Using the Density Functional Theory (DFT) calculations it was described the electronic structure and the UV-Vis absorption bands of the a new mononuclear cobalt (II) Schiff base complex CoL and of the ligand H2L (L= 5,5`-dihydroxy-2,2`-[o-phenylene-bis(nitrilomethylene)]diphenol), which were synthesized by a group of researchers from the “Petru Poni” Institute of Macromolecular Chemistry (Romania) and from the Institute of Chemistry of ASM (Republic of Moldova). For both compounds considered, a full geometry optimization is performed by means of all-electron spin-restricted DFT calculations employing the B3LYP hybrid functional using the standard all-electron split-valence basis set 6-31G. The geometry optimization was carried out in the spatial nuclear configuration of considered compounds corresponds to the C2v point group of symmetry. The most important bond distances and angles in optimized molecular structures are in a close agreement with the experimental ones. The electronic spectra were obtained from the configuration interaction (CI) calculations at the optimized geometries. The energies and electronic configurations of the terms are given below together with the experimental data on the UV-VIS spectra.figureOn the basis of calculations one can conclude that the electronic absorption spectrum of the ligand arises from π→π* transitions and can be explained within the four-orbital model. The absorption bands of the complex can be attributed with the Co→L electron transfer and electron density transfer from both the metal and the peripheral rings to the central ring of the ligand.