribution_description: English: A manganese porphyrin catalyst developed by Noite et al capable of successive epoxidation of alkene polymer.
context_page_description: Supramolecular catalysis is not a well-defined field but it generally refers to an application of supramolecular chemistry, especially molecular recognition and guest binding, toward catalysis. This field was originally inspired by enzymatic system which, unlike classical organic chemistry reactions, utilizes non-covalent interactions such as hydrogen bonding, cation-pi interaction, and hydrophobic forces to dramatically accelerate rate of reaction and/or allow highly selective reactions to occur. Because enzymes are structurally complex and difficult to modify, supramolecular catalysts offer a simpler model for studying factors involved in catalytic efficiency of the enzyme. Another goal that motivates this field is the development of efficient and practical catalysts that may or may not have an enzyme equivalent in nature.
  A closely related field of study is asymmetric catalysis which requires molecular recognition to differentiate two chiral starting material or chiral transition states and thus it could be categorized as an area of supramolecular catalysis, but supramolecular catalysis however does not necessarily have to involve asymmetric reaction.
context_section_description: Processive enzymes are proteins that catalyze consecutive reactions without releasing its substrate. An example of processive enzymes is RNA polymerase which binds to a DNA strand and repeatedly catalyzes nucleotide transfers, effectively synthesizing a corresponding RNA strand.
  Nolte and coworkers developed an artificial processive enzyme in a form of manganese porphyrin rotaxane that treads along a long polymer of alkene and catalyze multiple rounds of alkene epoxidation. Manganese (III) ion in the porphyrin is the molecule's catalytic center, capable of epoxidation in the presence of an oxygen donor and an activating ligand. With a small ligand such pyridine that binds manganese from inside the cavity of the rotaxane, epoxidation happens outside the catalyst. With a large bulky ligand such as tert-butyl pyridine that does not fit inside the cavity however, epoxidation happens on the inside of the catalyst.
caption: A manganese porphyrin catalyst developed by Nolte et al. capable of successive epoxidation of alkene polymer.
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