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One of the main goals of computational methods is to identify reasonable geometries for target materials. Organometallic complexes have been investigated in this dissertation research, entailing a significant challenge based on transition metal diversity and the associated complexity of the ligands. A large variety of theoretical methods have been employed to determine ground state geometries of organometallic species. An impressive number of transition metals entailing diverse isomers (e.g., geometric, spin, structural and coordination), different coordination numbers, oxidation states and various numbers of electrons in d orbitals have been studied. Moreover, ligands that are single, double or triple bonded to the transition metal, exhibiting diverse electronic and steric effects, have been investigated. In this research, a novel de novo scheme for structural prediction of transition metal complexes was developed, tested and shown to be successful.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22702号 / 工博第4749号 / 新制||工||1742(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 大江 浩一, 教授 近藤 輝幸, 教授 中尾 佳亮 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

The synthesis and comprehensive characterization of diamine and diimine derivatives of thioindigo are reported. X-ray crystal structures demonstrate a planar structure for the diimine derivatives and a twisted conformation for the diamines. The diamine compounds absorb in the UV (λmax 324 nm - 328 nm), and exhibit moderate fluorescence (ΦF = 0.25, 0.045). A transient triplet state is observed in laser flash photolysis (LFP) experiments, with lifetimes an order of magnitude longer than those of the triplet state of thioindigo. The diimine compounds absorb at longer wavelengths than the diamines (λmax 495 nm - 510 nm), but are still slightly blue-shifted from thioindigo. The diimines have molar extinction coefficients 17 – 70% higher than thioindigo. The diimine compounds are not emissive, and LFP studies show transient species with microsecond lifetimes. The transient absorption spectra and quenching experiments of the diimines are consistent with trans-cis isomerisation about the central double bond. Mono- and diruthenium hexafluoroacetylacetonate (hfac) complexes of thioindigo-N,Nʹ-diphenyldiimine have been prepared. The monoruthenium complex was isolated as a racemic mixture and the diruthenium complexes were isolated as the meso (ΔΛ) and rac (ΔΔ and ΛΛ) diastereomers. Extensive structural characterization of the compounds revealed intrinsic diastereomeric differences in the X-ray crystal structures, cyclic voltammograms, and NMR spectra. Variable temperature NMR experiments demonstrated that the rac diastereomer undergoes conformational exchange with a rate constant of 8700 sec-1 at 298 K, a behavior that is not observed in the meso diastereomer. Ground state optical properties of the complexes were examined, showing that all the complexes possess metal-to-ligand charge transfer (MLCT) absorption bands in the near-infrared (λmax 689 nm – 783 nm). The compounds do not display photoluminescence in room temperature solution-phase experiments or in experiments at 77 K. Ultrafast transient absorption spectroscopy measurements revealed excited states with picosecond lifetimes. Unexpectedly, the transient absorption measurements revealed differences in the transient spectra and disparate time constants for the excited state decay of the diastereomers, which are linked to the conformational changes observed in the NMR experiments. Investigations into the synthesis of azaDIMEs and azaDicarbazolyls are described. Examination of the Buchwald-Hartwig amination produced reaction conditions that enabled preparation of amino-diindoles. Oxidation of the amino-diindoles to azaDIMEs was complicated by concomitant oligomerization of the substrates. Substitution of the reactive positions of the amino-diindole afforded increased stability towards oxidative oligomerization. Scalable synthetic routes to azaDicarbazolyl precursors were identified and optimized, and preparation of amino and azaDicarbazolyl compounds was explored. / Graduate / 2021-04-18

Simple and novel nuclease models have been synthesized. These involve metal-binding ligand 1,4,7,10-tetraazlcyclododecane (cyclen) tethered to an acridine ring (a DNA-binding group) by amide linkers of various lengths. Binding of these probes to DNA was studied by monitoring changes in their UV-visible spectra affected by the presence of DNA. Titration of these compounds with increasing amounts of pBR322 DNA caused hypochromic effects and shifted the acridine absorption at 360nm to a longer wavelength. Under biologically relevant conditions (37°C and pH 7.4), specific transition metal complexes of these compounds are found to be highly effective catalysts toward the hydrolysis of plasmid DNA. This is demonstrated by their ability to convert the super-coiled DNA (form I) to open-circular DNA (form II). Structure-activity correlation studies show that hydrolytic activity depends on both the structure of ligand (L1>L2>L3) and the nature of metal ion cofactor (Co3+>Zn2+>Cr2+>Ni2+>Cu2+>Fe3+).

Metal-organic frameworks are a new class of crystalline, porous solid-state materials with metal ions periodically linked by organic linkers. This gives rise to one-, two- or three-dimensional structures. Here, we compare the stability of similar metal sites toward external ligand (solvent) induced disruption of the coordination environment in metal complexes and in metal-organic frameworks. Our experimental results show that a metal site as node of a metal-organic framework retains much higher stability compared to a similar metal site in a metal complex.

<p> Reaction of the hydrated trichlorides of rhodium and Iridium with hexamethyldewarbenzene gave the complexes, (C5Me5MCl2)2 (M=Rh, Ir). A mechanism for this reaction is proposed.</p> <p> The dichloro complexes, (C5Me5MCl2)2, were reacted with a number of di- and tri-enes in ethanol in the presence of base and gave a variety of pentamethylcyclopentadienyl complexes of M(l) and M(lll). Evidence for a hydrido intermediate is presented and the hydrido- and deuterido- complexes, C5Me5IrH(D)ClPPh3, were isolated and characterised.</p> <p> The isomers endo-H and exo-H pentamethylcyclopentadiene(cyclopentadienyl) rhodium were isolated and showed significant differences in their properties. Cyclooctadienes reacted with (C5Me5MCl2)2 to give C5Me5M(1,5-C8H12) via the intermediacy of the π-2-cyclooctenyl complexes C5Me5MCl(C8H13); mechanisms are presented to account for the observed products. Cyclohexadienes gave the complexes, C5Me5M(1,3-C6H8). 1,4-Cyclohexadiene was isomerised to 1,3-C6H8; the rhodium complex, C5Me5Rh(1,3-C6H8), was a very active catalyst for the disproportionation of 1,3-C6H8 to cyclohexene and benzene, both ethanol and base were cocatalysts.</p> <p> Mass spectral data for these and other organo-metallic complexes are presented.</p> / Thesis / Doctor of Philosophy (PhD)

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Yes / Half-sandwich metal complexes are of considerable interest in medicine, material, and nanomaterial chemistry. The design of libraries of such complexes with particular reactivity and properties is therefore a major quest. Here, we report the unique and peculiar reactivity of eight apparently 16-electron half-sandwich metal (ruthenium, osmium, rhodium, and iridium) complexes based on benzene-1,2-dithiolato and 3,6-dichlorobenzene-1,2-dithiolato chelating ligands. These electron-deficient complexes do not react with electron-donor pyridine derivatives, even with the strong σ-donor 4-dimethylaminopyridine (DMAP) ligand. The Ru, Rh, and Ir complexes accept electrons from the triphenylphosphine ligand (σ-donor, π-acceptor), whilst the Os complexes were found to be the first examples of non-electron-acceptor electron-deficient metal complexes. We rationalized these unique properties by a combination of experimental techniques and DFT/TDFT calculations. The synthetic versatility offered by this family of complexes, the low reactivity at the metal center, and the facile functionalization of the non-innocent benzene ligands is expected to allow the synthesis of libraries of pseudo electron-deficient half-sandwich complexes with unusual properties for a large range of applications.