Research On Novel 1,8-naphthalimide-based Cationic Spectral Probes

H⁺ and Cu²⁺ play important roles in environmental and biological systems.H⁺participates in many chemical and physiological processes,such as steel rusting,cell proliferation and apoptosis,ion transport,muscle contraction and so forth.As a trace element,Cu²⁺ plays a major role in blood and nervous systems.The loss or excess of Cu²⁺ will cause many diseases.So the detection of H⁺ and Cu²⁺ is very important.Spectral probes have been widely used in monitoring ions due to their convenient operation,high sensitivity and selectivity,as well as low cost.In this work,three spectral probes for H⁺ and Cu²⁺ were designed and synthesized with1,8-naphthalimide as fluorophore.The structure of the probes was characterized.The responsiveness of the probes to H⁺ and Cu²⁺ were studied by UV-vis absorption and fluorescence spectra.The sensing mechanism and cytotoxicity were also examined.A 1,8-naphthalimide-based spectral H⁺ and Cu²⁺ probe with receptors from hydrazine and furfural（BNFA）: In CH3CN/H2O（1/1,v/v,pH=1.9⁵.2）,the dye could be used to monitor Cu²⁺ via triple channels: the reduction of UV-vis absorption（4.6-fold）and the fluorescence intensity（5.4-fold）,as well as the fluorescence blueshift（19 nm）.The absorbance at 461 nm（A461）and fluorescence intensity at 558nm（F558）showed good linear relationship with the concentration of Cu²⁺ in the range of 0⁶ μM.The detection limits evaluated by colorimetric and fluorescent titration were 6.10×10-7 and 2.62×10-7 mol/L,respectively.While in CH3CN/H2O（1/1,v/v,pH=6.2¹2.0）,BNFA could be used as a triple-channel colorimetric probe and a fluorescence probe for H⁺.BNFA could recognize H⁺ through the increase of absorbance ratio at 573 and 461 nm（A573/A461）,the decrease of the fluorescence intensity at 552 nm（F552）,and the color change from light purple to dark purple.A 1,8-naphthalimide-based spectral H⁺ and Cu²⁺ probe with receptors from hydrazine and 3-methyl-2-thiophenecarboxaldehyde（BNMT）: In CH3CN/H2O（1/1,v/v,pH=2.2⁶.0）,BNMT also could be used to monitor Cu²⁺ via triple channels:the reduction of UV-vis absorption（6.1-fold）and fluorescence（23-fold）intensity,as well as fluorescence blueshift（43 nm）.The absorbance at 471 nm（A471）and fluorescence intensity at 571 nm（F571）showed good linear relationship with the concentration of Cu²⁺ in the range of 0²5 μM.The detection limits evaluated by colorimetric and fluorescent titration were 3.12×10-7 and 2.44×10-7 mol/L,respectively.While in CH3CN/H2O（1/1,v/v,pH=6.0¹2.1）,BNMT could be used as a triple-channel colorimetric probe and a fluorescence probe for H⁺.BNMT could recognize H⁺ through the increase of absorbance ratio at 581 and 471 nm（A581/A471）,the decrease of the fluorescence intensity at 571 nm（F571）,and the color change from shallow yellow to deep blue.A 1,8-naphthalimide-based fluorescent Cu²⁺ probe and colorimetric pH switch with receptors from hydrazine and tris（hydroxymethyl）methyl aminomethane（BNGT）: In CH3CN/H2O（1/99,v/v,pH=5.2⁶.5）,BNGT could be used to monitor Cu²⁺ with the increase of fluorescence intensity at 392 nm（9.2-fold）and 754 nm（9.4-fold）,accompanied by the change of florescent color from colorless to bright blue.The detection limits evaluated by fluorescent titration at 392 nm and754 nm were 2.64×10-7 and 2.45×10-7 mol/L,respectively.In CH3CN/H2O（1/99,1/1,8/2,v/v）,BNGT could recognize the change of 0.2 pH units（from 5.8 to 6.0）via triple channels: the increase of maximum absorption wavelength and intensity,as well as the color change from colorless to magenta.As Cu²⁺ spectral probes,BNFA,BNMT and BNGT all exhibit 1:1 stoichiometry to Cu²⁺,and the detection process was irreversible.While as H⁺ probes and pH switches,these three probes could monitor H⁺ reversibly.They all have high selectivity and sensitivity,as well as strong anti-interference for the recognition of H⁺and Cu²⁺.Besides,it is worth mentioning that BNFA is more cytotoxic and BNGT is very low cytotoxic,whereas BNMT is almost noncytotoxic.