Quantum chemical investigation on interaction of 5-fluorouracil with cucurbiturils

The electronic structure and stability of the encapsulated complexes of 5-fluorouracil (5FU) into cucurbit[n = 5-8]uril (CB[n]) in water were studied by means of PM6 and DFT computations. Among cucurbit[n]urils (n = 5-8) with different inner sizes, 5FU complexes with cucurbit[n = 6, 7]uril were more stable than those with cucurbit[n = 5, 8]uril. According to DFT computations, 5FU complex with the doubly inverted cucurbit[6]uril was the most stable and the mono- and doubly inverted isomers of CB[7] can also form relatively stable complexes. [GRAPHICS] .