The goal of this project was to design a new kind of tagged supramolecular structural motif. These systems are modular in design and able to bind to DNA. The motif can be represented as TAG-LA-BL-BAS (TAG = NMR active phosphine ligand, LA = light absorber, BL = bridging ligand and BAS = bioactive site). The TAG provides a NMR probe for the characterization of supramolecular complexes as well as for the future investigation of the metal complex−DNA interaction process. In this project the phosphorous ligand PEt₂Ph was selected as the TAG due its ability to provide an easy ³¹P NMR probe in the research. The LA represents the light absorber which could be photoexcited by photons of proper energy, here a Ru<sup>II</sup>(tpy)(PEt₂Ph)(BL) chromophore is used. The bridging ligands are those bidentate polyazine ligands that can connect two metal center together in a polymetallic system and have a low energy π* orbital. The BAS represents the bioactive sites for binding to DNA, in this case the cis-Pt<sup>II</sup>Cl₂ moiety based on previous studies with cisplatin.
The Ru-Pt bimetallic complexes [(tpy)Ru(PEt₂Ph)(BL)PtCl₂](PF₆)₂ (BL = bpm or dpp) and their precursors were designed, successfully synthesized and characterized. The synthesis followed a building block approach, allowing variation of the supramolecular system. The final bimetallic complexes were made without need for Al₂O₃ column chromatograph, important due to the presence of the labile P<sup>II</sup>Cl₂ center.
The bimetallic complexes and all of their monometallic precursors were fully characterized by FAB MS, electrochemistry, electronic absorption and ³¹P NMR spectroscopy. The Ru-Pt bimetallic complex containing the bpm bridging ligand and its precursors were also characterized by ¹H NMR. The FAB MS spectra of the complexes is characterized by the appearance of the parent ion peaks [M-PF₆]⁺ and [M-2PF₆]⁺ . The cyclic voltammogram of all complexes show metal based oxidation(s) and ligand based reductions. The electronic absorption spectra of the complexes are characteristic of the lowest lying Ru to bridging ligand MLCT (metal to ligand charge transfer) transition with higher energy bridging and terminal ligand based Pi to Pi* transitions. The electronic absorption data are consistent with the electrochemical data. The ³¹P NMR technique provides an efficient and easy characterization method for the complexes, showing the utility of this structural moiety.
The DNA binding activity of the bimetallic complexes were studied by non-denaturing agarose gel electrophoresis and the results show that these tagged bimetallic complexes can bind to DNA through the cis-Pt<sup>II</sup>Cl₂ moiety. This binding has a more pronounced retardation effect on DNA migration than cis-[Pt(NH₃)₂Cl₂] (cisplatin), but less than [Ru(bpy)₂(dpq)PtCl₂](CF₃SO₃)₂. The DNA binding study establishes these bimetallic complexes with a NMR tag ligand, PEt₂Ph, as a new kind of DNA binding agent. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/33393 |
| Date | 14 June 2001 |
| Creators | Fang, Zhenglai |
| Contributors | Chemistry, Brewer, Karen J., Kingston, David G. I., Hanson, Brian E., Winkel, Brenda S. J. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | Thesis_Fang.pdf |
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