Chemistry & Biochemistry Masters Theses

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Browsing Chemistry & Biochemistry Masters Theses by browse.metadata.program "Chemistry and Biochemistry"

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    Diastereoselective Conjugate Radical Additions to ~-Pyrones
    (North Dakota State University, 2009) Yu, Arvin Zillion
    A convenient protocol for functionalization of ~-pyrones has been developed. Conjugate radical addition and tandem addition-trapping protocols allowed accessing highly substituted pyrones in a single operation with high selectivity. Different radical sources were utilized in the reaction. nOe experiments were performed to confirm the relative stereochemistry of the substituents in the conjugate addition products. Initial studies on the enantioselectivity of the reaction were carried out. Unfortunately, the catalysts chosen for the initial studies did not show any promise regarding enantioselectivity.
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    Regioselective and Enantioselective Nitrone Cycloadditions to Alkynones.
    (North Dakota State University, 2010) Dunkle, Kelsey Lynn
    There has been a need in agriculture, medicine, and organic chemistry for enantiopure isoxazolines. A direct method for their synthesis is from the cycloaddition of 1,3-dipoles and alkynes. Alkynones are difficult substrates to use in cycloadditions due to their high reactivity and sometimes instability. Due to their high reactivity it is often difficult to control regio- endo/exo, and enantioselectivities in dipolar cycloadditions of alkynones. This thesis details the cycloadditions of nitrones and alkynones using chiral Lewis acids leading to isoxazolines with high regio-and enantiocontrol. A chiral bisoxazoline-zinc(II) complex successfully catalyzed the enantioselective 1,3-dipolar cycloaddition reaction of nitrone and alkynone derivatives. This is the second successful reported method for the catalytic enantioselective 1,3- dipolar cycloaddition of nitrones and alkynone derivatives. Yields for the cycloadducts were good to near quantitative and enantioselectivities were generally good reaching a high of 86 % ee. The 4-isoxazolines were isolated as single reg101somers.
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    Synthesis and Photophysics of Platinum(II) Terdentate and Bidentate Complexes.
    (North Dakota State University, 2010) Yi, Jing
    Platinum(ll) terdentate and bidentate complexes possess square-planar d8 configuration. The moderate metal-to-ligand charge-transfer (1MLCT) absorption, 3MLCT emission, and broadband excited-state absorption are the unique spectroscopic features for these complexes. In my thesis work, two series of terdentate platinum(II) complexes and one bidentate platinum(II) complex were designed and synthesized. The photophysical properties, such as the electronic absorption, photoluminescence, and triplet excited-state absorption, are investigated systematically. Chapter I introduced the representative work on the synthesis and photophysical studies of the terdentate and bidentate platinum(II) complexes reported in the literature. The motivation for my thesis project was briefly discussed. In Chapter 2, the synthesis and photophysical properties of two platinum 6-phenyl-4- (9,9-dihcxylfluoren-2-yl)-2,2 '-bipyridine complexes with phenothiazinyl (PTZ) acetylide ligand were discussed. Their UV-vis absorption and emission characteristics in solutions and LB films were systematically investigated. The triplet transient difference absorption and reverse saturablc absorption were also studied for these complexes. Both complexes exhibit a broad metal-to-ligand charge-transfer / ligand-to-ligand charge-transfer / intraligand charge-transfer (1MLCTi1LLCTi11LCT) absorption band between 400 and 500 nm and a 'MLCT/'ILClill",ll"' emission band at -594 nm at room temperature, which blue shifts at 77 K. Both UV-vis absorption and emission spectra show negative solvatochromic effect. Both of the complexes also exhibit broad and moderately strong triplet transient absorption from the near-UV to the near-IR spectral region. In addition, LB films of them were prepared and characterized by AFM technique. The UV-vis absorption and emission spectra of the LB films of them were also investigated and compared with those obtained in solutions. In Chapter 3, the synthesis and photophysical studies of a series of platinum 6-phenyl- 4-(7-benzothiazolyl-9, 9-diethyltluoren-2-yl)-2,2' -bi pyridine complexes with different acetylides ligands, such as, nitrophenyl acetylide, tluorenyl acetylide, and benzothiazolyltluorenyl acetylide, were discussed. The complex bearing nitrophenyl acetylide ligand exhibited quite distinct photophysical properties compared to the other two complexes. In Chapter 4, one platinum bis(mesitylimino)acenaphthene complex was synthesized. The lowest-energy absorption band was attributed to 1MLCT transitions, which was much broader and red-shifted (extending from 490 nm to 800 nm) compared to those reported for other diiminc Pt(II) complexes.