Research On Dendritic Fluorescent Probes For Heavy Metal Ions

Four simple 1,8-naphthalimide derivates were synthesized with aliphatic amine and 1,8-naphthalimide as primary raw materials, and their selectivity to heavy metal ions was examined, which determined that the receptors was put in the 4-C position of the 1,8-naphthalimide in the design of novel heavy metal ion probes in this paper.The intermediate N-(3-aminopropyl)-4-bromo-1,8- naphthalimide (APBN) was synthesized. Three chloride atoms in 2,4,6-trichloro-1,3,5-triazine (CNC) were substituted with APBN to give another intermediate TNPT with three APBN, and the three bromide atoms in TNPT were displaced by N,N-dimethylethanediamine to obtain a novel 1,8- naphthalimide fluorescent probe TMNPT. Their structures were characterized by FTIR, MS, 1H-NMR and elementary analysis. The effects of synthesis conditions and process methods after reaction finishing on the yields and purities of the products were also investigated.The solubility of APBN and TNPT was studied. APBN has good solubility in dimethylsulfoxide(DMSO)and N,N-dimethylformamide (DMF). It can be dissolved a little in N-methyl pyrrolidone(NMP), methanol, ethanol, acetone, tetrahydrofuran(THF), dichloromethane and chloroform, and it is slight soluble in water, acetonitrile and ethyl acetate. TNPT has good solubility in N-methyl pyrrolidone(NMP). It can be dissolved a little in DMSO, DMF, THF, chloroform and dichloromethane, and it is slight soluble in methanol, ethanol, acetonitrile, acetone and ethyl acetate. The photo-physical properties of TMNPT in DMF were studied. The UV-Vis maximum absorption of 2.0×10^-5 mol/L TMNPT in DMF was 431 nm with the molar absorption coefficient 5.00 M-1·cm-1, the fluorescence maxima wavelength of this TMNPT solution was 523 nm.pH has great effect on the fluorescence spectra of TMNPT. In the range of pH2.08～9.08, the fluorescence intensity of TMNPT rapidly decreased with the rise of pH, but the fluorescence wavelength was stable. When pH increased from 9.08 to 11.26, the fluorescence intensity of TMNPT slightly increased also with a fluorescence wavelength redshift from 535 nm to 555 nm.Compared to the reported dendritic heavy metal ion probes, TMNPT has better selectivity and sensitivity to Fe³⁺.