Nonlinear optical studies of fullerene–arylethyne hybrids

Abstract

The fullerene–arylethyne hybrids 2 and 3 were synthesized in order to investigate their NLO activities. The β values for 2 and 3 were obtained by hyper Rayleigh scattering measurements. The arylethynyl fullerenes 3a–f exhibit β values in the range 20–361 × 10⁻³⁰ esu. Interestingly, the β values for 3a,b are higher than those for 3c–f; a good correlation was obtained between the Hammett σ_p values of the para substituents of 3 and their β values. The ¹H-NMR and E_1/2 data indicate that the fullerene moieties of 3 attract electrons from the arylethynyl groups in the ground state. The β values for 2a–c are higher than those for 3a–f; the para-carborane–fullerene dyad 2c exhibits an exceptionally high β value (1189 × 10⁻³⁰ esu). The electronic characteristics of the carbon and boron clusters are discussed.