This thesis describes the synthesis, structure, equilibriaand other properties of novel thallium(III) monomeric andplatinum-bonded complexes with nitrogen donor ligandsethylenediamine, diethylenetriamine, triethylenetetramine,porphyrin, 2,2'-bipyridine and 1,10-phenanthroline in solutionand in solid. The existence of three complexes withthe general formula[Tl(en)n]3+(n = 1-3) and their overall stability constantshave been established in pyridine. All three complexes wereidentified by their205Tl and1H NMR chemical shifts and205Tl-1H coupling constants. The formation process of thecomplexes was followed by1H NMR spectroscopy. The crystal structure of[Tl(en)3](ClO4)3was determined; the thallium(III) ion isN-coordinated in a distorted octahedral geometry. Two [Tl(dien)n]3+(n = 1-2) complexes were proved to exist insolution and the structure of the bis-complex [Tl(dien)2]2+inu-facialisomers was determined in solid. In addition,crystal structures of [Tl(en)2CN](ClO4)2with cyanide bridging between two Tl(en)2units forming an infinite chain structure and of[Tl(tren)2(CN)2](ClO4) with a distorted pseudo-octahedral coordinationaround thallium were determined. Thallium(III) complexes with2,2'-bipyridine and 1,10-phenanthroline have been studied inDMSO using205Tl,13C and1H NMR spectroscopy. In addition, aseven-coordinated thallium was found in the crystal structureof [Tl(bipy)3(dmso)](ClO4)3, and six-coordinated thallium in pseudo-octahedralgeometry in [Tl(phen)2Cl2](ClO4). The solvated complex [Tl(dmso)6]3+has been prepared using concentrated aqueoussolution of Tl(ClO4)3by a solvent replacement reaction in DMSO, and thewater-free solid compound [Tl(dmso)6](ClO4)3was crystallized from DMSO. The structure of thecomplex [Tl(dmso)6]3+is a regular octahedron with the Tl-O bonddistance 2.224(3) Å. It represents an easy and secure wayto introduce water-free Tl(III) into organic phase withoutreduction. Through several reactions, novel heteronuclear Pt-Tlcomplexes with the composition [(NC)5Pt-Tl(tpp)]2-, [(NC)5Pt-Tl(thpp)]2-, [(NC)5Pt-Tl(bipy)n](n = 1-2), [(NC)5Pt-Tl(en)n-1](n = 1-3) and [(NC)5Pt-Tl(phen)n](n = 1-2), have been synthesized in solution.Multinuclear NMR (195Pt,205Tl,13C and1H), Raman spectroscopy and X-ray diffraction dataare fully compatible with formation of unsupported Pt-Tl bondedcomplexes both in solution and in solid. The huge1J(195Pt-205Tl) spin-spin coupling constants (48-66 kHz) wereobserved by both195Pt and205Tl NMR spectroscopy in solution and they providea strong evidence of formation of the Pt-Tl bond in solution.In all six determined crystal structures of the Pt-Tl compoundsa very short Pt-Tl bond is found with distances2.6117(5)-2.6375(5) Å. The calculated values of Pt-Tlforce constants (1.38-1.91 N/cm) are characteristic for asingle metal-metal bond. In the Pt-Tl compounds, the oxidation state of the metalions is intermediate between the stable states PtII/PtIVand TlIII/TlI, respectively, and this is reflected by their195Pt and205Tl chemical shifts. It turns out that N-donorligands can really stabilize the Pt-Tl bond both in solutionand in solid. The character of the metal-metal bond anditstheoretical basis are discussed. <b>Keywords:</b>Thallium, Platinum, Cyanide, N-donor ligand,Metal-metal bond, Multinuclear NMR, Raman spectroscopy, X-raydiffraction, Equilibrium, Spin-spin coupling.

The molecular characteristics that affect the activity of various dirhodium complexes are reported. The importance of the axial position in the action of dirhodium compounds was studied. Three dirhodium complexes with increasing number of accessible axial coordination sites were synthesized and characterized. In cis-[Rh2(u-OAc)2(np)2]2+ (np = 1,8- naphthyridine) both axial sites are available for coordination, whereas for cis-[Rh2(u-OAc)2(np)(pynp)]+2 (pynp = 2-(2-pyridyl)1,8-naphthyridine) and cis-[Rh2(u-OAc)2(pynp)2]+2 the pyridyl arm on the ligand pynp blocks one and two axial sites, respectively. The availability of the axial positions affects the in vitro and in cellulo activity of these complexes demonstrating that open axial coordination sites are necessary for biological activity. The inhibitory activity of derivatives of dirhodium-dppz complexes (dppz = dipyrido[3,2-a:2',3'-c]phenazine) has also been investigated. The dppz derivatives included compounds with electron-withdrawing (Cl, CN, and NO2) as well as electro-donating (MeO and Me) substituents. These compounds inhibit transcription of T7-RNA polymerase by reducing accessible cysteine residues. The activity correlates with the electron withdrawing character of the substituent on the dppz ligand. Density functional theory (DFT) calculations reveal that the lowest unoccupied molecular orbitals (LUMOs) in the series are ligand-based pi* orbitals localized on the phenazine ring. These complexes represent the first family of dirhodium complexes whose inhibitory ability can be tuned by controlling their redox properties. The effect of the presence of diimine ligands in the dirhodium core in both in vitro and in cellulo activity is discussed. The presence of one diimine ligand allows for dual binding, intercalation and covalent, as observed by melting temperature and relative viscosity measurements, as well as electrophoretic mobility shift assay (EMSA). The mono-substituted dirhodium complexes are effective against HeLa and COLO-316 cell lines, with [Rh2(u-O2CCH3)2(n1-O2CCH3)(dppz)]+ being the most effective compound of the series. Results of the comet assay indicate that all of the monosubstituted complexes studied damage nuclear DNA, although in different degrees. The cytotoxic effect of these complexes is not affected by the presence of glutathione. The addition of the second diimine ligand hinders the ability of the complexes to damage DNA. The bis-substituted complexes are also slightly less cytotoxic than their mono-substituted congeners. Thus, the number of equatorial positions occupied by diimine ligands play a critical role in the mechanism of cytotoxicity of dirhodium(II,II) complexes. Finally, the results also demonstrate that improving the internalization of the dirhodium complexes can be achieved by co-incubation with cell penetrating peptides. This work provides a foundation for the preparation of new and more effective dirhodium complexes.

High Pressure Die Casting (HPDC) is low-cost technique for the mass production of complex, non-ferrous parts. Despite its benefits such as dimensional accuracy, surface quality and high production rate / some mechanical drawbacks limit use of HPDC in production of critical parts especially under dynamical loads. This study aims to improve impact resistance and surface hardness of die cast parts by means of tool steel inserts. These inserts act as a barrier between the impactor and die casting alloy, in order to avoid surface deformation and reduce stress localization which leads crack formation. Except the impact surface, whole insert is embedded into the die casting alloy by placing them on specially machined die casting molds prior to the metal injection. The mentioned method was evaluated by mechanical test and micro-examinations which were applied on AISI D2 tool steel inserted A518.0, A413.2 and Zamak5 alloy samples. To see the effect of inserts on energy absorbance under single destructive loads, both monolithic (conventional) and inserted (produced by mentioned technique) samples were subjected to Charpy impact test. In order to observe its behavior under non-destructive, cyclic, low velocity impacts / a dedicated real rifle part was produced by this method and tested in the real service loads. Explicit Finite Elemental Analysis was also carried out to understand how the inserts increases the energy absorbance and protect the die cast body by simulating both destructive and non-destructive impact loads. In addition to these, micro-examinations were also conducted especially on insert-die casting alloy interface for chemical and physical interactions, defects and stability. In regards of experimental findings, mechanical feasibility of the method was achieved. It was proved that steel inserts improve energy absorbance, stress distribution and impact-surface hardness of die cast products.

<p>This thesis describes the synthesis, structure, equilibriaand other properties of novel thallium(III) monomeric andplatinum-bonded complexes with nitrogen donor ligandsethylenediamine, diethylenetriamine, triethylenetetramine,porphyrin, 2,2'-bipyridine and 1,10-phenanthroline in solutionand in solid.</p><p>The existence of three complexes withthe general formula[Tl(en)_n]³⁺(n = 1-3) and their overall stability constantshave been established in pyridine. All three complexes wereidentified by their²⁰⁵Tl and¹H NMR chemical shifts and²⁰⁵Tl-¹H coupling constants. The formation process of thecomplexes was followed by¹H NMR spectroscopy. The crystal structure of[Tl(en)₃](ClO₄)₃was determined; the thallium(III) ion isN-coordinated in a distorted octahedral geometry. Two [Tl(dien)_n]³⁺(n = 1-2) complexes were proved to exist insolution and the structure of the bis-complex [Tl(dien)₂]²⁺in<i>u-facial</i>isomers was determined in solid. In addition,crystal structures of [Tl(en)₂CN](ClO₄)₂with cyanide bridging between two Tl(en)₂units forming an infinite chain structure and of[Tl(tren)₂(CN)₂](ClO₄) with a distorted pseudo-octahedral coordinationaround thallium were determined. Thallium(III) complexes with2,2'-bipyridine and 1,10-phenanthroline have been studied inDMSO using²⁰⁵Tl,¹³C and¹H NMR spectroscopy. In addition, aseven-coordinated thallium was found in the crystal structureof [Tl(bipy)₃(dmso)](ClO₄)₃, and six-coordinated thallium in pseudo-octahedralgeometry in [Tl(phen)₂Cl₂](ClO₄).</p><p>The solvated complex [Tl(dmso)₆]³⁺has been prepared using concentrated aqueoussolution of Tl(ClO₄)₃by a solvent replacement reaction in DMSO, and thewater-free solid compound [Tl(dmso)₆](ClO₄)₃was crystallized from DMSO. The structure of thecomplex [Tl(dmso)₆]³⁺is a regular octahedron with the Tl-O bonddistance 2.224(3) Å. It represents an easy and secure wayto introduce water-free Tl(III) into organic phase withoutreduction.</p><p>Through several reactions, novel heteronuclear Pt-Tlcomplexes with the composition [(NC)₅Pt-Tl(tpp)]^2-, [(NC)₅Pt-Tl(thpp)]^2-, [(NC)₅Pt-Tl(bipy)_n](n = 1-2), [(NC)₅Pt-Tl(en)_n-1](n = 1-3) and [(NC)₅Pt-Tl(phen)_n](n = 1-2), have been synthesized in solution.Multinuclear NMR (¹⁹⁵Pt,²⁰⁵Tl,¹³C and¹H), Raman spectroscopy and X-ray diffraction dataare fully compatible with formation of unsupported Pt-Tl bondedcomplexes both in solution and in solid. The huge¹J(¹⁹⁵Pt-²⁰⁵Tl) spin-spin coupling constants (48-66 kHz) wereobserved by both¹⁹⁵Pt and²⁰⁵Tl NMR spectroscopy in solution and they providea strong evidence of formation of the Pt-Tl bond in solution.In all six determined crystal structures of the Pt-Tl compoundsa very short Pt-Tl bond is found with distances2.6117(5)-2.6375(5) Å. The calculated values of Pt-Tlforce constants (1.38-1.91 N/cm) are characteristic for asingle metal-metal bond.</p><p>In the Pt-Tl compounds, the oxidation state of the metalions is intermediate between the stable states Pt^II/Pt^IVand Tl^III/Tl^I, respectively, and this is reflected by their¹⁹⁵Pt and²⁰⁵Tl chemical shifts. It turns out that N-donorligands can really stabilize the Pt-Tl bond both in solutionand in solid. The character of the metal-metal bond anditstheoretical basis are discussed.</p><p><b>Keywords:</b>Thallium, Platinum, Cyanide, N-donor ligand,Metal-metal bond, Multinuclear NMR, Raman spectroscopy, X-raydiffraction, Equilibrium, Spin-spin coupling.</p>

This dissertation comprises the investigation of two subjects in the field of dimetal paddlewheel-type compounds containing metal-metal bonds: unsolvated transition metal carboxylates and triply bonded divanadium compounds. The first subject is very mature; dichromium tetraacetate was first synthesized in 1844, and hundreds of dimetal tetracarboxylates have been structurally characterized to date. A general question concerning the complexes of the type M2L4-Xn (where n = 0 to 2) is the extent to which the M-M distances are influenced by the presence of axial ligands, X. However, virtually none of the carboxylato complexes crystallize without axial ligands. In the solid state, in the absence of a coordinating solvent, the dimetal units often act as axial ligands to one another. In order to exclude axial coordination, both from donor solvent molecules, and from the aggregation of M24+ units, we have successfully used the bulky 2,4,6-triisopropylbenzoate ligand to bridge the dimetal core. We have investigated the triisopropylbenzoato complexes of some metals which are known for their ability to form a vast array of tetracarboxylato complexes, namely chromium, copper, molybdenum, and rhodium, and have found that these novel compounds display some interesting structural and chemical properties. The second subject of this dissertation is much more contemporary. Although compounds containing multiple bonds between metal atoms have been known since 1964, the first triply-bonded divanadium compound was not synthesized until 1992, and only two additional compounds of this type have been made in the intervening ten years. In order to extend this chemistry, several additional compounds containing a triply bonded V24+ core have recently been characterized. In our study of these compounds, we have discovered the first example of a stable paddlewheel-type compound with a M23+ core.

No description available.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xii, 286 p.; also includes graphics (some col.). Includes bibliographical references (p. 273-286). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

No description available.

No description available.