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

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 3AmPyH(2), DADPMH(2) and DADPEH(2) 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 center dot center dot center dot O hydrogen-bond interactions between the aforementioned guests and the crown ether hosts.