Host-Guest Complexes and Pseudorotaxanes of Cucurbit[7]uril with Acetylcholinesterase Inhibitors

Pseudorotaxanes may be assembled in aqueous solution using dicationic acetylcholinesterase inhibitors, such as succinylcholine, BW284c51, and alpha,omega-bis(trialkylammonium)alkane dications (or their phosphonium analogues), its bolaform axles and cucurbit[7]uril (CB[7]) as the wheel. With the exceptions of the shorter [(CH3)(3)N(CH2)(n)N(CH3)(3)](2+) (n = 6, 8) dications, the addition of it second CB[7] results in the translocation of the First CB[7], Such that the hydrophobic -NR3+ and -PR3+ end groups (R = Me or Et) are located in the cavities of the wheels, while the central portion of the axles extend through the CB[7] portals into the bulk solvent. In the case of the [Quin(CH2)(10)Quin](2+) (Quin = quinuclidinium) dication, the CB[7] host(s) resides only on the quinuclidinium end group(s). The 1.1 host-guest stability constants range from 8 x 10(6) to 3 x 10(10) M-1 and are dependent oil both the nature of the end group as well its the length and hydrophobicity of the central linker. The magnitude of the stability constants for the 2.1 complexes closely follow the trend observed previously for CB[7] binding with the NR4+ and PR4+ cations.