Proton-Ionizable Crown Compounds. 2. Synthesis, Complexation Properties, and Structural Studies of Macrocyclic Polyether-Diester Ligands Containing a 4-Hydroxypyridine Subcyclic Unit

A series of macrocyclic polyether-diester ligands containing a proton-ionizable 4-hydroxypyridine subcyclic unit has been prepared. These new macrocyclic ligands form stable complexes with both alkylammonium perchlorate salts and with alkylamines. The crystal structure for one of these complexes with an alkylamine shows that the hydroxy proton has been donated to the amine with the resultant formation of a 4-pyridone unit. Chiral dimethyl-and diphenyl-substituted macrocycles containing the 4-hydroxypyridine subcyclic unit exhibit chiral recognition for the enantiomers of 2-(1-naphthyl)ethylamine and their hydrogen perchlorate salts.