Virginia Tech
    • Log in
    View Item 
    •   VTechWorks Home
    • ETDs: Virginia Tech Electronic Theses and Dissertations
    • Doctoral Dissertations
    • View Item
    •   VTechWorks Home
    • ETDs: Virginia Tech Electronic Theses and Dissertations
    • Doctoral Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Supramolecular Ru II, Pt II Complexes Bridged by 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz)

    Thumbnail
    View/Open
    etd-01222010-190842_Zhao_SL_D_2010-revised.pdf (14.89Mb)
    Downloads: 191
    etd-01222010-190842_Zhao_SL_D_2010_Copyright.pdf (517.3Kb)
    Downloads: 26
    Date
    2010-01-12
    Author
    Zhao, Shengliang
    Metadata
    Show full item record
    Abstract
    The main theme of this dissertation is the study of two racemic compounds: a bimetallic complex, [(tpy)Ru(tppz)PtCl](PF₆)₃, and a trimetallic complex, [ClPt(tppz)Ru(tppz)PtCl](PF₆)₄, in solution and in the solid state, where tpy is 2,2':6',2''-terpyridine and tppz is 2,3,5,6-tetrakis(2-pyridyl)pyrazine. These two supramolecular assemblies display remarkably different stereochemistry, electrochemistry and photochemistry. The chapters in this document deal with a multidisciplinary project that is fundamental to the design and synthesis of similar entities with potential applications as antitumor agents. Chapter 1 gives an overview on the metal polyazine supramolecules. More specifically, the section is focused on the tridentate ruthenium and platinum metallic supramolecular assemblies with emphasis on their functionality and the methods used to study such systems. Chapter 2 describes the design and syntheses of the title complexes and their analogs using a building block strategy. The details of the experimental methods are included in this section. Chapter 3 presents the identification of the title complexes in solution and in the solid state by means of single crystal crystallography, mass spectrometry including FAB-MS and ESI-MS, and multiple NMR techniques including 1D ¹H-NMR, ¹⁹⁵Pt-NMR and 2D COSY, NOESY and ¹⁹⁵Pt-¹H HMQC, as well as dynamic ¹H-NMR at variable temperatures. The bi- and tri-metallic complexes are crystallized in the chiral space group of C2/c and P21/c as racemic compounds. The interconversion of the three steroisomers, M-M, P-P and M-P of trimetallic complexes are detected in the NMR timescale. The assignments of the atypical NMR resonance of the bi- and tri-metallic complexes are supported with the help of multidimensional NMR techniques and NMR spectroscopy of known systems. The process of assigning the NMR spectra is accomplished step by step with complexities presented by ring current effects. The 1D-fiber, 2D-plate and 3D-flowerlike topography of the trimetallic complex of [ClPt(tppz)Ru(tppz)PtCl](PF₆)₄ was illustrated by SEM. Chapter 4 demonstrates the electrochemical and photochemical differences between the title complexes and a comparison to known systems. Electrochemically, the RuII,PtII bimetallic and trimetallic complexes display RuII/III oxidations at 1.63 and 1.83 V and ligand-based reduction at -0.16 and -0.03 V versus Ag/AgCl, respectively. Spectroscopically, the Ru(dπ)⟶ tppz(π*) MLCT transitions are red-shifted relative to the monometallic synthons ([(tpy)Ru(tppz)](PF₆)₂, λmaxabs = 472 nm and [Ru(tppz)₂](PF₆)₂, λmaxabs = 478 nm) occurring in the visible region, centered at 530 and 538 nm in CH₃CN for [(tpy)Ru(tppz)PtCl](PF₆)₃ and [ClPt(tppz)Ru(tppz)PtCl](PF₆)₄, respectively, consistent with the bridging coordination of the tppz ligand. [ClPt(tppz)Ru(tppz)PtCl](PF₆)₄ displays an intense emission (Φem = 5.4×10₄) from the Ru(dπ)⟶ tppz(π*) ³MLCT state at RT with λmaxem = 754 nm and lifetime ofτ„ = 80 ns in CH₃CN solution. The trimetallic complex, [ClPt(tppz)Ru(tppz)PtCl](PF₆)₄, exhibits a strong emission property in the solid state with λmaxem = 764 nm, which was also studied by confocal laser induced emission scanning microscopy. By contrast, a barely detectable emission was observed for the bimetallic complex, [(tpy)Ru(tppz)PtCl](PF₆)₃. The redox and luminescence differences between bi- and tri-metallic complexes is the consequence of the nature of these supramolecular assemblies. All together the data suggest strong PtPt interactions in solution providing for assembly of these molecules into dimers or larger assemblies. Chapter 5 reports the applications of these complexes as bioactive species interacting with DNA. The prelimary data show the title complexes bind to DNA producing larger changes in DNA migration during gel electrophoreses than does the well-established anticancer drug, cisplatin. Preliminary study indicates trimetallic complex [ClPt(tppz)Ru(tppz)PtCl](PF₆)₄ can photochemically condenses DNA. This data could provide a form for development of a new class of photodynamic therapy agents in cancer treatment. Chapter 6 concludes with summaries of current research and perspective for further work.
    URI
    http://hdl.handle.net/10919/77321
    Collections
    • Doctoral Dissertations [15775]

    If you believe that any material in VTechWorks should be removed, please see our policy and procedure for Requesting that Material be Amended or Removed. All takedown requests will be promptly acknowledged and investigated.

    Virginia Tech | University Libraries | Contact Us
     

     

    VTechWorks

    AboutPoliciesHelp

    Browse

    All of VTechWorksCommunities & CollectionsBy Issue DateAuthorsTitlesSubjectsThis CollectionBy Issue DateAuthorsTitlesSubjects

    My Account

    Log inRegister

    Statistics

    View Usage Statistics

    If you believe that any material in VTechWorks should be removed, please see our policy and procedure for Requesting that Material be Amended or Removed. All takedown requests will be promptly acknowledged and investigated.

    Virginia Tech | University Libraries | Contact Us