Self-assembly and characterization of a giant metallocycle

A giant, 100-membered metallocycle 3 was prepared via coordination bond-based self-assembly from W-shaped ligand 9 and a palladium complex. Metallocycle 3 may create three topologically discrete subcavities, thus capable of binding up to three molecules of a diamide guest by hydrogen-bonding interactions. Elemental analysis, 1H NMR, and the ESI-mass spectra, and vapor pressure osmometry (VPO) data were all consistent with the structure of 3. N,N,N′,N′-tetramethylterephthalamide G was used as a guest for the binding study, and ESI-mass spectrum clearly displayed a characteristic, intense peak at m/z 1542 (41%), attributed to the fragment [3·G3-3CF3SO3]3+ of 1:3 (host/guest) complex. The 1H NMR titration experiments gave association constants of 2300 ± 300 and 1200 ± 200 M−1 in CDCl3 at 25 °C for two identical outer cavities, with weak positive cooperativity (Hill coefficient h = 1.3).