Study On Synthesis,Structures,DNA Interactions And Magnetic Properties Of Schiff Base Complexes

Schiff base is a class of stable imine connected on the nitrogen atom with an alkyl or aryl,which is synthesized by the condensation of an amine and an aldehyde or ketone.Because of the flexibility of Schiff base ligand,various types Schiff base ligands can be created by modulating the substitution groups of amines or carbonyl compounds.Schiff base ligands and their metal complexes play an important role in Medicinal Chemistry,which are known to exhibit a wide variety of pharmacological effects,including anti-inflammatory,antibacterial,and chemotherapeutic activities.In addition,compared with the Schiff base ligands,the Schiff base metal complexes show increased biological activities.In an attempt to obtain more insight into the potential applications of Schiff base metal complexes in life sciences and material areas,herein our study focused on synthesis,characterization and properties detection of Schiff base metal complexes.Object:To provide some potential application evidences of Schiff base metal complexes in chemical nucleases and molecule-based magnetic materials,several Schiff base metal complexes were synthesized.Their crystal structures,biological activate.as well as magnetic properties were studied.Methods:Several Schiff base ligands:2-amino-3-((E)-(pyridine-2-ylmethylene)amino)maleonitrile(H2L1),(Z)-4-chloro-2-((pyridine-2-ylmethylene)amino)phenol(HL2),(Z)-2-((pyridin-2-ylmethylene)amino)phenol(HL3),(Z)-4-methyl-2-((pyri-dine-2-ylmethylene)amino)phenol(HL4),(Z)-4-nitro-2-((pyridin-2-ylmethylene')am-ino)phenol(HL5).and(Z)-4-chloro-2-((pyridine-2-ylmethylene)amino)benzenthiol(L6)were syntheszed using 2-pyridyl aldehyde,diaminomaleonitrile,2-amino-4-chl-orophenol,2-aminophenol.2-amino-4-methylphenol,2-amino-4-nitrophenol and 2-amino-4-chlorothiophenol as the raw materials.Their Co(?),Ni(?).Zn(?)and Cu(?)complexes were synthesized and characterized by IR,1H-NMR and X-ray crystallography,respectively.Absorption spectroscopy,fluorescence spectroscopy and agarose gel electrophoresis were applied to assess the interaction between Schiff basemetal complexes and DNA.To detect the magnetic property of the complex,variable temperature magnetic susceptibility test was performed by an Mpms-7 SQUID-type magnetometer.Result:Three mononuclear Schiff base complexes,[Co(HLl)2]·Cl·(MeOH)2(1),[Ni(HLl)2]4·EtOH(2),[Zn(HL2)(L2)]2·(N03)2(3)and a 1D alternating chain copper complex Cu4(L3)2(OAc)8(4)were synthesized and identified by infrared spectroscopy,X-ray crystallography and ultraviolet-visible spectroscopy.Fluorescence spectroscopy revealed that the fluorescence of Ethidium Bromide-DNA(EB-DNA)solution was quenched with the addition of complexes 1,2,3.4 solution,and the apparent binding constants(Kapp)of the complexes were 9.14 x 105 M-1,3.20 × 105 M-1,1.36 ×105 M-1 and 1.46 x 106 M-1,respectively.The results of absorption spectroscopy titration indicated that the complexes are capable of interacting with DNA,and the binding constant(Kb?2.56 x 104M-1)of 1D alternating chain copper complex 4 indicated its moderate DNA affinity.DNA cleavage experiments performed by agarose gel electrophoresis proved that complex 4 can induce DNA single strand break in physiological condition,and the DNA cleavage activity increased significantly in the presence of H2O2.Variable temperature magnetic susceptibility tests showed that the effective magnetic moment of complex 4 decreased gradually with the temperature lowering,but the effective magnetic moment rised sharply when the temperature was below 10 K,indicating that complex 4 might involve in both antiferromagnetic and ferrornagnetic exchange pathways.Conclusion:Based on molecular design,four new Schiff base metal complexes were synthesized and their crystal structures were identified by single crystal X-ray crystallography.The single crystal diffraction analysis result reveals that complex 1-3 display mononuclear units;complex 4 has a 1D alternating chain structure.in which copper ions have two different coordination environments and various spin exchange modes.DNA interaction studies suggest that the complexes we reported here can interact with DNA.Particularly,in physiological condition,complex 4 has DNA cleavage activity,and this activity can significantly increase in the presence of H2O2,which implies this complex has great potential for chemical nuclease development.Magnetism studies of complex 4 show it exhibits both antiferromagnetic and ferromagnetic exchange pathways,which is consistent with its unique 1D alternating chain structure,indicating a great value in the research field of structure-magnetism relationship.