Synthesis And Antibacterial Activity Of Diaminopyridine Bis-schiff Base And Their Complexes

2,6-pyridinediamine is commonly used as organic dyes and chemical agent, which hasbroad application in organic synthesis and in chemical analysis. Schiff bases of aldehydeswith aminopyridines are structurally related to compounds participating in vitamin B6chemistry, such Schiff bases and their complexes have the practical value inpharmaceutical applications, like in antipyretic, antimicrobial activity, and so on.In this paper, both the reaction mechanism and synthetic process of Schiff base, aswell as synthetic method of their complexes, have been introduced in detail. This paperreviewed mostly their applied research focused on biological activity, catalytic properties,oxygen carrier activity, electrochemical character and anti-corrosion, chemical analysis,functional materials, etc. Two kinds of bis-Schiff bases were synthesized under microwaveirradiation with solvent-free condition. The one was N,N’-bis(salicylidene)-2,6-pyridinedi-amine(L1), the other was N,N’-bis(2-hydroxy-3-ethoxyphenylmethylidene)-2,6-pyridinedi-amine(L2). The effects of the molar ratio of raw materials, reaction time and microwaveirradiation power on the synthetic technology were investigated. Then, eight kinds ofcoordination compounds with bis-Schiff base were synthesized by solid phase synthesismethod at room temperature, and thorium(IV) complexes of ligands of L1and L2were notreported before. Their structures of ligands and their metal complexes were confirmed byelemental analysis, infrared spectrum, ultraviolet spectrum,1H NMR spectrum and molarconductance and TG-DTA analysis. The nature of inhibition of biological activity of themwas explored. The main contents and results of this paper could be generalized as follow:(1) Two kinds of bis-Schiff bases were synthesized under microwave irradiation withsolvent-free condition with salicylaldehyde, O-vanillin and2,6-pyridinediamine as basematerials. The synthetic conditions of them were discussed. The results by bothsingle-factor and orthogonal experiments showed that the salicylaldehyde to2,6-pyridinediamine ratio was2.2:1, the reaction time was5min, microwave power was 600W, the yield of the ligand L1was up to90.3%; and the process conditions of theligand L2were as follows: the ratio of O-vanillin to2,6-pyridinediamine ratio was2.3:1,the reaction time was5min, microwave power was600W, the yield was up to91.3%.Their structures were characterized by elemental analysis, infrared spectrum, ultravioletspectrum and1H NMR spectrum, and the compounds obtained were final objectiveproducts.(2) Eight kinds of complexes with bis-Schiff base were synthesized by solid phasesynthesis method at room temperature with L1, L2, copper acetate, nickel acetate, zincacetate and thorium nitrate as base materials, and thorium(IV) complexes ofN,N’-bis(salicylidene)-2,6-pyridinediamine and N,N’-bis(2-hydroxy-3-methoxyphenylme-thylidene)-2,6-pyridinediamine were not reported before. Their structures were confirmedby elemental analysis, infrared spectrum, ultraviolet spectrum, molar conductance andTG-DTA analysis, and the compositions of the transition metal complexes with bis-Schiffbase were inferred.(3) The antimicrobial effect of ligands and complexes against Escherichia coli, Lactic acid bacteria and Aspergillus flavus was tested by filtering paper method. Bacteriostasis ofthem was investigated with the concentrations of2mmol·L-1. Results of the antibioticexperiments indicated that ligands and complexes could obviously resist Escherichia coli,Lactic acid bacteria and Mucedine. Bacteriostatic efficacy of complexes was superior toligands, and the antimicrobial effect of copper(II) complex of L1was the best. Theantimicrobial effect of copper(II) complex of L2was studied in various concentrations.Results showed that the bacteriostatic efficacy of copper(II) complex of L1was irregularwith the varying of concentrations, the inhibition zone diameter and bacteriostatic activitywas optimizing with the concentrations of4mmol·L-1.