Spectroscopic study of cyclen-based 19F NMR probe for detection of hydrogen sulfide.

A cyclen-based 19F NMR probe (F-cyclen) for hydrogen sulfide (H2S) has been prepared and evaluated for its complex formation ability with Cu2+ ions and responsivity to H2S. F-Cyclen was readily synthesized by reacting cyclen with 4-(trifluoromethyl)benzyl bromide. Visible absorption spectrophotometry showed that, same as the original cyclen, F-cyclen formed a 1:1 complex with Cu2+ ions. The 19F NMR signal of F-cyclen at 16.5 ppm gradually decreased in intensity with increasing CuCl2 concentration, with trifluoromethane sulfonic acid sodium salt (TFMSNa) used as an internal standard (0 ppm). When the Cu2+-F-cyclen complex was subjected to an increasing concentration of Na2S (as H2S donor), its corresponding 19F NMR signal of F-cyclen at 16.5 ppm gradually increased in intensity. The regression curve between the 19F NMR signal intensity ratio of F-cyclen to TFMSNa and Na2S concentration showed good linearity (r = 0.986) over the Na2S concentration range of 25-150 μM.