Synthesis and ion transport activity of oligoesters containing an environment-sensitive fluorophore

A series of oligoesters based on a rigid triphenyl-diyne core is described. The molecules were readily synthesized from key intermediates, and retained good solubility properties. One of the compounds displayed modest ion transport activity in vesicles, was capable of forming highly conducting single channels in planar bilayers and exhibited an irregular non-linear current-voltage response. All the reported molecules had minimal aqueous fluorescence while being highly fluorescent in less-polar media including lipid vesicles; their partitioning into the membrane could be monitored by a significant blue-shift and increase in fluorescence intensity, as well as a decreased extent of quenching in vesicles over that in water. The combined data indicated that the compounds are highly aggregated in aqueous solution, which limits their membrane partitioning and ion transport activity, in agreement with mechanisms proposed for other 'simple' oligoester channels.