Synthesis And Nonlinear Optical Properties Of Platinum (â…¡)Acetylide Complexes With Multi-branched Donor-acceptor Structures

Platinum acetylides are a new type of heavy metal aromatic alkynes that have been researched intensively in recent years. The heavy metallic ion and the large π-conjugated systems confer these organometallic oligomers great unique properties, especially the great nonlinear optical property. Molecules containing heavy metal ions and rigid structures always exhibit large reverse saturable absorption due to the spin-orbit coupling between the d orbital of the transition metal ion and the conjugate π electron, which can enhance their reverse saturable absorption properties greatly.In this thesis, a series of conjugated platinum (II) acetylide complexes with multi-branched donor-acceptor structures (1-6) were synthesized. The target products were characterized via elemental analysis,’HNMR, MS, etc., respectively.The UV-vis absorption spectra, luminescence spectra, fluorescence quantum yields, and phosphorescence quantum yields of these complexes1-6were tested. Finally the nonlinear absorption and the first order hyperpolarizability were measured using open aperture Z-scan technique and solvatochromic method, respectively. The absorption maxima of the triazine-centered complexes (1-3) are38-40nm red-shifted compared to those of the triphenylamine-centered complexes (4～6). The luminescence spectra of the complexes4-6in air-saturated chloroform showed two main emission peaks, in which the peak with shorter wavelength was ascribed to their fluorescence, and the peak with longer wavelength was ascribed to their phosphorescence. However, only the fluorescence has been detected for1～3in air-saturated chloroform. The molecular first order hyperpolarizabilities of the six target compounds were tested using solvatochromic method, and their molecular hyperpolarizabilities are in the range of4.06×10-29～2.11×10-28cm5/esu, which is much higher than that of some other common nonlinear optical materials. The results indicated that complexes2and5exhibit excellent nonlinear absorption properties. The ratios of the effective nonlinear absorption cross section to ground-state absorption cross section σeff/σ0of complexes1～6are in the range of4～22, aeffis far bigger than σ0, which indicates that this kind of compounds has the characteristics of the saturated absorption.