Department of Physics, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway.
J Phys Chem A. 2010 Mar 18;114(10):3431-42. doi: 10.1021/jp9091514.
A series of four new trans-diphosphine Pt(II) diacetylide complexes, with a thiophene and two benzenoid rings in each acetylide ligand, have been synthesized and characterized with respect to optical absorption, spectrally and time-resolved luminescence, and optically nonlinear properties such as two-photon absorption cross section and optical power limiting. Density functional theory (DFT) calculations of a few ground state conformations of three Pt(II) diacetylide structures showed similar total energy for each geometry-optimized rotamer but some differences in the vertical excitation energies and in the ligand-to-metal charge-transfer character. The wavelengths of the calculated excitations were found to be red-shifted compared with peaks in the optical absorption spectra, but the general trends and shifts of wavelengths between the different structures are well reproduced. Static emission spectra for degassed samples in THF solution of the larger compounds showed small Stokes shifts and low fluorescence quantum yields, indicating fast intersystem crossing to the triplet manifold. More pronounced differences between the compounds were displayed in the phosphorescence data, in terms of spectral emission wavelengths and decay times. For instance, the phosphorescence decay of the compound with the thiophene ring close to the Pt center was found to be significantly faster than for the other compounds. A possible relationship between triplet lifetime and conformation of the compounds is discussed. It was also demonstrated that the quenching of the excited triplet states in air-saturated samples involves energy transfer to the oxygen triplet state, and subsequent generation of singlet oxygen showing the typical emission at approximately 1275 nm. The amount of produced singlet oxygen followed the phosphorescence yields of the solute molecules. Two-photon absorption cross sections (sigma(2)) were measured and showed values on the order of 10 GM at 780 nm for all compounds. Optical power limiting measurements of the new complexes in THF using 5 ns pulses, showed only slightly better performance at the wavelength of 532 nm compared to that of similar platinum compounds with only two aryl rings in each ligand. At 600 nm the complexes with three aryl rings were significantly better optical limiters than the smaller compounds with two aryl rings in the ligands.
一系列四个新的反式二膦合铂(II)二炔化物配合物，每个炔配体中都有噻吩和两个苯环，已被合成并进行了光学吸收、光谱和时间分辨发光以及光非线性性质（如双光子吸收截面和光限幅）的表征。对于三个 Pt(II)二炔化物结构的几个基态构象的密度泛函理论（DFT）计算表明，每个几何优化旋转异构体的总能量相似，但垂直激发能和配体到金属电荷转移特性存在一些差异。计算出的激发波长与光学吸收光谱中的峰相比出现红移，但不同结构之间的波长趋势和偏移得到了很好的重现。较大化合物在 THF 溶液中进行脱气的静态发射光谱显示出较小的斯托克斯位移和低荧光量子产率，表明快速的系间窜越至三重态。在磷光数据中，不同化合物之间显示出更明显的差异，表现在光谱发射波长和衰减时间上。例如，与其他化合物相比，靠近 Pt 中心的噻吩环的化合物的磷光衰减明显更快。讨论了三重态寿命与化合物构象之间的可能关系。还证明了在空气饱和样品中激发三重态的猝灭涉及能量转移到氧三重态，随后生成单线态氧，其典型发射波长约为 1275nm。产生的单线态氧的量与溶质分子的磷光产率一致。测量了双光子吸收截面（sigma(2)），并发现所有化合物在 780nm 处的约 10 GM 量级的值。使用 5ns 脉冲在 THF 中对新配合物进行的光限幅测量表明，与每个配体中只有两个芳环的类似铂配合物相比，在 532nm 波长处的性能仅略有改善。在 600nm 处，具有三个芳环的配合物比配体中具有两个芳环的较小化合物更有效地成为光学限幅器。
