TY - JOUR
T1 - Diazacoronand linked β-cyclodextrin† dimer complexes of brilliant yellow tetraanion and their sodium(I) analogues
AU - West, Lee C.
AU - Wyness, Oska
AU - May, Bruce L.
AU - Clements, Philip
AU - Lincoln, Stephen F.
AU - Easton, Christopher J.
PY - 2003/3/7
Y1 - 2003/3/7
N2 - Complexation of the Brilliant Yellow tetraanion, 34-, by two new diazacoronand linked β-cyclodextrin (βCD) dimers 4,13-bis(2-(6A-deoxy-β-cyclodextrin-6A-yl)aminoethyla midomethyl- and 4,13-bis(8-(6A-deoxy-β-cyclodextrin- 6A-yl)aminooctylamidomethyl)-4,13-diaza-1,7,10-trioxacyclopentadecane , 1 and 2, respectively, has been studied in aqueous solution. UV-visible spectrophotometric studies at 298.2 K, pH 10.0 and I = 0.10 mol dm-3 (NEt4ClO4) yielded complexation constants for the complexes 1·34- and 2·34-, K1=(1.08 ± 0.01) × 105 and (6.21 ± 0.08) × 103 dm3 mol-1, respectively. Similar studies at 298.2 K, pH 10.0 and I = 0.10 mol dm-3 (NaClO4) yielded K3=(4.63 ± 0.09) × 105 and (3.38 ± 0.05) × 104 dm3 mol-1 for the complexation of 34- by Na+·1 and Na+·2 to give Na+·1·34- and Na+·2·34-, respectively. Potentiometric studies of the complexation of Na+ by 1 and 2 by the diazacoronand component of the linkers to give Na+·1 and Na+·2 yielded K2 = (2.00 ± 0.05) × 102 and (1.8 ± 0.05) × 103 dm3 mol-1, respectively, at 298.2 K and I = 0.10 mol dm-3 (NEt4ClO4). For complexation of Na+ by 1·34- and 2·34- to give Na+·1·34- and Na+·2·34- K2K3/K1 = K4 = 8.6 × 102 and 9.8 × 103 dm3 mol-1, respectively. The pKas of 1H44+ are 7.63 ± 0.01, 6.84 ± 0.02, 5.51 ± 0.04 and 4.98 ± 0.03, and those of 2H44+ are 8.67 ± 0.02, 8.11 ± 0.02, 6.06 ± 0.02 and 5.14 ± 0.05. The larger magnitude of K1 for 1 by comparison with K1 for 2 is attributed to the octamethylene linkers of 2 competing with 34- for occupancy of the annuli of the βCD entities while the competitive ability of the dimethylene linkers of 1 is less. A similar argument applies to the relative magnitudes of K3 for Na+·1 and Na+·2. Increased electrostatic attraction probably accounts for K3 > K1 for Na+·1·34- and 1·34- and for Na+·2·34- and 2·34-. The lesser magnitudes of K2 and K4 for Na+·1 and Na+·1·34- compared with those for Na+·2 and Na+·2·34- are attributed to the octamethylene linkers of 2 producing a more hydrophobic environment for the diazacoronand than that produced by the dimethylene linkers of 1. 1H NMR spectroscopic studies and the synthesis of 1 and 2 are described.
AB - Complexation of the Brilliant Yellow tetraanion, 34-, by two new diazacoronand linked β-cyclodextrin (βCD) dimers 4,13-bis(2-(6A-deoxy-β-cyclodextrin-6A-yl)aminoethyla midomethyl- and 4,13-bis(8-(6A-deoxy-β-cyclodextrin- 6A-yl)aminooctylamidomethyl)-4,13-diaza-1,7,10-trioxacyclopentadecane , 1 and 2, respectively, has been studied in aqueous solution. UV-visible spectrophotometric studies at 298.2 K, pH 10.0 and I = 0.10 mol dm-3 (NEt4ClO4) yielded complexation constants for the complexes 1·34- and 2·34-, K1=(1.08 ± 0.01) × 105 and (6.21 ± 0.08) × 103 dm3 mol-1, respectively. Similar studies at 298.2 K, pH 10.0 and I = 0.10 mol dm-3 (NaClO4) yielded K3=(4.63 ± 0.09) × 105 and (3.38 ± 0.05) × 104 dm3 mol-1 for the complexation of 34- by Na+·1 and Na+·2 to give Na+·1·34- and Na+·2·34-, respectively. Potentiometric studies of the complexation of Na+ by 1 and 2 by the diazacoronand component of the linkers to give Na+·1 and Na+·2 yielded K2 = (2.00 ± 0.05) × 102 and (1.8 ± 0.05) × 103 dm3 mol-1, respectively, at 298.2 K and I = 0.10 mol dm-3 (NEt4ClO4). For complexation of Na+ by 1·34- and 2·34- to give Na+·1·34- and Na+·2·34- K2K3/K1 = K4 = 8.6 × 102 and 9.8 × 103 dm3 mol-1, respectively. The pKas of 1H44+ are 7.63 ± 0.01, 6.84 ± 0.02, 5.51 ± 0.04 and 4.98 ± 0.03, and those of 2H44+ are 8.67 ± 0.02, 8.11 ± 0.02, 6.06 ± 0.02 and 5.14 ± 0.05. The larger magnitude of K1 for 1 by comparison with K1 for 2 is attributed to the octamethylene linkers of 2 competing with 34- for occupancy of the annuli of the βCD entities while the competitive ability of the dimethylene linkers of 1 is less. A similar argument applies to the relative magnitudes of K3 for Na+·1 and Na+·2. Increased electrostatic attraction probably accounts for K3 > K1 for Na+·1·34- and 1·34- and for Na+·2·34- and 2·34-. The lesser magnitudes of K2 and K4 for Na+·1 and Na+·1·34- compared with those for Na+·2 and Na+·2·34- are attributed to the octamethylene linkers of 2 producing a more hydrophobic environment for the diazacoronand than that produced by the dimethylene linkers of 1. 1H NMR spectroscopic studies and the synthesis of 1 and 2 are described.
UR - http://www.scopus.com/inward/record.url?scp=0042320337&partnerID=8YFLogxK
U2 - 10.1039/b209759c
DO - 10.1039/b209759c
M3 - Article
SN - 1477-0520
VL - 1
SP - 887
EP - 894
JO - Organic and Biomolecular Chemistry
JF - Organic and Biomolecular Chemistry
IS - 5
ER -