Enzyme-mimetic catalyst architectures: the role of second coordination sphere in catalytic activity

Enzymes with well-defined three-dimensional structure have in-built information for molecular organization in the near vicinity of the active sites-popularly known as enzyme architecture. Over the past few years, molecular assembly has been exploited in creating artificial enzyme or catalyst architectures. Emergent spatiotemporal structure and catalytic activity can be achieved through controlled assembly of suitable molecular building blocks. The programmed molecular assembly governed by the scheme of molecule architectonics can generate enzyme-mimetic catalyst assembly architecture. Apart from the conventional ligand-metal interaction in the first coordination sphere of a catalyst, a second coordination sphere plays a key role in the catalytic activity of enzymes. This review attempts to unravel the balancing act between molecular architectonics and second coordination spheres in catalyst assembly architecture development. Judicious design and exploitation of state-of-the-art biomimetic catalyst architecture derived from small molecules, sugars, nucleic acids, peptides, and proteins are discussed under the above-mentioned framework. Metal-coordinated molecular assembly architectures of specific catalytic properties are considered with respect to the nature of molecular assembly and experimental conditions. The concise and critical discussion provides a holistic view of enzyme-mimetic architectures and their second coordination spheres through a reductionistic approach based on the molecular architectonics of simple and modular molecular building blocks.