Nonlinear Optical Properties of Conjugated Platinum(II) Acetylides with Multibranched Donor-Acceptor Structures

Six conjugated platinum(II) acetylides with multibranched donor-acceptor structures (1-6) were synthesized. The absorption maxima of triazine-centered complexes 1-3 are red-shifted by 36-43 nm compared with those of triphenylamine-centered complexes 4-6. The luminescence spectra of 4-6 in air-saturated chloroform showed one fluorescence peak and one phosphorescence peak. However, only one fluorescence peak was detected for 1-3 in air-saturated chloroform. The transient absorption spectra of the compounds indicate the effective intersystem crossing from S-1 to T-1. The nonlinear optical properties of 1-6 in N,N-dimethylformamide were studied using open Z-scan method. The results indicate that complexes 1 and 6 exhibit good nonlinear optical performance. The ratios of the effective nonlinear absorption cross section to ground-state absorption cross section sigma(eff)/sigma(0) of complexes 1-6 are in the range of 4-22.