Bryan W. Eichhorn, Ph.D. - US grants

This grant will support research in the synthesis of new high temperature superconducting compounds. By identifying new classes of materials which exhibit this unusual behavior, the common features that are identified in the different materials may provide insight into the nature of the physical mechanism responsible for this phenomenon. This grant was selected from more than 260 proposals submitted in response to a solicitation for proposals in High Temperature Superconductivity in April, 1989. The research is supported by the Solid State Chemistry Program with a significant contribution from the university.

The aim of this research is to investigate synthesis, structure, and properties of new early transition metal sulfide phases. The proposed compounds will have perovskite related or layer structures and transition metals with do to d1 configurations. A variety of synthetic techniques will be employed such as BaCl2 flux reactions, CS2 sulfiding reactions, and sulventothermal reactions. All compounds will be characterized by XRD, transport, and magnetic measurements. These compounds will allow comparisons of the structures and properties of isocompositional oxides and sulfides in the areas where metal insulator transitions occur. The importance of structure and covalency in the formation of new metallic solids will be addressed. %%% The aim of this research is to investigate synthesis, structure, and properties of new classes of unexplored solid state materials. These compounds will comprise early transition metals (Ti, Zr, Hf, V, Nb, Ta) and sulfur. Attempts are made to design features into these materials that are known to be important in the copper oxide superconductors. The atomic structure and properties of the new materials will be determined. The importance of structure and bonding in the formation of new materials, with desirable properties such as metallic behavior and/or superconductivity, will be addressed.

This award from the Chemistry Research Instrumentation Program will assist the Department of Chemistry at the University of Maryland in the purchase of an upgrade for an electron spin resonance (ESR) spectrometer. This upgrade is essential if the PI's are to make much more effective of the present equipment. The research projects that will be enhanced by the acquisition of this equipment include: 1) Studies of the electronic structure of organometallic 15-electron complexes, 2) Formation and electonic structure studies of 17 electron dihydride complexes, 3) Photochemical and electrochemical generation of arylnitrenium (Ar-N-R+) ions, probable intermediates in chemical carcinogenesis, and the study of their electronic structure, 4) ESR studies of organometallic and molecular-based inorganic polymers with bulk ferromagnetism and low dimensional conductivity, 5) ESR studies of enzyme-stablized radicals in biological processes. %%% An electron spin resonance (ESR) spectrometer provides information about the electronic structure of molecules and can detect the presence of "free radicals" which play an important in many chemical and biological interactions.

With this award, the Inorganic, Bioinorganic, and Organometallic Program supports research on odd-electron organometallic compounds by Dr. Rinaldo Poli of the Chemistry Department, University of Maryland at College Park. Dr. Poli will prepare new organometallic compounds of molybdenum, chromium, vanadium, and tungsten which contain 15 or 17 electrons and investigate their reactivity using EPR and other methods. Pairing energies and orbital splittings for the stabilization of these `open shells` in organometallic systems will be determined, thus increasing understanding of reactive intermediates in catalytic cycles. Most stable organometallic compounds contain 18 valence electrons, or in some instances 16, and do not exhibit a wide variety of oxidation states. By investigating species which have an odd number of electrons and accommodate a wider variety of ligands, information on the role of spin pairing in reaction kinetics will be obtained. This information will be valuable in the design of reactive species which may serve as new catalytic agents for organic synthesis.

Dr. Bryan Eichhorn, Chemistry Department, University of Maryland - College Park, is supported by the Inorganic, Bioinorganic, and Organometallic Chemistry Program of the Chemistry Division to investigate the synthesis and characterization of transition metal derivatives of soluble group 14 and 15 Zintl ions. The compounds will be prepared from the reactions between zero valent transition-metal complexes and Zintl anions. The targeted complexes will be among the first anionic transition-metal Zintl ion clusters. These species contain few or no attendant ligands or organic groups and will contain highly nucleophilic transition-metal centers. The use of these complexes in the activation of small molecules will be investigated. In general metal atoms tend to lose electrons to form positively charged ions. However, there is a class of negatively charged species called Zintl ions which are composed of several (usually between 7 and 12) metal atoms which are clustered together. This project aims at preparing such negatively charged clusters in which one of the components is a transition-metal. Since the transition-metals have important, e.g., catalytic properties, the new species to be prepared in this research are envisioned to possess the ability to activate small molecules and perform chemical transformations more efficiently than presently known Zintl species.

This project involves the development of low temperature methasis routes to new and novel metastable superlattices containing alternating layers such as metal sulfide/metal oxide, metal nitride/metal oxide or metal oxide/metal oxide composites. The primary goal is to develop a generic rational synthetic strategy for preparing composite superlattice materials with interesting phenomena that include metallic/magnetic superlattices as magnetic memory or magnetoresistive materials, dielectric/superconducting superlattices exhibiting interlayer tunneling behavior and proximity effects, and ferrimagnetic/superconducting superlattices. Strategies to be developed include: 1) Metal Oxide/Metal Chacogenide Superlattices through Soft Chemistry, and 2) Metathesis Chemistry with Layered Nitride Halide Compounds. Collaborations with the Center for Suerconductivity Research at the University of Maryland will provide a wealth of new structure-property correlations that will be of interest to the solid state/condensed matter community as a whole.
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This project involves the development of new materials synthesis and processing tools to optimize the search for high performance materials such as electronic and magnetic materials. Due to the strong collaborations that have been arranged with the Center for Superconductivity Research at the University of Maryland, the education component of this project is particularly strong in that it will provide excellent training for undergraduate, graduate, and postdoctoral fellows interested in working in industry.
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With this award from the Major Research Instrumentation (MRI) Program, the Department of Chemistry at the University of Maryland in College Park will acquire an X-ray photoelectron spectrometer. This equipment will enhance research in a number of areas: a) nanostructure reactivity and registration at solid surfaces; b) derivatization of metal and metal oxide surfaces via molecular and mesoscopic self assembly; c) chemical vapor deposition of metal oxides; d) combinatorial synthesis of functional oxides; and e) soft chemical routes to novel solid state materials.

The X-ray photoelectron spectrometer (XPS) is used for chemical analysis. It irradiates a sample with a beam of monochromatic X-rays and the energies of the resulting photoelectrons are measured and related to specific elements. XPS often plays a crucial role in defining the system under study. The work to be carried out by these investigators represents a highly coherent attack on a range of issues at the forefront of materials chemistry.

This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports Professor Bryan Eichhorn at the University of Maryland to synthesize and study the properties of a new class of ligand-free inorganic binary clusters comprising catalytically-active transition metals and heavy group 14 and group 15 elements. Oxidation of these complexes in solution yields bimetallic nanoparticles with improved selectivity in heterogeneous catalytic applications. The research aims at developing catalysts with bifunctional activities through the use of active supports or multi-component catalyst particles, and the room temperature synthesis of different phases of alloy nanoparticles. The project will investigate the chemistry of catalytic processes of bimetallic catalysts including those for CO oxidation and lean NOx reduction in O2-rich exhaust gases.

Monometallic and bimetallic nanoparticles are used in a wide variety of applications including optical devices, magnetic nanostructures, and electronic devices. This research will provide synthetic methodologies for bimetallic molecular precursors to advance the technology of heterogenous catalysts. Graduate students, undergraduate students and postdoctoral associates will receive excellent training in synthetic materials methodology and the study of bimetallic heterogeneous catalysts.

With support from the Major Research Instrumentation (MRI) Acquisition Program, the Department of Chemistry and Biochemistry at the University of Maryland College Park (UMD) will acquire a 600 MHz spectrometer. The spectrometer will improve the diverse research capabilities at UMD in chemistry, biochemistry and materials science, as well as enhance research at Howard University and the Catholic University of America. Research that will be impacted include the design of catalysts for Ziegler-Natta polymerization, basic understanding of protein folding, synthesis of nanoparticles for use in hydrogen fuel cells, and the design of synthetic ion channels.

Nuclear Magnetic Resonance (NMR) spectroscopy is the most broadly used tool available to chemists for the elucidation of the structure of molecules. It is used to identify unknown substances and to provide information on the arrangement and connectivity of atoms in molecules. This award will provide these essential analytical capabilities to chemists, biochemists, and chemical engineers at the three institutions sharing the use of the nmr facility at UMD. To maximize the training component of the award, a course in practical nmr spectroscopy for senior and first-year graduate students will be established. The course will be co-taught by participating faculty from the three institutions.

Technical Abstract

The University of Maryland will form a regional microscopy facility through the acquisition of key instrumentation for a pair of new transmission electron microscopes (TEMs). The requested equipment includes analytical spectrometers for a JEOL 2100F field-emission TEM (installation 2/06) and specialized specimen holders for use with a new JEOL 2100 LaB6 TEM (installation 7/06). The spectrometers include an energy dispersive X-ray spectrometer and an electron energy loss spectrometer with spectral camera. The specimen holders will allow heating to 1273 K and cryogenic specimen transfer at 77 K. These additions to our facility will create a one-of-a-kind regional university facility in the Washington, DC metropolitan area, and will be a shared experimental facility for the NSF-MRSEC at UMD. Some of the research areas to be addressed with the requested instrumentation include: (a) structure and composition of multi-functional materials (both hybrid organic-inorganic systems and multiferroic self-assembled nanocomposite films); (b) the understanding of auditory sensory cells in birds and fish; (c) the structure and composition of doped semiconductor nanomaterials for spintronic applications; and (d) phase transitions of ferromagnetic shape memory alloys. The microscopy facility will be used in educational programs for undergraduate, graduate and postdoctoral students, and for training student researchers at the University of Maryland and five university partners in the DC area. The microscopes will enhance our K-12 educational outreach activities by providing virtual microscopy courses over the web and support other campus activities such as the ASM Materials Training Camp for teachers and Project Lead the Way.

Lay Abstract

Transmission electron microscopy is one of the most powerful tools for research in the fields of nano- and bio- technology. These microscopes can magnify up to 1.5 million times and allow the observation of materials at the atomic level. Through this proposal, the University of Maryland will acquire spectrometers for our new microscopes allowing us to form a unique new regional facility for cutting edge electron microscopy research and training across all educational levels. The facility will service the needs of institutions throughout the Washington, DC metropolitan area, including five partner Universities. This facility builds on a strong foundation at the University of Maryland in the areas of electron microscopy, nanotechnology and bioscience and will allow researchers to find pathways to better magnetic sensors, faster microelectronic devices, materials that change shape under applied fields, new nanoparticle catalysts, the understanding of sensory cells used in hearing and other biological functions. Many of these projects are also keystone areas in the Materials Research Science and Engineering Center already funded at UMD by NSF. The microscopy facility will be used in educational programs for undergraduate, graduate and postdoctoral students, and for training student researchers at the University of Maryland and five university partners in the DC area. The microscopes will enhance our K-12 educational outreach activities by providing virtual microscopy courses over the web and support other campus activities such as the ASM Materials Training Camp for teachers and Project Lead the Way.

wWith this award from the Chemistry Research Instrumentation and Facilities: Multi User program (CRIF:MU), the Department of Chemistry and Biochemistry at the University of Maryland will acquire a single crystal X-ray diffractometer. It will be utilized in research projects including 1) amidinate-based catalysts for living Ziegler-Natta polymerization 2) dirhodium catalyst 3) hydrocarbon activation catalysts 4) bimetallic nanoparticles from binary clusters 5) cucurbit[n]urils macrocycles and 6) self-assembled ionophores. The requested diffractometer will be housed in the University of Maryland's X-Ray Crystallographic Center. Catholic University, a Primarily Undergraduate Institution(PUI) and Howard University, a Historically Black College and University (HBCU) will have access to the proposed X-ray facility via collaborative agreements.

The technique of single-crystal X-ray crystallography allows accurate and precise determination of the full three dimensional structure of a molecule, including bond distances and angles, and it provides accurate information about the spatial arrangement of the molecule relative to the neighboring molecules. These studies will have an impact in a number of areas, especially synthetic chemistry.
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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

The award, as submitted to the Inorganic, Bioinorganic and Organometallic (IBO) program, supports work by Professor Bryan Eichhorn at the University of Maryland to carry out fundamental studies on the preparation of molecular clusters containing rare-earth atoms (i.e., La, Y, Gd) with direct, covalent metal-metal bonds. As there are no previous examples of such compounds known to date and the development of this chemistry will represent a major breakthrough in inorganic and cluster science, this award is made through the EArly-concept Grants for Exploratory Research (EAGER) Program. Professor Eichhorn and his group employ a unique, reduced metal halide synthesis device (the Schnockel reactor) to prepare solutions of the rare earth monohalides and dihalides. Sterically-encumbered amido and carboxylato ligands are incorporated to promote the formation of low-nuclearity clusters, i.e., La2 and La4 clusters. Controlled disproportionation reactions at higher temperatures are being used to generate larger "metalloid" clusters with high nuclearity La cores. The targeted f-block elements (i.e., Gd, Nd) are used to produce highly magnetic clusters resulting from direct coupling of f-electrons. Such magnetic nanoclusters provide fundamental insight into the nature of direct metal-metal bonding for rare-earth elements and could be directly applicable as magnetic storage components, magnetic imaging agents, and catalysts for organic transformations.