Supramolecular complexes obtained from porphyrin-crown ether conjugates and a fullerene derivative bearing an ammonium unit

A methanofullerene derivative with an ammonium subunit (1) has been prepared and its ability to form a supramolecular complex with a porphyrin-crown ether conjugate evidenced by NMR, UV-vis, electrospray mass spectrometry (ES-MS) and luminescence experiments. Interestingly, in addition to the ammonium-crown ether recognition, intramolecular stacking of the fullerene moiety and the porphyrin subunit has been evidenced. Due to this additional recognition element, the association constant for the supramolecular complex is increased by two orders of magnitude when compared to the K, values found for the complexation of I with benzo-18-crown-6. Finally, non-covalent systems resulting from the association of cation I with porphyrin derivatives bearing two crown ether subunits have been investigated. Intramolecular C-60-porphyrin interactions have also been evidenced within these supramolecular complexes. As a result, the 2:1 complexes are very stable as shown by the ES-MS studies. (c) 2005 Elsevier Ltd. All rights reserved.