Construction Of Novel Hemicyanine Dyes Based On Thiophene Donor-acceptor Systems And Exploration Of Their Application Properties

In view of the fact that the absorption wavelengths and emission wavelengths of most of the existing hemicyanine dyes with typical positive charge structure are still lied in the visible region,and most of the hemicyanine dyes using C=C double bond to detect anions have the problem of single fluorescence opening or fluorescence quenching form.To remedy the above disadvantages,thiophene（bithiophene and thiophene）was used as the electron donors,and indole iodonium salt,benzoindole iodonium salt and quinoline iodonium salt were used as the electron acceptors,which constructed four kinds of hemicyanine dyes with double positive charges in this paper.Basic properties of dyes were studied,and the application of dyes as probes was investigated in detail.The major research work of this paper was as follows:（1）Two probes ND-BTP and BI-BTP with A-π-D-π-A structure were prepared using indole iodonium salt and benzoindole iodonium salt as electron acceptors and[2,2’]-bithiophene-5-5’-dicarboxaldehyde as electron donor.The two probes exhibited emission at 658 nm and 683 nm in H₂O,respectively,and the Stokes shifts were respectively up to 116 nm and 91 nm.ND-BTP could highly recognize to SO₃^2-in PBS（10 m M,p H=7.4）with a lowest detection concentration of 27.6 n M,which was a type of ratio probe with high sensitivity.BI-BTP could sensitively identify Cl O^-and SO₃^2-/HSO₃^-,which was a kind of multi-purpose probe.In addition,the two probes exhibited low toxicity and good cell membrane permeability,which could realize the fluorescence imaging detection of recognized species in He La cells.（2）Based on the first idea,two small molecule fluorescent probes QI-BTP and QI-ST1 with symmetrical structure were synthesized by fixing quinoline iodonium salt as electron withdrawing group and thiophene（[2,2’]-bithiophene-5-5’-dicarboxaldehyde,thieno[3,2-b]thiophene-2,5-dicarbaldehyde）as electron donor groups.The two probes showed excellent photophysical properties,and the Stokes shift of QI-BTP reached 137 nm in H₂O.Probes QI-BTP and QI-ST1 efficiently recognized SO₃^2-in PBS（10 m M,p H=7.4）and H₂O solutions with detection limits of 14.0 n M and 10.5 n M,respectively.Simultaneously,the two probes also displayed the superiorities of good anti-interference ability,steady luminescence and broad p H application range.In addition,two probes exhibited low cytotoxicity and could realize the fluorescence imaging detection of exogenous and endogenous SO₃^2-in living cells.