Materials Science

F. Albert Cotton (New Inorganic Materials) We plan to synthesize linear and ladder polymers by linking bimetal units with dicarboxylic acids. To do this we shall employ the following bimetal units: together with any of a great range of dicarboxylate anions, O2C-X-CO2. By varying M (for example, Mo, W, Rh) and the linking unit X it will be possible to build in structural and redox properties that can be varied so that the polymers will combine with a variety of other molecules to give composites with a great range of properties.

Kim R. Dunbar (Inorganic Materials: Design and Synthesis) A main challenge in the field of molecular materials is the design of assemblies with specific physical properties. The discovery in the mid-1980's of the first molecules to exhibit a spontaneous magnetization below a critical temperature TC spawned a completely new field of research, namely molecular magnetism, and research groups all over the world are involved in activities aimed at understanding how paramagnetic molecules engage in spin interactions. Our research is aimed at the syntheses, structural determination and magnetic characterization of a related series of cluster compounds. NSF-REU students will be preparing clusters in a state-of-the-art laboratory equipped with inert atmosphere dry-boxes and many tools of characterization including FT-IR spectroscopy, electrochemistry, UV-visible spectroscopy, thermal gravimetric analysis, differential scanning calorimetry as well as a magnetometer and a CCD area detector single crystal X-ray diffractometer in departmental facilities

Francois P. Gabbai (Heavy atom induced room temperature phosphorescent materials) Recent studies in our laboratory have revealed that trimeric ortho-tetrafluorophenylene mercury (1) forms binary complexes with arenes. These complexes, which adopt extended stacked structures, result from the formation of secondary p-interactions between the aromatic derivative and the three Lewis acidic mercury centers of 1. This supramolecular complexation mode leads to a perturbation of the photophysical properties of the arene which displays intense room temperature phosphorescence (RTP) as a result of a mercury heavy atom effect. REU students joining our group will be invited to investigate novel light emitting materials formed by interactions of 1 with various chromphores.  The central objective of this research is to develop lnew luminophores that could be incorporated in organic light emitting diodes (OLEDs).  Single crystal X-ray crystallography, UV-Vis and luminescence spectroscopy, solution and solid-state NMR spectroscopy, electrochemistry and theoretical calculations are some of the methods that will be used in this project.

Tim R. Hughbanks (Excising Zr-based Clusters from Solids: A Route to a New Solution Cluster Chemistry) A major area of research in our group has been concerned with the exploitation of cluster-based solids as precursors for studying clusters in solution. In particular we have focussed on centered 6-metal zirconium halide (Cl, Be, I) molybdenum chalcogenide (S, Se, Te) clusters. These cluster compounds involve [(Zr6Z)X12]X6 (Z = an interstitial element, e.g., H, B, C, N, Mn, Fe, Co; X = Cl, Br, I) or [Mo6Ch8] (Ch = S, Se, Te) clusters. As synthesized in the solid state, these clusters are crosslinked in various ways to form continuous solid state cluster networks. We have found methods of excising these clusters from the solid state so that we can both develop their solution chemistry and use the clusters as building blocks to assemble new solid state compounds with interesting or useful properties.

Stephen A. Miller (New polymer architectures from next-generation transition metal catalysts) The annual worldwide production of polyolefins exceeds 60,000,000,000 kg; by the year 2005, this figure is expected to double. A significant fraction of this quantity can be traced to cracking or polymerization facilities located in the state of Texas. Polyolefin production in Texas represents 70 percent of the U.S. market, 18 percent of the world market, and is a $26 billion per year industry. Given the enormous importance of polyethylene, polypropylene, polystyrene, and other polyolefins-and the availability of their respective monomers-a very important goal is the development and understanding of new transition metal polymerization catalysts for the formation of polyolefins with novel or enhanced properties. The Miller research group is currently designing and synthesizing transition metal catalysts capable of making new polymers which have the potential to enter the commodity polymer market. Objectives include: 1) the development of new routes to elastomeric polyolefins from propylene and from other alpha-olefins; 2) the investigation of binary and ternary catalyst systems for preparing blends of polyolefins with properties that can be quantitatively correlated with the catalysts employed; 3) the use of well-defined catalysts for synthesizing stereoregular, non-random copolymers from readily available monomers; and 4) the investigation of ion pairing effects in the catalytic species responsible for olefin polymerization and the measurement of how ion pairing impacts important parameters such as activity and stereocontrol.

Raymond E. Schaak (Synthesis of Nanoscale Solid-State Materials)  We are merging ideas from traditional solid-state chemistry with new ideas from nanoscience in order to design and synthesize new nanoscale materials with structures and properties that are different from bulk materials.  We use methods from solution chemistry to synthesize complex solid-state materials at temperatures that are significantly lower than those required for analogous bulk systems, and as such we have unprecedented control over the formation of solids.  To date, this approach ("metallurgy in a beaker") has yielded a host of new late transition metal solids with interesting magnetic, electronic, superconducting, optical, and catalytic properties, including electrically conducting AuCu nanowires, ferromagnetic FePt₃, catalytically active Au-Pd nanoalloys, and superconducting Ag₂Pd₃S.  Students working on this project will gain experience with a unique combination of synthesis and characterization techniques from both solution chemistry and solid-state chemistry, and will explore the formation of novel multimetallic materials with unusual shapes, structures, and properties.

For more information, write the Graduate Student Advisor: gradmail@mail.chem.tamu.edu.

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