UREA-BASED POLYACETYLENES AS AN OPTICAL SENSOR FOR FLUORIDE IONS

Novel acetylenes carrying urea groups, 1-（4-ethynylphenyl）-3-（4-nitrophenyl） urea （1）, 1-（4-propargyl）-3-（4- nitrophenyl） urea （2）, were synthesized and polymerized with rhodium catalyst. Polymers [poly（1） and poly（2）] with moderate molecular weights were obtained in good yields. The anion sensing ability of poly（1） and poly（2） was estimated using the tetra-n-butylammonium （TBA） salts of a series of anions in DMF. Upon the addition of F, the color of the DMF solution of poly（1） and poly（2） immediately turned to a different color, while the color of solution changed slightly upon addition of C1, HSO4-, Br-, and NO3-, indicating the F- sensing ability of poly（1） and poly（2）. The 1H-NMR titrations of poly（1） revealed that the colorimetric response of poly（1） was triggered by the urea/F interaction through the hydrogen bonding and/or deprotonation process. The absorption spectra titration and Hill plot analysis were carried out to measure the F binding ability, and the Hill coefficient in the poly（1）/F complexation was found to be 5.8. This result clearly indicated that this binding mode between poly（1） and F was based on a positive homotropic allosterism.