Investigation of ethene-bisfullerenes and their derivatives as photovoltaic system [C28X1=X2C28]: Semiempirical study

A computational study of C28X1=X2C28 complexes using semiempirical methods (AM1 and PM3) was presented. The difference between the most stable and the least stable was about 50 Kcal/ mol for PM3 and 30 Kcal/mol for AM1. The study of the frontier orbitals in the ground state revealed that the LUMO energy levels of the C28X1 =X2 C28 complexes for X2 =C compare reasonably well with that on the C28 fullerene cage (acceptor moiety). The HOMO energy levels of these complexes (X1 =Si, Ge; X2 =C) were quite similar. The LUMO and LUMO+1 localized on the C28 cage subunit on the X2 (X2 = C) behave as acceptor of electron, while HOMO and LUMO+3 which are localized on the C28 cage on the X1 side (X1 =Si and Ge) behave as electron donor.