MOLECULAR DESIGN AND HOST-GUEST COMPLEXATION PROPERTIES OF SUPRAMOLECULAR BIS-PORPHYRIN 'MOLECULAR TWEEZERS'

A computational study of a series of space separated bis-porphyrin “ molecular tweezers” 1 using the AM1 method has been conducted (Figure 1).[1, 2] It was found that bis-porphyrin systems possessing polycyclic spacers are significantly less rigid than previously thought.[3, 4] Variation of the metal-metal separation distance does not cause a significant energy change thus enabling these molecules to easily adjust to the optimal bonding distance required for complexation of various pyridyl ligands. Binding energies for a series of guests were estimated and indicated that the preferred complexation occurs within the cavity of these molecular tweezers (selective binding). With a help of molecular design, bis-porphyrin 1, having a more flexible framework incorporating two “ molecular hinges” was synthetised. Its complexation with several bis-pyridyl guests was studied by NMR and UV spectroscopy.