Dipartimento Scienze Chimiche, University of Catania, viale A. Doria 6, 95125 Catania, Italy.
J Org Chem. 2010 Mar 5;75(5):1437-43. doi: 10.1021/jo902328y.
A mononuclear (M20) and a dinuclear (M40) uranyl chiral macrocyclic complex, incorporating both a salen unit containing two phenyl rings linked to a chiral diimine bridge and the (R)-BINOL unit, behaves as an efficient ditopic receptor for achiral and chiral quaternary ammonium salts. Binding affinities in chloroform solution have been measured for 1:1 complexes of many quaternary salts encompassing tetramethylammonium (TMA), tetraethylammonium (TEA), tetrabutylammonium (TBA), and acetylcholine (ACh), as well as trimethylanilinium (TriMAn), benzyltrimethylammonium (BnTriMA), (alpha-methylbenzyl)trimethylammonium and pyrrolidinium cations. The anion of the salt is bound by the hard Lewis acidic uranyl site, with an increasing binding efficiency on increasing the anion hardness (I(-) < Br(-) < Cl(-)), whereas CH-pi or pi-pi attractions by binapthyl moiety, or the salicylaldehyde unit, or the phenyl rings of diimine bridge ensure the recognition of the cation partner. Optimized structures of receptor-anion-cation ternary complexes obtained by MM calculations are supported by 2D-ROESY NMR measurements.
单核（M20）和双核（M40）铀手性大环配合物，同时包含一个水杨醛单元，其中含有两个连接到手性二亚胺桥的苯环和（R）-BINOL 单元，作为手性和非手性季铵盐的有效双位点受体。已经在氯仿溶液中测量了许多季铵盐的 1:1 配合物的结合亲和力，这些季铵盐包括四甲基铵（TMA）、四乙基铵（TEA）、四丁基铵（TBA）和乙酰胆碱（ACh），以及三甲铵（TriMAn）、苄基三甲基铵（BnTriMA）、（α-甲基苄基）三甲基铵和吡咯烷阳离子。盐的阴离子通过硬路易斯酸性铀位点结合，随着阴离子硬度的增加（I（-）<Br（-）<Cl（-）），结合效率增加，而BINAP 部分、水杨醛单元或二亚胺桥的苯环确保识别阳离子配体。通过 MM 计算得到的受体-阴离子-阳离子三元配合物的优化结构得到了 2D-ROESY NMR 测量的支持。
