Synthesis Of N/O-donor Metal Complexes With 2D Structure And Study Of Fluorescence Sensing Performance In Aqueous Solution

Metal coordination polymer is one of the most popular materials in recent years,which is an important development of molecular coordination chemistry.There are now a variety of metal coordination polymer systems with a wide range of applications,among which the development of sensors is remarkable.These sensors are designed to detect explosives,antibiotics and metal ions conveniently,quickly and sensitively.They have practical significance and application prospect.The structural stability of metal coordination polymers makes them reusable compared with organic molecules,so they are a kind of important and practical sensors.In this paper,semi-rigid polycarboxylic acid and β-diketone ligands were used as primary ligands,and nitrogen heterocyclic ligands were used as auxiliary ligands to construct transition metal and rare earth complexes.The application of complexes in fluorescence detection in aqueous solution was discussed in detail as follows:(1)Ligand L1 was synthesized from 3-hydroxybenzoic acid methyl ester and 1,3,5-tribromo-2,4,6-trimethylbenzene by simple reaction.Two transition metal complexes {[Zn(HL)(bpy)1.5]·2DMF·3H2O}(1)and {[Cd(HL)(phen)(H2O)]2·H2O}n(2)were synthesized by L1,nitrate of transition metal and nitrogen heterocyclic ligands by solvothermal method.The fluorescence properties of complex 1 and 2 were studied and it was found that the complex 1 could be used as a ratiometric fluorescent sensor,which can efficiently and sensitively detect tryptophan in aqueous solution.The detection limit of complex 1 for tryptophan was 29.4 nM,which was better than most reported literatures.Complex 2 selectively detected trinitrophenol via fluorescence quenching.The Ksv of complex 2 for detection of trinitrophenol was 3.4×104 M-1 and the detection limit was 0.91 μM.(2)Two transition metal complexes with two-dimensional structure{[Zn(HL)(phen)]· DMF ·H2O} n(3)and {[Cd(HL)(bpy)]· DMF ·2H2O}n(4)were obtained by solvothermal method by reacting L1,nitrate of transition metal and nitrogen heterocyclic ligands.Complexes 3-4 were stirred in EuCl3/TbCl3 aqueous solution.Post-modified complexes Eu@3、Tb@3 and Tb@4 were successfully obtained,which were functionalized by rare-earth elements.The fluorescence properties of Tb@3 and Tb@4 were fully characterized and it was found that Tb@3 and Tb@4 could be used as quenched probes,which efficiently and sensitively detected phosphate and iron ion in aqueous solution.The Ksv of Tb@3 for phosphate detection was 9.9×104 M-1 and the detection limit was 21 nM.The Ksv of Tb@4 for iron ion detection was 6.3×104 M-1 and the detection limit was 3.76 μM.(3)The ligand L2,2-(4-aldehydephenyl)imidazole[4,5-f]1,10-phenanthroline was synthesized from 5,6-phenanthrolindione and terephthalaldehyde.Four mononuclear rare earth complexes[Ln(dbm)3(L2)]n{Ln=Eu(1),Sm(2),Gd(3),Tb(4);dbm=dibenzoylmethane}(5-8)were obtained by solvent volatilization after the reaction of L2,dbm and chloride salts of rare earth metal.The fluorescence properties of complex 5 were characterized.It was found that the fluorescence properties of complex 5 were influenced by solvents and showed excellent fluorescence performance in aqueous solution,which could be used as a multifunctional probe for fluorescence detection.The Ksv of complex 5 for ciprofloxacin was 1.4 ×105 M-1 and the detection limit was 0.43 μM,the Ksv of complex 5 for iron ion detection was 2.3 ×104 M-1 and the detection limit was 7.03 μM.