Theoretical studies of the spectroscopic properties of (L)Pt [(1,2-η²)-Ph-(C{triple bond, long}C)_n-Ph] (L = dppp or (PPh₃)₂, n = 1 or 2)

Electronic structures and spectroscopic properties of (L)Pt[(1,2-η²)-Ph-(C{triple bond, long}C)_n-Ph] (n = 1, L = (PPh₃)₂ (1), n = 1, L = dppp (2), and n = 2, L = (PPh₃)₂ (3)) are studied by the ab initio and DFT methods, respectively. The ground- and excited-state structures are optimized by the B3LYP and CIS methods, respectively. The calculated bond lengths and bond angles in the ground-state agree well with the corresponding experimental values and the structures in the ground and excited-states have only slightly change. At the TD-DFT level with the PCM model, the absorption and emission spectra in solution are obtained. The lowest-energy absorptions of 1-3 are attributed to the mixing MLCT/ILCT transitions and phosphorescent emissions are attributed to coming from the combination of ³MLCT/³ILCT transitions. Furthermore, the lowest-energy absorptions and emissions of 1-3 are red-shifted in the order 1 < 2 < 3. It is shown that with the increase of the π-conjugated effect of alkyne or electron-donating ability of the phosphane atom, lowest-energy emission energy for 1-3 is correspondingly decreased.