Transmembrane ion transport meditated by bis-macrocyclic bolaamphiphiles

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Abstract
A suite of fourteen bolaamphiphiles was prepared by a modular construction approach from a set of subunits. Macrocyclic tetraesters from maleic anhydride were linked by bis sulfide ‘linkage’ units to one of the two equivalent alkenes. The remaining alkene reacted with sulfur nucleophiles to add polar ‘head’ groups. The structural variables included head group type and charge, wall unit functionality, and variable hydrogen bonding capability at the linkage unit. The transport activities of the suite of compounds were assessed in a vesicle bilayer system. The most active materials had hydrogen bonding capability at the linkage unit, and ammonium or carboxylate charged head groups. The apparent kinetic orders greater than one and the selectivities observed are consistent with pore formation by aggregates in the bilayer membrane. The influence of structural variables on the transport activity suggest that the aggregates have defined properties that are amenable to structural control via synthesis.