Studies On The Synthesis, Characterization, And Biological Activity Of The 2-amine-5-methylpyridin Schiff Base Complexes

The coordination compounds are more and more important for their various structures and extensive uses.The applied foreground of these compounds will be extensive in the field of catalysis,bioactivity and material atc. Thus, studies on the characterization and application of the synthesis of novel Schiff base complexes are significant to the development of coordination chemistry.Two Schiff base ligands which are derived from 2-amine-5-methylpyridin-O-vanillin (HL1),2-amine-5-methylpyridin-2-hydroxy-l-naphthaldehyde(HL2) have been prepared,and fifteen complexes of transition or lanthanidenitrates metal have been synthesized. Three single crystals of Schiff base ligands have been obtained.All these Schiff base ligands and complexes are first reported by the author. These ligands were characterized by X-ray crystal diffraction, and obtained their structures.These complexes were characterized by elemental analysis,'HNMR, IR spectra,UV spectra, molar conductance analysis.TG-DTG and molar conductance analysis, and the suggested structures of the complexes were concluded. Fluorescence of Schiff base ligands and some of their complexes have been studied.The antibacterial activities of ligands and parts of their metal complexes were also studied.Seven transition or lanthanidenitrates metal complexes with Schiff base ligand from 2-amine-5-methylpyridin-O-vanillin (HL1) were synthesized.The crystal of the ligand belongs to monoclinic, P21/C space group, molecular formula is C3oH28N602,M=504.58.The unit cell parameter are:a=11.5995(6)A,α=90.000(5)°b=4.9546(2)A,β=117.609(4)°,c=23.9983(12)A,γ=90.000(5)°,V=1222.15(10) A3, Z=4, F(000)=512, Dc=1.317 Mg/m3,μ=0.090 mm-1.R1=0.0609, wR2= 0.1728和R1=0.0911,wR2=0.1985.The molecules is formed a dimer through intermolecular hydrogen bonds, which make the molecule more stabile.The compo-sitions of the metal complexes are confirmed to be:[CuL1(CH3COO)(CH3OH)]; [NiL1(CH3COO)(CH3OH)]·H2O;[CoL1(CH3OH)] CH3COO·H2O;[ZnL1(CH3COO) (CH3OH)];[LnL1(NO3)(H2O)] NO3·H2O (Ln=La, Pr, Sm).The synthesis of ligand and complexes was in non-aqueous solvents. All the ligand and complexes were are all stable and could be preserved in the air for a long time.The complexes are colored and powered substance and difficult to dissolve in the water. The nitrogen atom, oxygen atom of hydroxybenzene of Schiff base were all coordinated to the metal ions. Water molecules are exists as crystalwater or coordinated water. The carboxyl and acetic acid are coordinated to the metal ions in bidentate fashion or dissociated outside.Five transition metal complexes with Schiff base ligand from 2-amine-5-methyl pyridin-2-hydroxy-1-naphthaldehyde (HL2) were synthesized.The crystal of the ligand belongs to monoclinic, P21/C space group, molecular formula is C17H14N2O, M=261.29, The unit cell parameter are:a=4.8703(2)A,b=9.5525(5)A,β= 98.353(2)°,c=14.0804(6))A,γ=90.000(5)°,V=648.12(5)A3,Z=2,F(000)=274, Dc=1.339Mg/m3,μ=0.085 mm-1,R1=0.0419,wR2=0.1094, R1=0.0562,wR2= 0.1196.The molecules is formed one-dimensional zigzag chain through intermolecular hydrogen bonds, which make the molecule more stabile.The compositions of the transition metal complexes are confirmed to be:[CdL2 (CH3COO) (H2O)]·H2O; [CoL2(CH3COO) (H2O)]:[ZnL2 (CH3COO) (H2O)];[CuL2(CH3COO) (H2O)]·H2O; [CoL2(CH3COO) (H2O)];[NiL2 (CH3COO) (H2O)]·H2O;The synthesis of ligand and complexes was in non-aqueous solvents.All the ligand and complexes were are all stable and could be preserved in the air for a long time.The complexes are colored and powered substance and difficult to dissolve in the water. The nitrogen atom, oxygen atom of hydroxybenzene of Schiff base were all coordinated to the metal ions. Water molecules are exists as crystalwater or coordinated water. The acetic acid is coordinated to the metal ions in bidentate fashion.The crystal of the Schiff base derived from 4-aminoantipyrine and isophthalaldehyde belongs to monoclinic, P21/C space group, molecular formula is C30H28N6O2, M=504.58,The unit cell parameter are:a=6.1375(1)A,α=90.000(5)°b=24.6571(4)A,β=94.781(1)°,c=17.7487(3)A,γ=90.000(5)°,V=2676.62(8)A3, Z=4,F(000)=1064,Dc=1.252 Mg/m3,μ=0.081 mm-1.R1=0.0463,wR2=0.1153和R1=0.0788,wR2=0.1323.The molecular structure of C30H28N6O2 is calculated using the Amsterdam density functional theory with the gradient corrected GGA: BLYP method. The standard DZ basis sets are applied all atoms.Atom coordinates used in the calculation are from crystallographic data. The crystal structure is calculated on energy optimized and frequency.All calculations are performed using the ADF program package.The calculation results disclose that the calculated data and the tested data of parts of the bond lengthes and bond angles are similar. The relationship between fine micromechanism of the compound and its chemistry activities position are also expatiated according to the theory of molecular orbital (HOMO and LUMO) in this dissertation.The excitation and emission peak wavelengths(λex/λem) of HL1 and HL2 are 291nm/379 nm,251nm/368 nm and 291 nm/390 nm,329 nm/390 nm respectively in fluorescence spectra. The excitation and emission peak wavelengths(λex/λem) of the Schiff base complexes of [LaL1(NO3)(H2O)] NO3·H2O, [CuL2(CH3COO)(H2O)]·H2O are 301nm/368 nm and 281 nm/400 nm,338 nm/400 nm,389 nm/400 nm respectively in fluorescence spectra. The four ligands and complexes have good fluorescence. Compared with the ligands, the excitation peaks and the emission peakof their complexes have changed, and the fluorescence intensity increases.Combinating Achar differential and Coats-Redfern integral method which fits the thirty kinetic equations, the calculating program was designed. The kinetic equations of thermal decomposition for complexes and the corresponding kinetic parameters were gained. The kinetic parameters include E,A,order of reaction and correlation coefficient, etc.The activation entropyΔS≠and activation free-energyΔG≠for some thermal decomposition stage were also calculated.The thermal decomposition kinetic function of [NiL1(CH3COO)(CH3OH)]·H2O in step(3)may be expressed as f(α)=1/2(1-α)[-ln(1-α)]-1,and the kinetic equation of thermal decomposition may be expressed as:dα/dt=A exp(-E/RT)f(α)=A exp(-E/RT) 1/2(1-α)[-ln(1-α)]-1,E=554.89kJ·mol-1,lnA=117.52,r=0.9950,ΔS≠=727.3 J·mol-1·K-1,ΔG≠=167.2kJ·mol-1.The thermal decomposition kinetic function of [CuL2(CH3COO)(H2O)]·H2O in step(3) may be expressed as f(α)=1/2(1-α)[-ln(1-α)]-1,and the kinetic equation of thermal decomposition may be expressed as:dα/dt=A exp(-E/RT)f(α)=A exp(-E/RT) 1/2(1-α)[-ln(1-α)]-1,E=507.85kJ·mol-1,lnA=102.26, r=0.9196,ΔS≠=600.6 J·mol-1·K-1,△G≠=191.9 kJ·mol-1.The antibacterial activities of ligands and parts of their metal complexes were also studied against Escherichia coli and Staphylococcus aureus bacteria by inhibition zone method.The antibacterial activities of tested compounds were in a concentration-dependent manner. The ligand HL1 and complexes [CoL1(CH3OH)] CH3COO·H2O showed the higher antibacterial activity than other tested complexes and were sensitive against two tested bacteria. The results indicate that metal complexes have higher antibacterial activities than their ligands, disclosing transition metal ions play an important role in antibacterial activity.