Furthermore, the position that the two axial SubPc units acquire in this assembly gives rise to unique supramolecular recognition sites suitable for the complexation of fullerenes. Thus, the binding ability of this hybrid towards different fullerene derivatives, namely C60, C70, C60-PCBM and C70-PCBM, has been analyzed through UV-vis absorption, fluorescence and NMR titrations. It has been demonstrated that syn-compounds display a unique fullerene complexation mode. Initially, the formation of a 1:1 supramolecular complex, where the axial octylthio-substituted SubPcs embraces a guest molecule with remarkable association constants of around 106 - 104 M-1, is observed. The spatially-defined cavity generated by the rigid and short alkynyl linkers shows a higher affinity for the bigger fullerene derivatives. Then, a secondary supramolecular interaction between the perfluorinated SubPc syn dimer unit and another fullerene molecule has been detected and quantified, with significant binding constants of 104-103 M-1 that depend on the size and the host-guest electrostatic interactions, leading to the formation of the final 1:2 supramolecular ensemble [2].
Pristine and endohedral fullerene-subphthalocyanine conjugates [3,4] both covalent and supramolecular have been also prepared and studied as artificial photosynthetic systems.
[1] C. G. Claessens, D. González-Rodríguez, M. S. Rodríguez-Morgade, A. Medina, T. Torres, Chem. Rev. 2014, 114, 2192–2277.
[2] G. Zango, M. V. Martínez-Díaz, T. Torres, in preparation
[3] L. Feng, M. Rudolf, O. Trukhina, Z. Slanina, F. Uhlik, X. Lu, T. Torres, D. M. Guldi, T. Akasaka, Chem. Commun. 2015, 51, 330-333.
[4] M. Rudolf, O. Trukhina, J. Perles, L. Feng, T. Akasaka, T. Torres, D. M. Guldi, Chem. Sci. 2015, 6, 4141-4147.