Geometries were optimized using PBE functional , which proved the right choice for this class of compounds , while the investigation of excited states was done with CAM-B3LYP hybrid functional . The latter better describes long-range charge transfer states and overcomes issues with convergence and computation time. The 6-31G(d, p) basis sets for C, O and H as well as LANL2DZ pseudopotentials for Pt were implemented . The calculations have been done in vacuum using the Gaussian 16 software .