MENTORS / PROJECTS

Design and development of ionic liquid loaded supports (ILLS) for metals as heterogeneous catalysts (Collaborative project between Drs. Jang, Ni and Headley)

Ionic liquid loaded supports (ILLS) for metals as heterogeneous catalysts receive great attention because they offer the advantages of both homogenous and heterogeneous catalysis in one system, in addition to the fact that such systems use minimum amount of expensive ionic liquids. The ionic liquids loaded on traditional metal oxide supports have unique solubility for reactants and products and the metal catalyst particles can move around freely in ionic liquids, which can potentially produce high throughput desirable reaction products. This collaborative project will focus on Pd catalyst, using Pd nitrate and Pd chloride as precursors, supported on [BMIM][BF4] loaded silica, alumina and titania, the three most common supports. The research plan includes synthesis, characterization and the reaction testing.

1. Synthesis includes the loading of the ionic liquid to three supports with impregnation procedures followed by non-thermal plasma reduction with argon.
2. Characterization will include surface area and pore volume changes of supports before and after the loading of ionic liquid. The loading and the stability against temperature and atmosphere of ionic liquid on supports will be analyzed by NMR, TGA-MS and in-situ FT-IR  STEM and TEM techniques will be used to determine the thickness of the ionic film on supports and the metal particle size after the plasma reduction.
3. Reaction testing will use selective reduction of acetylene to demonstrate the benefit of the proposed Pd/ILLS reduced by argon non-thermal plasma.
 
The Development of Porphyrin Based Anion Receptors and Study of their Recognition Properties Using Mass Spectroscopy (Collaborative project between Drs. Starnes and Angel)

This project is centered on the design and synthesis of receptors for anions and molecules of biomedical and environmental significance. The research is multidisciplinary working at the interface between organic chemistry and biological, analytical, and separation chemistry. Specifically, the project centers on the synthesis of porphyrin based receptors for anions of environmental importance such as nitrite, nitrate, perchlorate, sulfate, and pertechnetate. The student working on this project will initially perform molecular modeling experiments in order to determine if a proposed host has the necessary geometry to bind a target anion. The student will then synthesize the host molecule. After isolating, purifying, and characterizing the host molecule the student will study its anion recognition properties. The student will use techniques such as NMR, IR, and MS to characterize all material. We will attempt to grow crystals for x-ray analysis. The recognition studies will be performed using NMR, UV/Vis, fluorescence and mass spectroscopy. The collaborative nature of this work centers on the use of mass spectroscopy to examine the molecular recognition properties of our hosts. Mass spectroscopy provides us the ability to better and more rapidly characterize our receptors and their complexes. The student working on this project will learn to use the mass spectrometer to study molecular recognition properties of the receptor by searching for host:guest complexes in competition experiments (one host plus multiple anion guests to see which complex proves to be the most stable under the MS conditions). Thus, using MS, we would also be able to monitor molecular recognition properties of our hosts in a mixture of guest targets because the complexes would each have different molecular weights. The student will use MS to determine association constants between our host and guest targets. A student working on this project will gain experience in molecular modeling, synthetic organic chemistry, NMR, IR, UV/Vis, fluorescence and mass spectroscopy.
 
Ionic Liquid-Supported (ILS) Chiral Ligands and Their Applications as Homogeneous Catalysts for Asymmetric Reactions(Collaborative project between Drs. Ni & Headley)

Homogeneous asymmetric catalysis using chiral phosphorus ligands is one of the most important developments in modern chemistry. However, a major problem associated with most homogeneous catalyst systems is the separation and recycling of these precious chiral phosphine ligands. These problems can be overcome by immobilization of chiral ligand/metal catalysts onto soluble ionic liquids (ILs) supports because the solubility of ILs can be tuned readily by modification of their cations and anions. To date, the use of ionic liquid supported (ILS) chiral ligand/metal complexes as catalysts for the asymmetric reactions are very less studied and the problems associated with leaching and/or stability of the reactive ILS chiral catalysts in ILs still remain to be solved. This research proposal seeks to fund a three year project directed toward the design, synthesis, characterization of a series of new category of ILS chiral phosphorus ligands and their application with metal complexes as recyclable homogeneous catalysts for the asymmetric reactions including hydrogenation reactions and 1,4-addition reactions. Dr. Ni has successful background in academia and experience in organometallic chemistry and ionic liquid chemistry. The proposed project will divided into two parts: (1) A series of ILS chiral phosphorus ligands will be synthesized and characterized; (2) the effects that ILS chiral phosphorus ligands have on two types of asymmetric reactions, the hydrogenation reactions of prochiral enamides, β-keto esters, and acetophenone and the conjugate addition reactions of organoboronic acids to α,β-unsaturated ketones, will be studied. For these reactions, ILS chiral phosphorus ligands combination with transition metal will serve as the chiral catalysts. 

Proteomics of the Cellular Membrane: Mass Spectrometry of Fragments Selectively Cut from Extracellular Membrane Proteins (Collaborative project between Drs. Angel and Kostić) 

Proteomics, an offshoot of the bioinformatics and genomics revolution, is the study of all proteins a cell makes. In medical research, proteomics is indispensable for identifying the unique proteins expressed by various normal and diseased cells. Unfortunately, the complexity of such mixtures makes analysis of a crude cell extract nearly impossible. For better reliability, particular fractions of proteins must be isolated before being analyzed. The cell membrane is an especially rewarding target because it contains numerous proteins that control a cell’s interactions with its environment, including other cells in the body. These proteins are troublesome to study intact because they are very large, insoluble, and embedded in the cell membrane. If these proteins can be cut into smaller fragments, however, they become more tractable. In this project Dr. Kostić will use palladium(II) reagents synthesized in the lab to cleave proteins and simultaneously label them with a metal tag that will allow chromatographic purification. Dr. Angel will develop the procedure for separating protein fragments by HPLC. Angel will use the mass to charge ratio and the characteristic “fingerprints” of attached palladium isotopes to identify several key fragments diagnostic of each cellular protein.  
 
Characterization of supported Pd and promoted Pd catalysts with Non-thermal Plasma modifications (Collaborative project between Dr. Jang, PI  and Dr. Overbury of Oak Ridge NL)

It is demonstrated that non-thermal plasmas using non-reducing gases can reduce supported Pd nitrate catalysts. By monitoring the FT-IR nitrate peak at ~1380 cm-1 and using the scanning transmission electron microscope (STEM) technique it is confirmed that 30 minutes of air plasma treatment can reduce ~20% of Pd nitrate supported on TiO2 to Pd metal while H2 plasma treatment can achieve 100% reduction. The discoveryof the reduction capacity of non-thermal plasma using non-reducing gases is an important step toward novel design and development of supported metal catalysts. Novel catalysts can be produced with a simple, inexpensive, effective and environmental procedure. The objective of this collaborative project, teamed between Dr. Jang and Dr. Overbury of Oak Ridge National Lab (ORNL), is to investigate the fundamental interaction between non-thermal RF plasma and the supported metal catalysts for the design and development of novel catalysts.  On-line monitoring with mass spectrometer and emission spectrometer during plasma procedures and detailed characterization of the surface property changes of Al2O3 and TiO2 supported Pd catalysts will be studied to understand the fundamental effects of plasma modifications on supported metal catalyst materials. The changes of (i) supports and (ii) supported palladium catalysts will be characterized with in-situ FT-IR, temperature programmed techniques, XPS, XRD and STEM with EDX before and after plasma treatments. STEM, XPS and XRD analyses will be carried out via the user program funded by the Center of Nanophase Materials Sciences of ORNL. The characterization results will be related to the reaction results of selective hydrogenation of acetylene obtained in the PI’s laboratory.

The Development of Ionic Liquids Modified with Anion Recognition Sites (Collaborative project between Drs. Starnes, Headley, and Ni)

This project centers on the design and synthesis of ionic liquids that contain anion binding sites. Thus, an ionic liquid will be tailored to contain sites or macrocycles that contain hydrogen bond donating sites such as sulfonamide(s), urea(s), thiourea(s), ammonium, or quaternary ammonium sites to determine 1. if the ionic liquid retains its ionic liquid nature and 2. if the new ionic liquid can extract anions from an aqueous solution. The relevance of the work centers on the fact that there are many anionic species of environmental concern (such as nitrite, nitrate, perchlorate, sulfate and pertechnetate to name a few) and the fact that developing extraction agents and sensors for these species remains a challenging feat due in part to the hydrophilic nature of some target anions. It is known that motifs containing hydrogen bond donating sites make for good anion recognition sites. Coupled with the polar nature of ionic liquids, these modified ionic liquids might make for good extraction agents for anions of environmental importance.
 Thus, a student working on this project will synthesize ionic liquids containing anion recognition elements. The student will then conduct extraction experiments to determine how efficiently the modified ionic liquids can extract anions from an aqueous solution (will the extractions follow a Hoffmeister trend, anti-Hoffmeister, or will it be possible to develop ionic liquid anion hosts that are selective for the anion of choice?). The student will also determine binding constants of the ionic liquid anion host with a variety of anions; this can be accomplished by preparing a solution of a normal ionic liquid (one that doesn’t contain the desired anion binding site) doped with a known concentration of the ionic liquid anion host , then titrating the resulting solution with known concentrations of anion guests. Students working on this project will gain experience in synthetic organic chemistry, ionic liquids, NMR, UV/Vis and fluorescence spectroscopy, and extraction techniques.