Studies On The Interactions Of Heterocyclic Complexes And DNA And Its Electrocatalysis Of Nitrite

Heterocyclic complexes are widely exiting in nature, and their applications are also widely. It is not only the main ingredients of natural medicines, but also the main ingredients of the man-made compounds, such as medicine, dye, material and pesticide, etc. Heterocyclic complexes are one of the important organic reagents which owning strong chelate capacity in the analytical chemistry, and thus they are widely used to determine the inorganic ions. Those complexes, which own the planar and aromatic rings, have the ability in showing good kinetic stability and wonderful spectroscopic information. They can insert into the DNA duplex by planar and aromatic ring and can stack among the bases of DNA to be more stable by means of Ï€-stack. Therefore they have been widely used as DNA structure probes, "molecular light switches", DNA-medicated electron transfers, DNA footprint reagents and DNA cleaving reagents in recent years. In this thesis, Dipyridophenazine Complex of Ruthenium's Electrocatalysis of Nitrite and interactions of [Ru(phen)2dppz]2+ and methylene blue-Co (II) system with herring sperm DNA were studied by electrochemical, UV-spectrophotometric and fluorescent methods, which enhance and develope the application of these two heterocyclic complexes in determining inorganic ions such as NO₂^-, in being DNA structure probes, and in medicating electron transfers in the formation of M-DNA as a molecular wire. The main contents are listed as follows:1. The Electrochemical Behavior of Ruthenium (II) Polyphenanthroline Complex and Its Electrocatalysis of NitriteThe electrochemical behavior of [Ru(phen)2dppz]2+ (phen=1,10-phenanthro-line; dppz=dipyrido[3,2-a:2',3'-c]phenazine) was studied. In H2SO4 solution (pH= 1.8), a couple of reversible redox peaks appeared at the potentials of-0.161 V and -0.195 V (vs. SCE) at a glassy carbon eletrode, respectively. Using chronocoulo-metry, the maximum adsorption amount of 7.84×10^-11 mol/cm2 was obtained andthe adsorption coefficient was equal to 7.90×105 L/mol. Its adsorption obeyed Langmuir isotherm. It was found that the complex could electrocatalyze the reduction of nitrite, and the catalytic reaction mechanism was also proposed.2. Electrochemical Studies on the Interactions of Dipyridophenazine Complex of Ruthenium and Herring Sperm DNACyclic voltammetry (CV) and single-step chronocoulometry were used to study the interaction of [Ru(phen)2dppz]2+ with herring sperm DNA. The addition of DNA caused a diminution in the peak current and a positive shift in the peak potential of the complex of [Ru(phen)2dppz]2+. The 12 mV positive shift in the peak potential of [Ru(phen)2dppz]2+ indicates that [Ru(phen)2dppz]2+ binds 2.6 times more strongly to DNA than its reductive form. In addition, by using fluorimetric and UV-spectrophotometric methods along with the studies on the effect of denatured DNA and the effect of NaCl solution, it was also found that the binding mode was intercalation. The decrease of peak current is proportional to the concentration of DNA, which can be applied to estimate DNA concentration.3. Spectroscopic and Electrochemical Studies of DNA-Co (II)- MB ComplexesThe electrochemical behavior of methylene blue [3,7-bis (dimethylamino) phenothiazine-5-ium chloride, MB] as a intercalator has been investigated at dsDNA modified carbon paste electrode (CPE). MB binds to dsDNA via intercalation, which causes the peak current of MB to decrease at the dsDNA modified carbon paste electrode compared to bare CPE and causes the intensity of UV visible absorption of MB to decrease after the addition of DNA. However, the UV absorption intensity and the voltammetric peak current of the MB increase obviously when Co (II) is added. The results of these experiments shown above indicate the release of the MB from DNA duplex and the formation of metal-DNA (M — DNA). The result of chronocoulometric experiments at DNA-modified electrodes indicates M-DNA can mediate electron transfers as a molecular wire.