Thesis (M.S.)--Youngstown State University, 2009. / Includes bibliographical references (leaves 116-118). Also available via the World Wide Web in PDF format.

Four structural isomers of platinum(II) complexes with C-deprotonated R-C^N^N-R’ cyclometallated ligands (R-C^N^N-R’ = -extended 6-aryl-2,2’-bipyridine derivatives containing 2-naphthyl, 3-isoquinolinyl, 1-isoquinolinyl or 2-quinolinyl moieties) have been synthesized with their photophysical properties investigated. The one bearing a 3-isoquinolinyl moiety shows the highest emission quantum yield among the four and hence has been extensively modified to give a series of complexes with different ancillary ligands (chloride, iodide, phenoxide, or acetylide). Most of these complexes show vibronic emission (max = 515–644 nm) with high emission quantum yield (up to unity) in degassed CH2Cl2; one of them has been used for OLED fabrication and shows a maximum EQE of 8.15 % with current efficiency of 25 cd A–1. The photocatalytic properties of these derivative complexes for oxidative tertiary amine functionalization have also been examined. Several highly robust and emissive platinum(II) complexes supported by two types of tetradentate O^N^C^N ligand systems (Φem up to 0.99; Td up to 520 ℃) have been synthesized and show different emission energies (λmax = 482–561 nm). Most of them exhibit excimeric emission in solution state at room temperature which are dependent on the modifications on the tetradentate O^N^C^N ligands. DFT/TDDFT calculations reveal that the metal complex showing the most intense excimeric emission possesses an excimeric excited state with a localized structure, which is unusual for these classes of platinum(II) complexes. Based on this finding, WOLED (ηL(max) = 71.0 cd/A, ηp(max) = 55.8 lm/W, ηExt = 16.5 %, CIE = 0.33, 0.42, CRI = 77) and WPLED (ηL(max) = 17.0 cd/A, ηp(max) = 9.1 lm/W, ηExt = 9.7 %, CIE = 0.43, 0.45, CRI = 78) based on this complex have been fabricated with high efficiency achieved. Palladium(II) complexes containing C-deprotonated R-C^N^N-R’ cyclometallated and pentafluorophenylacetylide ligands exhibit phosphorescence in both solid state and fluid solutions at room temperature with some of them exhibiting aggregation-induced emission (AIE). These complexes have been applied as photosensitizers in light-induced oxidative functionalization of secondary and tertiary benzylic amines as well as in light-induced hydrogen production, with a maximum of 175 turnovers for hydrogen produced. Palladium(II) complexes containing two types of tetradentate dianionic O^N^C^N ligand systems (Systems 1 and 2) have been prepared and show constrasting photophyical properties. A full scale time-resolved spectroscopic analysis has been done on some of these complexes and a platinum(II) analogue. These complexes are found to have similar excited state decay pathway( 〖S_1〗^i→〖S_1〗^f→T) with ΦISC of about unity. The emission efficiency of System 2 complexes is superior to that of System 1 complexes, which is ascribed to the suppression of excited state distortion on the basis of the results of DFT calculations. A lower radiative decay rate of System 2 palladium(II) complexes relative to the platinum(II) analogue has been found, which could be due to their lower spin-orbit coupling constant. One of the palladium(II) complexes has been applied in vacuum-deposited OLEDs with maximum current density, power efficiency and EQE of 20.0 cd A^(-1), 13.6 lm W^(-1) and 7.4 % respectively. In addition, applications of these palladium(II) complexes as photosensitizers for oxidation of secondary amines have been examined. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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published_or_final_version / abstract / toc / Chemistry / Doctoral / Doctor of Philosophy

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Polynuclear lanthanide complexes have attracted increasing interest in coordination and materials chemistry as they generally possess aesthetically pleasing molecular structures and display interesting properties possibly for useful chemical and materials applications. The work described herein concerned with the exploratory synthesis, structural characterization, and property investigation of a number of polynuclear lanthanide and silver complexes with selected organic ligands. Details of this thesis work are summarized in the following chapters: Chapter 1 offers a background of the research, with an emphasis on lanthanide-containing compounds and polynuclear silver complexes. Synthetic methodologies, novel structural characteristics, and interesting physical properties toward possible applications are surveyed in order to convey the justification of this thesis work. Chapter 2 describes the design and synthesis, structural characterization of a series of dinuclear lanthanide complexes with 1-(2-pyridylazo)-2-naphthol. The photophysical properties of these complexes pertinent to optical-limiting applications are evaluated. Chapter 3 details the halide-templated assembly of dodecanuclear and pentadecanuclear lanthanide hydroxide complexes featuring histidine as supporting ligand via the ligand-controlled hydrolysis. Salient structural features of these complexes are discussed. Chapter 4 reports the synthesis, structural characterization, and spectroscopic studies of the giant polynuclear lanthanide complexes containing a 60-metal cluster core when threonine was used as the supporting ligand. Carbonate has been identified as a novel anionic template in these clusters. These Ln60 cluster complexes feature a sodalite cage structure with 24 vertex-sharing cubane-like [Ln₄(μ₃-OH) ₄]⁸⁺ units. Their magnetic and optical properties are measured and discussed. Chapter 5 describes the unexpected discovery of a polynuclear silver complex with histidine, first isolated from the reaction of a halide-containing polynuclear lanthanide hydroxide complex and then rationally prepared by using silver nitrate and histidine. A series of analogous silver complexes with other amino acids have subsequently prepared and structurally characterized. Chapter 6 details two silver-amino acid helicates composed of individual helical coordination polymers. Optically pure helicates were obtained by using enantiomerically pure amino acids. While silver-glutamate possesses a double-helical structure, silver-aspartate displays an unprecedented six-strand helical structure. Chapter 7 summarizes the results presented in Chapters 2-6 and elaborates on some future research directions toward which each of these projects may be heading.

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Fluorous chemistry has seen a number of advances since its birth in the early 1990s. One of the most attractive characteristics of fluorous solvents is their unique solubility properties depending on temperature. This phenomenon has led to the development of a wide range of catalysts that are modified with fluorous tags and are used in biphasic catalysis and easily recovered. Many fluorous phase transfer catalysts are confined to bringing small ions into fluorous media by using fluorous onium or crown ether vehicles. The most popular method to bring transition metal complexes into fluorous media is quite limited, usually resulting in ligand tuning and thus a change in reactivity at the metal center. This can be circumvented by pairing a cationic transition metal with a highly fluorous anion rendering the neutral species highly fluorophilic. To achieve this goal, we chose to use fluorous BArf₆, [B(3,5-C₆H₃(Rf₆)₂)₄]⁻, as the mode of transport and pair it with classic Werner-type complexes that recently have been shown act as organocatalysts in enantioselective Michael additions. The literature synthesis of Na[B(3,5-C₆H₃(Rf₆)₂)₄] (3) was improved and through salt metathesis two new fluorophilic salts were made. The Werner-type trication [Co(en)₃]³⁺ was solubilized in PFMC (perfluoromethylcyclohexane) to generate [Co(en)₃][B(3,5-C₆H₃(Rf₆)₂)₄]₃ (4). This fluorophilic salt was found to be preferentially soluble in fluorous media with a partition coefficient in PFMC/H₂O of 99.0:1.0 and in PFMC/CH₃C₆H₅ of >99.3:<0.7. Another Werner-type trication, [Co(R,R-chxn)₃]³⁺, was also paired with [B(3,5-C₆H₃(Rf₆)₂)₄]⁻ to afford [Co(R,R-chxn)₃][B(3,5-C₆H₃(Rf₆)₂)₄]₃ (5), whose partition coefficients in PFMC/H₂O and PFMC/CH₃C₆H₅ were the same as 4. Within the scope of Werner-type complexes, this work constitutes a significant stride toward developing a series of compounds that bring the concept of organocatalysis into fluorous media. The new compounds 3-5 show high preferences for the fluorous phase and provide a baseline for future Werner-type salt metathesis with fluorous BArf₆.