Theoretical and experimental study on the molecular recognition of adrenaline by supramolecular complexation with crown ethers.

The protonated adrenaline (PAd(+)) forms supramolecular complexes with crown ethers by extensive hydrogen bond and ion-dipole interactions. Recent experiments and calculations have demonstrated the molecular recognition of PAd(+) through the supramolecular complexes formed between 12-crown-4 (12C4) and 15-crown-5 (15C5). In the present article, 18-crown-6 (18C6), 21-crown-7 (21C7), and dibenzo-24-crown-8 (DB24C8) are selected as model molecules of crown ethers to investigate systematically the cavity effect on the molecular recognition between the crown ethers and protonated adrenaline. The calculational results demonstrate that the capabilities of molecular recognition increase with the size of cavity of crown ethers. The experimental results of cyclic voltammetry (CV) are consistent with the calculational results that crown ethers can form stable supramolecular complexes with PAd(+), and the supramolecular complexes become more stable with the increasing size of crown ether.