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(CCR)2(PH3)2] (R = H (1) and Ph (2)) and trans-[PtII(CCH)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 PtPt 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(CCPh)2(PPh2CH2PPh2)]2 in the solid state at 298 K.

The present calculations show the featured dz2→pz transition absorptions for 1–3 at 237, 246 and 352 nm, respectively. Compared with 1, ca. 10 nm red shift of absorption wavelength results from the conjugated phenyl ring on alkynyl group for 2, and ca. 110 nm red shift is caused by the PtPt interaction for 3.Figure optionsDownload as PowerPoint slide