A theoretical analysis, based on density functional theory, has been carried out on the electronic properties of eosin yellowish (2',4',5',7'-tetrabromofluorescein), a dye used for photovoltaic applications. In particular different oxidation states of the bare molecule as well as its complexes with a Zn dication have been considered, with the aim to gain some insights on its electro- and photochemical behavior. The calculations have been carried out both in the gas phase and in solution, this last modeled by a continuum model. Besides the agreement with the experimental data, our results allow for a better interpretation of the spectroscopic properties of this dye and their tuning by interaction with the solvent or metal atom in aqueous solution.