Zhang Ling, Morshedi Mahbod, Schwich Torsten, Kobayashi Rika, Humphrey Mark G
Research School of Chemistry, Australian National University Canberra ACT 2601 Australia
National Computational Infrastructure, Australian National University Canberra ACT 2601 Australia.
Chem Sci. 2024 May 14;15(23):8731-8739. doi: 10.1039/d4sc01127a. eCollection 2024 Jun 12.
The light-intensity dependence of multi-photon absorption (MPA) affords outstanding spatial control. Furthermore, compared to the higher-energy photons needed for analogous linear absorption, the lower-energy photons involved in MPA often correspond to important wavelengths, such as those of the biological and telecommunications "windows". It is therefore of crucial importance to develop molecules that exhibit outstanding MPA cross-sections. However, although progress has been made with two-photon absorption, there is currently a dearth of efficient instantaneous -photon absorbers ( > 2), a key reason being the scarcity of structure-property studies required to understand higher-order MPA. We herein report systematically-varied metallodendrimers up to third-generation in size, together with their nonlinear absorptive responses over the spectral range 600-2520 nm. We show that the dendrimers exhibit exceptional instantaneous three- to six-photon absorption cross-sections, with maximal values increasing with dendrimer generation and installation of solubilizing group, and we report that changing the groups at the dendrimer periphery can shift the wavelengths of the PA maxima. We also describe time-dependent DFT studies that have facilitated assignment of the key linear and nonlinear transitions and disclosed the crucial role of the metal in the outstanding MPA performance.
多光子吸收（MPA）对光强的依赖性提供了出色的空间控制。此外，与类似线性吸收所需的高能光子相比，MPA中涉及的低能光子通常对应于重要波长，例如生物和电信“窗口”的波长。因此，开发具有出色MPA截面的分子至关重要。然而，尽管在双光子吸收方面取得了进展，但目前缺乏高效的瞬态多光子吸收剂（>2），一个关键原因是缺乏理解高阶MPA所需的结构-性质研究。我们在此报告了尺寸达第三代的系统变化的金属树枝状大分子，以及它们在600-2520 nm光谱范围内的非线性吸收响应。我们表明，树枝状大分子表现出异常的瞬态三至六光子吸收截面，最大值随树枝状大分子代数和增溶基团的引入而增加，并且我们报告改变树枝状大分子外围的基团可以使PA最大值的波长发生移动。我们还描述了含时密度泛函理论研究，这些研究有助于确定关键的线性和非线性跃迁，并揭示了金属在出色的MPA性能中的关键作用。
