Inhibition of C(2)-H/D exchange of a bis(imidazolium) dication upon complexation with cucubit[7]uril

摘要

Inclusion of the α,α'-bis(3-(1-methylimidazolium))-p-xylene dication in cucurbit[7]uril (CB[7],K_CB[7] = (4.3 x 10~9 M~(-1),with C-H-"O=C hydrogen bonding between the guest C(2)-protons and the carbonyl oxygens of the host portals,inhibits the H/D exchange for the C(2)-proton with k_(OD) (25 °C,D_2O) decreasing from 1.2 x 10~3 M~(-1) s~(-1) (pK_a = 22.3) in the absence of CB[7] to 0.9 M~(-1) s~(-1) (pK_a = 25.4) in the presence of 1.1 equiv.CB[7].