Synthesis And DNA Binding Studies For The Ternary Complexes Of Rare Earth Or Transition Metal With Polypyridine And Amino Acids

Nowadays,people has substantial interest in ternary complexes of amino acid and polypyridine,the studies indicated these complexes not only could bind to DNA base pairs by intercalation or partly intercalation function,but also had good nucleases activity,which may cleave DNA and RNA at fixed location.In this paper,the complexes of Samarium(â…¢),Lanthanum(â…¢), Zinc(â…¡)and Copper(â…¡)With 2,6-bis(benzimidazy-2')pyridine were synthesized in the hydrothermal condition and characterized by UV, infrared spectroscopy,fluorescence spectra,¹HNMR and elemental analyses,they are[SmL₂(Tyr)ONO₂](NO₃)₂,[SmL(His)Cl₃],[LaL(Tyr)Cl₃],[ZnL(Met)](NO₃)₂,[ZnL(Asn)](NO₃)₂,[ZnL(His)](NO₃)₂,[CuL(Met)]NO₃,[CuL(Asn)]NO₃ and[CuL(His)]NO₃. The result is that the complexes have been synthesized sucessfully.The study of these complexes interaction with DNA using absorption, luminescence titration and viscosity measurements,suggest:the absorbance of the complexes decreases,but the wavelength has no red shift with increasing DNA concentration;the emission intensity grows slowly in absence and existence of DNA respectively([LaL(Tyr)Cl₃], ZnL(His)](NO₃)₂ except);On increasing the amount of complexes [CuL(Met)]NO₃,[CuL(Asn)]NO₃,[ZnL(Asn)](NO₃)₂,[ZnL(His)](NO₃)₂,the viscosities of DNA rise at begin then go down,while the others just decrease.In summary,the results show that the complexes could bind to DNA by partial banding.The complex[CuL(Asn)]NO₃ is also found to produce cleavage of pBR322DNA in the presence of reducing agents such as ascorbate/H₂O₂,and complexes[SmL₂(Tyr)ONO₂](NO₃)₂,[SmL(His)ONO₂](NO₃)₂ can monitor the conversion of supercoiled DNA to nicked DNA without oxidant or reducer.In addition,the changes of the UV spectra and fluorescence spectra of complexes depended on pH were studied.As a whole,transition metal complexes are more sensitive than rare earth complexes,and complexes more sensitive in acid condition than alkaline.The absorbance keeps decreasing of complex as pH increasing and wavelength has some shift red,new peaks appear at some pH.But the absorbance of[CuL(His)]NO₃ keeps increasing at frist and then going done quickly.For fluorescence spectra,the intensity of the Complexes[SmL₂(Tyr)ONO₂](NO₃)₂ and [LaL(Tyr)Cl₃]grows with the increase of pH during acid condition,and goes down in alkaline media,whereas Complexes[ZnL(His)](NO₃)₂, [CuL(Met)]NO₃,[CuL(Asn)]NO₃ and[CuL(His)]NO₃ rise in the beginning then come down during the range of pH(about 1-13),even their luminescence reaches lifetime when pH is very low and top. Especially,the changes of[ZnL(His)](NO₃)₂ and[CuL(Met)]NO₃ are almost linear with pH in acid or alkaline respectively.