Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5258, Japan.
Photochem Photobiol Sci. 2022 Aug;21(8):1445-1458. doi: 10.1007/s43630-022-00234-y. Epub 2022 May 9.
The photochromic molecules showing wavelength-selective or light intensity-dependent photoresponse are receiving increased attention in recent years. Although a photoswitch with a single chromophore can control the ON and OFF states of a function, that consisting of multi-chromophores would be useful for the specific control in complex systems. Herein, we designed stepwise two-photon induced photochromic molecules (PABI-PIC and PABI-PIC2) consisting of two different photochromic units (PABI and PIC). One-photon absorption reaction in the UV light region of PABI-PIC generates the short-lived transient biradical (BR) that absorbs an additional photon in the visible and UV light region in a stepwise manner to produce the two-photon photochemical product, the quinoidal species (Quinoid). The photochromic properties of these transient species are completely different in color and fading speed. In addition, PABI-PIC also shows the excitation wavelength-dependent photochromism because the excited states of the PABI and PIC units are electronically orthogonal. Therefore, the stepwise photochromic properties of PABI-PIC are easily controlled depending on the excitation light intensity and wavelength. These molecular designs are important for the development of advanced photoresponsive materials.
近年来，对具有波长选择性或光强依赖性光响应的光致变色分子的研究受到了越来越多的关注。虽然含有单个生色团的光开关可以控制功能的开和关状态，但由多个生色团组成的光开关对于复杂体系中的特定控制将是有用的。在这里，我们设计了由两个不同的光致变色单元（PABI 和 PIC）组成的逐步双光子诱导光致变色分子（PABI-PIC 和 PABI-PIC2）。PABI-PIC 在紫外光区的单光子吸收反应产生短寿命瞬态双自由基（BR），它以逐步的方式在可见和紫外光区吸收额外的光子，产生双光子光化学反应产物醌型物种（Quinoid）。这些瞬态物种的光致变色性质在颜色和褪色速度上完全不同。此外，PABI-PIC 还表现出与激发波长有关的光致变色性，因为 PABI 和 PIC 单元的激发态在电子上是正交的。因此，PABI-PIC 的逐步光致变色性质可以根据激发光强度和波长很容易地进行控制。这些分子设计对于开发先进的光响应材料非常重要。
