Photoactive Preorganized Subphthalocyanine-based Molecular Tweezers for Selective Complexation of Fullerenes

The development of new chromophoric receptors able to bind curved carbon nanostructures is central to the quest for improved fullerene-based organic photovoltaics. We now report the synthesis and characterization of a subphthalocyanine-based multicomponent ensemble consisting of two electron-rich SubPc-monomers rigidly attached to the convex surface of a electron-poor SubPc-dimer. Such a unique configuration, especialy in terms of the two SubPc-monomers, together with the overall stiffness of the tether endows the multicomponent system with a well-defined tweezer-like topology to embrace a fullerene in its inner cavity efficiently. The formation of a 1:1 complex was demonstrated in a variety of titration studies with either C60 or C70. In solution, the underlying association constants were on the order of 105 M-1. Detailed physicochemical experiments revealed a complex scenario of energy- and electron-transfer processes upon photoexcitation in the absence and presence of fullerenes. The close proximity of the fullerenes to the electron-rich SubPcs enables a charge shift from the initially formed reduced SubPc-dimer to either C60 to C70.