Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xvii, 171 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Claudia Turro, Dept.of Chemistry. Includes bibliographical references (p. 168-171).

Thesis (Ph. D.)--University of Hong Kong, 1989.

Thesis (M. Phil.)--University of Hong Kong, 1989.

The syntheses, structures, photophysical properties and applications of three types of photoluminescent organoplatinum(II) complexes containing N-heterocyclic carbene (NHC) ligands are described. The tetradentate dianionic bis(phenolate-NHC) type ligands provide a superior scaffold for constructing thermally stable and efficient deep-blue phosphorescent Pt(II) complexes with λmax of ~440-460 nm and solid-state emission quantum yields of ~30%. Highly efficient blue OLEDs with CIEx, y of (0.19, 0.21) were fabricated based on these emitters with maximum brightness, peak current efficiency and power efficiency of ~9500 cd m^(-2), 24 cd A^(-1) and 17 lm W^(-1), respectively. Structural modification by extending the π-conjugation of the tetradentate bis(phenolate-NHC) ligand leads to strongly phosphorescent platinum(II) complexes with long-lived emissive electronic states that can be used as a luminescent sensor for oxygen. DFT/TDDFT calculations and time-resolved spectroscopic characterizations were performed to gain insight into the structure-photophysics correlation. The N-heterocyclic carbene (NHC) ligand was incorporated into Pt(II) complexes containing tridentate deprotonated 1,3-bis(2-pyridyl)benzene (N^C^N) type ligand. In addition to the [(N^C^N)Pt(NHC)]PF6 type complexes with (N^C^N) in η3-tridentate coordination mode, Pt(II) complexes with η2-bidentate (N^CN) ligands, namely [(N^CN)Pt(NHC)2]PF6, have been isolated and structurally characterized. The highly phosphorescent [(N^C^N)Pt(NHC)]PF6 complexes were used for solution-processed green OLEDs fabrication. The peak current efficiency of 12.5 cd A^(-1) and maximum brightness higher than 2000 cd m^(-2) were achieved. The presence of the pendent pyridyl motif causes quenching of emission of the [(N^CN)Pt(NHC)2]PF6 complexes in solution at room temperature. Turning on solid-state emission of [(N^CN)Pt(nBu2Im)2]PF6 in the presence of an acidic vapor revealed its potential as a luminescent chemosensor. A class of dicationic platinum(II) terpyridyl complexes containing NHC ligand, namely [Pt(tpy)(NHC)](PF6)2, has been synthesized and structurally characterized. Even in the presence of the strong σ-donating NHC ligand, these complexes are non- or weakly emissive in solution at room temperature. However, this class of complexes displays intense emissions in solid state (298 K and 77 K), in glassy solution (77 K butyronitrile) and in PMMA (2 wt.%, 298 K). The ligand (terpyridine) displacement reaction arising from CN attack onto the Pt(II) center has been observed for [Pt(tpy)(nBu2Im)](PF6)2 leading to its application as a chemodosimeter for selective cyanide sensing in aqueous solution. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

The photochemistry of several tribromo-compounds, R−CBr3 (R = CH2OH, CH2OC(O)CF3, COOH) have been studied by utilizing nanosecond transient absorption (ns-TA) and femtosecond transient absorption spectroscopy. Femtosecond transient absorption experiments showed that isomer species R−CBr2−Br were formed after excitation of R−CBr3 within several picoseconds. The absorption band of the isomers R−CBr2−Br showed a strong solvent dependence upon changing the solvent from cyclohexane to acetonitrile. The absorption wavelength of the proposed isomer intermediates and the spectral shift in cyclohexane and acetonitrile were consistent and supported by results from time-dependent density functional theory (TDDFT) calculations. The decay of the isomer intermediates were significantly shortened by the presence of water and alcohols which indicated that R−CBr2−Br intermediates are likely to react with water and alcohols. Second-order Møller-Plesset perturbation theory (MP2) calculations were employed to investigate the structures and energies of the OH-insertion reactions of R−CBr2−Br when water/alcohol molecules (up to three) were explicitly involved in the reaction complex. The reaction mechanisms examined were found to be dramatically catalyzed by the hydrogen bonding of the water molecules causing the molecule to undergo decomposition. The calculations indicate that the isomer species are able to react with water and alcohol via a water catalyzed OH-insertion/HBr elimination reaction to produce a R−CBr2(OH) product. The ab initio calculations suggested that the R−CBr2(OH) product can undergo a similar water catalyzed reaction mechanism to form R−C(O)Br. The acyl bromide type compounds were also studied using ab initio calculations. The dependence on the substituent group R was found to influence the decomposition pathways that form various final products. The results of the experimental and computational results discussed in this thesis were summarized and some issues were detailed that could be prospects for further study in the future. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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Gridded, regional photochemical models use simplified photochemical reaction mechanisms, and two commonly used mechanisms are the [California] Statewide Air Pollution Research Center (SAPRC) mechanism and the Carbon Bond (CB) mechanism. Versions of the mechanisms currently in use include SAPRC99 and the CB-IV version from 1996. For the modeling done of the summer of 2000 in southeast Texas, the SAPRC99 mechanism leads to concentrations of ozone that are 30-45 ppb higher than with CB-IV, and is more sensitive to reductions in NOx emissions. Differences between the mechanisms could have significant consequences for determining the levels of emission reductions that will be required to demonstrate attainment with the National Ambient Air Quality Standard (NAAQS) for ozone, with concentrations averaged over 8 hours. Therefore, various modeling tools, together with chamber experiments were used to diagnose the differences between the mechanisms. These differences are due to differences in both reaction rate parameters/stoichiometry and the condensation methods in the mechanisms. Major reasons for the differences are differences in aromatics and free radicals chemistries, which lead to higher radical concentrations in the SAPRC formulation.

No description available.

published_or_final_version / Chemistry / Master / Master of Philosophy