TY - JOUR
T1 - Cyclodextrin complexation of a stilbene and the self-assembly of a simple molecular device
AU - Lock, Julia S.
AU - May, Bruce L.
AU - Clements, Philip
AU - Lincoln, Stephen F.
AU - Easton, Christopher J.
PY - 2004/2/7
Y1 - 2004/2/7
N2 - (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-.
AB - (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-.
UR - http://www.scopus.com/inward/record.url?scp=1342345854&partnerID=8YFLogxK
U2 - 10.1039/b310519a
DO - 10.1039/b310519a
M3 - Article
SN - 1477-0520
VL - 2
SP - 337
EP - 344
JO - Organic and Biomolecular Chemistry
JF - Organic and Biomolecular Chemistry
IS - 3
ER -