TY - JOUR
T1 - Cyclodextrin and modified cyclodextrin complexes of E-4-tert-butylphenyl- 4′-oxyazobenzene
T2 - UV-visible,1H NMR and ab initio studies
AU - May, Bruce L.
AU - Gerber, Jacobus
AU - Clements, Philip
AU - Buntine, Mark A.
AU - Brittain, David R.B.
AU - Lincoln, Stephen F.
AU - Easton, Christopher J.
PY - 2005/4/21
Y1 - 2005/4/21
N2 - α-Cyclodextrin, β-cyclodextrin, N-(6A-deoxy-α- cyclodextrin-6A-yl)-N′-(6A-deoxy-β- cyclodextrin-6A-yl)urea and N,N-bis(6A-deoxy-β- cyclodextrin-6A-yl)urea (αCD, βCD, l and 2) form inclusion complexes with E-4-tert-butylphenyl-4′-oxyazobenzene, E-3-. In aqueous solution at pH 10.0, 298.2 K and I = 0.10 mol dm-1 (NaClO4) spectrophotometric UV-visible studies yield the sequential formation constants: K11 = (2.83 ± 0.28) × 10 5 dm3 mol-1 for αCD-E-3, K21 = (6.93 ± 0.06) × 103 dm3 mol-1 for (αCD)2·E-3-, K11 = (1.24 ± 0.12) × 105 dm3 mol-1 for βCD·E-3-, K21 = (1.22 ± 0.06) × 104 dm3 mol-1 for (βCD) 2·E-3-, K11 = (3.08 ± 0.03) × 105 dm3 mol-1 for l·E-3 -, K11 = (8.05 ± 0.63) × 104 dm3 mol-1 for 2-E-3 and K12 = (2.42 ± 0.53) × 104 dm3 mol-1 for 2·(E-3-)2. 1H ROESY NMR studies show that complexation of E-3- in the annuli of αCD, βCD, 1 and 2 occurs. A variable-temperature 1H NMR study yields κ(298 K) = 6.7 ± 0.5 and 5.7 ± 0.5 s-1, ΔH‡ = 61.7 ± 2.7 and 88.1 ± 4.2 kJ mol-1 and ΔAS‡ = - 22.2 ± 8.7 and 65 ± 13 J K-1 mol-1 for the interconversion of the dominant includomers (complexes with different orientations of αCD) of αCD·E-3- and (αCD)2·E-3-, respectively. The existence of E-3- as the sole isomer was investigated through an ab initio study.
AB - α-Cyclodextrin, β-cyclodextrin, N-(6A-deoxy-α- cyclodextrin-6A-yl)-N′-(6A-deoxy-β- cyclodextrin-6A-yl)urea and N,N-bis(6A-deoxy-β- cyclodextrin-6A-yl)urea (αCD, βCD, l and 2) form inclusion complexes with E-4-tert-butylphenyl-4′-oxyazobenzene, E-3-. In aqueous solution at pH 10.0, 298.2 K and I = 0.10 mol dm-1 (NaClO4) spectrophotometric UV-visible studies yield the sequential formation constants: K11 = (2.83 ± 0.28) × 10 5 dm3 mol-1 for αCD-E-3, K21 = (6.93 ± 0.06) × 103 dm3 mol-1 for (αCD)2·E-3-, K11 = (1.24 ± 0.12) × 105 dm3 mol-1 for βCD·E-3-, K21 = (1.22 ± 0.06) × 104 dm3 mol-1 for (βCD) 2·E-3-, K11 = (3.08 ± 0.03) × 105 dm3 mol-1 for l·E-3 -, K11 = (8.05 ± 0.63) × 104 dm3 mol-1 for 2-E-3 and K12 = (2.42 ± 0.53) × 104 dm3 mol-1 for 2·(E-3-)2. 1H ROESY NMR studies show that complexation of E-3- in the annuli of αCD, βCD, 1 and 2 occurs. A variable-temperature 1H NMR study yields κ(298 K) = 6.7 ± 0.5 and 5.7 ± 0.5 s-1, ΔH‡ = 61.7 ± 2.7 and 88.1 ± 4.2 kJ mol-1 and ΔAS‡ = - 22.2 ± 8.7 and 65 ± 13 J K-1 mol-1 for the interconversion of the dominant includomers (complexes with different orientations of αCD) of αCD·E-3- and (αCD)2·E-3-, respectively. The existence of E-3- as the sole isomer was investigated through an ab initio study.
UR - http://www.scopus.com/inward/record.url?scp=18444394309&partnerID=8YFLogxK
U2 - 10.1039/b415594g
DO - 10.1039/b415594g
M3 - Article
SN - 1477-0520
VL - 3
SP - 1481
EP - 1488
JO - Organic and Biomolecular Chemistry
JF - Organic and Biomolecular Chemistry
IS - 8
ER -