Albota M, Beljonne D, Brédas J L, Ehrlich J E, Fu J Y, Heikal A A, Hess S E, Kogej T, Levin M D, Marder S R, McCord-Maughon D, Perry J W, Röckel H, Rumi M, Subramaniam G, Webb W W, Wu X L, Xu C
School of Applied Physics and Engineering, and Developmental Resource for Biophysical Imaging Opto-Electronics, Cornell University, Ithaca, NY 14853, USA.
Science. 1998 Sep 11;281(5383):1653-6. doi: 10.1126/science.281.5383.1653.
A strategy for the design of molecules with large two-photon absorption cross sections, delta, was developed, on the basis of the concept that symmetric charge transfer, from the ends of a conjugated system to the middle, or vice versa, upon excitation is correlated to enhanced values of delta. Synthesized bis(styryl)benzene derivatives with donor-pi-donor, donor-acceptor-donor, and acceptor-donor-acceptor structural motifs exhibit exceptionally large values of delta, up to about 400 times that of trans-stilbene. Quantum chemical calculations performed on these molecules indicate that substantial symmetric charge redistribution occurs upon excitation and provide delta values in good agreement with experimental values. The combination of large delta and high fluorescence quantum yield or triplet yield exhibited by molecules developed here offers potential for unprecedented brightness in two-photon fluorescent imaging or enhanced photosensitivity in two-photon sensitization, respectively.
基于激发时共轭体系两端到中间或反之的对称电荷转移与双光子吸收截面δ增大相关的概念，开发了一种设计具有大双光子吸收截面分子的策略。合成的具有供体-π-供体、供体-受体-供体和受体-供体-受体结构基序的双（苯乙烯基）苯衍生物表现出异常大的δ值，高达反式芪的约400倍。对这些分子进行的量子化学计算表明，激发时会发生大量对称电荷重新分布，并且计算得到的δ值与实验值吻合良好。本文开发的分子所具有的大δ值与高荧光量子产率或三重态产率的结合，分别为双光子荧光成像中实现前所未有的亮度或双光子敏化中增强光敏性提供了潜力。
