The ground and excited-state properties of [Ru(bpy)(tpy)dMSO](2+) (bpy = 2,2'-bipyridine, tpy = 2,2':6',2"-terpyridine; dmso = dimethyl sulfoxide) have been studied by the means of density functional theory (DFT). In particular, the singlet ground state and the potential energy surface of the lowest triplet were investigated along the coordinate involved in the S --> O linkage isomerization of dmso. The time-dependent-DFT approach (TDDFT) was used to interpret the absorption spectra of the system, while a DeltaSCF procedure was applied to compute the emission spectra. The good agreement between computed and experimental spectra highlights the power of DFT approaches in the description of complex transition metal containing systems. In addition, this method allows the full description of the ground and excited potential energy surfaces of [Ru(bpy)(tpy)dmso](2+) which can only be roughly derived from experimental data, thus providing clues for further improvement in the engineering of phototriggering materials.