Spectroscopic properties of mono- and binuclear platinum(II) alkynyl complexes with phosphine ligands: A theoretical study

Based on their MP2 optimized structures in the ground states, we obtained solution absorption spectra for trans -[PtII(Ctriple bond; length of mdashCR)2(PH3)2] (R = H (1) and Ph (2)) and trans -[PtII(Ctriple bond; length of mdashCH)2(PH2CH2PH2)]2 (3) under the time-dependent density functional theory calculations. These absorptions agree with experimental observations. The unrestricted MP2 optimization performed for 3 in the lowest-energy triplet excited state shows that upon excitation the Ptsingle bondPt distance shortens about 0.347 Å with respect to the 3.188 Å one in the ground state. The UMP2 calculations estimated that its 3[σ∗(dz2)σ(pz)]3[σ∗(dz2)σ(pz)] excited state produces the 531 nm emission, corresponding to the 580 nm one of trans-[PtII(Ctriple bond; length of mdashCPh)2(PPh2CH2PPh2)]2 in the solid state at 298 K.