The UV-visible and fluorescence spectra, and cyclic and differential pulse voltammograms of the solutions of belts 5a-c in dichloromethane are shown in Fig. and, respectively. The results showed evidently the belt-sizedependent photophysical and electrochemical properties. In the electronic absorption spectra, although the absorption spectral patterns appear similar, the maximum absorption bands at the shortest and longest wavelength in the region of 300 nm to 470 nm undergo intriguingly a hypsochromic and a bathochromic shift, respectively, with decreasing belt sizes. Notably, a longestwavelength maximum absorption band at 447 nm with extinction coefficient () of 9700 M -1 cm -1 was observed for small belt 5a. For belts 5b and 5c, it blueshifted to 423 nm and 413 nm with extinction coefficients increasing to 21100 M -1 cm -1 and 35900 M -1 cm -1 , respectively. Based on absorption onsets, the optical gaps (Eg opt ) of 5a-c were determined (Fig. ). Under the irradiation of