Abstract To study the structure-property relationship as well as the intramolecular charge transfer properties of typical ladder-conjugated molecules, three ladder-conjugated molecules named LT2, LT3 and BPTF-2 were systematically investigated by UV-vis absorption spectra and fluorescence spectra, the open-aperture Z-scan technique, two-photon excited fluorescence and femtosecond pump-probe experiments. These ladder-conjugated molecules employ the same fluorene group as the π -bridge and the central core, with substituent changes at the terminal position. These molecules exhibit a large two-photon absorption response and two molecules emit intense two-photon fluorescence at a wavelength of 800 nm, which is a commonly used wavelength in two-photon absorption/two-photon fluorescence applications. Our results indicate that the π -bridge and the terminal group play an important role in determining the two-photon absorption response. The dynamic results obtained from degenerated pump-probe experiments revealed that the evolution times of the intramolecular charge transfer state were >1000 ps, >1000 ps, and 40 ps for LT2, LT3 and BDTF-2, respectively. The results match those of the two-photon absorption responses and the fluorescence emission properties of these ladder-conjugated molecules. Our results also indicate that ladder-conjugated molecules have potential applications in two-photon absorption/two-photon fluorescence fields.

中文翻译：

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三种可溶性梯形共轭分子的非线性光学响应和超快动力学：端基效应研究

摘要 为研究典型梯形共轭分子的结构-性质关系以及分子内电荷转移特性，利用紫外-可见吸收光谱和荧光光谱系统研究了三种梯形共轭分子LT2、LT3和BPTF-2。开放孔径 Z 扫描技术、双光子激发荧光和飞秒泵浦探针实验。这些梯形共轭分子使用与 π 桥和中心核相同的芴基团，在末端位置发生取代基变化。这些分子表现出较大的双光子吸收响应，并且两个分子在 800 nm 波长处发出强烈的双光子荧光，这是双光子吸收/双光子荧光应用中常用的波长。我们的结果表明 π 桥和末端基团在确定双光子吸收响应中起重要作用。从退化泵-探针实验获得的动态结果表明，LT2、LT3 和 BDTF-2 的分子内电荷转移状态的演化时间分别为 >1000 ps、>1000 ps 和 40 ps。结果与这些梯形共轭分子的双光子吸收响应和荧光发射特性相匹配。我们的结果还表明梯形共轭分子在双光子吸收/双光子荧光领域具有潜在应用。从退化泵-探针实验获得的动态结果表明，LT2、LT3 和 BDTF-2 的分子内电荷转移状态的演化时间分别为 >1000 ps、>1000 ps 和 40 ps。结果与这些梯形共轭分子的双光子吸收响应和荧光发射特性相匹配。我们的结果还表明梯形共轭分子在双光子吸收/双光子荧光领域具有潜在应用。从退化泵-探针实验获得的动态结果表明，LT2、LT3 和 BDTF-2 的分子内电荷转移状态的演化时间分别为 >1000 ps、>1000 ps 和 40 ps。结果与这些梯形共轭分子的双光子吸收响应和荧光发射特性相匹配。我们的结果还表明梯形共轭分子在双光子吸收/双光子荧光领域具有潜在应用。