Study On The Synthesis And Fluorescence Properties Of High Resistance Porphyrin Fluorescent Probes

Porphyrin is an excellent near infrared fluorescent chromophore,on which the fluorescent probe based can effectively reduce the interference of background fluorescence in complex biological samples in the near infrared region,and improve accuracy and resolution of the detection.However,at present,mostly of porphyrin-based near-infrared fluorescent sensors are cationic probes.Neutral and anionic probes are rarely reported due to the weaker interaction of neutral molecules and anions in the process of recognition,and most of them achieve the purpose of identification through the chemical reaction with analytes and the changes of the fluorescence intensity.Therefore,it is more challenging to design and synthetize neutral and anion porphyrin-based fluorescent sensors.At the same time,it has been shown that the selectivity of fluorescent probe can be improved by changing the position of the substituents in the fluorophore.The improvement of the selectivity of the probe will avoid the influence of the interfering ions in the organism and the environment,which makes the probes more accurate for the detection of target compounds.In this paper,according to PET mechanism,we obtaind some porphyrin-based fluorescent sensors which can recognize sulfide anion,thiophenol and mercaptoamino acids.These probes display weak fluorescence due to the photo-induced electron transfer and high steric hindrance.However,the fluorescence is obviously improved when the PET process was inhibited upon addition of analytes.The main researches are as follows:First of all,we developed two kinds of fluorescent sensors M1 and M2 with different substituted hydroxyphenyl porphyrin as matrix and 2,4-dinitrobenzene sulfonyl moiety as recognition group for S2-detection,and the structure was characterized by 1HNMR and mass spectrometry.The test conditions of two probes were optimized,and the results show that the two probes had good response to sulfur ions.But,it was found that the probe M1 is more selective than M2 with comparison.According to the analysis,though the attack of mercapto amino acid is inhibited by the high steric hindrance of probe M1 to some extent,smaller sulfur ions are still able to enter.So,the steric hindrance effect is helpful to improve the selectivity.The linear range of the probe M1 was 3×10-6 mol/L ~9×10-6 mol/L,the detection limit was 40 nM,And the linear range of M2 was 1×10-6 mol/L ~8×10-6 mol/L,the detection limit was 62 nM.Secondly,based on the abovementioned analysis,we demonstrated a porphyrin-based fluorescent turn-on probe M3,which is based on the steric hindrance effect to distinguish thiophenol.The probe has a good response to thiophenol and a good linear relationship in the range of 1×10-6 mol/L ~7×10-6 mol/L,and the detection limit is 54 nM.Finally,we obtaind a fluorescence enhanced probe M4 containing ortho maleimide modified porphyrin which can be used in mercapto amino acid detection.Cyclization reaction occurs when the addition of mercapto amino acid(Cys、Hcy、GSH),which results in the inhibition of PET process and the recovery of fluorescence.At the same time,we detected 6 kinds of non-mercapto amino acids.The results show that the fluorescence spectras of the system do not change,which indicate that the probe M4 can be used to distinguish mercapto amino acids and non mercapto amino acids.