Synthesis, third-order nonlinear absorption and refraction of fullerene dyads containing fluorene

Two new fullerene–fluorene dyads, N-methyl-2-(2-fluorenyl)-3,4-[60]fuller-pyrrolydine (1) and N-methyl-2-(2-fluorenyl)-3,4-[70]fullerpyrrolydine (2), were synthesized and their structures were confirmed by MALDI-MS, 1H NMR and FT-IR. Their electrochemical and optical properties were investigated by cyclic voltammetry and Z-scan technique, including, electronic potentials, two-photon absorption cross-sections (σ2), nonlinear refractive indexes (n2), microscopic second-order hyperpolarizabilities (γR) and third-order nonlinear susceptibilities (χI(3) and χR(3)). Importantly, the χI(3) and σ2 in 2 were increased above 35% due to [70]fullerene unit than that of 1.