Supramolecular complexation and collective optical properties induced by linking two methyl salicylates via a σ-bridge
Supramolecular complexation and collective optical properties induced by linking two methyl salicylates via a σ-bridge
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通过σ桥连接两个水杨酸甲酯诱导的超分子络合和集体光学特性
DOI：
10.1021/acs.jpcb.2c00842
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发表时间：
2022
期刊：
影响因子：
3.3
通讯作者：
and T. Akutagawa
中科院分区：
文献类型：
--
作者：
M. Takahashi;K. Sakai;K. Sambe;and T. Akutagawa
超分子络合物或聚合物由非共价分子间作用力如π-π和偶极-偶极相互作用形成，具有呈现激子在多个分子上扩散所带来的集体光学性质的潜力，如在J-聚集体中所见。在这方面，具有较大π体系和偶极矩的分子是有利的。然而，我们在这里报道，通过σ桥连接两个水杨酸甲酯(MS)合成的二元型分子，对于形成具有集体光学性质的稳定聚集体是有效的。在浓度大于10~(-2)M的CHCl_3溶液中，MS-二联体发生自缔合，在稀溶液(λ_(Max)=334 nm)中，吸收带(λ_(Max)=464 nm)发生红移，超过8300 cm~(-1)。在这个带的激发下，观察到强烈的绿色荧光，而不是聚集引起的猝灭。吸收带和荧光带都有很好的振动级数，它们是近镜像关系，产生了600 cm-1的小斯托克斯位移。根据单晶X射线分析结果建立的聚集体模型，从理论上对这些特征光学性质进行了合理的解释。1H核磁共振测量表明，未连接的MS在高浓度下也形成聚集体，尽管吸收测量没有提供任何证据。由此推测，MSS的连接稳定了聚集体的MS堆积结构，导致在多个分子上产生离域的激发态。
Supramolecular complexes or polymers, formed by noncovalent intermolecular forces such as π–π and dipole–dipole interactions, have the potential to render collective optical properties brought about by excitons spreading over multiple molecules, as seen in J-aggregates. In this respect, molecules with a large π-system and dipole moment are advantageous. However, we report here that methyl salicyate (MS) dyad-type molecules, synthesized by connection of two MSs via a σ-bridge, are effective for forming stable aggregates with collective optical properties. The self-association of MS-dyads occurs in a CHCl3solution at a high concentration of over 10–2M, which is recognized by the appearance of an absorption band (λmax= 464 nm) bathochromically shifted beyond 8300 cm–1from the band in the dilute solution (λmax= 334 nm). Upon excitation of this band, an intense green fluorescence is observed without aggregation-caused quenching. The absorption and fluorescence bands, both of which have well-resolved vibronic progressions, are in a near-mirror image relationship, yielding a small Stokes shift of 600 cm–1. A reasonable explanation for these characteristic optical properties is provided from theoretical considerations on the aggregate model constructed based on the results of single-crystal X-ray analysis. The1H NMR measurements suggest that unconnected MSs also form aggregates at high concentrations, although the absorption measurements do not provide any evidence for this. It is thus presumed that the connection of MSs stabilizes the MS stacking structure of the aggregates, leading to the generation of an excited state delocalized over multiple molecules.