The dependence of spectra on basis set and geometry as well as TDM analysis for the S 1 and S 2 states are given in Ref. 23. The excited states of azobenzene have also been investigated with higher level wave function based methods (such as CC2, ADC(2), and CASPT2), but these methods are too costly for large aggregates considered in what follows; therefore, we do not discuss them here.