Studies On The Synthesis, Characterization, And Antibacterial Activity Of 2-aminoterephthalic Acid Schiff Base Coordination Polymers

Schiff base metal coordination polymers are a class of compounds that have been studied extensively because of their attractive chemical and physical properties, and their wide-ranging applications in numerous scientific areas. Thus, studies on the synthesis of novel Schiff base coordination polymers, their characterization and application has vital significance.2-aminoterephthalic acid is an important organic intermediate. It could be an interesting co-monomer for the aniline copolymerization because it contains two carboxyl groups linked to the aromatic ring. In this paper, there Schiff base ligands derived from the reaction of 2-aminoterephthalic acid and 2-hydroxy-1-naphthaldehyde(H3L1),2-aminoterephthalic acid and o-vanillin(H3L2) 2-aminoterephthalic acid and salicylaldehyde (H3L3) have been prepared, and twelve coordination polymers of transition or lanthanidenitrates metal with these ligands. The compounds were characterized by elemental analysis, IR spectrum, UV-vis spectrum, 1H NMR, X-ray diffraction single-crystal analysis, TG-DTG, conductance measurements and gel permeation chromatography. The fluorescence spectra and antibacterial activity of ligands and partial polymers were studied.The crystal of Cu(C19H11NO5)n·n(C2H6O) was obtained of 2-aminoterephthalic acid and 2-hydroxy-1-naphthaldehyde(H3L1) with copper acetate. X-ray diffraction single-crystal analysis is carried out for the structural determination. The crystal data are as follows:Orthorhombic system, space group pbca, a= 8.7745 (18) A, b= 18.613(4) A, c= 24.644(5) A,α= 90°;β= 90°,γ= 90°, V= 4024.9(14) nm3, Z= 8, dcalcd= 1.462g/cm3, R1= 0.0521, wR2=0.1647(total reflections), The metal iron Cu (Ⅱ) is five-coordinated with a distorted square-pyramidal geometry. Each ligand serves as a bridging ligand to link Cu(Ⅱ) ions through carboxy] oxygen atoms, leading to a two-dimensional coordination polymer.The compositions of transition metal polymers with Schiff base ligand from 2-aminoterephthalic acid and 2-hydroxy-1-naphthaldehyde(H3L1) were confirmed to be:[C,9H11NO5Cd]n·3nH2O, [C19H10NO5Zn]n·H2O, [C19H11NO5Cd]n·3nH2O。The compositions of transition metal polymers with Schiff base ligand from 2-aminoterephthalic acid and o-vanillin(H3L2) were confirmed to be: [C16H10O6NCu]n-2nH20, [C16H10O6NCo2]n·3nH2O, [C16H10O6NMn2]n·nH2O, [C16H10O6NNi2]n-nH20.The compositions of transition or lanthanidenitrates metal polymers with Schiff base ligand from 2-aminoterephthalic acid and salicylaldehyde (H3L3) were confirmed to be:[C15H9NO5Cu]n-n(CH3CH2OH)(H2O), [C15H8NO5Co2·4H2O]n, [C15H8NO5Ce·(NO3)2]n·n(CH3CH2OH),[C15H8NO5Ce·(NO3)2]n·n(CH3CH2OH).All of the complexes are stable and can be preserved in the air for a long time. The complexes are colored and powered substances. The nitrogen atom of Schiff base, oxygen atom of hydroxybenzene. carboxyl in ligands were all coordinated to the metal ions. Water molecules and solvent molecules are coordinated or lied in crystal substances. Carboxyl is coordinated to the metal ions in a monodentate or bidentate fashion, and the nitrate ions in a monodentate fashion.Combinating Achar differential and Coats-Redfern integral method which fits the thirty kinetic equations, the calculating program of thermal decomposition for complexes was designed. The kinetic equations of corresponding kinetic parameters were obtained. The kinetic parameters include E, A, order of reaction and correlation coefficient etc. The activation entropyΔS≠and activation free-energyΔG≠for some thermal decomposition steps were also calculated.The thermal decomposition kinetic function of [C19H11NO5 Cd]n·3nH2O in step(2) may be expressed as f(α)=1/4(1-α)[-1n(1-α)]-3, and the kinetic equation of thermal decomposition may be expressed as:da/dt=A-exp(-E/RT)-f(a)=A·exp(-E/RT)·1/4(1-α)[-1n(1-a)]-3, E=1268.7 kJ·mol-1 lnA=216.8, r=0.9812,ΔS≠=1501.5 J·mol-1·k-1,ΔG≠=244.7 kJ-mol-1.The thermal decomposition kinetic function of [C16H10O6NCo2]n-3nH20 in step(1) may be expressed, as f(α)=1/4(1-α)[-1n(1-α)]-3, and the kinetic equation of thermal decomposition may be expressed as:da/dt=A·exp(-E/RT)-f(a)= A·exp(-E/RT)·1/4(1-α)[-1n(1-α)]-3, E=222.7 kJ-mol-1, lnA=67.97, r=0.9975,ΔS≠=318.6 J·mol-1·k-1,ΔG≠=107.1 kJ-mol-1.The thermal decomposition kinetic function of [C15H8NO2·4H2O]n in step(1) may be expressed asf (α)=1/4(1-α)[-1n(1-a)]-3, and the kinetic equation of thermal decomposition may be expressed as:da/dt=A·exp(-E/RT)·f(α)= A·exp(-E/RT)·1/4(1-α)[-1n(1-α)]-3, E=343.8 kJ-mol-1, lnA=79.93, r=0.9871,ΔS≠=416.0 J·mol-1·k-1,ΔG≠=152.4kJ·mol-1.All ligands and part of polymers with fluorescence properties were studied. The excitation and emission peak wavelengths(λem/λem) of the Schiff base polymers of [C15H8NO5Co2·4H2O]n, [C19H11NO5Cd]n·3nH2O. [Cu(C19H11NO5)n·n(C2H6O),[C16H10O6NCu]n·2nH2O are 366.8 nm/438.6 nm,372 nm/493 nm,368 nm/487 nm,368 nm/476 nm respectively in fluorescence spectra. The excitation peaks and the emission peaks of the polymers have changed except [C15H8NO5Co2·4H2O]n compared with the ligands. and the fluorescence intensity of the Cu(Ⅱ)polymers decreased significantly.Spectrophotometric method was used to determine the antibacterial activity of ligands and Cu(Ⅱ) polymers. Experiments indicate that the Cu(Ⅱ) polymers have a higher antibacterial activity than ligands and the [C15H9NO5Cu]n·n(CH3CH2OH)(H2O), [C16H10O6NCu]n·2nH20 polymers have better activity to Staphylococcus aureus and colibacillus, respectively, and the antibacterial activity was positively correlated with concentration.