Strong cooperative enhancement of two-photon absorption in double-strand conjugated porphyrin ladder arrays
Strong cooperative enhancement of two-photon absorption in double-strand conjugated porphyrin ladder arrays
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DOI：
10.1021/ja0649623
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发表时间：
2006-09-27
影响因子：
15
通讯作者：
Anderson, Harry L.
中科院分区：
文献类型：
--
作者：
Drobizhev, Mikhail;Stepanenko, Yuriy;Anderson, Harry L.
我们给出了一系列共轭卟啉低聚物的双光子吸收（2PA）光谱，这些卟啉低聚物含有n = 2、4、8和约13个单体单元，它们与丁二炔连接。我们证明，在共面双链阵列中，加入4,4 ' -联吡啶后自组装，共轭长度急剧增加，导致2PA的协同增强非常强。我们分析了双链和旋转自由单链阵列中2PA的标度，并展示了两种情况下的有效共轭长度如何与观察到的2PA性质相关联。通过引入2PA强度的“共轭特征”，我们表明，在双链排列中，共轭作用包含整个分子直至四聚体水平，而在单链排列中，除了n = 2外，共轭作用始终小于n，但一直增加到ln = 8。我们发现在峰值为1.3 μm的双链低聚物中具有极强的2PA截面，σ2≈105GM，可用于光纤器件的信号处理。
We present the two-photon absorption (2PA) spectra of a series of conjugated porphyrin oligomers containingN= 2, 4, 8, and ca. 13 monomer units,meso−mesoconnected with butadiyne linkers. We demonstrate that, in the coplanar double-strand arrays, self-assembled upon addition of 4,4‘-bipyridyl, the conjugation length increases dramatically, leading to very strong cooperative enhancement of 2PA. We analyze the scaling of 2PA in both the double-strand and rotationally free single-strand arrays and show how the effective conjugation length in both cases is linked to the observed 2PA properties. By introducing a “conjugation signature” for the 2PA strength, we show that, in double-strand arrangement, the conjugation embraces the whole molecule up to the tetramer level, whereas in single-strand arrangement, it is always less thanN, except forN= 2, but keeps increasing untilN= 8. Our finding of extremely strong 2PA cross section, σ2≈ 105GM, in double-strand oligomers peaking at 1.3 μm can find use for signal processing in fiber-optic devices.