Selective transportation of metal ions by photo-induced crown ether compounds

A novel photoresponsive system that we call a photo-induced crown ether (PIC) is described, in which excimers are used to fix the conformation of a molecule for relatively long periods. 1,n-bis(3-(1-pyrenyl)propylcarboxy)-oxaalkanes (DP3n: n=3–6), linear oligooxyethylenes with pyrenyl groups at both ends, were prepared and investigated to determine whether they might work as PICs. DP35 molecules were found to capture and transport calcium ions more effectively when they were irradiated. This result is consistent with the finding that five-unit crown ether transported the greatest amount of calcium ions.