Loading of a Phenanthroline-Based Platinum(II) Complex onto the Surface of a Carbon Nanotube via π–π Stacking

Stacking of the metal complex [(5,6-dimethyl-1,10-phenanthroline)(1S,2S-diaminocyclohexane)platinum(ii)]2+ (56MESS) onto the surface of two different fullerenes, a carbon nanotube (CNT), and a C60-buckyball was examined. The metal complex forms a supramolecular complex with multi-walled CNTs but not with buckyballs. Binding of 56MESS to the CNTs is highly efficient (90 %) but can be further stabilized by the addition of the surfactant, pluronic F-127, which resulted in a loading efficiency of 95 %. Molecular modelling shows that binding of 56MESS to the CNT is supported by the large surface area of the fullerene, whereas the more pronounced curvature and lack of a flat surface on the buckyball affects the ability of 56MESS to form bonds to its surface. The loading of 56MESS onto the CNT is via π–π stacking from the metal complex phenanthroline ligand and C–H···π bonding from the diaminocyclohexane ligand. 56MESS has 13 critical bonding points with the CNT, eight of which are π–π stacking bonds, but the metal complex forms only seven bonds with the buckyball. In addition, the loading of 56MESS onto the CNT results in a charge transfer of –0.111 eV; however, charge transfer is almost negligible for binding to the buckyball.