Master of Science (MS), Wright State University, 2006, Chemistry

Thermal and microwave polyol methods were investigated in the synthesis of various iron and cobalt core-shell nanoparticles. The reaction involved 1 mmol of an Fe+2 or Co+2 salt, bis-acetylacetanato [(Acac)2] iron (II), cobalt (Acac)2 or iron (II) acetate along with 1 mmol of a surfactant capping agent. The salt was reduced with 2 mmol of a 1,2 diol. When 1,2-hexadecanediol solid was used as a reducing agent, it was dissolved along with the metal salt and capping agent in octyl ether. When 1,2-hexanediol liquid was used as the reducing agent, it was also the solvent, and octyl ether was eliminated. For reactions in which octyl ether acted as the solvent, the capped nanoparticles were precipitated using ethanol. For reactions in which the solvent also acted as the reducing agent, the particles precipitated after nucleation and supersaturation of the polyol solvent/reducing agent.

Committee: Eric Fossum (Advisor) Subjects: Chemistry, Inorganic

PhD, University of Cincinnati, 2008, Arts and Sciences : Chemistry

A detailed study involving platinum(II) compounds with bis-2,6-pyrazolyl-phenyl type ligands have been undertaken in an effort to design a new architecture for building macrocyclic molecules with potentially coordinating tridentate ligands. Initial reports focused on platinum complexes with 2,6-bis-pyrazolyl-pyridine ligands. One complex, Pt(bpp)Ph +, exhibited an intense pink emission of the solid at 77 K, which is one of the first examples of a luminescent platinum compound with a bis-pyrazolyl-pyridine ligand. Herein we report the investigation of steric influence to promote C-H activation on the formation of monomeric and macrocyclic platinum(II) complexes, using methyl substituents on a series of anionic bis-pyrazolyl-phenyl ligands. Further studies of concentrated reaction mixtures at long reaction times result in exclusively trimeric products, whereas more dilute mixtures and shorter reaction times give only monomer products. Thus, careful control of the reaction conditions allows for selective activation of C-H bonds on the ligand giving isolated products of expected monomers and trimers, as well as surprising new dimeric products. In the course of our investigations of the monomeric platinum(II) products, we have discovered that four complexes react with dithiocarbamate accelerators most commonly used in latex processing, giving a colored response. Thus, the platinum complexes can be used as colorimetric indicators to detect allergenic dithiocarbamate compounds in latex products. In addition, we describe the synthesis and preliminary characterization of a potential two-electron reagent using a monomeric complex, Pt(4)Cl, and pip 2NNN, where 4 is 1,3-bis(3,5-dimethylpyrazolyl)benzene and (pip 2NNN) is 2,6-bis(piperidylmethyl)pyridine, to give Pt(4)(pip 2NNN) +.

Committee: William Connick (Advisor) Subjects: Chemistry, Inorganic

PhD, University of Cincinnati, 2007, Arts and Sciences : Chemistry

Novel Eu3+-containing macrocyclic complexes were synthesized and studied as anion sensing probe molecules. Several of these macrocycles exhibited unique luminescence responses to hydrogen-bond accepting anions (fluoride, acetate, and dihydrogen phosphate) in DMSO, even in the presence of a chloride ion background. The first series of compounds highlighted a high-yielding synthetic route for highly functional macrocycles that incorporate a Eu3+ chelate, aromatic antennae, thiourea groups as anion-binding units, and a variable linker that tunes the size and rigidity of the pocket. These macrocycles exhibited Eu3+ luminescence where emission intensity (λexc = 272 nm, λem = 614 nm) was correlated to the linker length. Anion-induced changes in emission intensity were dependent on the basicity of the anion, and emission enhancements were observed up to 77% upon titration with fluoride in one case. Through luminescence lifetime studies of the Eu3+ macrocycles and the study of a newly synthesized series of organic model compounds, it was determined that the luminescence response to anions was the result of interaction with the thiourea moieties and no evidence was observed for anion coordination to Eu3+. Additionally, two second-generation macrocycles were synthesized, incorporating an amine unit for stronger binding affinity. One of these macrocycles, featuring a pendant naphthalene antenna, responded to several anions in aqueous solution by means of a luminescence decrease of up to 30%. This general macrocyclic design shows promise for the development of Eu3+-based anion sensors that function in competitive solvents. In continuing work with lanthanide complexes, a new targeted Gd3+-based magnetic resonance imaging contrast agent was designed and synthesized for specific binding to the dopamine receptor protein. A relaxivity of 7.1 mM-1s-1 was measured for this complex at 400 mHz and 310 K. A Eu3+ analogue was also synthesized and structurally characterized. Luminescence (open full item for complete abstract)

Committee: Theresa Reineke (Advisor) Subjects: Chemistry, Inorganic

PhD, University of Cincinnati, 2007, Arts and Sciences : Chemistry

Vapochromism is a type of chemical sensing response in which a material reversibly absorbs a vapor and undergoes a color change. In this dissertation, the first examples of vapochromic simple salts (c.f., double salts) of [Pt(2,6-­bis(N-­methylbenzimidazoly-­2-­yl)pyridine)Cl]+(M) are described. A major finding from this research is that the vapochromic properties (selectivity, color, vapor capacity, response time) of these materials are readily modulated by changing the counter anion, thus allowing for preparation of a wide range of materials with different vapochromic properties. For example, M(Cl−) changes from orange to red in response to vapors of acetonitrile, methanol and chloroform, whereas M(PF6−) changes from orange to purple in response to acetonitrile but does not respond to methanol or chloroform. As solids, M(X−) (X = Cl−, PF6−, NO3−, CF3SO3−, BF4−) salts undergo color changes, from orange to red or purple upon exposure to various organic vapors, such as methanol, ethanol, acetonitrile, chloroform, nitromethane and methylamine. In the absence of vapor, four of the salts give rise to excimeric emissions, in which the excitation is delocalized over the 2,6-­bis(N-­methylbenzimidazoly­-2-­yl ligands of two adjacent complexes with strong ligand⋯ligand interactions. The triflate salts gives rise to emission characteristic of a lowest MMLCT (metal-metal-to-ligand charge transfer) state, which arises from significant interaction between adjacent Pt centers. The temperature dependence of the solid-state emission spectra of these complexes after exposure to organic vapors is indicative of formation of a lowest MMLCT (metal-metal-to-ligand charge transfer) state. This conclusion is supported by diffuse reflectance spectra which show that vapor exposure results in new absorbtion bands at longer wavelengths. Investigations of a series of salts with alkyl substituents on the tridentate ligand suggest that ligand substitution reduces vapochromic activity. However (open full item for complete abstract)

Committee: Dr. William Connick (Advisor) Subjects: Chemistry, Inorganic

PhD, University of Cincinnati, 2007, Arts and Sciences : Chemistry

A series of mononuclear poly(oxime) amine nickel(II) complexes has been shown to catalyze the oxidation of various substances. To further this work, a series of novel dinucleating ploy(oxime) amine ligands and their nickel complexes were synthesized. During this synthesis, a novel anion dependence on the nuclearity of the complex was discovered and investigated for two of the ligands. All of the dinuclear complexes were shown to catalyze the oxidation of various substances, including methanol, benzyl alcohol, and benzylamine. In addition to the oxygen reactivity, zinc complexes of the poly(oxime) amine ligands were shown to have hydrolysis reactivity. These complexes successfully catalyzed the hydrolysis of p-nitrophenyl acetate. Some preliminary kinetic data for the reaction was also obtained.

Committee: Dr. Michael Baldwin (Advisor) Subjects: Chemistry, Inorganic

MS, University of Cincinnati, 2006, Arts and Sciences : Chemistry

The α–hydroxy carboxylic acid group in marine siderophores is photoactive when bound to Fe(III). This photochemical reaction in natural sunlight reduces Fe(III) to Fe(II) making it more available for biological uptake. Iron complexes of α–hydroxy acid containing ligands inspired by these siderophores were synthesized and their photochemical reaction was studied. The ligands were synthesized starting from (S)-(-)-4-amino-2-hydroxy-butyric acid in 5 steps. First three steps include acid group protection in (S)-(-)-4-amino-2-hydroxy butyric acid with methyl ester. The alkylation on amine was carried out using ethyl bromoacetate and chloroacetohydroxamic acid to get ester forms of carboxylate(4A) and hydroxamate(4B) ligands. The final acid form of ligands (5A and 5B) was obtained after hydrolysis of the ester groups. Both these complexes, when mixed with bathophenonthroline disulfonate (BPDS), Fe(II) specific chelating agent, showed Fe(II) produced under different light conditions. Fe(II)(BPDS)3 band has characteristic band at 533 nm. This band was monitored by UV-Visible spectroscopy over time for the production of Fe(II). About 70 % of iron was trapped as Fe(II) in both the Fe(III)-carboxylate (Fe(III)(5A))and Fe(III)-hydroxamate (Fe(III)(5B)) complexes. The chiral center at the α–carbon of α–hydroxy acid group gives rise to well resolved circular dichroism (CD) bands in Fe(III)-carboxylate complex. The spectrum recorded after the irradiation of the complex solution in water showed that there was no more CD band present. This loss of CD band as a result of loss of chiral center in the ligand indicates oxidation of the α–hydroxy acid group as a result of photochemistry. However, under anaerobic conditions, the CD spectrum did not show complete loss of chirality. This incomplete photolysis of ligand showed that the ratio of metal:ligand for complete photochemical reaction is higher than 1:1. In summary, Fe(III)(5A) and Fe(III)(5B) complexes were found to undergo photoch (open full item for complete abstract)

Committee: Dr. Michael Baldwin (Advisor) Subjects: Chemistry, Inorganic

PhD, University of Cincinnati, 2005, Arts and Sciences : Chemistry

A detailed study of the structures and emission properties of platinum(II) bipyridine complexes with potentially facially-coordinating ligands has been undertaken in order to elucidate the relationship between electronic structure and the intramolecular interactions of a dangling nucleophile with a platinum(II) center at the vacant sites of a square planar complex. An examination of a series of platinum(II) bipyridyl complexes with 1,4,7-trithiacyclononane (ttcn) and 17 other structures of platinum(II) ttcn complexes reveals a correlation between the apical Pt•••S distance and the donor properties of the ancillary ligands, suggesting a means for using variations in ligand electronic properties to tune molecular structures. In frozen solutions, the bipyridyl complexes exhibit low-energy emissions (λ max, 570-645 nm), tentatively assigned as originating from a lowest, predominantly spin-forbidden metal-to-ligand charge-transfer (MLCT) excited state that is stabilized by Pt•••S interactions. A series of eight dimeric platinum(II) bipyridyl complexes with pyrazolate bridging ligands also has been characterized. Although several of the complexes have relatively short Pt•••Pt separations (~3.2 A), there is no evidence of strong metal-metal interactions, and the emission spectra and lifetimes are consistent with a lowest bipyridine-centered triplet π-π* excited state, whose energy can be tuned by altering the substituents on the diimine ligands. A series of ten platinum(II) bipyridyl complexes with bis(pyrazol-1-yl) methane and tris(pyrazol-1-yl) methane (Tpm) also has been examined. 1H NMR spectra of the Tpm derivatives suggest that the non-coordinating pyrazolyl arm is directed away from the platinum center; the X-ray crystal structures of two complexes support this conclusion, and the accumulated data point to weaker Pt•••N(pyrazolyl) axial interactions than the Pt•••S interactions found for the ttcn complexes. Interestingly, the emissions from these complexes have vary (open full item for complete abstract)

Committee: Dr. William Connick (Advisor) Subjects: Chemistry, Inorganic

PhD, University of Cincinnati, 2004, Arts and Sciences : Chemistry

Ni(II) complexes containing amidates and thiolates have been shown to react with O2 via irreversible ligand oxidation. We have constructed a series of Ni(II) complexes based on a tripodal amine bis(oxime) ligand framework. These complexes display oxygen reactivity upon deprotonation of the oximes without requiring irreversible ligand oxidation. This project investigated the reaction involving one of the complexes in the library, [Ni(TRISOXH 3 )(NO 3 )(H 2 O)](NO 3 )· (H 2 O), where TRISOXH 3 = (tris(1-propan-2-onyl oxime)amine). It was discovered that the reaction of this complex with molecular oxygen is contingent upon the presence of a source of hydrogen atoms. This two-hydrogen atom donor acts as a substrate. Several primary alcohols, including the relatively inert methanol, and amines were catalytically oxidized by this reaction. Spectroscopic analysis using a variety of techniques has demonstrated that reversible oxidation occurs on the oximate nitrogen to form an iminoxyl radical. Many of the other complexes in the series were also investigated to examine their electronic structure, their electrochemical properties, and their ability to oxidize methanol.

Committee: Dr. Michael Baldwin (Advisor) Subjects: Chemistry, Inorganic

PhD, University of Cincinnati, 2004, Arts and Sciences : Chemistry

Using density-functional theory and vibrational spectroscopy, various theoretical models are evaluated for application to Ni(TRISOXH 3 )Cl 2 , the precursor to a novel oxygen-activating complex. Geometry optimizations and frequency calculations were performed using DFT and compared to the X-ray crystal structure and vibrational spectra. The best geometry resulted from B3LYP/6-31G(d) & 6-311++G** with only a 1.0% average deviation from experimental bond distances not influenced by intermolecular interactions. Nickel complexes with isotope substituted TRISOXH 3 ligands were synthesized. The isotope shifts in the vibrational spectra were observed and compared to the predicted shifts to facilitate the assignment of 28 normal modes. A modified wavenumber linear scaling procedure was applied to the assigned theoretical wavenumbers and yielded a 3-fold improvement in absolute deviation from experimental frequencies over the unscaled values. Further application of this model is applied to complexes of the form Ni(TRISOXH 3 )X 2 where X is fluoride, bromide, iodide, methanol, and/or water to evaluate ligand effects on metal-oxime interactions. Complexes where X is bromide or iodide exhibited very similar geometries and vibrational frequencies to Ni(TRISOXH 3 )Cl 2 , while significant structural and electronic differences were observed when X is water or fluoride.

Committee: Dr. Michael Baldwin (Advisor) Subjects: Chemistry, Inorganic

PhD, University of Cincinnati, 2004, Arts and Sciences : Chemistry

A series of square planar platinum(II) complexes with the mer-coordinating tridentate ligand, pip2NCN- (pip2NCNH = 1,3-bis(piperdylmethyl) benzene) has been synthesized. The lowest emissive excited states of these complexes can be tuned by varying the properties of the monodentate ligand. Colorless halide complexes and the pyridine adduct exhibit weak red emissions originating from a lowest triplet ligand field (³LF) excited state. In contrast, yellow-green emissions from Pt(pip2NCN)(4-phenylpyridine)+ originate from a lowest ³π-π* state. Similarly, (Pt(pip2NCN))2(m­L)2+ dimers exhibit emission from a lowest ³LF excited state (L=1,2-bis(4-pyridyl)ethane), a lowest ³π-π* excited state (L=trans-1,2-bis(4-pyridyl)ethylene or 4,4'-bipyridine) or a lowest triplet metal-to-ligand charge-transfer excited state (L=pyrazine), depending on the bridging ligand. A series of platinum(II) terpyridyl complexes with aryl ligands has been synthesized. The complexes undergo two one-electron reduction processes near -0.9 and -1.4 V vs. Ag/AgCl. In the cyclic voltammograms of complexes unsubstituted at the 2 and 6 positions of the aryl ligand, the first reduction exhibits larger (>59 mV) differences between the anodic and cathodic peak potentials than observed for complexes with methyl groups at the 2 and 6 positions. The accumulated data are consistent with the formation of dimers that reduce at different potentials than the monomers, causing the first reduction wave to appear broadened. Protection of the axial sites of the metal center appears to interfere with dimerization. 77 K glassy solution emission measurements confirm that steric effects can be utilized to control intermolecular metal···metal and ligand···ligand stacking interactions in solutions of these complexes. The first examples of platinum complexes that undergo reversible and cooperative thermal two-electron transfer have been prepared. The tpy ligand of Pt(tpy)(pip2NCN)+ is tridentate and the pip2NCN- ligand is monode (open full item for complete abstract)

Committee: Dr. William Connick (Advisor) Subjects: Chemistry, Inorganic

PhD, University of Cincinnati, 2003, Arts and Sciences : Chemistry

Solganol, Myochrysine and Auranofin are gold drugs used in the treatment of Rheumatoid Arthritis, a degenerative disease of the joints. [Au(CN) 2 ] - is the biotransformation product of these drugs which has been found in the urine of patients who have been treated with these drugs. Concerns over the expected toxicity of [Au(CN) 2 ] - have led us to seek a less toxic analogue which may have a similar therapeutic profile. The thiocyanate complex seems to be a logical choice if cyanide is playing a role in the toxicity. The syntheses, and characterization of the salts of [Au(SCN) 2 ] - are presented. The salts have some unusual, unexpected characteristics, namely, as the counter ion decreases in size the anion forms an oligomeric chain of gold atoms with varying interaction distances. The crystallography has shown that the [Au(SCN) 2 ] - is an intact anionic species. For the Ph 4 P + salt, the anion is a monomer whereas for the (n-Bu) 4 N + salt is a dimer, and as the cation decreases in size an oligomer forms. The oligomerization is observed only in the solid state of the salts. The oligomeric complexes have an unusual emission, which is not present in the monomeric complexes. The Na + , K + , Rb + , Cs + , NH 4 + , (n-Bu) 4 N + , and Me 4 N + salts emit at various wavelengths, and are due entirely on the Au-Au interaction.

Committee: Dr. Richard C. Elder (Advisor) Subjects: Chemistry, Inorganic

PhD, University of Cincinnati, 2002, Arts and Sciences : Chemistry

Gold-based drugs have been used in the treatment of rheumatoid arthritis for over 60 years, yet the mechanism of action or these drugs is not understood clearly. This study focuses on an early step in the transport mechanism of gold drugs, namely the interaction of dicyanogold(I) (a common bio-transformation product of gold drugs) with human serum albumin (the most abundant protein in blood serum). These binding studies involve both qualitative and quantitative characterization of the binding interaction between dicyanogold(I) and two forms of human serum albumin (HSA): HSA with cysteine-34 in the native form and HSA with a blocking group bound to the sulfur of cysteine-34 (HSA*AA). The blocked protein is HSA treated with iodoacetamide so that cysteine-34, a known binding site for gold drugs, is prevented from participating in other covalent interactions. Each form of HSA was characterized using two mass spectrometry techniques. FT-ICR-MS with electrospray ionization uses an acidic environment to add up to 60 protons to the HSA, lowering the mass to charge ratio to a value that can be detected easily by the mass spectrometer so that the intact protein can be characterized. MALDI-TOF-MS forms predominantly singly charged ions, thus it is necessary to perform an enzymatic digest of the HSA before analysis. Subsequently, individual fragments were studied yielding information about the form of cysteine-34 (native vs. blocked). A series of experiments were conducted in which the effect of changing the conditions of the system on the equilibrium constant, Keq, was studied. These experiments include varying the initial concentration of dicyanogold(I) used, the ionic strength of the buffer solution and the incubation temperature of the system. Additionally, a series of experiments that tested the reversibility of this binding were conducted. Reversed phase ion-pairing chromatography was used to determine that the gold species released from the protein after establishing equ (open full item for complete abstract)

Committee: Dr. Richard Elder (Advisor) Subjects: Chemistry, Inorganic

Master of Science, University of Toledo, 2007, Chemistry

This thesis reports the reactions of aluminum and gallium alkyls with two ligands, di(3-methylindolyl)pyridylmethane (L'H2), and di(3-methylindolyl)(1-methylimidazolyl)methane (L''H2). A series of bidentate complexes HLMR2 (L = L', M = Al, Ga, R = tBu; L = L'', M = Al, R = Me, Et, iBu, tBu; L = L'', M = Ga, R = tBu) and a tridentate complex L'GatBu were synthesized. Stoichiometry plays an important role in reactions of L'H2 and L''H2 with Me3Al and Et3Al, as excess of the aluminum alkyl results in the formation of bimetallic complexes LAl2R4 (L= L', L'' ; R = Me, Et). The previously reported bis-aluminum complex, L'Al2Me4 was characterized by X-ray crystallography. This is the first reported example of a group 13 complex with a bridging i2–c1:c1–N indolyl group. The characterization of the new complexes was carried out by 1H, 13C and 2-dimensional NMR spectroscopy as well as X-ray crystallography

Committee: Mark Mason (Advisor) Subjects: Chemistry, Inorganic

Doctor of Philosophy, The Ohio State University, 2008, Chemistry

Single-site metal alkoxides are used to catalyze the controlled ring-opening polymerization (ROP) of lactides and other cyclic esters. In this study, a new trispyrazolylborate ligand, Tp*, containing a 3-substituted pyrazole with ─CMe2CH2OMe group has been synthesized. By synthesizing this new ligand we aimed that this ligand can form a pocket around Ca2+ in order to protect the metal center against ligand scrambling, transesterification, or deactivation by impurities, such as water. First, the synthesis of 3-(2-methoxy-1,1-dimethylethyl)pyrazole, pz*H is described together with its reactions with the borohydrides MBH4, where M = Li, Na, and K, under melt conditions. At 180°C, this procedure leads to a mixture of products for M = Li, and at higher temperatures, a derivative LiTp'pz*H is isolated, wherein a B-H bond and a methyl group have been eliminated and a B-O bond has been formed. For M = Na, the reaction proceeds to give NaTp* but at higher temperatures NaB(pz*)4 is obtained. The reactions involving KBH4 and pz*H yield the dinuclear complex K2(Tp*)2pz*H. The reaction between NaTp* and TlOAc in dichloromethane at room temperature gives TlTp* along with NaOAc. TlTp* reacts with methyllitium in diethylether to give LiTp* and thallium metal, and, similarly, TlTp*and KH react in THF to give KTp* and Tl(0). In addition, the heavier alkaline earth metal iodides (Tp*MI where M = Ca, Sr and Ba) were synthesized by using TlTp* and the corresponding metal diiodide, MI2 in THF. However, Tp*MgI and Tp*ZnI were obtained from the reaction of MI2 and NaTp* in THF and dichloromethane, respectively. The reaction between Ca[N(SiMe33)](THF)2 and TlTp*yieldsTp*Ca[N(SiMe3)]2-via [CaTp*]+{Ca[N(SiMe3)2)3]}-.-Heating-Tp*CaN(SiMe3)2-gives-CaTp*2-by disproportionation. Whereas MgTp*2 is prepared from MgBu2 and TlTp* in THF. Both CaTp*3 and MgTp*2 exist as salts in the solid state: [Tp*M]+[Tp*], but in solution the CaTp*3 undergoes dynamic Tp* exchange on the NMR time-scale. Slower liga (open full item for complete abstract)

Committee: Malcolm Chisholm (Advisor); James Cowan (Other); T. RajanBabu (Other) Subjects: Chemistry, General; Chemistry, General; Chemistry, Inorganic; Chemistry, Polymer

Master of Science, The Ohio State University, 2007, Chemistry

The ability of Rh2(μ-O2CCH3)4 (1), cis-[Rh2(μ-O2CCH3)2(CH3CN)6]2+ (2), cis-[Rh2(µ-O2CCH3)2(dppz)(η1-O2CCH3)(CH3OH)]+ (dppz = dipyrido[3,2-a:2',3'-c]phenazine) (3), and cis-[Rh2(µ-O2CCH3)2(bpy)(dppz)]2+ (bpy = 2,2'-bipyridine) (4) to transverse a membrane bilayer was determined through quenching of DNA-bound SYBR Green I (SG) encapsulated within the interior of a vesicle. For comparison, quenching studies were performed with the known DNA binders ethidium bromide (EtBr), methyl viologen (MV2+), Hoechst 33258 and 2-methyl-antrhacene (2-Me-An). Emission quenching experiments were performed with DNA-bound SG (SG-DNA) free solution to determine the ability of the known DNA-binding compounds and the dirhodium series to affect the luminescence of the dye. The known minor groove binder Hoechst 3328 produced the most quenching of SG-DNA, likely due to displacement of the dye from the duplex. Within the dirhodium series, the degree of quenching correlates to the DNA binding constant of each complex. Complex 3, with the largest kb, produced the greatest quenching of SG-DNA. Each of the complexes in the dirhodium series can quench SG-DNA emission through various mechanisms, including displacement, energy transfer, and charge transfer. In each case, close proximity to the SG-DNA emissive species is a requirement. Therefore, a correlation between the association of each complex in the series with SG-DNA and its quenching ability is not unexpected. When SG-DNA was encapsulated in POPC vesicles, compounds added to the outside of the vesicles can only quench the SG-DNA emission if they are able to penetrate the bilayer membrane. The vesicles with encapsulated DNA-bound SG, SG-DNA@POPC, were incubated for 4 hours and the emission was monitored at 520 nm. Quenching was retained for the known DNA-binders, EtBr and Hoechst 33258. In the dirhodium series, complexes 1, 2, and 4 maintained at least some of their quenching ability, showing that these complexes are able to transverse the l (open full item for complete abstract)

Committee: Claudia Turro (Advisor) Subjects: Chemistry, Inorganic

Doctor of Philosophy, The Ohio State University, 2007, Chemistry

Density functional theory (DFT) calculations were performed to investigate the orbital interactions responsible for stereoactive lone pair distortions in ternary metal oxides. The calculations revealed that the stereoactivity of the lone pair is dependant upon the strength of interaction between the A-cation and the surrounding oxygen ligands. The resulting second order Jahn-Teller distortions are dependant upon the interactions and relative energies of the cation s, cation p, and oxygen p orbitals near the Fermi-level. The calculations also reveal fundamental differences in the orbital interactions responsible for the stereoactivity in Sn 2+, Pb 2+, and Bi 3+containing compounds. Ternary metal oxides involving Sr 2+, Pb 2+, and Ag +were also analyzed using DFT in order to evaluate the impact each cation plays on the band gap. Pb 2+and Ag +effectively reduce the band gap relative to Sr 2+by introducing electronically active states in close proximity to the valence band and conduction band edges. DFT calculations were performed on nine structural models of BaTaO 2N, SrTaO 2N, and CaTaO 2N revealing several similarities and differences in the local structure of each material. The calculations predict several trends: (i) a local cis configuration is more stable than a trans configuration, (ii) models involving a Ta 5+displacement are more stable than models in which the Ta 5+position is constrained to retain the inversion center of the undistorted octahedron, and (iii) the tendency for octahedral tilting increases from BaTaO 2N to SrTaO 2N to CaTaO 2N.

Committee: Patrick Woodward (Advisor) Subjects: Chemistry, Inorganic

Doctor of Philosophy, The Ohio State University, 2007, Chemistry

One of the advantages of using light as a reactant in a chemical reaction is the generation of an excited state that is able to overcome high activation barriers that are not accessible by heating. In addition, the light can be spatially controlled, by focusing the photons onto a given area; such control is not possible in conventional thermal reactions. The spatial control of light has been shown to be advantageous in a number of applications including cancer therapy, signaling, and data storage. The photophysical properties and photochemistry of various complexes that may be potentially useful in these three applications will be discussed in this dissertation. The work presented here focuses on the photochemical and photophysical properties of both bimetallic and mononuclear complexes. It is the goal of this dissertation to examine several of the processes possible once a complex is excited, including photochemical reactions, isomerizations, and differences in photophysical properties. There is a brief introduction at the beginning of each chapter that describes the possible photochemical applications related to the work presented and necessary background information in the specific area.

Committee: Claudia Turro (Advisor) Subjects: Chemistry, Inorganic

Doctor of Philosophy, The Ohio State University, 2006, Chemistry

New carbonyl complexes of divalent ytterbium and transition metals of groups 6, 7 of the periodic table have been prepared. The syntheses were carried out in systematic fashion with the aim of establishing general procedures suitable for preparation of a range of compounds of this type. The products obtained were characterized by means of IR spectroscopy and X-ray single crystal diffraction. Nineteen X-ray structures are reported herein, of which only one has been published before. The compounds studied can be divided into two major groups: the solvent-separated ion pairs, where the YbII cation is surrounded with solvent molecules acting as ligands, preventing interaction with the metal carbonylate anion; and complexes with the bridging carbonyl ligands (isocarbonyl ligands), where the cation and the anion are bound together through a –CO- link. New instances of condensation of the solvent-separated ion pairs into the isocarbonyl complexes have been discovered, and the mechanism for such transformation was proposed. The novel [Hg(W(CO)5)2]2- anion was discovered and characterized by X-ray single crystal diffraction. Its reactivity was briefly investigated.

Committee: Sheldon Shore (Advisor) Subjects: Chemistry, Inorganic

Doctor of Philosophy, The Ohio State University, 2006, Chemistry

Ru(II) complexes that combine the mode of action of cisplatin and that of PDT were investigated in water and their binding to duplex DNA were investigated. Cis-[Ru(bpy)2(NH3)2]2+ and cis-[Ru(bpy)2(CH3CN)2]2+ bind to 9-ethylyguanine and 9-methylguanine and to single and double stranded DNA . The quantum yields upon irradiation of cis-[Ru(bpy)2(CH3CN)2]2+ in water is at 350 nm = 0.377(3), 400 nm = 0.207(1), 450 nm = 0.222(18) and for cis-[Ru(bpy)2(NH3)2]2+ at is 350 nm = 0.024(2) and 400 nm = 0.018. The higher quantum yield of photoaqaution observed upon irradiation of cis-[Ru(bpy)2(CH3CN)2]2+ resulted in greater covalent DNA binding to both single and double stranded DNA. Binding of both complexes to 9-ethylguanine and 9-methyl guanine was also observed upon irradiation but not in the dark. The photolysis of cis-[Ru(bpy)2(CH3CN)2]2+ and [Ru(phpy)CH3CN)4]+ in aqueous solution at 420 nm results in the formation of oxo dimers of Ru(II)/II) of molecular formula [(H2O)(bpy)(phpy)RuIIORuII(phpy)(bpy)(OH2)]H+.H2O and [(CH3CN)(H2O)(phpy)Ru(II)ORu(II)(phpy)(H2O)(CH3CN)]H+.H2O respectively. Cis-[Ru(phpy)(bpy)(CH3CN)2]+and [Ru(phpy)CH3CN)4]+ bind to 9-ethylguanine and 9-methylguanine upon irradiation. Binding of [Ru(phpy)CH3CN)4]+to single stranded 15 mer DNA sequences was observed upon irradiation at 420 nm, however, no binding to single stranded DNA was observed upon irradiation of cis-Ru(phpy)(bpy)(CH3CN)2]+. No binding to double stranded DNA was observed upon irradiation of cis-[Ru(phpy)(bpy)(CH3CN)2]+ and [Ru(phpy)(CH3CN)4]+ at 420 nm. Cis-[Ru(quo)2(py)2] binds to 15-mer DNA sequences upon irradiation in aqueous solution at 345 nm. Binding to duplex DNA was observed upon irradiation of cis-[Ru(quo)2(py)2] at 345 nm. Irradiation of cis-[Ru(quo)2(py)2] at 420 nm also resulted in the metal complex binding to DNA.

Committee: Claudia Turro (Advisor) Subjects: Chemistry, Inorganic

Doctor of Philosophy, The Ohio State University, 2006, Chemistry

Molybdenum and tungsten have a rich chemistry in quadruply-bonded paddlewheel complexes that are very similar in many ways, yet significantly different in other ways. Details and findings from Density Functional Theory studies of homoleptic and heteroleptic ligand complexes as well as simple pairs of dimers linked by a bifunctional oxalate bridge are discussed. Special interest is given to metal-to-ligand interactions in paddlewheel complexes and metal-to-bridge interactions in simple pairs of dimers. Computational studies provide great insight, reliable explanations, and qualitative predictions of physicochemical properties. A new series of dimolybdenum and ditungsten paddlewheel complexes with mixed amidinate-carboxylate ligands of the form trans-M2(O2CCH3)2(iPrNC(R)NiPr)2 where M = Mo, W and R = Me, CCtBu, CCPh, or CCFc have been synthesized and characterized with the exception of the tungsten complex where R = Me. The synthesis of a series of complexes with each metal allowed for the analysis and comparison of molecular structural features, spectroscopic properties, and electrochemical behavior. The dinuclear centers exhibit redox chemistry which is dependent upon the nature of the ancillary ligand, and the electrochemical properties can be tuned through ligand modifications. DFT calculations on model complexes are used to help assign observable UV-vis absorptions and electrochemical redox behavior. The use of amidate complexes of the form M2(mhp)4, where M = Mo, W and mhp is the anion of 2-hydroxy-6-methylpyridine, as building blocks in simple molecular assemblies including simple pairs of dimers and molecular squares is also explored. Metathesis reactions employing solvento derivatives of Mo2(mhp)4 and attempts to prepare solvento derivatives of W2(mhp)4 are discussed. For simple pairs of dimers, the cooperative effect of linkers to electronically couple dimetal units is observed through electrochemistry. Finally, the preliminary findings of using the unique t (open full item for complete abstract)

Committee: Malcolm Chisholm (Advisor) Subjects: Chemistry, Inorganic