- American
Chemicial Society
- 57th
Southwest Regional Meeting
- October
17-20, 2001
- San
Antonio, Texas
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- Barron
Research Group Abstracts
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REACTIONS OF METAL AMIDES
WITH Ga2(tBu)4(neol)2
: A SCHIFF BASE-TYPE LIGAND
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- 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
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- 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.
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- GALLIUM ARYLOXIDE
POLYMER REACTION WITH AROMATIC AMINES: A NEW TYPE OF
CHEMICALLY-TRIGGERED SWITCH
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- 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
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- 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.
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- LIQUID PHASE DEPOSITION OF SILICON
DIOXIDE
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- Elizabeth Whitsitt and Andrew R.
Barron, Department of Chemistry, Rice University, Houston, TX
77005
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- 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.
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Strengthening Porous Alumina Bodies Using
Carboxylate-Alumoxane Nanoparticle Ceramic
Precursors
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- Kimberly A. DeFriend-Varela and
Andrew R. Barron, Department of Chemistry, Rice University,
Houston, TX 77005
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- 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.
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- Carboxylate-Alumoxanes: Formation of
Alumina Based Hollow Nanospheres
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- Kimberly A. DeFriend-Varela and
Andrew R. Barron, Department of Chemistry, Rice University,
Houston, TX 77005
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- 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.
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- Crosslinking of Boronic acids with
Glycols
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- Naureen Shahid, Andrew R. Barron,
Department of Chemistry, Rice University, Houston, TX,
77005
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- 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.
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Replica Molding of Patterned Features in
Carboxylate-Alumoxane Ceramic Precursors Through Soft
Lithography
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- J. R. Loscutova, Andrew R. Barron,
Department of Chemistry, Rice University, Houston, TX,
77005
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- 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.
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CATALYTIC H/D EXCHANGE OF AROMATIC
COMPOUNDS
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- 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
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- 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.
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- LEWIS ACIDITY OF GROUP 13
HALIDES
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- 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
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- 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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