No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18471号 / 工博第3907号 / 新制||工||1600(附属図書館) / 31349 / 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 小澤 文幸, 教授 辻 康之, 教授 中村 正治 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

The hydrophobic effect has been a topic of research for decades, not only due to its importance as the primary building block of much of chemistry (it dictates which solvent can dissolve which solutes) and biology (guiding protein binding and gene expression) but also due to it being a fundamental physical process. The commonly held opinion is that 'like dissolve like', implying polar substances can readily mix with other polar substances, and similarly for apolar ones, but polar and apolar would separate and tend to stay isolated from one another (like oil in water). We have developed a quantitative imaging method that can be used in tandem with Raman spectroscopy in order to investigate the effect of high pressure on a model hydrophobic system - water and methane. Our study revealed an unexpectedly large increase in the amount of methane that can readily mix with water once a rather modest pressure has been applied to the system. Thus, the solubility of CH4 in H2O starts abruptly increasing at 1.3 GPa and reaches a maximum of 44(3) mole % at 2.1 GPa, showing no pressure dependence upon further compression. We have tried to reproduce the observed experimental behaviour using classical molecular dynamics simulations deploying a range of widely used water potentials (SPC/E, TIP4P, TIP3P), but unfortunately no quantitative or even qualitative agreement was reached with experiments. Finally, in order to understand the atomic level changes that enable this increased amount of methane to dissolve in water, we have performed neutron scattering measurements along with EPSR (empirical potential structure refinement) fits to the data in order to solve the structure of the fluid mixture. These revealed a tendency towards maintaining the H-bond network present in water and homogeneous mixing. Despite the network staying similar to the one found in pure fluid water at milder pressures and temperatures (close to ambient conditions), the H-bonds seem more disordered and show a greater variability in their lengths.

N-phenylpyridin-2-amine , treated with stochiometric amount of palladium(II) acetate in dichloromethane at 65-70¢J for 4 h, to give high yield palladacycle 53. The reaction of palladacycle 53 with potassium aryltrifluoroborates in 1,4-dioxane at 140¢J for 24 h, could give a variety of N-(2-pyridinyl)carbazoles 55a-55m via sequential C-H bond activation. Carbazole derivative 55a reacted with irdium chloride gave iridium dimer, which followed by addition of picolinic acid via ligand exchange will form iridium complexes, which can further be utilized as OLEDs materials.

This thesis is composed of two parts. The palladium-catalysted synthesis of 2-arylphenols and carbazoles via carbon-hydrogen (C-H) bond activation is described. Treatment of 2-phenoxypyridines with two and a half equivalents of potassium aryltrifluoroborate and 10 mol % of Pd(OAc)2 in the presence of two equivalents of Ag2CO3, one equivalent of p-benzoquinone (BQ), and four equivalents of DMSO with (or without) H2O at 130-140 oC for 48 h in dried CH2Cl2 gave the ortho-arylated 2-phenoxypyridines in modest to excellent yields. The investigation of kinetic isotope effect (kH/kD) is determined to be 5.25, which indicates that C-H bond cleavage occurs in the rate-determining step. 2-(Biphenyl-2-yloxy)pyridines was treated with methyl trifluoromethanesulfonate and subsequently sodium methoxide to give the 2-arylphenols to demonstrate the pyridine is a removable directing group. On the other hand, a novel one-pot synthesis for N-pyridylcarbazoles by the reaction of N-phenylpyridin-2-amines with potassium aryltrifluoroborates using Pd(OAc)2 as the catalyst is presented. For instance, reaction of N-phenylpyridin-2-amines with four equivalents of potassium aryltrifluoroborate under the optimal reaction condition gave N-pyridylcarbazoles in 67% yield along with N-(biphenyl-2-yl)pyridin-2-amine in 13% yield. The investigation of kinetic isotope effect (kH/kD) for first C-H bond activation/C-C bond formation step is determined to be 2.14, and that of the second C-H bond activation/C-N bond formation steps is 1.18. On the basis of KIE analysis, it might indicate that first C-H activation undergo direct C-H bond cleacage, and second step should be via electrophilic aromatic substitution.

A one-pot synthesis of ortho-arylated 9-(pyridin-2-yl)-9H-carbazoles via C-H bond activation, in which palladium(II)-catalyzed cross-coupling of 9-(pyridin-2-yl)-9H-carbazoles with potassium aryltrifluoroborates is presented. Silver nitrate and tert-butanol were proved to be the best oxidant and solvent for the process, respectively. The product yields fluctuated from modest to excellent, and the reaction showed sufficient functional group tolerance. p-Benzoquinone served as an important ligand for the transmetalation and reductive elimination steps in the catalytic process. The key intermediate of the reaction, 9-(pyridin-2-yl)-9H-carbazole palladacycle was isolated and confirmed by X-ray crystallography. The kinetic isotope effect (kH/kD) for the C-H bond activation step was measured as 0.87. In addition, Hammett experiment gave a negative rho value, -2.14 with a reasonable correlation (R2 = 0.90). The directing group, pyridyl was demonstrated as a removable functional group. Finally, a rational catalytic mechanism is presented based on all experimental evidence.

The results from density functional theory (DFT) studies into C–H bond activation, hydrogen transfer, and alkyne–to–vinylidene isomerization are presented in this work. The reaction mechanism for the reductive elimination (RE) of methane from [ κ3- TpPtIV(CH3)2H (1)] (Tp = hydridotris(pyrazolyl)borate) by oxidative addition (OA) of benzene to form [ κ3-TpPtIV(Ph)2H] (19) was investigated through DFT calculations. For 31 density functionals, the calculated values for the barriers to methane formation (Ba1) and release (Ba2) from 1 were benchmarked against the experimentally reported values of 26 (Ba1) and 35 (Ba2) kcal•mol-1, respectively. The values for Ba1 and Ba2, calculated at the B3LYP/DZP level of theory, are 24.6 and 34.3 kcal•mol-1, respectively. The best performing functional was BPW91 where the m.a.e. for the calculated values of the two barriers is 0.68 kcal•mol-1. Classic and newly proposed mechanisms for metal-mediated hydrogen transfer (HT) were analyzed with density functional theory (DFT) and Bader's "Atoms In Molecules" (AIM) analysis. Seven sets of bonding patterns that characterize theconnectivity in metal-mediate HT were found from the analysis of representative models for σ-bond metathesis ( σBM), oxidative addition / reductive elimination (OA/RE), and alternative mechanisms. The mechanism for the formation of the alkynyl, vinylidene complex, [(PiPr3)2Rh(CCPh)(CC(H)(Ph))] (2), by the addition of two equivalents of phenylacetylene (PA) to [( η3-C3H5)Rh(PiPr3)2] (1) was studied through DFT calculations. Two experimentally observed intermediates on the reaction coordinate are the η2-PA, alkynyl complex, [(PiPr3)2Rh( η2-HCCPh)(CCPh)] (Ia) and the fivecoordinate, pseudo square-pyramidal, RhIII–H complex, [(PiPr3)2Rh(H)(CCPh)2] (Ib), and were found to be in equilibrium. The relative energies of Ia, Ib, and 2 (relative to 1 + 2PA) depend on the phosphine that was used in the calculation; the predicted product is 2 with PiPr3 and PEt3 but Ia with PMe3, PMe2Ph, PMePh2, PPh3, and PH3. The equilibrium between Ia and Ib was calculated with PEt3 and one conformation of PiPr3. We investigated the mechanism for the formation of 2 from Ia, and a lower energy pathway where the π-bound PA of Ia slips to bind through the σ-C–H bond prior to the formation of 2 through hydrogen migration was found.

No description available.

A CuI fully fluorinated O-donor monodentate alkoxide complex, K[Cu(OC4F9)2] (1), was previously shown to form a trinuclear copper–dioxygen species with a {Cu3(3-O)2} core, TOC4F9, upon reactivity with O2 at low temperature. A significantly expanded kinetic and mechanistic study of TOC4F9 formation is reported using stopped-flow spectroscopy. The TOC4F9 complex performed catalytic oxidase conversion of para-hydroquinone (H2Q) to para-benzoquinone (BQ) and hydroxylation of 2,4-di-tert-butylphenolate (DBP) to catecholate, making TOC4F9 the first tri-copper species to perform tyrosinase (both monooxygenase and oxidase) chemistry. As opposed to 1, when K+ is fully encapsulated in {K(18C6)}[Cu(OC4F9)2] (4), O2 was not reduced under identical conditions. To study the effects of both alkali cation and the degree of encapsulation on reduction of O2, derivative complexes were synthesized with Na+ (16), {Na(DME)}+ (17), {Na(15C5)}+ (18), {K(15C5)}+ (19), {K(15C5)2}+ (20), Cs+ (21), {Cs(18C6)}+ (22), and {Cs(18C6)2}+ (23). Reduction of O2 was found to be encapsulation-dependent, and cation size was also determined to affect the chromophore observed. These results suggest that cation…F/O interactions between the CuI complexes assemble aggregates that are required to form reactive {Cun−O2} species. However, catalytic oxidation of H2Q to BQ and sub-stoichiometric oxidation of DBP to catecholate occurred regardless of whether a {Cun−O2} intermediate was detected, suggesting that a reactive species may self-assemble in the presence of substrate in all complex derivatives unable to reduce O2. A series of heteroleptic mixed phosphine/alkoxide 3d complexes was designed to evaluate PPh3 as a protecting group. Complexes of the form [(Ph3P)2M(OC4F9)2] (M= Fe (24), Co (25), Ni (26), Zn (27)) and [(Ph3P)2M(pinF)] (M= Co (31), Ni (32), Zn (33)) were prepared and characterized, along with related complexes with non-reactive L-donors for comparison, [(DME)Fe(OC4F9)2] (28) and [(Ph3PO)2M(OC4F9)2] (M= Fe (29), Ni (30)). Dimeric [Fe2(-O)(OPPh3)2(OC4F9)4] (36) was isolated after O2 reactivity with 24, and 28 and 29 were able to generate intermediate species capable of both oxidation of H2Q to BQ and oxygen atom transfer of thioanisole to methyl phenyl sulfoxide. The choice of fluorinated ligand influences O2 reactivity with CoII (25, 31), but not for NiII (26, 32). Related dimeric compounds [Co2(pinF)2(THF)4)] (34) and [Zn2(pinF)2(THF)2)] (35) were also isolated.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20192号 / 理博第4277号 / 新制||理||1615(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 依光 英樹, 教授 丸岡 啓二, 講師 西村 貴洋 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM