Diazacoronand linked β-cyclodextrin dimer complexes of Brilliant Yellow tetraanion and their sodium(I) analoguesβ-Cyclodextrin = cyclomaltoheptaoseElectronic supplementary information (ESI) available: Molar absorbance and 2D NMR ROESY spectra of 1 and 2, and their complexes with 34–. See http://www.rsc.org/suppdata/ob/b2/b209759c/.
作者:Lee C. West、Oska Wyness、Bruce L. May、Philip Clements、Stephen F. Lincoln、Christopher J. Easton
DOI:10.1039/b209759c
日期:2003.2.27
Complexation of the Brilliant Yellow tetraanion, 34â, by two new diazacoronand linked β-cyclodextrin (βCD) dimers 4,13-bis(2-(6A-deoxy-β-cyclodextrin-6A-yl)aminoethylamidomethyl- 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 dmâ3
(NEt4ClO4) yielded complexation constants for the complexes 1·34â and 2·34â, K1
=
(1.08 ± 0.01)
à 105 and (6.21 ± 0.08)
à 103 dm3 molâ1, respectively. Similar studies at 298.2 K, pH 10.0 and I
= 0.10 mol dmâ3
(NaClO4) yielded K3
=
(4.63 ± 0.09)
à 105 and (3.38 ± 0.05)
à 104 dm3 molâ1 for the complexation of 34â by Na+·1 and Na+·2 to give Na+·1·34â and Na+·2·34â, 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)
à 102 and (1.8 ± 0.05)
à 103 dm3 molâ1, respectively, at 298.2 K and I
= 0.10 mol dmâ3
(NEt4ClO4). For complexation of Na+ by 1·34â and 2·34â to give Na+·1·34â and Na+·2·34âK2K3/K1
=
K4
= 8.6 à 102 and 9.8 à 103 dm3 molâ1, 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 34â 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+·1·34â and 1·34â and for Na+·2·34â and 2·34â. The lesser magnitudes of K2 and K4 for Na+·1 and Na+·1·34â compared with those for Na+·2 and Na+·2·34â 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 syntheses of 1 and 2 are described.
研究了两种新的二氮环状联接的 β-环糊精 (βCD) 二聚体 1 和 2 对亮黄四负离子 (34⁻) 的络合行为,实验在水相中进行。通过在 298.2 K、pH 10.0 和 I = 0.10 mol dm⁻³ (NEt4ClO4) 的条件下进行紫外-可见光分光光度法研究,得到了络合物 1·34⁻ 和 2·34⁻ 的络合常数,分别为 K1 = (1.08 ± 0.01) × 10⁵ 和 (6.21 ± 0.08) × 10³ dm³ mol⁻¹。相似的实验条件下,在 298.2 K、pH 10.0 和 I = 0.10 mol dm⁻³ (NaClO4) 下,得到 Na⁺·1 和 Na⁺·2 对 34⁻ 的络合的 K3 = (4.63 ± 0.09) × 10⁵ 和 (3.38 ± 0.05) × 10⁴ dm³ mol⁻¹,形成 Na⁺·1·34⁻ 和 Na⁺·2·34⁻。通过电位法研究了 Na⁺ 与 1 和 2 的络合,得到 K2 = (2.00 ± 0.05) × 10² 和 (1.8 ± 0.05) × 10³ dm³ mol⁻¹,实验在 298.2 K 和 I = 0.10 mol dm⁻³ (NEt4ClO4) 下进行。Na⁺ 与 1·34⁻ 和 2·34⁻ 的络合形成 Na⁺·1·34⁻ 和 Na⁺·2·34⁻,得出的 K2K3/K1 = K4 = 8.6 × 10² 和 9.8 × 10³ dm³ mol⁻¹。
1H44⁺ 的 pKa 值分别为 7.63 ± 0.01、6.84 ± 0.02、5.51 ± 0.04 和 4.98 ± 0.03,而 2H44⁺ 的 pKa 值为 8.67 ± 0.02、8.11 ± 0.02、6.06 ± 0.02 和 5.14 ± 0.05。与 2 的 K1 相比,1 的 K1 更大的原因在于 2 的八亚甲基联接链与 34⁻ 竞争 βCD 单元的环槽位置,而 1 的二亚甲基联接链的竞争能力较弱。类似的论证也适用于 Na⁺·1 和 Na⁺·2 的 K3 的相对大小。增强的静电吸引力可能解释了 Na⁺·1·34⁻ 和 1·34⁻ 与 Na⁺·2·34⁻ 和 2·34⁻ 之间 K3 > K1 的现象。Na⁺·1 和 Na⁺·1·34⁻ 的 K2 和 K4 较 Na⁺·2 和 Na⁺·2·34⁻ 小,归因于 2 的八亚甲基联接链为二氮环状结构提供了比 1 的二亚甲基联接链更疏水的环境。文中还描述了 1H NMR 光谱研究和 1、2 的合成方法。