Guest encapsulation and coronene–C60 exchange in supramolecular zinc porphyrin tweezers, grids and prisms

Abstract

Using a variant of the HETPHEN concept, heteroleptic 2D and 3D metallosupramolecular structures, such as tweezer T, grid G and tetragonal prism P, were fabricated quantitatively and characterised by (1)H NMR, (13)C NMR, (1)H-(1)H COSY, DOSY as well as ESI-MS. All structures encapsulate C60, with P showing the highest binding affinity (Kassoc = 3.3 × 10(6) M(-1)). The association constant increases along the series T < G < P, most likely due to the enhanced structural rigidity and better coplanarity of the two zinc porphyrin units. In contrast to T and G, the tetragonal prism P shows notable encapsulation of coronene (Kassoc = 1.1 × 10(4) M(-1)). In T and G, on the other hand, complexation of coronene is kinetically inhibited by the bulky mesityl rings at the porphyrin periphery. As illustrated in the facile displacement of coronene by C60 in coronene@P to furnish C60@P, P behaves as a flexible and guest-adaptive host.