Figure 2.

(a): Normalized electronic absorption spectra of compound 4 in acetone (red line), tetrahydrofuran (black line), and chloroform (blue); (b): Normalized electronic absorption spectra for compounds 4 (red line) and 7 (black line) in tetrahydrofuran; (c): Normalized electronic absorption spectra for compounds 4, 5, and 6 in chloroform.