Cyclodextrin complexation of a stilbene and the self-assembly of a simple molecular deviceElectronic Supplementary Information (ESI) available: NMR spectra. See http://www.rsc.org/suppdata/ob/b3/b310519a/
作者:Julia S. Lock、Bruce L. May、Philip Clements、Stephen F. Lincoln、Christopher J. Easton
DOI:10.1039/b310519a
日期:——
(E)-4-tert-Butyl-4′-oxystilbene, 1−, is thermally stable as the (E)-1− isomer but may be photoisomerized to the (Z)-1− isomer as shown by UV-vis and 1H NMR studies in aqueous solution. When (E)-1− is complexed by αCD two inclusion isomers (includomers) form in which αCD assumes either of the two possible orientations about the axis of (E)-1− in αCD·(E)-1− for which 1H NMR studies yield the parameters: k1(298 K)
= 12.3 ± 0.6 s−1, ΔH1‡
= 94.3 ± 4.7 kJ mol−1, ΔS1‡
= 92.0 ± 5.0 J K−1 mol−1, and k2(298 K)
= 10.7 ± 0.5 s−1, ΔH2‡
= 93.1 ± 4.7 kJ mol−1, ΔS2‡
= 87.3 ± 5.0 J K−1 mol−1 for the minor and major includomers, respectively. The βCD·(E)-1− complex either forms a single includomer or its includomers interchange at the fast exchange limit of the 1H NMR timescale. Complexation of 1− by N-(6A-deoxy-α-cyclodextrin-6A-yl)-N′-(6A-deoxy-β-cyclodextrin-6A-yl)urea, 2, results in the binary complexes 2·(E)-1− in which both CD component annuli are occupied by (E)-1− and which exists exclusively in darkness and 2·(Z)-1− in which only one CD component is occupied by (Z)-1− and exists exclusively in daylight at λ
≥ 300 nm. Irradiation of solutions of the binary complexes at 300 and 355 nm results in photostationary states dominated by 2·(E)-1− and 2·(Z)-1−, respectively. In the presence of 4-methylbenzoate, 4−, 2·(Z)-1− forms the ternary complex 2·(Z)-1−·4− where 4− occupies the second CD annulus. Interconversion occurs between 2·(Z)-1−·4− and 2·(E)-1−
+
4− under the same conditions as for the binary complexes alone. Similar interactions occur in the presence of 4-methylphenolate and 4-methylphenylsulfonate. The two isomers of each of these systems represent different states of a molecular device, as do the analogous binary complexes of N,N-bis(6A-deoxy-β-cyclodextrin-6A-yl)urea, 3, 3·(E)-1− and 3·(Z)-1−, where the latter also forms a ternary complex with 4−.
(E)-4-叔丁基-4'-氧基芪,1−,与 (E)-1− 异构体一样热稳定,但可以光致异构化为 (Z)-1− 异构体,如 UV-vis 和所示水溶液中的 1H NMR 研究。当 (E)-1− 与 αCD 络合时,形成两种包合异构体(包含异构体),其中 αCD 呈现围绕 αCD·(E)-1− 中的 (E)-1− 轴的两种可能的方向之一,其中 1H NMR 研究得出参数:k1(298 K)
= 12.3 ± 0.6 s−1, ΔH1‡
= 94.3 ± 4.7 kJ mol−1, ΔS1‡
= 92.0 ± 5.0 J K−1 mol−1, 和 k2(298 K)
= 10.7 ± 0.5 s−1, ΔH2‡
= 93.1 ± 4.7 kJ mol−1, ΔS2‡
对于次要包含体和主要包含体,分别 = 87.3 ± 5.0 J K−1 mol−1。 βCD·(E)-1− 复合物要么形成单个包含体,要么在 1 H NMR 时间尺度的快速交换极限下形成其包含体交换。 1− 与 N-(6A-脱氧-α-环糊精-6A-基)-N′-(6A-脱氧-β-环糊精-6A-基)脲 2 络合,得到二元络合物 2·(E )-1−,其中两个 CD 分量环都被 (E)-1− 占据,并且仅存在于黑暗中;2·(Z)-1−,其中只有一个 CD 分量被 (Z)-1− 占据,并且只存在于日光下的 λ 处
≥300纳米。在 300 和 355 nm 处照射二元配合物溶液会产生分别以 2·(E)-1− 和 2·(Z)-1− 为主的光稳态。在 4-苯甲酸甲酯存在下,4−, 2·(Z)-1− 形成三元络合物 2·(Z)-1−·4−,其中 4− 占据第二个 CD 环。相互转换发生在 2·(Z)-1−·4− 和 2·(E)-1− 之间
+
4− 在与单独的二元复合物相同的条件下。类似的相互作用发生在 4-甲基苯酚盐和 4-甲基苯基磺酸盐的存在下。每个系统的两种异构体代表分子装置的不同状态,N,N-双(6A-脱氧-β-环糊精-6A-基)脲, 3, 3·(E) 的类似二元复合物也是如此。 -1− 和 3·(Z)-1−,其中后者也与 4− 形成三元络合物。