Lock Julia S, May Bruce L, Clements Philip, Lincoln Stephen F, Easton Christopher J
Department of Chemistry, University of Adelaide, Adelaide, SA 5005, Australia.
Org Biomol Chem. 2004 Feb 7;2(3):337-44. doi: 10.1039/b310519a. Epub 2003 Dec 22.
(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 (1)H NMR studies in aqueous solution. When (E)-1(-) is complexed by alphaCD two inclusion isomers (includomers) form in which alphaCD assumes either of the two possible orientations about the axis of (E)-1(-) in alphaCD.(E)-1(-) for which (1)H NMR studies yield the parameters: k(1)(298 K)= 12.3 +/- 0.6 s(-1), DeltaH(1)(++)= 94.3 +/- 4.7 kJ mol(-1), DeltaS1(++)= 92.0 +/- 5.0 J K(-1) mol(-1), and k(2)(298 K)= 10.7 +/- 0.5 s(-1), DeltaH(2)(++)= 93.1 +/- 4.7 kJ mol(-1), DeltaS2(++)= 87.3 +/- 5.0 J K(-1) mol(-1) for the minor and major includomers, respectively. The betaCD.(E)-1(-) complex either forms a single includomer or its includomers interchange at the fast exchange limit of the (1)H NMR timescale. Complexation of 1(-) by N-(6(A)-deoxy- alpha-cyclodextrin-6(A)-yl)-N'-(6(A)-deoxy- beta-cyclodextrin-6(A)-yl)urea, 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 lambda > or = 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(6(A)-deoxy- beta-cyclodextrin-6(A)-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'-氧代芪（1(-)）作为（E）-1(-)异构体具有热稳定性，但在水溶液中通过紫外可见光谱和（1）H核磁共振研究表明，它可能会光异构化为（Z）-1(-)异构体。当（E）-1(-)与α-环糊精络合时，会形成两种包合异构体（包结物），其中α-环糊精围绕（E）-1(-)在α-环糊精中的轴采取两种可能取向中的任意一种。对于（E）-1(-)，（1）H核磁共振研究得出以下参数：次要和主要包结物的k(1)(298 K)= 12.3 ± 0.6 s(-1)，ΔH(1)(++)= 94.3 ± 4.7 kJ mol(-1)，ΔS1(++)= 92.0 ± 5.0 J K(-1) mol(-)1，以及k(2)(298 K)= 10.7 ± 0.5 s(-1)，ΔH(2)(++)= 93.1 ± 4.7 kJ mol(-1)，ΔS2(++)= 87.3 ± 5.0 J K(-1) mol(-1)。β-环糊精.（E）-1(-)络合物要么形成单一包结物，要么其包结物在（1）H核磁共振时间尺度的快速交换极限下相互转换。1(-)与N-(6(A)-脱氧-α-环糊精-6(A)-基)-N'-(6(A)-脱氧-β-环糊精-6(A)-基)脲络合，会生成二元络合物2.（E）-1(-)，其中两个环糊精组分环都被（E）-1(-)占据，且仅在黑暗中存在；以及2.（Z）-1(-)，其中只有一个环糊精组分被（Z）-1(-)占据，且仅在波长λ≥300 nm的日光下存在。在300和355 nm处照射二元络合物溶液，分别会导致以2.（E）-1(-)和2.（Z）-1(-)为主的光稳态。在4-甲基苯甲酸盐（4(-)）存在下，2.（Z）-1(-)形成三元络合物2.（Z）-1(-).4(-)，其中4(-)占据第二个环糊精环。在与单独二元络合物相同的条件下，2.（Z）-1(-).4(-)和2.（E）-1(-)+4(-)之间会发生相互转化。在4-甲基苯酚盐和4-甲基苯磺酸盐存在下也会发生类似的相互作用。这些体系中每一个的两种异构体代表分子器件的不同状态，N,N-双(6(A)-脱氧-β-环糊精-6(A)-基)脲（3）的类似二元络合物[3.（E）-1(-)和3.（Z）-1(-)]也是如此，其中后者也会与4(-)形成三元络合物。
