We report the time-dependent density functional theory study of the absorption spectrum of an iron complex exhibiting photoisomerization properties. The role of the exchange-correlation functionals and, in particular, the effects of the inclusion of long-range corrections have been considered. The vertical transitions have been analyzed in terms of natural transition orbitals and have shown that the spectrum is dominated by ligand-to-metal charge-transfer transitions, an occurrence that could be promising for future applications of these complexes.