Cruz Carla, Delgado Rita, Drew Michael G B, Felix Vitor
Departmento Química, CICECO, Universidade de Aveiro, Portugal.
Org Biomol Chem. 2004 Oct 21;2(20):2911-8. doi: 10.1039/B412059K. Epub 2004 Sep 14.
The 28-membered octaazamacrocycle Me2[28]py2N6 was used as a receptor for the molecular recognition of aromatic and aliphatic carboxylate substrates. The receptor-substrate binding behaviour of (H6Me2[28]py2N6)6+ with an aliphatic (-O2C(CH2)nCO2-, n=0 to 4) and an aromatic (phthalate, isophthalate, terephthalate, 4,4'-dibenzoate, benzoate, 3- and 4-nitrobenzoate) series of carboxylate anions was evaluated by 1H NMR spectroscopy (carried out in DMSO-d6 at 300 K). Two association constants were found for most of the studied cases, except for 3- and 4-nitrobenzoate for which only K1 was determined. For oxalate, malonate, benzoate and dibenzoate anions only the beta2 constants could be obtained. The values of the first association constant cover a range from 2.86 to 3.69 (log units), and the second stepwise constant from 2.15 to 2.89 (also in log units). No special selectivity was found but the highest values were determined for adipate and the lowest for the monoprotic 3- and 4-nitrobenzoates. Single crystal X-ray structures of H6Me2[28]py2N6 6+ with terephthalate, 1, and 4,4'-dibenzoate (2) were determined showing supramolecular entities with general formula (H6Me2[28]py2N6).(substrate)2(PF6)2.4H2O. These anions are the building blocks of an extensive 3-D network of hydrogen bonds.
28元八氮大环化合物Me2[28]py2N6被用作识别芳香族和脂肪族羧酸酯底物的受体。通过1H NMR光谱法（在300 K下于DMSO-d6中进行）评估了(H6Me2[28]py2N6)6+与脂肪族（-O2C(CH2)nCO2-，n = 0至4）和芳香族（邻苯二甲酸酯、间苯二甲酸酯、对苯二甲酸酯、4,4'-二苯甲酸酯、苯甲酸酯、3-和4-硝基苯甲酸酯）系列羧酸根阴离子的受体-底物结合行为。除3-和4-硝基苯甲酸酯仅测定了K1外，大多数研究案例均发现了两个缔合常数。对于草酸根、丙二酸根、苯甲酸根和二苯甲酸根阴离子，仅能获得β2常数。第一步缔合常数的值范围为2.86至3.69（对数单位），第二步常数范围为2.15至2.89（同样为对数单位）。未发现特殊的选择性，但己二酸酯的值最高，单质子化的3-和4-硝基苯甲酸酯的值最低。测定了H6Me2[28]py2N6 6+与对苯二甲酸酯（1）和4,4'-二苯甲酸酯（2）的单晶X射线结构，显示出通式为(H6Me2[28]py2N6).(底物)2(PF6)2.4H2O的超分子实体。这些阴离子是广泛的三维氢键网络的构建单元。
