Recognition Studies of a Pyridine-Pendant Calix[4]arene with Neutral Molecules: Effects of Non-covalent Interactions on Supramolecular Structures and Stabilities

A new calix4]arene derivative containing hydrogen bond acceptors,5,11,17,23-tetra-tert-butyl-25,27-bis(4-pyridylmethyl)oxy]-26,28-dihydroxycalix4]arene (L), has been synthesized. ¹H-NMR titrations in chloroform-d werecarried out to investigate the host–guest chemistry ofL towards neutral molecules containing a widevariety of hydrogen bond donor groups such as aldehydederivatives of p-tert-butylcalix4]arenes(compounds 3 and 4), acetylacetone,1,2-diaminoethane, 2,6-diaminopyridine, catechol,resorcinol, hydroquinone, phthalic acid, isophthalicacid and terephthalic acid. L can formcomplexes with resorcinol, phthalic acid and catecholin 1 : 1 (log K = 3.13), 1 : 1 (log K = 5.41) andpolymeric fashions, respectively. In addition, thesolution structures of these complexes have beenrevealed by NOESY experiments. L forms a 1 : 1complex with resorcinol by hydrogen bonding and vander Waals interactions resulting in a supramolecularframework. The phthalic acid molecule interacts withL via hydrogen bonding and is included into thelower rim cavity of L.