[reaction: see text] NMR diffusion measurements were used to probe the differences in the characteristics of the hexameric capsule of [c]-undecane resorcin[4]arene (1b) in a CDCl(3) solution in the absence and presence of tetrahexylammonium bromide (THABr). It was found that the nonencapsulated THABr forms a 1:1 complex with 1b, which is in fast exchange with its constituents. We found that water molecules seem not to participate in the construction of the THABr hexameric capsule of 1b in a CDCl(3) solution, in contrast to the finding in the absence of THABr, where the major species in CDCl(3) seems to be [(1b)(6)(H(2)O)(8)].