Synthesis Of The Rare Earth Metal Complexes Involving Bis-benzimidazole And Their Interaction With DNA

The development of the interaction between small molecule and nucleic acid was fully described in the dissertation paper.It involved interaction modes and research methods and research techniques.The development direction and prospects were also expatiated.The recent advances in the study of benzimidazoles and their derivatives and their application in medicine,corrosion resistance,aerospace were reviewed too.The bis(2-benzimidazolylmethyl)amine(BBA) has been synthesized rapidly under the microwave irradiation.The method is very simple, inexpensive,and green.The reaction time was shortened to 17 min,being eighty five times faster than the conventional methods.The yield was enhanced to 75%,being two times higher than conventional methods,and the dosage of solvent was a quarter less than the usual one.Moreover the optimum synthesization condition under microwave irradiation was also explored.The four Complexes of Lanthanum(â…¢),Samarium(â…¢), Europium(â…¢) and Dyrosium(â…¢) with bis(2-benzimidazolylmethyl)amine were synthesized in the conventional condition,and characterized by UV, infrared spectroscopy,fluorescence spectra,elemental analyses,NMR, molar conductivity,cyclic voltammetry.The results showed that the complexes have been synthesized successfully and general chemical formula is[Ln(BBA)₂(NO₃)₂]NO₃(Ln=La,Sm,Eu,Dy).Absorption,luminescence titration,viscosity and cyclic voltammetry measurements were used to study of these complexes and ligand interaction with DNA.It suggests:the absorbance of the complexes and ligand all decrease,but the wavelength has not red shifted with increasing DNA concentration;the emission intensity grows rapidly in absence and existence of DNA respectively;on increasing the amount of complexes, the viscosities of DNA go down at the beginning,then rise(except [La(BBA)₂(NO₃)₂]NO₃),while on increasing the amount of ligand,the viscosity of DNA rise gradually;the peak current of complexes decreases, anodic peak potential shifted negatively,and cathode peak potential moved positively appreciably,by addition of DNA.Results show that the ligand could bind to DNA by partial banding;these complexes bind to DNA by weak partial intercalation and electrostatic binding.The ligand containing two benzimidazole groups form a near planar geometry is mainly partially bound to DNA,while the complexes involving four benzimidazole groups and two nitrate anion form a distorted octahedral dodecahedron geometry interact with DNA by weak partial insertion and electrostatic binding.So the ligand binding to DNA is stronger than these complexes.We also found that complexes of La or Eu can act as an effective artificial nuclease,promoting the hydrolysis of plasmid DNA under the physiological pH and temperature. In addition,the dependence of the changes of the UV spectra and fluorescence spectra of BBA and Eu complexes on pH were studied.As a whole,the absorbance of BBA and complexes kept decreasing and disappeared as pH increasing and the wavelength moved red with some new peaks appearing at some pH.For fluorescence spectra,the intensity of the complexes and BBA grown with the increasing of pH between 1.5 and 5.1,and began to go down between 5.1 and 9.5.But the change of fluorescence spectra,the intensity of the complexes was more quickly and sensitive than of BBA.So Eu complexes would to a novel DNA molecular switch in the future.