The present paper reports a comprehensive quantum mechanical investigation on the luminescence properties of several mono- and dinuclear platinum (II) complexes. The electronic structures and geometric parameters are briefly analyzed together with the absoption band's of all complexes. In all cases agreement; with experiment is remarkable. Next, emission (phosphorescence) spectra from the first triplet states have been investigated by comparing different computational approaches and taking into account also vibronic effects. Once again, agreement with. experiment is good, especially using unrestricted electronic computations coupled to vibronic contributions. Together with the intrinsic interest of the results, the robustness and generality of approach, open the opportunity for computationally Oriented chemists to provide accurate results for the Screening of Large targets which could be of interest in molecular materials design.