OCTOPUS MOLECULES AT THE AIR-WATER-INTERFACE - MECHANICAL CONTROL OVER TENTACLE ORIENTATION

Alkylation of 37,38,39,40,41,42-hexahydroxycalix[6]arene with a series of brominated poly(ethylene glycol) monomethyl ethers [i.e., CH3O(CH2CH2O)nCH2CH2Br, where n = 0, 1, 2, and 3] yields octopus molecules 1a, 1b, 1c, and 1d, respectively. Examination of the monolayer properties of 1b and 1c reveals that their polyether "tentacles" lie at the air-water interface at low surface pressures and are forced down into the subphase when the film is compressed. Similar behavior has been observed for 1d, but only over a saturated aqueous NaCl subphase. In the condensed state, calixarenes 1a-1d have their tentacles tucked beneath their aromatic core. For calix[6]arene 1a, the polyether moieties have been found to be too short to be moved back and forth between surface of water and the subphase. Introduction of bulky p-tert-butyl groups onto the upper rim of the calix[6]arene framework significantly reduces intermolecular polyether interactions. Qualitatively, similar behavior has been found with analogous calix[4]arene-based octopi.