* Denotes undergraduate coworkers

Anionic Polyelectrolytes for Solid State Battery Applications

Jason T. Manka*, Miroslaw Trznadel, Piotr Kaszynski, and Andrienne C. Friedli

Two approaches to boron-containing solid-state electrolytes were pursued. A polymer electrolyte design relies on the doping of lithium salts of boron clusters into homopolymers such as known poly(1a) and our poly(1b). The polyelectrolyte design incorporates boron clusters, non-nucleophilic anions, into the poly(1c) polymer through covalent bonding.

The class of monomers related to 1 undergoes a retro-Diels-Alder reaction (rDA). We have modeled the reaction with B3LYP/6-31G*, and calculated thermodynamic and kinetic parameters from NMR data. First order rate constants for the rDA of 1a were k = 1.91-14.2 x 10^-5 s^-1 measured at four different temperatures between 124 and 150 °C. Activation parameters were Ea = 34.5 ± 0.5 kcal/mol and ln A = 1.77 ± 0.03 x 10⁴.

Figure 1. ¹H NMR spectra showing progress of rDA reaction of 1a at 124 °C.

Figure 2. Plot of ln(x+1) versus time for 1a at 124, 130, 140 and 150 °C, where x is the mole ratio of 1a to 1,4-dimethoxy-2-butene. Rate constants were derived from the line slopes.

Manka, J. T. *; Douglass, A. G.; Kaszynski, P.; Friedli, A. C . "An Experimental and Theoretical Investigation of the Retro Diels-Alder Reaction"J. Org. Chem. 2000, 65, 5202.

Understanding NMR Behavior of Some Diethyl Chlorosilanes.

Nathan R. Tilton*, Cherkitra A. Swanson*, and Andrienne C. Friedli

While synthesizing new organosilane precursors for films, we observed unexpected NMR behavior in certain diethylsilanes. Specifically, in Et₂PhSiCl and Et₂SiCl₂ there was no discernible difference in the chemical shifts of the methylene and methyl protons, while ¹³C NMR clearly indicated two different carbons. Increasing the NMR field from 200 to 400 MHz gave a hint of coupling. In order to better understand this phenomenon, we measured proton NMR for several ethyl silane derivatives and performed geometry optimizations, followed by isotropic NMR chemical shift calculations using the 6-31G* basis set in Gaussian 98 for PhEt₂SiX and Et₂X₂ (X = H, F, Cl, Br). This model correlated poorly with the experimental data and we will use B3LYP in the future.

Synthesis of Amino- and Ester-terminated Organosilanes for Surface Derivatization of Biosensors David E. Noga*, Cynthia R. Allison*, Adam F. Farmer*, and Andrienne C. Friedli, Middle Tennessee State University, Murfreesboro, Tennessee.

Organosilanes have been used as precursors for coatings that change properties and chemistry of surfaces. We modify planar and spherical surfaces with end-functionalized organosilanes for applications in biosensors or patterned surfaces. Here we report the synthesis of 10-amino-1-trimethoxysilyldecane (1), t-butyl 10-trimethoxysilyldecanoate (2), and derivatives. Ester 2 was synthesized in three steps from commercial 10-undecenoyl chloride. The synthesis of 1 was carried out in four steps via a modified Curtius reaction involving the conversion of 10-undecenoyl chloride to the trifluoroacetamide, alkaline hydrolysis to the amine, and hydrosilylation to 1. Protection and deprotection procedures for the silane precursors and their siloxane films were investigated.

Potentially Liquid Crystalline Dyes for Nonlinear Optics

R. William Tilford*, Deborah G. Anderson*, and Andrienne C. Friedli

We have synthesized and characterized 1[n] n=0-2 and converted the aldehydes into stronger acceptors by Knoevenagel condensation with dicyanomethane or diethyl thiobarbituric acid. These are similar in structure to known NLO model compounds 2[n] and 4[n]. UV/vis spectroscopy shows slight solvatochromism, a good indicator of nonlinear optical behavior. Observation with polarizing microscopy reveals a wide-range Smectic A phase in 1[2]. Characterization of compounds 1[n] is complicated by overlap in the vinyl region of the 1H NMR spectra, which is nicely resolved at 400 MHz. We have also investigated similar donor-acceptor compounds based on indoline and tetrahydroquinoline. The calculated AM1 pyramidalization at nitrogen and aromatic C-N bondlength were correlated with known NLO behavior and the prediction made that our 1[n] and 4[n] derivatives will be poorer NLO materials than 2[n], 3[n], or 5[n].

Correlation of Dye Color With Structure: Modular Organic Laboratory Experiments. Andrienne C. Friedli, Cameron K. Gren*, and Elizabeth C. Moll*

A set of modular synthetic, spectroscopic, and computational laboratory experiments and a demonstration involving colorful donor-acceptor benzylidine dyes was assembled for the organic classroom and laboratory. The synthetic modules describe the relatively rapid preparation and isolation of compounds 1aA-1dE and 2bA, 2bD with a variety of donor/acceptor combinations via a Knoevenagel condensation. This allows an opportunity for further spectroscopic analysis using UV or ¹H NMR. Spectroscopic experiments range from rudimentary (spectrum) to intermediate level (Beer's Law plots) to advanced studies (solvatochromism). Computational modules allow analysis of the reactivity and electronic structure of the dyes using molecular modeling packages and challenge students to predict or confirm observed properties of compounds with structures 1-4. In a typical adaptation, students synthesize a large variety of compounds collectively and measure or compute their properties. In this way, they can compare results and make conclusions about the effect of molecular structure upon properties.

Peptidomimetics of D-Alanyl-D-Alanine as Novel Antibacterials

Greg Moody*, James M. Jones*, Jesse Carrick*, Brian Smith*, Terry Parsons*

Tao Meng, Garry Pennycuff, Xintao Wang, Wosenu Mergo, and Norma K. Dunlap

A series of peptidomimetics of D-alanyl-D-alanine have been designed as potential inhibitors of the D,D-peptidases. These enzymes function in the cross-linking of peptidoglycan strands in the bacterial cell wall and are the target of b-lactam antibacterials. The synthesis of intermediates 1 and 2 have been completed, with only deprotection steps remaining to complete the syntheses. Decoupling and COSY experiments allowed the assignment of the stereochemistry at C-2 of the precursor alkene 3.

N. K. Dunlap, W. Mergo, J. M. Jones*, and J. D. Carrick* "A General Procedure for a One-Pot Oxidative Cleavage/Wittig Reaction of Glycols," Tetrahedron Letters 2002, 3923.

Analogs of epi-Podophyllotoxin as Probes of the Topoisomerase Binding Site

Mohammed Q'Shadid, Ian Romaine, and Norma K. Dunlap

The antitumor agents etoposide and teniposide are inhibitors of topoisomerase II. In the absence of drug/enzyme x-ray crystal structures, a series of analogs of these compounds are being prepared as probes of the enzyme binding site. Transfer NOE will be used to gain information on enzyme-drug interactions. Some initial targets are compounds 1 and 2.

Nucleotide and Nucleoside Adducts of meso-Butadiene Diepoxide

Leah Wong and Norma K. Dunlap

The petrochemical butadiene has numerous industrial uses, but is also a significant pollutant which has been shown to be carcinogenic in animal models. The genotoxicity is believed to arise from the formation of DNA adducts of the oxygenated metabolic products of butadiene. The meso-diepoxide is believed to be the most cytotoxic. We have initiated a project to synthesize stereoisomerically pure adducts of meso-diepoxide with adenosine, guanosine and also of oligonucleotides containing the adducts. These adducts will be useful as standards for comparison to butadiene-derived DNA adducts formed in vivo. The aminotriol 1, and a model adduct 2 have been prepared and formation of the adenosine adduct is in progress.

Telluronium Iodide as a ¹²⁵Te NMR Shift Reference

Allen J. Bailey*, Jessica C. Shamblin*, William H. Ilsley, and Judith M. Iriarte-Gross

Tellurium compounds are of interest for new materials for applications in electronics and optics. ¹²⁵Te NMR spectroscopy is principal method of characterization for tellurium-containing compounds, since the relative abundance is 12.5% and the chemical shift (range 5500 ppm) has high sensitivity to substituents. However, a universal standard has not yet been found.

Previous studies of a common solvent, (CH3)₂Te, found it to be solvent, temperature, and concentration dependent. Our studies of (CH3)₃TeI demonstrated it to be a good aqueous reference, with chemical shift insensitivity between pH 2.6-10.3 and a small dependence upon temperature (7 ppm between 285 and 310 K). Ab initio calculations (3-21G* support the hypothesis that (CH₃)₃TeI is ionic and the cation undergoes inversion.

Iriarte-Gross, J. M.; Ilsley, W.; Bailey, A.*"Investigation of Trimethyltelluronium Iodide as a Tellurium-125 NMR Chemical Shift Reference and Its Structure," Proceedings of the National Council of Undergraduate Research, 1998.

pH Studies of Te(OH)₆

Freneka F. Minter*, Judith M. Iriarte-Gross

Telluric Acid, Te(OH)₆, is a potential ¹²⁵Te NMR (Tellurium-125 Nuclear Magnetic Resonance) spectroscopy chemical shift reference and a potential sol-gel precursor. Telluric acid is stable in air and can be purchased commercially. Previous work has shown the Te(OH)₆is insensitive to concentration, temperature, and to acidic pH. In the basic pH range of 6 to 10, a precipitate formed in the Te(OH)₆ solution. We have conducted additional pH studies on Te(OH)₆. We have also characterized the Te(OH)₆ solutions and precipitates using ¹H and ¹²⁵Te NMR spectroscopy and FT-IR.

Synthesis of Selenium and Tellurium Alkoxides

Hadi D. Arman*, S. Timothy Decha-Umphai*, Judith M. Iriarte-Gross

The syntheses of selenium, [Se(OR)₄], and tellurium, [Te(OR)₄], alkoxides are being investigated. These compounds will be characterized by ¹H, ¹³C, ⁷⁷Se, and ¹²⁵Te NMR spectroscopy. These alkoxides are precursors for the sol-gel process. We are exploring the different properties of higher order selenium and tellurium alkoxides.

Studies of Selenious Acid Doped Sol-Gel Materials

Salar Sadjadi*, Judith M. Iriarte-Gross, William H. Ilsley, Barry A. Farris

The process of silica sol-gel reactions leading to the production of glass through the use of selenious acid has been the essential part in developing new techniques related to the controlled synthesis of selenium dioxide, SeO₂, doped silicate. An experimental method using either the methoxy or ethoxy ligand was developed and optimized to synthesize silicate materials which contain selenium. Two different analytical techniques were used to analyze materials formed from the sol-gel solutions. Infrared Spectroscopy was used for the analysis of solid materials, and Nuclear Magnetic Resonance (NMR) Spectroscopy was used for the analysis of liquid materials. Results will be presented and discussed.

Studies of Telluric Acid Doped Sol-Gel Materials

Sayena Sadjadi*, Judith M. Iriarte-Gross, William H. Ilsley, Barry A. Farris

The silica sol-gel process using telluric acid and tellurium dioxide powder provides a new method of investigation in producing telluric acid and tellurium dioxide incorporated silicate glasses and ceramics. An experimental method was developed to synthesize telluric acid and tellurium dioxide doped sol-gel materials. The pH of the reaction was varied. Proton NMR chemical shifts, FT-IR data, and computational calculations are reported and discussed.
 
 

Tellurium Silicate Chemsitry

Kenneth King*, Judith Iriarte-Gross, William H. Ilsley

Tellurium incorporated sol-gel glasses were produced using tellurium tetrachloride, TeCl₄, as a reagent within a silicon ethoxide sol-gel system. The pH was varied as was the alcohol used. The glasses were analyzed using infrared spectroscopy and ¹H NMR spectroscopy. Preliminary results show that tellurium had been incorporated into the sol-gels.
 
 
 
 

Selenium Silicate Studies

Scarlette Hodge*, Judith Iriarte-Gross, William H. Ilsley

Selenium-containing sol-gel glasses were produced using selenium dioxide, SeO₂, or selenium tetrachloride, SeCl₄, combined with a silica sol-gel system. The reactions were stirred for 24 hours and aliquots were taken out each day. The samples were analyzed using infrared spectroscopy and ¹H NMR spectroscopy. Our preliminary results indicate that Se has been incorporated into the structure of the glass.
 
 

Synthesis and Analysis of Selenium and Tellurium Alkoxides

Sorawit Timothy Decha-Umphai*, Whitney Lee*, Joanna Velasquez* and Judith M. Iriarte-Gross

Metallic alkoxides have been widely studied as precursors for sol-gel materials. Certain studies have shown that metallic alkoxides can create sol-gel materials with higher melting points and other unique properties. Selenium and tellurium alkoxides as sol-gel precursors have not been studied in detail. A procedure has been found to synthesize selenium or tellurium alkoxides using the non-hydrolytic process. The first approach to synthesize a selenium or tellurium alkoxide was to perform the reaction macroscopically on the bench. However, an alternate procedure was developed to synthesize the alkoxide in an NMR tube, which allowed for a convenient analysis of the synthetic intermediates and products. Results obtained using ¹H, ¹³C, and ⁷⁷Se or ¹²⁵Te NMR spectroscopy are discussed.
 
 
 
 

Experimental And Theoretical Selenium-77 NMR Chemical Shifts for the Series,

(CH₃)_4-XSi(SeCH₃)_X, x = 1 — 4

Zahra Rezaei*, Judith M. lriarte-Gross, William H. Ilsley

The nature of the selenium-silicon bond in the series, (CH₃)_4-xSi(SeCH₃)_x, was investigated using both experimental and theoretical methods. Selenium-77 NMR chemical shift data, absolute shielding constants, calculated selenium-silicon bond lengths and bond angles were determined. Gas phase Ab-Initio calculations such as Hartree-Fock (HF), Density Functional Theory (DFT), and second order Moller-Pesset Pertubation Theory (MP2) methods have been conducted on these compounds and will be discussed. Current work is focusing on similar studies for the analogous tellurium compounds.
 
 
 
 

Synthesis and Quantitative Studies of Tellurium Silicate Sol-Gel Materials

Valencia Smartt*, Judith M. Iriarte-Gross, and William Ilsley

In this research, tetraethyl orthosilicate, Si (OCH₂CH₃)₄, was doped with telluric acid, Te(OH)₆, or tellurium (IV) chloride, TeCl₄. A sol-gel product was synthesized. The reaction time, pH and quantity of reactants were varied. Intermediates and products were analyzed by IR and NMR spectroscopy. Computational calculations were conducted to determine the molecular geometries of the proposed intermediates and products.
 
 

Synthesis and Analysis of Selenium Silicate Sol-Gel Materials

Samuel Deputy*, Judith M. Iriarte-Gross, and William Ilsley

Selenium dopes sol-gel glasses were produced using selenious acid, H₂SeO₃, or selenium (IV) chloride, SeCl₄, as dopants within a tetraethyl orthosilicate, Si(OCH₂CH₃)₄, sol-gel matrix. The pH of the system was varied as were reaction times. The intermediates and glasses were analyzed using IR and NMR spectroscopy. Computational calculations were conducted to identify the molecular geometries and energies of the compounds being studied.

Is the Oxidizing Agent Ce(IV)/SiO₂ a Genuine Example of a Solid-Supported-Reagent System? Jennifer G. Martin-Tarpley,* David G. Lancaster*, James C. Howard, and Martin V. Stewart

Traditional procedures for conducting organic reactions where both the starting compound and the reagent are present in the same homogeneous medium have been extended to heterogeneous conditions by stirring a solution of the starting material over a solid-supported reagent, which often gives a higher product yield under milder conditions. For example, the oxidizing agent Ce(IV)/SiO₂ is prepared by coating silica gel with ceric ammonium nitrate and is used to oxidize hydroquinones to their corresponding 1,4-benzoquinone. Analytical results from ¹H NMR spectroscopy, including detection limits measured from the signal-to-noise ratio, demonstrate that this heterogeneous oxidation only occurs when Ce(IV) is supported on the surface of silica gel and is not promoted by the individual components of this solid-supported reagent either separately or when physically mixed. Thus, no reaction is detected by ¹H NMR spectroscopy when 2,5-di-tert-butylhydroquinone is stirred for five minutes at room temperature over either powdered ceric ammonium nitrate or silica gel alone or over a physical mixture of both powdered ceric ammonium sulfate and silica gel; however, a quantitative yield of 2,5-di-tert-butyl-1,4-benzoquinone is obtained when the hydroquinone is similarly stirred over a sample of silica gel whose surface was previously coated with ceric ammonium nitrate. This experiment confirms that the oxidizing agent Ce(IV)/SiO₂ is a genuine example of a solid-supported-reagent because it constitutes a discrete chemical system that has reactive properties not displayed by its individual components or by a physical mixture of them.