京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22278号 / 理博第4592号 / 新制||理||1659(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 北川 宏, 教授 竹腰 清乃理, 教授 吉村 一良 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

This is a study involving some of the chemistry of osmium tetroxide in perchloric acid solution. The research was originally instigated from a seminar report on the ruthenium III thiocyanate complex ion which was studied in perchloric acid solution. The seminar report given by Craig Townsend discussed how a spectrophotometric study by Yaffe and Voight (1951) was made of the ruthenium III thiocyanate complex ion, Similar possibilities were recognized as being possible in attacking the problem of an osmium thiocyanate complex or complexed. Some of the chemistry involved in the study of the ruthenium III thiocyanate complex will be discussed later. It will now suffice to say that the complex was studied by reacting ruthenium IV perchlorate and sodium thiocyanate to produce the complex ion. Townsend (1953), following the general procedure of Yaffe and Voight, took osmium tetroxide and sodium thiocyanate in a perchloric acid solution and reacted them to produce a rose colored osmium thiocyanate complex ion. He then determined a general formula and a value for the dissociation constant for the complex. Many problems were encountered in the Townsend study; and, therefore, there was reason for further study along these same lines. Some of the general characteristics of osmium and its related elements will be noted first.

Hard and ultra-incompressible materials are of great interest due to their important applications in industry. A common route to design hard materials is combining transition metals with light and small covalent elements. Light elements such as carbon, oxygen, nitrogen and boron have been considered as good candidates. This study includes the synthesis of ReB2, OsB2 and another higher boride AlMgB14. Most of the techniques used for ReB2 synthesis reported 1:2.5 Re to B ratio because of the loss of the B during high temperature synthesis. However, as a result of B excess, the amorphous boron, located along the grain boundaries of polycrystalline ReB2, would degrade the ReB2 properties. Therefore, techniques which could allow synthesizing the stoichiometric ReB2 preferably at room temperature are in high demand. This thesis reported the synthesis of ReB2 powders using mechanochemical route by milling elemental crystalline Re and amorphous B powders in the SPEX 8000 high energy ball mill for 80 hours. The formation of boron and perrhenic acids are also reported after ReB2 powder was exposed to the moist air environment for a twelve months period of time. The synthesized ReB2 powder was characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, secondary ion mass spectrometry and Raman spectroscopy. OsB2 also shows its attractive properties. The hardness of orthorhombic OsB2 was reported to be 37 GPa, when the applied load is lowered to 0.245N. However, only one of the three predicted phases has been synthesized. In this study, the hexagonal OsB2 has been synthesized by the mechanochemical method. The lattice parameters of the Hex-OsB2 are iv α=β=90°, γ=120°; a=b=2.9047 Å, c=7.4500 Å. The synthesized OsB2 powder was annealed at 1050°C for 6 days, but no phase change was found. This shows that the Hex-OsB2 is very stable. Another promising hard material, AlMgB14, was also studied in this thesis. The AlMgB14 was synthesized at 1050 °C under normal pressure. Several different routes were tried and compared. It shows AlMgB14 cannot be synthesized merely by ball milling, which can bring the risk of oxidization. Magnesium metal is preferred to use as one of the raw materials.

The design and construction of a coincidence spectrometer and its application to the study of the decay of Os¹⁹³ are presented. / Thesis / Doctor of Philosophy (PhD)

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Addition reactions of ten neutral nucleophiles and seven anionic nucleophiles with the pentaosmium pentadecacarbonyl carbido cluster Os5C(CO)15 have been kinetically studied and several important reactivity trends have been established. The calculated activation parameters support an associative mechanism involving the attack of nucleophiles on the parent cluster in the rate-limiting step. Decarbonylation reactions of neutral arachno clusters Os5C(CO)15L have also been kinetically studied and different reactivity trends have been observed. Reactions of Os5C(CO)15 with both neutral and anionic nucleophiles produce corresponding arachno clusters in good yield. Neutral arachno clusters decarbonylate when heated to yield corresponding nido clusters. All studied anionic arachno clusters are resistant to decarbonylation, but most of them readily react with organic acids to form corresponding hydrido clusters. Reactions of anionic arachno clusters with methyl triflate yielded several new clusters. Exploration of metal-ligand bond lengths in the respective pairs of arachno and nido clusters yielded a valuable conclusion with regard to steric effects prevalent in these molecules. The mechanisms for polyhedral structural rearrangements between arachno and nido derivatives of the pentaosmium carbido cluster have been proposed. Thermolysis of cluster Ru3[Ph2PCH(Me)PPh2](CO)10 in the presence of diphenylacetylene yields alkyne-substituted clusters Ru3(PhCCPh)[Ph2PCH(Me)PPh2](CO)8 and Ru3(PhCCPh)[Ph2PCH(Me)PPh2](CO)7 as the major products. The backbone-modified diphosphine in both clusters has facilitated the growth of single crystals suitable for X-ray crystallography. The kinetics for the conversion between two clusters have been investigated and the calculated activation parameters were found to be inconsistent with a rate-limiting step involving a dissociative loss of CO.

The goal of this research was to develop stereochemically defined multimetallic systems for use as light absorbers and electron donor / light absorber dyads in photoinitiated electron transfer and electron collection. The basis for the stereochemical control was provided by the symmetric bridging ligands 2,3,5,6-tetra(pyridyl)pyrazine (tpp) and 2,2'-bipyrimidine (bpm). The symmetric bidentate ligand 4N-perylene was designed and the majority of the synthesis was completed. The bimetallic complexes [(tpy)M(tpp)Ru(LLL)]²⁺, where M = Ru or Os and LLL = Cl₃, (CH₃CN)₃, tpp, or (dpq)Cl, and the model monometallic complexes [(tpy)M(tpp)]²⁺, where M = Ru or Os, and [(tpy)Ru(CH₃CN)₃]²⁺ were synthesized and characterized using electrochemistry, UV-vis spectroscopy, and UV-vis spectroelectrochemistry. The bimetallic complexes were investigated as potential light-absorber / electron-donor complexes to be used in larger supramolecular devices for photoinitiated electron collection and electron transfer. The electrochemistry showed that the relative energy of the metal orbitals is suitable for the metal in the (tpy)M(tpp) coordination environment to act as an electron donor. These bimetallic complexes possess extremely complicated UV-vis spectroscopy due to the number of possible transitions. The assignment of the UV-vis spectroscopy and the electrochemistry of these complexes was greatly facilitated by the UV-vis spectroelectrochemistry. The metal-to-metal charge transfer spectra of the mixed-valence species of the bimetallic complexes were obtained using NIR spectroelectrochemistry and indicate a significant degree of metal-metal communication through the bridging tpp. The bimetallic complexes [(tpy)Ru(tpp)Ru(tpy)]⁴⁺, [(tpy)Ru(tpp)Ru(tpp)]⁴⁺ [(tpy)Os(tpp)Ru(tpp)]⁴⁺, and [(tpy)Ru(tpp)Ru(CH₃CN)₃]⁴⁺ were found to have emission lifetimes on the order of 100 ns. The complexes [(bpy)₂Ru(bpm)]²⁺, [(bpy)₂Ru(bpm)Ru(bpy)₂]⁴⁺, [(bpm)₂IrCl₂]⁺, and {[(bpy)₂Ru(bpm)]₂IrCl₂}⁵⁺ were synthesized and characterized using electrochemistry, UV-vis spectroscopy, and UV-vis spectroelectrochemistry. The complex {[(bpy)₂Ru(bpm)]₂IrCl₂}⁵⁺ is a LA-EC-LA device for photoinitiated electron collection. The UV-vis spectroelectrochemistry of these complexes facilitated the assignment of the UV-vis spectroscopy as well as the electrochemistry. The UV-vis spectrum of the electrochemically generated two electron reduced form of {[(bpy)₂Ru(bpm)]₂IrCl₂}⁵⁺ was obtained. This spectrum is critical in the understanding of future studies of the photochemically generated two electron reduced species. The symmetric, planar, bidentate bridging ligand 4N-perylene was designed. This ligand would eliminate some of the isomers associated with multimetallic complexes bridged by unsymmetric bidentate bridging ligands. The large π system of 4N-perylene would likely result in a low energy π* orbital compared to dpp, dpq, or bpm. The ligand 4N-perylene would hold bridged metals at a greater distance than 2,2'-bipyrimidine and should facilitate the formation of multimetallic complexes. The synthesis of 1,8-dichloro-2,7-naphthyridine has been completed. 1,8-dichloro-2,7-naphthyridine is a possible reactant in the homo-coupling reaction of a substituted 2,7-naphthyridine to form 4N-perylene. The stereochemically defined molecular systems developed in this work show great promise for use in larger supramolecular complexes designed for photoinitiated electron transfer and electron collection. / Ph. D.

A series mixed metal supramolecular complexes were synthesized and studied by electrochemistry, photophysics and photochemistry. The complexes consisted of a single RuII or OsII polyazine light absorber bound to a cis-RhIIICl2 moiety through a polyazine bridging ligand. A related class of supramolecule is known to perform photoinitiated electron collection, photocatalysis of hydrogen from water, DNA photomodification and is known to kill mammalian cells; all with visible light irradiation. The complexes studied herein, [(bpy)2Ru(bpm)RhCl2(phen)](PF6)3, [(bpy)2Ru(dpp)RhCl2(phen)](PF6)3, [(bpy)2Os(dpp)RhCl2(phen)](PF6)3, and [(tpy)OsCl(dpp)RhCl2(phen)](PF6)2 were synthesized in moderate yields (54-84%) by reaction of the appropriate monometallic visible light absorbing subunit with a slight excess of K[(phen)RhCl4]·3H2O (bpy = 2,2'-bipyridine, bpm = 2,2'-bipyrimidine, 1,10-phenanthroline, dpp = 2,3-bis(2-pyridyl)pyrazine, and tpy = 2,2':6',2"-terpyridine). Voltammetric analysis of [(bpy)2Ru(bpm)RhCl2(phen)](PF6)3 revealed a reversible oxidation at 1.76 V (vs. Ag/AgCl) (RuIII/II). A reversible reduction at â 0.14 V (bpm0/-), and quasi-reversible reductions at â 0.77 V and â 0.91 V each corresponded to a one electron process, bpm0/â , RhIII/II and RhII/I. The electrochemistry of [(bpy)2Ru(dpp)RhCl2(phen)](PF6)3 showed a reversible oxidation at 1.61 V (RuIII/II), and quasi-reversible reductions at â 0.39 V, â 0.74 V and â 0.98 V. The first two reductive couples corresponded to two electrons, consistent with Rh reduction. [(bpy)2Os(dpp)RhCl2(phen)](PF6)3, and [(tpy)OsCl(dpp)RhCl2(phen)](PF6)2 each exhibited reductions similar to the dpp bridged Ru,Rh dyad, but with OsIII/II based oxidations at 1.24 V and 0.83 V, respectively. The complexes [(bpy)2Ru(bpm)RhCl2(phen)](PF6)3 and [{(bpy)2Ru(bpm)}2RhCl2](PF6)5 display Ru(dπ)â bpm(π*) CT (MLCT) transitions at 581 nm and at 594 nm, respectively. The dpp bridged Ru,Rh bimetallic and Ru,Rh,Ru trimetallic display Ru(dπ)â dpp(π*) CT transitions at 509 nm and 518 nm, respectively. Similarly, [(bpy)2Os(dpp)RhCl2(phen)](PF6)3 absorbs strongly at 520 nm versus 534 nm for [{(bpy)2Os(dpp)}2RhCl2](PF6)5, both with low energy tails at 800 nm indicative of Os centered MLCT transitions. Overlapping Os(dπ)â dpp(π*) and Os(dπ)â tpy(π*) transitions occur at 536 nm with low energy tails at 856 nm for both [(tpy)OsCl(dpp)RhCl2(phen)](PF6)2 and [{(tpy)OsCl(dpp)}2RhCl2](PF6)3. Emission from [{(bpy)2Ru(dpp)}RhCl2](PF6)5 and [(bpy)2Ru(dpp)RhCl2(phen)](PF6)3 at room temperature and 77 K was red shifted and less intense than emission from [(bpy)2Ru(dpp)Ru(bpy)2](PF6)4, consistent with quenched emission from a Ru(dπ)â dpp(π*) 3MLCT state. Transient absorption spectroscopy supported assignment of the emissive state as Ru(dπ)â dpp(π*) CT in nature. The complexes [(bpy)Ru(dpp)RhCl2(phen)](PF6)3 (τ =18 ns) and [{(bpy)2Ru(dpp)}2RhCl2](PF6)5 (τ = 16 ns) each exhibit shorter lived 3MLCT states than the Ru,Ru dyad (τ = 125 ns) in acetonitrile consistent with favorable electron transfer to Rh(III) to generate a metal to metal charge transfer (3MMCT) state. The photochemistry of [{(bpy)2Ru(dpp)}2RhCl2]Cl5, [{(tpy)OsCl(dpp)}2RhCl2]Cl3, [(bpy)2Ru(dpp)RhCl2(phen)]Cl3, and [(tpy)OsCl(dpp)RhCl2(phen)]Cl2 with DNA was investigated using gel electrophoresis and selective precipitation of a DNA/metal complex adduct. An array of high intensity LEDs was designed, constructed and validated to accommodate these high throughput photochemical experiments with DNA. Each of the metal complexes is suggested to undergo photobinding with DNA as well as to photocleave DNA. A 3MMCT state or a thermally accessible Rh centered 3LF state each are proposed as leading to photobinding, while a 3MMCT state is thought to be involved in DNA photocleavage. / Ph. D.