Ammonium–crown ether based host–guest systems: N–H⋯O hydrogen bond directed guest inclusion featuring N–H donor functionalities in angular geometry

Abstract

This article demonstrates crown ether based host–guest adduct formation in a series of crystalline solids 1–7, in which ammonium-type cationic guests have been integrated with various crown ethers. Addition of more than two equivalents of perchloric acid to an acetonitrile solution of 3-aminopyridine (3AmPy), 4,4′-diaminodiphenylmethane (DADPM) or 4,4′-diaminodiphenylether (DADPE) generates the doubly protonated anilinium (or ammonium) cationic species (written as 3AmPyH₂, DADPMH₂ and DADPEH₂ respectively) which act as guests to the various crown ether hosts present in solution. The relevant compounds crystallize as their perchlorate salts and they have been structurally characterized through X-ray diffraction. The major driving force towards host–guest complexation in the compounds 1–7 is found to be the N–H⋯O hydrogen-bond interactions between the aforementioned guests and the crown ether hosts.