Subphthalocyanine metallo-organic cage as catalytic molecular photoreactor for the functionalization of fullerenes

Abstract

ABSTRACT Subphthalocyanines (SubPcs) are aromatic chromophores with a bowlshaped structure and outstanding optoelectronic properties. The cavity formed by a C3-symmetry trispyridyl-SubPc, Pd(II)-metalloorganic capsule has proved an optimal, shape-complementary space for the complexation of C60. Taking advantage of the intense green light absorption of the SubPc components of the capsule, and their ability to transfer energy/electrons from the excited state, our group has recently described the unprecedented use of SubPc cages as molecular photoreactors to perform photoredox-triggered addition of diphenylamine radicals over encapsulated C60. Unfortunately, the reaction could only be performed using stoichiometric amounts of the cage due to inhibition of the SubPc cavity by the addition compound. Here, we describe the preparation of a more flexible SubPc cage built with a related C1-symmetry trispyridyl-SubPc (C1-SubPc-cage), which could facilitate the exchange between the complexed addition compound and pristine fullerene, thus allowing to use it in catalytic amounts. After assessing the ability of C1-SubPc-cage to host C60, the addition of α-aminoalkyl radicals in the presence of the cage under green light irradiation was tested. Curiously, optimisation of the reaction conditions (using catalytic amounts of C1-SubPc-cage in diluted solutions) rendered a different reaction outcome, that is, a cyclopropanated fullerene, in remarkably high yields.