Pessêgo, MárciaSilva, José P. daMoreira, JoséGarcía-Río, Luís2013-12-092013-12-092013Pessêgo, Márcia; Da Silva, José P.; Moreira, José A.; García-Río, Luis. Differences in Cucurbit[7]uril: Surfactant Complexation Promoted by the Cationic Head Group, ChemPlusChem, 78, 9, 1058-1064, 2013.21926506AUT: JMO01545;http://hdl.handle.net/10400.1/3231The formation of host/guest complexes between cucurbit[7]uril (CB7) and tetradecyltrialkylammonium bromide surfactants with trimethyl (C14TMA+), triethyl (C14TEA+), and tripropyl (C14TPA+) head groups was studied. Complexation was studied by ESI-MS, isothermal titration calorimetry (ITC), and NMR spectroscopy. The structure of the complexes is strongly dependent on the surfactant head group. Both 1:1 and 2:1 complexes are formed with all cationic surfactants. The magnitude of the K1:1 binding constants decreases with the alkyl length of the head group, whereas that of the K2:1 binding constants is independent of the nature of the surfactant head group. Distinct structures were found for the 1:1 and 2:1 complexes. C14TMA+ and C14TPA+ surfactants form 1:1 inclusion complexes that comprise the head group close to the CB7 portal and 2:1 external complexes with both host molecules near the head group. The 1:1 complexes between C14TEA+ and CB7 showed that the head group was centered inside the CB7 cavity, whereas in the 2:1 complex the second molecule of CB7 was located at the end of the main alkyl chain.engjournal article2013-12-04http://dx.doi.org/10.1002/cplu.201300164