Synthesis And Properties Of Metal Ion Fluorescent Probe Molecules Based On Rhodamine B

Although some transition metal ions are indispensable to the human body,the serious environment pollution,which may result in heavy harm to human health,has been a big problem caused by excessive amount of metal ions with the development of the industrial society.It is urgent to find convenient,rapid and precise methods to detect the metal ions.The fluorescence sensors detect the metal ions qualitatively and quantitatively according to the relationship between the concentration of the metal ions and the fluorescence properties via measuring the changes of the fluorescence spectrum.The fluorescence sensors have attracted great interest due to the low cost,high sensitivity,less toxicity and good selectivity comparing to the other detecting methods.In this paper,three new fluorescence sensors were designed and synthesized by using rhodamine B as the chromophoric group,and it was realized to detect the Cu2+ and Hg2+in aqueous solution qualitatively and quantitatively.The intermediates containing special functional groups were selected to prepare the hydrazine derivative as the recognition group,and then the target fluorescence sensors were prepared by connecting the intermediates to rhodamine B.The structures of the three compounds were characterized by using 1HNMR,mass spectrometry and elemental analysis techniques,and the sensing properties and the mechanisms to the transition metal ions of the target sensors were studied detailedly.A characteristic ringopen reaction of 1 occurred only in the presence of Cu2+,and the color of the solution changed from colorless to pink quickly,which made it realized to tell the presence of Cu2+with naked-eye.The intensity of the fluorescence of 1(575 nm,the characteristic fluorescence of rhodamine B)increased to maximum value in 15 min after mixed with Cu2+,the detection limit was measured of 8.99×10-8 mol/L,and the binding ratio between 1 and Cu2+ determined using Job ’s Plot was 1to2.The sensing properties of 1 applied to living cells were also studied,and the results showed that compound 1 could permeate through the cell membrane and recognize the Cu2+ in living cell successfully.The color of the solution of compound 2 changed from colorless to pink,and to deep blue rapidly in the presence of Cu2+.The detection limit was measured of 8.81×10-7 mol/L,and the binding ratio between 2 and Cu2+ determined using Job’s Plot was also 1to2.The color of the solution of compound 2 changed from colorless to pink in the presence of Hg2+quickly after adding a little amount of Cu2+,however the color of the solution of 2 in the presence of Hg2+ could not change rapidly in the absence of Cu2+.These results indicated that 2 can be good naked-eye chemosensor to Cu2+ and Hg2+ with high selectivity.The sensing mechanisms of compound 1 and 2 were also studied using Gaussian program,mass spectrometry and Job’s Plot methods.The structure of compound 3 was designed for sensing metal ions contained in biological macromolecules based on the results reported in the literatures,however the properties of 3 still haven’t been studied because of the short of the time.