Search

Ultracold atomic system provides us a versatile platform to address problems ranging from quasi-particle excitations supported by a variety of ground states, to cold collisions which could lead to a precise determination of interatomic molecular potential, and to atomtronics focusing on atomic analogues of electronic components. In this dissertation, I describe our efforts in exploring a wide topic range by our \Rb Bose Einstein condensate (BEC) machine and \Li - \Rb mixture machine, including magnons, which are collective spin excitations supported by Rb F = 1 ferromagnetic BEC ground state, cold elastic collisions between Li and Rb co-trapped in a spherical quadrupole trap, and Li spin dynamics in a spin bath formed by Rb.

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.

Solid-state NMR was applied to investigate atomic-level structure in heterogeneous materials that have proven challenging to study by existing physical methods. The ability of solid-state NMR to provide accurate structural information in these materials was demonstrated, and solid-state NMR techniques were applied to study chemical structure in bone tissue and to investigate the interactions of organic guest molecules inside a zeolite framework. It was proven that accurate distances could be reliably obtained using 2D Lee-Goldburg Cross-Polarization under Magic-Angle Spinning. Distance measurements were made on natural abundance solids for the first time using this technique. The ability to obtain 1H spectra with correct chemical shift values using 2D correlation experiments was demonstrated. The sensitivity of a Frequency-Switched Lee-Goldburg Heteronuclear Correlation experiment was improved by a factor of 2.4, facilitating the investigation of natural abundance materials. Structural changes in apatite minerals upon carbonate substitution were explored. Hydroxide ion changed orientation within the hydroxide channel to hydrogen bond with surrounding phosphate and carbonate ions. Carbonate ion was located within the apatite lattice. Molecular modeling suggests that carbonate oxygens occupy the same O1-O3-O3' oxygen positions as phosphate in hydroxyapatite. An ordered water layer was directly observed for the first time on bone mineral crystallite surfaces. This layer may mediate the interaction between bone mineral and collagen, an interaction responsible for the unique biomechanical properties of bone. Three structural roles for water were discovered in synthetic carbonated apatite, deproteinated bone and unmodified bone mineral. Isolated water molecules occupy hydroxide ion vacancies in the calcium-lined hydroxide channel. Other crystal waters occupy non-channel vacancies. Bone mineral-organic matrix interactions were directly observed in bone tissue using a 1H-31 P chemical shift correlation experiment. Signals observed above 7 ppm were concluded to arise from mineral-H2O-collagen hydrogen-bonding interactions. Spectral differences between model apatites and unmodified bone mineral suggest significant structural differences. A novel method for preparing polyaniline (PANI) nanowires was developed. Guest p-aminobenzoic acid (PABA) molecules were loaded onto porous zeolite hosts from solution. Upon drying, the PABA molecules reacted to form PANI. Oxidized PANI is a semiconductor, and the presence of isolated radicals was evident in NMR spectra.