The structural design of supramolecular self-assemblies plays a crucial role in determining their physical properties and reactivity. Supramolecular chemistry involves the study of non-covalent interactions, such as hydrogen bonding, van der Waals forces, - stacking, and electrostatic interactions, which drive the formation of complex structures from simpler molecular building blocks. The resulting supramolecular systems can exhibit unique properties and functions that are not observed in individual components.1. Host-guest complexes: These supramolecular systems involve the formation of complexes between a host molecule and a guest molecule. The host molecule typically has a cavity or a pocket that can accommodate the guest molecule through non-covalent interactions. The physical properties and reactivity of the guest molecule can be significantly altered upon complexation. For example, cyclodextrins are a class of host molecules that can encapsulate hydrophobic guest molecules, improving their solubility in water and protecting them from degradation.2. Metal-organic frameworks MOFs : MOFs are a class of porous materials formed by the self-assembly of metal ions or clusters and organic linkers. The structural design of MOFs can be tailored by choosing different metal ions and organic linkers, resulting in materials with tunable pore sizes, shapes, and functionalities. This allows MOFs to be used in various applications, such as gas storage, catalysis, and drug delivery. For example, MOFs with high surface area and appropriate pore sizes can efficiently capture and store greenhouse gases like CO2 and CH4.3. Supramolecular polymers: These are formed by the self-assembly of monomeric units through non-covalent interactions. The physical properties of supramolecular polymers, such as mechanical strength, elasticity, and responsiveness to external stimuli, can be tuned by controlling the strength and nature of the non-covalent interactions between the monomers. Supramolecular polymers have found applications in the development of self-healing materials, responsive hydrogels, and drug delivery systems.4. Supramolecular catalysts: The self-assembly of molecular components can lead to the formation of catalytic sites with unique reactivity and selectivity. For example, the self-assembly of metal ions and organic ligands can create metallo-supramolecular cages that can encapsulate substrate molecules and promote selective catalytic transformations. These supramolecular catalysts can be used in various chemical reactions, such as hydroformylation, olefin polymerization, and enantioselective catalysis.5. Supramolecular sensors: The selective binding of target analytes by supramolecular systems can lead to changes in their physical properties, such as fluorescence, color, or conductivity. These changes can be used to design supramolecular sensors for the detection of various analytes, such as metal ions, anions, and biomolecules. For example, supramolecular systems based on crown ethers or calixarenes can selectively bind metal ions, leading to changes in their fluorescence or color, which can be used for sensing applications.In summary, the structural design of supramolecular self-assemblies has a significant impact on their physical properties and reactivity. By carefully selecting the molecular building blocks and controlling the non-covalent interactions, supramolecular systems with tailored properties and functions can be developed for various applications in different fields of chemistry.