Double-Threaded Dimer and Supramolecular Oligomer Formed by Stilbene Modified Cyclodextrin: Effect of Acyl Migration and Photostimuli
Double-Threaded Dimer and Supramolecular Oligomer Formed by Stilbene Modified Cyclodextrin: Effect of Acyl Migration and Photostimuli
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DOI：
10.1021/jo101936t
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发表时间：
2011-01-21
影响因子：
3.6
通讯作者：
Harada, Akira
中科院分区：
文献类型：
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作者：
Kanaya, Akira;Takashima, Yoshinori;Harada, Akira
我们观察到芪-α-环糊精（StiO-alpha-CD）的超分子结构通过光辐射和迁移而发生变化。二苯乙烯衍生物在λ = 340 nm的照射下显示光诱导异构化，得到2-cis-StiO-α-CD，在λ = 254 nm的照射下得到2-trans-StiO-α-CD。2D NMR和扩散系数的研究表明，2-trans-StiO-alpha-CD形成一个双线程的二聚体，但2-cis-StiO-alpha-CD的变化，超分子低聚物的光致异构化过程中30分钟。我们发现，在中性条件下发生的相互迁移的一个芪组（StiO）的α-CD。α-CD的StiO基团（StiO-alpha-CD）在StiO-alpha-CD的仲羟基（α-CD的较宽边缘）上的C2和C3位置之间移动，得到3-反式-StiO-alpha-CD。3-trans-StiO-alpha-CD形成超分子寡聚体，而3-cis-StiO-alpha-CD变为双螺纹二聚体，表明3-StiO-alpha-CD在2-StiO-alpha-CD的超分子结构中产生相反的结果。热异构化（迁移）非常缓慢。约300 h达到平衡状态。此外，从α-CD的C3位置到C2位置的trans-StiO基团的迁移速率常数（k（trans 3-> 2））快于从α-CD的C2位置到C3位置的k（trans 2-> 3）。另一方面，从α-CD的C2位置到C3位置的顺式-StiO基团的k（顺式2-> 3）比从C3位置到C2位置的k（顺式3-> 2）快，意味着k（顺式2-> 3）> k（顺式3-> 2），这与k（反式3-> 2）> k（反式2-> 3）的结果相反。稳定的双螺纹二聚体的形成将抑制水溶液中StiO-alpha-CD的StiO基团的迁移。
We observed changing supramolecular structures of stilbene-alpha-cyclodextrin (StiO-alpha-CD) by photoirradiation and migration. Stilbene derivatives show photoinduced isomerization under irradiation with lambda = 340 nm to give 2-cis-StiO-alpha-CD and with lambda = 254 nm to give 2-trans-StiO-alpha-CD. Photoisomerization of StiO-alpha-CD shows the photostationary state during 30 min. 2D NMR and diffusion coefficient studies revealed that 2-trans-StiO-alpha-CD forms a double-threaded dimer but 2-cis-StiO-alpha-CD changes to a supramolecular oligomer by photoirradiation. We found that the mutual migration of a stilbene group (StiO) on alpha-CD occurs under neutral conditions. The StiO group of alpha-CD (StiO-alpha-CD) moves between the C2 and C3 positions on the secondary hydroxyl group of StiO-alpha-CD (the wider rim of alpha-CD) to give 3-trans-StiO-alpha-CD. 3-trans-StiO-alpha-CD forms a supramolecular oligomer, whereas 3-cis-StiO-alpha-CD changes to a double-threaded dimer, indicating that 3-StiO-alpha-CDs gives the opposite results in the supramolecular structures of 2-StiO-alpha-CDs. The thermal isomerization (migration) is very slow. It takes about 300 h to reach the equilibrium state. Moreover, the migration rate constant (k(trans3 -> 2)) of the trans-StiO group from the C3 position to the C2 position of alpha-CD is faster than k(trans2 -> 3) from the C2 position to the C3 position of alpha-CD. On the other hand, k(cis2 -> 3) of the cis-StiO group from the C2 position to the C3 position of alpha-CD is faster than k(cis3 -> 2) from the C3 position to the C2 position, meaning k(cis2 -> 3) > k(cis3 -> 2), which is the opposite result for k(trans3 -> 2) > k(trans2 -> 3). The formation of a stable double-threaded dimer would suppress the migration of the StiO group of StiO-alpha-CDs in aqueous solutions.