Solid-state supramolecular chirogenesis: High optical activity and gradual development of zinc octaethylporphyrin aggregates
Solid-state supramolecular chirogenesis: High optical activity and gradual development of zinc octaethylporphyrin aggregates
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DOI：
10.1002/anie.200250524
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发表时间：
2003-01-01
影响因子：
16.6
通讯作者：
Kuroda, R
中科院分区：
文献类型：
--
作者：
Borovkov, VV;Harada, T;Kuroda, R
17882003 Wiley-VCH Verlag GmbH&Co.KGaA，Weinheim DOI：10.1002/Ange.安格鲁200250524号。化学。2003,115,1788-1791年的资料)和CD光谱(图2a)表明只有少量的旋光性。这清楚地表明，固相和溶液中的初始结构和聚集态非常相似。四天后对同一样品的后续测量[5]显示了UV/VIS和CD光谱的广泛变化。在UV/Vis光谱中，初始B带的幅度明显减小，在λ=464 nm处出现了新的红移跃迁；在Q吸收区域也观察到了类似但较小的变化。这些观察结果表明，由于激子耦合理论[6]和其他文献中关于不同J聚集体的数据很好地符合了激子耦合理论[6]和其他文献中关于不同J聚集体的数据，这些观察结果表明，分子间的J型缔合形成了堆积的(ZnOEP·L)n物种。[1a，f，k，7]对同一固态样品的同时CD监测表明，在聚集态物种中诱导出了极高的光学活性。[8]具体地说，这包括在新的低能带区域(图2a)的强烈的Cd耦合和与卟啉Q跃迁相对应的明显的单色棉效应(见辅助信息)。虽然这种CD信号的光谱轮廓与固态条件下观察到的双(锌卟啉)/(S)-CHEA体系有些相似，并且诱导手性符号也是相同的，从而表明手性聚集体之间在结构组织和螺旋取向上的相似性，但有两个至关重要的区别。这是第一棉花效应(λCd=469 nm)的相当低的能量移动，以及在对应于第一棉花效应的波长(g=±0)处各向异性(G)因子的显著增强。015)，这比报道的典型允许的π-π转变的g因子大10-100倍。这显然是由于(ZnOEP·L)n形成了较大的J聚集体，并在聚集体内通过分子间激子耦合放大了手性。在双卟啉发色团的情况下，形成较大聚集体的可能性较小，因为与单体卟啉相比，其分子尺寸较大。此外，在双卟啉的情况下，通过相反取向的分子内耦合，分子间诱导的手性大大减少。[2a，b]然而，到目前为止所研究的所有其他手性胺在固态中与ZnOEP相互作用时不会产生任何超分子手性过程。[3]尽管尚不清楚CHEA选择性的确切来源，但很可能这些配体在所用胺中具有极高的结合能力[2c]，这可能对在[2c]中手性聚集体的形成有很大贡献。
1788 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/ange. 200250524 Angew. Chem. 2003, 115, 1788–1791 ing Information) and the CD spectrum (Figure 2a) indicates there is only minor optical activity. This indicates clearly that the initial structure and aggregation state of ZnOEP· L in the solid state is very similar to that in solution. Subsequent measurements of the same sample after four days [5] revealed extensive changes in the UV/Vis and CD spectra. In the UV/Vis spectrum the amplitude of the initial B band was considerably diminished, with a new bathochromically shifted transition appearing at λ= 464 nm; similar but smaller changes were also clearly observed in the Q absorption region. These observations suggest an intermolecular J-type association of the ZnOEP· L molecules to form a stacked (ZnOEP· L) n species, as they are in good agreement with exciton coupling theory [6] and other literature data on various J aggregates.[1a, f, k, 7] Simultaneous CD monitoring of the same solid-state sample showed induction of extraordinarily high optical activity in the aggregated species.[8] Specifically, this includes an intense CD couplet in the region of the new lowenergy B band (Figure2a) and conspicuous monosignate Cotton effects corresponding to the porphyrin Q transitions (see the Supporting Information). Although the spectral profile of this CD signal somewhat resembles that observed for the bis (zinc porphyrin)/(S)-CHEA system under solid-state conditions [2a] and the induced chirality sign is also the same, thus indicating similarity in the structural organization and helical orientation between the chiral aggregates, there are two crucially important differences. These are a considerable low-energy shift of the first Cotton effect (λCD= 469 nm) and a remarkable enhancement of the anisotropy (g) factor at the wavelength corresponding to the first Cotton effect (g= À0. 015), which is 10–100 times greater than the g factors reported for typical allowed π–π transitions. This is apparently a result of the formation of larger J aggregates of (ZnOEP· L) n and the amplification of chirality by intermolecular excitonic coupling within the aggregates. In the case of bisporphyrin chromophores the formation of larger aggregates is less probable because of the larger molecular size in comparison to the monomeric porphyrin. Furthermore, the intermolecularly induced chirality is considerably reduced in the bisporphyrin case by intramolecular coupling of opposite orientation.[2a, b] However, all other chiral amines studied to date do not generate any supramolecular chirogenic processes upon interaction with ZnOEP in the solid state.[3] Although the precise origin of the selectivity of CHEA is not yet well understood, it is likely that the exceptionally high binding ability of these ligands among the amines used [2c] may contribute greatly to the formation of chiral aggregates in the