UV-visible absorption spectra
The UV-visible absorption spectra of AB1 and AB2 are
plotted in Figure 5 and the calculated maximum peak of the UV-visible
absorption (λabs), excitation energy (E), oscillation strength
(f ), of the compounds AB1 and AB2 are
summarized in Table 6. The peaks of the absorption spectra of theAB2 (λabs = 312 nm) is red-shifted compared with the moleculeAB1 (λabs = 287 nm). It can be said that the introduced
NO2 groups has greatly affected the absorption spectra
due to the increased intermolecular interactions in solid phase. The
electronic excitations of both compounds are controlled by the
transition from HOMO to LUMO.