Calculations of the geometries, electronic structures and nonlinear second-order optical susceptibilities of spiroannelated quinone-type methanofullerenes

The equilibrium geometries, electronic structures and UV-vis spectra of a s eries of spiroannelated quinone-type methanofullerenes have been determined by using Zerner's intermediate neglect of differential overlap method. The results show that between fullerene and the addend there exists a special interaction, "periconjugation". which results in through-space orbital inte ractions. The calculated UV-vis spectra are in good agreement with experime nts. On the basis of the electronic spectra, the beta values are calculated . The results show that spiroannelated quinone-type methanofullerenes have quite large beta values. We attribute the large beta values to both the cha rge transfer from C-60 to benzoquinone and on the C-60 three-dimensional co njugated sphere.