A novel phenylacetylene derivative containing urea groups was synthesized and polymerized with a Rh catalyst to give the corresponding polymer, poly(1) with moderate number-average molecular weights. The poly(1) was soluble in toluene, CHCl3, CH2Cl2, THF, DMF, and DMSO, but insoluble in hexane, diethyl ether and MeOH. The specific rotation and circular dichroism(CD) spectroscopic studies revealed that poly(1) took predominantly one-handed helical structures. The presence of intramolecular hydrogen bonding was confirmed by liquid-state IR spectroscopy. The helicity of poly(1) could be tuned by temperature and anion. The helical conformation of the polymer was stable against Br- but susceptible to F-.
A novel conjugated polymer, poly(1), containing thiourea moieties in main chain is synthesized via Suzuki coupling reaction. The addition of cuprous ion quenches the fluorescence of poly(1), whereas the fluorescence changes slightly upon addition of other metal ions, exhibiting the fluorescent almost turn-off sensing ability towards Cu^+. When hydrogen peroxide was added to the solution containing poly(1) and Cu^+, Cu^+ was oxidized into Cu^(2+), resulting in the fluorescence recovery. The H_2O_2 released from glucose oxidation by glucose oxidase(GOD) also recovered the fluorescence of poly(1)/Cu^+ solution. The results indicated that the poly(1)/Cu^+ solution could serve as a sensing platform for hydrogen peroxide and glucose.
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 Cl-, 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.
