10.1021/jo902328y.s001 Maria E. Amato Maria E. Amato Francesco P. Ballistreri Francesco P. Ballistreri Salvatore Gentile Salvatore Gentile Andrea Pappalardo Andrea Pappalardo Gaetano A. Tomaselli Gaetano A. Tomaselli Rosa M. Toscano Rosa M. Toscano Recognition of Achiral and Chiral Ammonium Salts by Neutral Ditopic Receptors Based on Chiral Salen-UO<sub>2</sub> Macrocycles American Chemical Society 2010 phenyl rings anion Neutral Ditopic Receptors Chiral Ammonium Salts chiral diimine bridge recognition chiral quaternary ammonium salts Lewis acidic uranyl site MM TBA TMA receptor CH cation NMR complex 2010-03-05 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Recognition_of_Achiral_and_Chiral_Ammonium_Salts_by_Neutral_Ditopic_Receptors_Based_on_Chiral_Salen_UO_sub_2_sub_Macrocycles/2786419 A mononuclear (<b>M20</b>) and a dinuclear (<b>M40</b>) uranyl chiral macrocyclic complex, incorporating both a salen unit containing two phenyl rings linked to a chiral diimine bridge and the (<i>R</i>)-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), (α-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<sup>−</sup> < Br<sup>−</sup> < Cl<sup>−</sup>), whereas CH−π or π−π 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.