Electronic structures and spectra of conducting anthracene derivatives

Theoretical studies on anthracene and a series of its derivatives were performed using the AM1 method and DFT. Based on B3LYP/6-31G(d) optimized geometries, the electronic, IR and NMR spectra of anthracene oligomers were calculated using the Indo/Cis, AM1 and B3LYP/6-31G(d) methods, respectively. The energy gaps of the oligomers decreased and the main absorptions in the electronic spectra of the oligomers were red-shifted, whereas the IR frequencies for some of the C=C and C–H bonds were blue-shifted with increasing chain length and in the presence of substituents. The 13C-NMR chemical shifts of the bridged carbon atoms were upfield shifted in the presence of an electron-donating group, while the chemical shifts of the carbon atoms on the two side rings of the anthracene moiety shifted downfield in the presence of an electron-withdrawing group.