Highly constrained guests in complexes ofp-tert-butylcalix[6]arenedianion: Pentane-1,5-diammonium and choline

Abstract

The structures of the complexes of choline and pentane-1,5-diammonium withp-t-bu-calix[6]arenedianion were determined. Both salts display the calixarene moiety at 1,2,3-alternate conformation, withtwo concave surfaces formed by three aromatic rings, and the phenolate units are at distal positions,interacting with two phenol units by hydrogen bonds.The salt of pentane-1,5-diammonium shows the diammonium connecting both calixarene dianionunits, and one NH3+is locatedendo-calix position and the other occupies anexo-calix position. Thet-butylgroups and the calix cavity constrains the pentane-1,5-diammonium chain to nearsyn-eclipsedandgaucheconformations. The other semi-calix accomodates a THF solvent molecule. The salt of cholineshows the trimethylammonium groups of choline units immersed in these concave surfaces, with severalinteractions N+–C–H—pinteractions with the aromatic semi-cavities