Twisted Cucurbit[n]urils

Abstract

Two new twisted cucurbiturils, cucurbit[13]uril (tQ[13]) and cucurbit[15]uril (tQ[15]), have been synthesized and separated, and their structures have been confirmed by NMR spectroscopy and MALDI-TOF mass spectrometry together with the X-ray structures of two new complexes, {Dy(H2O)4Cd(H2O)4tQ[13]}·2.5[CdCl4]·65H2O and {Cd0.5(H2O)2tQ[15]}·[CdCl4]·47H2O. tQ[15] is the largest cucurbit[n]uril (Q[n]) in the Q[n] family reported to date. The X-ray diffraction studies of both complexes indicated that these large tQ[n]s effectively exhibit two different cavities-a central cavity and two side cavities. Preliminary host-guest behavior by each of the new systems was investigated by NMR studies.

Stimuli‐Responsive Cucurbit[n]uril‐Mediated Host‐Guest Complexes on Surfaces

“…Increasing the host cavity size from CB [5] to CB [8], increases the size of the guests forming 1 : 1 complexes. [5] Interestingly, the CB [8] host offers the possibility of including two guests.…”

“…[5] Interestingly, the CB [8] host offers the possibility of including two guests. [17,18] CB [8] includes either two different guests to form a 1 : 1 : 1 heteroternary complex or twice the same guest to form a 1 : 2 homoternary complex. Non-cooperative binding is conceived to be the most probable binding scenario for binding of two guests to CB [8].…”

“…[17,18] CB [8] includes either two different guests to form a 1 : 1 : 1 heteroternary complex or twice the same guest to form a 1 : 2 homoternary complex. Non-cooperative binding is conceived to be the most probable binding scenario for binding of two guests to CB [8]. [13,17,18] In the case of hetero-complexation, the electron-poor guest binds first to the CB [8] followed by the electron-rich guest in agreement with donor-acceptor behavior.…”

“…Non-cooperative binding is conceived to be the most probable binding scenario for binding of two guests to CB [8]. [13,17,18] In the case of hetero-complexation, the electron-poor guest binds first to the CB [8] followed by the electron-rich guest in agreement with donor-acceptor behavior. [10,13] CB [8] hetero- Table 1.…”

“…[1,2] CB[n] are methylene bridged glycoluril oligomers that appear in the condensation of glycoluril and formaldehyde. [3,4,5] This condensation reaction yields different CB[n] homologues ranging from CB [5] to CB [8], but also traces of higher homologues were isolated. [3][4][5][6][7][8] CB[n] have a common depth, but their width and volumes differ progressively with their ring size (Table 1, Figure 1).…”