SYNTHESIS AND COMPLEXATION PROPERTIES OF NEW UNSYMMETRICAL CRYPTANDS

Twelve novel unsymmetrical cryptands (1-12) containing various units (methylene, 2-methylenylpropylene, pyridine-2,6-diyldimethylene, o- and m-xylylene) each in two bridges have been synthesized by a one-step cyclization procedure. These cryptands were obtained by treating tetraalcohols 15-17, obtained from diethanolamine and diglycolyl dichloride followed by reduction or from diethanolamine and the appropriate oligoethylene glycol dichloride or ditosylate, with methylene chloride, 3-chloro-2-(chloromethyl)-l-propene, alpha,alpha'-dibromo-o-xylene, alpha,alpha'-dibromo-m-xylene, and 2,6-pyridinediyldimethyl ditosylate. Cryptancls 7 and 11, containing two acetal functions, were obtained in yields of 59 and 40%, respectively. Bis(2-methylenepropylene)-bridged cryptand 4 was independently synthesized by another method. Complexation properties of nearly all of these cryptands with the alkali metal cations were studied by an NMR technique. Some of the results were verified by a calorimetric titration technique. Cryptands 5 and 9, containing a 2,6-pyridinediyldimethylene unit in two bridges, and 11, containing a methylene unit in two bridges, showed high selectivity for potassium over sodium ions by factors ranging from 40 to 200. Bisacetal-containing cryptand 7 exhibited high selectivity for sodium over potassium ions with a selectivity factor of over 1000.