Large cross-section enhancement and intramolecular energy transfer upon multiphoton absorption of hindered diphenylaminofluorene-C60 dyads and triads
Large cross-section enhancement and intramolecular energy transfer upon multiphoton absorption of hindered diphenylaminofluorene-C60 dyads and triads
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DOI：
10.1021/cm060718z
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发表时间：
2006-08-22
影响因子：
8.6
通讯作者：
Prasad, Paras N.
中科院分区：
文献类型：
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作者：
Padmawar, Prashant A.;Rogers, Joy E.;Prasad, Paras N.
合成并充分表征了 C-60-(酮基芴)(x) 受体-供体 (A-D) 分子连接中的空间位阻富勒烯基发色团二元组和三元组 C-60(> DPAF-C-9)(x)（x 分别 = 1 和 2）。芴环部分的C-9上连接两个3,5,5-三甲基己基大大提高了它们的溶解度，并使直接分子间芳族堆积接触变得更加困难。它们是第一系列具有高三光子吸收率（3PA）的富勒烯衍生物。因此，C-60(> DPAF-C-9)(2) 在飞秒区域中的 2PA 和 3PA 横截面值分别为 0.824 x 10(-48) cm(4) s（或 82.4 GM）和 6.30 x 10(-25) cm(6)/GW(2)，是许多二苯氨基芴衍生的 AFX 报道中最高的。发色团。利用位于 C-60 笼和芴发色团部分之间的酮连接体有利于 DPAF 环向 C-60 笼的分子极化。这可能是增强的 A-D 电子相互作用与最终观察到的多光子吸收截面相关的根本原因。以355 nm处的纳秒激光闪光光解结果为参考，800 nm处的飞秒泵浦探针实验获得的瞬态吸收数据明确证实了空气饱和苯中C-60(>DPAF-C-9)双光子激发过程的发生以及随后从双光子泵浦的DPAF-C-9部分到C-60笼部分的有效能量转移。
Sterically hindered fullerenyl chromophore dyad and triads, C-60(> DPAF-C-9)(x) (x = 1 and 2, respectively), in an acceptor-donor (A-D) molecular linkage of C-60-(keto-fluorene)(x) were synthesized and fully characterized. Attachment of two 3,5,5-trimethylhexyl groups on C-9 of the fluorene ring moiety greatly improves their solubility and makes direct intermolecular aromatic stacking contacts more difficult. They are the first series of fullerene derivatives showing high three-photon absorptivity (3PA). Accordingly, C-60(> DPAF-C-9)(2) exhibits 2PA and 3PA cross sections in the values of 0.824 x 10(-48) cm(4) s (or 82.4 GM) and 6.30 x 10(-25) cm(6)/GW(2), respectively, in femtosecond region among the highest ones reported for many diphenylaminofluorene-derived AFX chromophores. Utilization of a keto linker located immediately between C-60 cage and fluorene chromophore moieties facilitates molecular polarization of the DPAF ring toward the C-60 cage. That may serve as the fundamental cause for correlation of enhanced A-D electron interactions to, ultimately, observed multiphoton absorption cross sections. By using nanosecond laser flash photolysis results taken at 355 nm as the reference, transient absorption data obtained from femtosecond pump-probe experiments at 800 nm unambiguously verified the occurrence of two-photon excitation processes of C-60(> DPAF- C-9) in air-saturated benzene and subsequent efficient energy transfer from the two-photon pumped DPAF- C-9 moiety to the C-60 cage moiety.