SYNTHESIS OF MONOMERS FOR NEW CONJUGATED POLYMERS

This dissertation addresses the problem of synthesis of different monomers for donor and acceptor polymers in photovoltaic applications. In general, functionalization of conjugated polymers and understanding of molecular packing of electron donors and electron acceptors are very important to produce efficient solar cells. As a result, it is important to design and synthesize novel monomers which will require making new π-conjugated donors and acceptors polymers and understand the influence of these new polymers in bulk heterojunction to design polymer solar cells. In this study, two different monomers were synthesized. The first monomer was designed and synthesized to investigate the effect of π-conjugated linker directly attached to the polymer backbone where the polymer backbone was based on thiophene unit and conjugated linker was 1,2,3-triazole. In a different study, a conjugated monomer based on benzthiadiazole was designed and synthesized in order to synthesize new acceptor homopolymers and alternating copolymers. Two different monomers with different alkyl side chains based on benzthiadiazole were synthesized and subject to Suzuki and Stille polymerization to get respective polymers.

The O-H stretching vibrations of Ni⁺(H₂O) were measured using vibrationally mediated photodissociation (VMP) in a depletion experiment, only monitoring transitions from K’’=1. This revealed a O-H symmetric stretch at 3629 cm^-1 and antisymmetric O-H stretch at 3692 cm^-1.

Several electronic structure calculations complement the experiments using the BHandHLYP hybrid density functional and the 6-311++G(3dp, f) basis set. At this level of theory, Ni⁺(H₂O) is predicted to have C_2v symmetry and ²A₁ ground state. The Ni-O bond length is 1.95, the O-H bond lengths are .955 and the H-O-H angle is 108.2˚ The molecule is a near-prolate top, with rotational constants A=13.98 cm^-1, B=0.297 cm^-1 and C=0.296 cm^-1 . Analysis of the electronic and vibrational spectra reveals that binding to Ni⁺ removes electron density from the oxygen lone pairs, increasing the H-O-H bond angle from its value in bare H₂O. The electronic and vibrational spectra corresponds to 4s ¬3d transistion in Ni⁺. As a result of electronic excitation, the Ni-O bond stretches by .20 Å, and the H-O-H bond angle is reduced.

We have recently proposed a new model for the transition from initiation to elongation in T7 RNA polymerase. DNA-to-DNA FRET measurements have allowed mapping the changes that occur before promoter release. To observe the movements of the rotating domain after promoter release requires protein labeling. We are developing a new technique of affinity directed site specific labeling of the protein. We have also begun to explore an intein mediated strategy for direct labeling of T7 RNA polymerase.

A new method was developed for the determination of methylation and reduction of arsenic species (As(III), As(V) and DMA) in Mueller-Hinton growth media by E. coli based on anion-exchange chromatography with post column hydride generation and inductively coupled plasma optical emission spectrometry (HPLC-HG-ICP-OES). The method was successfully applied to the determination of metabolism of arsenic by E. coli by analyzing the growth media and the cell extracts. The investigations suggested that E. coli did not methylate any of the arsenic species but simply reduced As(V) to As(III).

The media created a “split peak” effect for DMA, resulting in shorter retention time for the majority of the bulk and longer retention time for the rest of the species. This effect is most likely due to the reaction of DMA with the protein present in the media, generating a positive complex, which resulted in the shifts in retention times.

Although the presence of hydride generation help enhances the arsenic signal by almost 30 times, it also affects the intensities of each arsenic species differently, some, such as As(III), benefit from the reaction than others, such as As(V). The studies revealed that when measuring different arsenic species in the absence of hydride generation, the ICP-OES sensitivity is not the same for all. Results from t- and F-tests suggested that AsB, DMA and As(V) are statistically the same, whereas As(III) and MMA, which are statistically indistinguishable, are from a different distribution.

MAY 2007

BENJAMIN PAPA KWESI NII YANKOS VANDERPUIJE, B.Sc, KWAME

NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY, GHANA

M.S., UNIVERSITY OF MASSACHUSETTS AMHERST

Directed by: Professor Richard W. Vachet

We have developed a straight forward method that uses monolayer protected clusters (MPCs) and mixed monolayer protected clusters (MMPCs) as selective extraction and concentration probes for peptides. After extraction with these nanoparticles (NPs), the peptides are analyzed by MALDI-TOF-MS to obtain their mass fingerprints. Application of the method to a test library of 146 tryptic peptides showed that cationic MPCs/MMPCs target negatively charged peptides while the anionic MPCs/MMPCs target positively charged peptides. The extraction with these NPs is also accompanied by high concentration factors such they can be used to extract and concentrate microcystin-LR at levels below the WHO guideline of 1μg/L.