American Chemicial Society
57th Southwest Regional Meeting
October 17-20, 2001
San Antonio, Texas
 
Barron Research Group Abstracts
 
 
 
 

REACTIONS OF METAL AMIDES WITH Ga2(tBu)4(neol)2 : A SCHIFF BASE-TYPE LIGAND

 
Laura G. van Poppel,a Simon G. Bott,b Andrew R. Barron.a*
aDepartment of Chemistry, Rice University, Houston, TX 77005 and bDepartment of Chemistry, University of Houston, Houston, TX 77204
 
We have recently reported the reaction of M(tBu)3 (M = Al, Ga) with 2,2-dimethyl propane-1,3 diol (neol-H2) which yields [M2(tBu)4(neol-H2)] and have demonstrated their application as bifunctional (two OH groups) tetradentate (4O) ligands for Al and Ga, as well as for some of the first row transition metals (Fe, Co, Cu, Ni). The electronic and magnetic properties of these complexes show that the "Ga2(tBu)4(neol)2" ligand is similar to a Schiff base type ligand. We will report on the investigation of the reaction of the Ga2(tBu)4(neol)2 ligand with M(NR2)4 (M = Ti, Zr, V, Cr) as a route to making new mixed metal complexes.
 
 
 
GALLIUM ARYLOXIDE POLYMER REACTION WITH AROMATIC AMINES: A NEW TYPE OF CHEMICALLY-TRIGGERED SWITCH
 
Laura G. van Poppel,a Simon G. Bott,b Andrew R. Barron.a*
aDepartment of Chemistry, Rice University, Houston, TX 77005 and bDepartment of Chemistry, University of Houston, Houston, TX 77204
 
The cleavage of a Ga2O2 alkoxide dimer by a Lewis base offers a new mechanism for a chemically-triggered solid state sensor or switch. The solid state reaction of [{(tBu)2Ga}2(m-OC6H4O)]n with a Lewis base (L) gives the monomeric species [(tBu)2Ga(L)]2(m-OC6H4),which when heated undergoes a polycondensation polymerization back to [{(tBu)2Ga}2(m-OC6H4O)]n. The complete thermal and spectroscopic characterization of this system will be presented.
 
 
 
LIQUID PHASE DEPOSITION OF SILICON DIOXIDE
 
Elizabeth Whitsitt and Andrew R. Barron, Department of Chemistry, Rice University, Houston, TX 77005
 
 
Liquid phase deposition of silicon dioxide using fluorosilicic acid solutions saturated with silicon dioxide has been both documented in the literature and patented for selected applications in the electronics industry. Our goals include increasing the currently attainable deposition rate of this process in order to make the method industrially feasible, and finding novel applications for this coating technique. We are able to coat materials whose surfaces have been selectively functionalized, at low temperatures in aqueous solvent. Characterization of the materials is performed using TEM, SEM, AFM, ATR and microprobe.
 

Strengthening Porous Alumina Bodies Using Carboxylate-Alumoxane Nanoparticle Ceramic Precursors

 
Kimberly A. DeFriend-Varela and Andrew R. Barron, Department of Chemistry, Rice University, Houston, TX 77005
 
We have investigated the use of carboxylate-substituted alumina nanoparticles, i.e. carboxylate-alumoxanes as a strengthening agent to ceramic bodies and surfaces. An equivalent to a CMCFC, ceramic matrix ceramic fiber composite, has also been developed at a low cost, by infiltrating a porous ceramic with aceto-alumoxane (A-A). The effects of metal doped alumoxanes to increase strength have been determined. ESEM, AFM, elemental mapping, pore size and surface area analysis, micro-hardness testing, and 3 point bend test results will be presented.
 
 
Carboxylate-Alumoxanes: Formation of Alumina Based Hollow Nanospheres
 
Kimberly A. DeFriend-Varela and Andrew R. Barron, Department of Chemistry, Rice University, Houston, TX 77005
 
The use of carboxylate-alumoxane nanoparticles has been previously studied as coatings and thermal insulators for damaged ceramic bodies, carbon composites, and carbon fibers. Currently the prospect of using alumoxanes to coat polystyrene nanospheres to inherently form alumina nanospheres is being investigated. Well-defined particles ranging in size is important for various applications including ceramics, pigments, catalysts, electrical, and medical diagnosis. These spheres can be altered by their chemical composition, calcination, or by reduction or oxidation reactions. Morphology, success of shape retention, and surface roughness has been determined through x-ray analysis, ESEM, and AFM imaging. Stepwise thermal decomposition was studied though TG-DTA. Strength of the nanospheres has been determined through micro-hardness testing.
 
 
Crosslinking of Boronic acids with Glycols
 
Naureen Shahid, Andrew R. Barron, Department of Chemistry, Rice University, Houston, TX, 77005
 
A variable pH 11B NMR study has been performed in order to investigate the reaction of phenyl boronic acid with a range of diols, including ethylene glycol and cis- and trans- cyclohexane 1,2-diol. The relationship of these complexes to the crosslinking of guar will be discussed, as well as, the development of bi-functional borate crosslinking agents. Other molecules of the type (HO)2B-R-B(OH)2 have been studied to see if there are benefits to crosslinking in the diol system versus plain B(OH)4. Alumoxanes with borate functionalities have been prepared and crosslinkings have been studied.
 

Replica Molding of Patterned Features in Carboxylate-Alumoxane Ceramic Precursors Through Soft Lithography

 
J. R. Loscutova, Andrew R. Barron, Department of Chemistry, Rice University, Houston, TX, 77005
 
Microfabrication of MEMS structures through the use of soft lithography has been a promising method for producing micrometer-scale features. Here, we explore the utility of soft lithography in generating high aspect ratio features in various carboxylate-alumoxane ceramic precursors. Soft lithographic techniques are employed to form a polydimethylsiloxane stamp or mold containing the imprinted patterns, and alumoxane green bodies are then prepared by replica molding of the stamp. Upon firing, these alumina ceramics are shown to reproduce the patterns formed by conformal contact with the stamp. SEM images of the ceramic bodies confirm the presence and aspect qualities of the imprinted features.
 

CATALYTIC H/D EXCHANGE OF AROMATIC COMPOUNDS

 
Catherine S. Branch,a Simon G. Bott,b Andrew R. Barron.a*
aDepartment of Chemistry, Rice University, Houston, TX 77005 and bDepartment of Chemistry, University of Houston, Houston, TX 77204
 
Reaction of a solid aromatic with deuterated benzene is catalyzed by either (C6H5Me)2Hg(AlCl4)2 or (C6H5Me)2Hg(GaCl4)2. Site selectivity and H/D exchange rates will be discussed. Kinetic measurements by 1H NMR spectroscopy are presented, as well as the reaction of the substrate with HgCl2, AlCl3, or GaCl3.
 
 
LEWIS ACIDITY OF GROUP 13 HALIDES
 
Catherine S. Branch,a Simon G. Bott,b Andrew R. Barron.a*
aDepartment of Chemistry, Rice University, Houston, TX 77005 and bDepartment of Chemistry, University of Houston, Houston, TX 77204
 
The goal of this work is to develop a quantitative measure of Lewis acidity. Reaction of Group 13 halides, MX3 (M = B, Al, Ga; X = F, Cl, Br, I), with 9-fluorenone yields a Lewis acid:base adduct, MX3(9-fluorenone). These adducts have been characterized by multinuclear NMR, IR and UV-visible spectroscopy, and single-crystal x-ray diffraction. The bond dissociation energies have been determined by variable temperature 1H NMR spectroscopy. A scale of relative Lewis acidity is presented.
 

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