Perforated monolayers: design and synthesis of porous and cohesive monolayers from mercurated calix[n]arenes

Mercuration of a series of O-alkylated calix(n)arenes (produced via reaction of tetrahydroxycalix(4)arene, pentahydroxylcalix(5)arene, hexahydroxycalix(6)arene, and heptahydroxycalix(7)arene with n-bromobutane and with n-bromohexadecane) afford an homologous series of calixarene-based surfactants that form stable monolayers at the air-water interface. Surface pressure-area isotherms, measured for each calixarene, yield limiting areas that are in excellent agreement with values predicted from space-filling models, if it is assumed that the base of each calixarene is parallel and the alkyl chains are perpendicular to the water surface. Introduction of malonic acid to the aqueous subphase results in a substantial increase in the cohesiveness of films derived from calix(4)arene-, calix(5)arene-, and calix(6)arene-based surfactants, as judged by changes in surface viscosity. X-ray photoelectron spectroscopic analysis of a Langmuir-Blodgett film, produced from a malonic acid stabilized calix(6)arene monolayer, shows a carboxylate/mercury ratio of 0.9.