Synthesis and photophysical properties of platinum(II) arylacetylides with donor–acceptor structures

The detailed relationship between the structure and the nonlinear mechanisms, as well as whether different nonlinear mechanisms of an organic molecule restrain each other are still not clear. In this paper, eight platinum(II) arylacetylides with donor–acceptor structures were synthesized and their photophysical properties were studied systematically. The properties of HOMO and LUMO were calculated using DFT method, the contribution of the metal dπ and charge transfer process are dominated by the skeleton structure of these complexes. The ligand-to-metal charge transfer (LMCT) happens when the molecule with D–π–Pt–π–D or D–π–Pt–π–Ar–π–Pt–π–D skeleton is excited, however the metal-to-ligand charge transfer (MLCT) and ligand-to-ligand charge transfer (LLCT) happen when the molecule with D–π–Pt–π–A, A–π–Pt–π–A or A–π–Pt–π–Ar–π–Pt–π–A skeleton is excited, respectively. The weak absorption in the visible area of these molecules provides a wide observation window for the application in optical limiter. The low fluorescent quantum yields and detectable room temperature phosphorescence indicate that the system-cross quantum yields of the title complexes containing Pt(II) is effective because of the spin-orbit coupling between the d orbitals of the Pt(II) and the large π-conjugated system. The first-order polarizabilities |βxxx| was determined by the solvatochromic method between 1.02 × 10−29 to 3.46 × 10−28 (cm5/esu).