Interaction of cucurbit[n]urils (n=6∼8) with three N-benzyl cage guests

Three N-benzyl cage guests with two moiety probes for different cucurbit[n]urils (n=6 similar to 8) have been synthesized and characterized by H-1 NMR spectroscopy and ESMS method, and they are N-benzylhexamethylene tetramine bromide (1), N-benzylquinuclidine bromide (2) and N-benzyl-1,4-diazabicyclo [2,2,2]octane bromide (3), and the probes are benzyl and three different small quaternary ammonium cage. Experimental results by using H-1 NMR technique reveal that the cucurbit[6]uril only includes the benzyl moiety of the title guest to form unsymmetrical host-guest complex with a 1:1 ratio; the cucurbit[7]uril selectively includes the benzyl moiety of 1 and 3, however, selectively includes cage moiety of 2, also to form unsymmetrical host-guest complex with a 1:1 ratio, the cucurbit[8]uril only includes the benzyl moiety of the title guest to form symmetrical host-guest complex with a 1:2 ratio.