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

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. [ABSTRACT FROM AUTHOR]