Synthesis Of 2,6-bis(Benzimidazol-2-yl) Pyridine And Amino Acids Complexes And Spectroscopic Studies Of DNA Binding

In this paper, the meaning and future of metal complexes andpolypyfidyl transition metal complexes, the development of the studyingof 2,6-bis(benzimidazol-2-yl)pyridine (H₂bzimpy), the applications andthe development of the studying of amino acids, electrochemical studyingof transition metal complexes binding to DNA, have been discussed.H₂bzimpy has been synthesized rapidly by microwave irradiation,The ten complexes of Copper(â…¡), Cadmium(â…¡), Zinc(â…¡), with2,6-bis(benzimidazy-2')pyridine and amino acids were synthesized in theconventional condition and characterized by UV, infrared spectroscopy,fluorescence spectra and elemental analyses, they are[CuL(Tyr)]NO₃·H₂O,[CuL(Trp)](NO₃)₂·H₂O,[CuL(Gly)]NO₃·H₂O,[CdL(Tyr)]Cl₂,[CdL(Trp)]Cl₂,[CdL(Gly)]Cl₂,[ZnL(Tyr)](NO₃)₂,[ZnL(Trp)](NO₃)₂,[ZnL(Gly)](NO₃)₂ and [ZnL(Cys)](NO₃)₂. The resultis that the complexes were synthesized successfully. The binding of thesecomplexes with calf thymus DNA has been investigated by absorption,luminescence titration and viscosity measurements. The results suggestthat the absorbance of the complexes decrease, but the wavelength havenot red shift with increasing DNA concentrations. The decrease is smallerthan the complexes with H₂bzimpy only. The emission intensity growsslowly in absence DNA respectively. On increasing the amount ofcomplexes [CuL(Gly)]NO₃·H₂O,[CdL(Gly)]Cl₂,[ZnL(Trp)](NO₃)₂, theviscosities of DNA rise at begin an then go down. The viscosities of DNA keep decreasing in the presence of increasing concentration of theother complexes. In summary, the results show that the two complexescould bind to DNA by partial or surface banding.In addition, the change of the UV spectra and fluorescence spectra ofcomplexes depend on pH are studied. They are very sensitive to solutionpH, and the wavelength become longer as pH increasing, even newwavelength could be show. [CuL(Tyr)]NO₃·H₂O as example, whenpH=7.9, I/I₀=0.5, and the wavelength changges from 315nm to 326nm.However, the change of fluorescence spectra is on the contract, it issensitive in the solution of pH＞7. The absorbance keep decreasing ofcomplex [ZnL(Tyr)](NO₃)₂,[ZnL(Trp)](NO₃)₂ as pH increasing, but theother increasing at frist, and then going down quickly. Since the complexacts as dibasic acids, in which N-H, COO-H and S-H protons onbenzimidazole moieties and amino acid are responsible for adeprotonation site. Both reduction potentials are strongly dependent onthe solution pH, which leads to the basis of a proton-induced molecularswitch. In inverse, the deprotonation of N-H, COO-H and S-H protonscan influence the electric charge distribution, electrochemical behaviorand spectra property.