<p>According to the famous axiom known as Moore’s Law the number of transistors that can be etched on a given piece of silicon, and therefore the computing power, will double every 18 to 24 months. For the last 40 years Moore’s prediction has held true as computers have grown more and more powerful. However, around 2020 hardware manufac-turers will have reached the physical limits of silicon. A proposed solution to this dilemma is molecular electronics. Within this field researchers are attempting to develop individual organic molecules and metal complexes that can act as molecular equivalents of electronic components such as diodes, transistors and capacitors. By utilizing molecular electronics to construct the next generation of computers processors with 100,000 times as many components on the same surface area could potentially be created.</p><p>We have synthesized a range of new pyridyl thienopyridine ligands and compared the electrochemical and photophysical properties of their corresponding Ru(II) complexes with that with the Ru(II) complexes of a variety of ligands based on 6-thiophen-2-yl-2,2´-bipyridine and 4-thiophen-2-yl-2,2´-bipyridine. While the electrochemistry of the Ru(II) complexes were similar to that of unsubstituted [Ru(bpy)3]2+, substantial differences in luminescence lifetimes were found. Our findings show that, due to steric interactions with the auxiliary bipy-ridyl ligands, luminescence is quenched in Ru(II) complexes that in-corporate the 6-thiophen-2-yl-2,2´-bipyridine motif, while it is on par with the luminescence of [Ru(bpy)3]2+ in the Ru(II) complexes of the pyridyl thienopyridine ligands. The luminescence of the Ru(II) com-plexes based on the 4-thiophen-2-yl-2,2´-bipyridine motif was en-hanced compared to [Ru(bpy)3]2+ which indicates that complexes of this category are the most favourable for energy/electron-transfer sys-tems.</p><p>At the core of molecular electronics are the search for molecular ON/OFF switches. We have synthesized a reversible double cyclome-tallated switch based on the Ru(tpy) complex of 3,8-bis-(6-thiophen-2-yl-pyridin-2-yl)-[4,7]phenanthroline. Upon treatment with acid/base the complex can be switched between the cyclometallated and the S-bonded form. This prototype has potentially three different states which opens the path to systems based on ternary computer logic.</p>

<p>The earliest landmark in computer technology was construction of the Electronic Numerial Integrator and Computer, ENIAC. Computational switching was performed with vacuum tubes and relays, rather large in size, making this computer rather unwieldy. The next milestone came with the integration of transistors into computers as the switching component. Since then, transistors have been miniaturised dramatically, resulting in the amount of components integrated on a computer chip increasing logarithmically with time. The components are nowadays so small and so densely packed that problems with leak currents and cross-talk can arise and the lower limit for transistor size will soon be reached. In order to meet increasing demands on the size and performance of electronics, a new paradigm is due – the molecular electronics approach.</p><p>Oligothiophenes have been shown to possess the physical and chemical characteristics required for electron/energy transport in molecular systems. However oligothiophenes must be electronically coupled to other components within a molecular circuit for them to be functional. In this work, different modes of incorporation of [2,2’]-bipyridinyl functionalities onto the ends of prototypic oligothiophene wires have been examined. The bipyridine connectors allow complexation to metal centres which can then function as a source or sink of electrons in the circuit. Ruthenium tris-bipyridine complexes, in particular, possess interesting electrochemical and photophysical characteristics, making them suitable for use in molecular electronics.</p><p>This thesis reports synthetic strategies to a range of novel ligands based on the [2,2’]-bipyridinyl system, together with a study of the redox and fluorescence properties of their ruthenium tris-bipyridine complexes. The mode of connection between the chelating bipyridine and the first member of the oligothiophene chain was found to have a profound effect upon the fluorescence lifetimes and intensities of the resulting complexes. The discovery of complexes exhibiting long and intense fluorescence (a requirement for directed electron/energy transfer within molecular networks) thus forms an important design element in future prototypes.</p>

According to the famous axiom known as Moore’s Law the number of transistors that can be etched on a given piece of ultra-pure silicon, and therefore the computing power, will double every 18 to 24 months. However, around 2020 hardware manufacturers will have reached the physical limits of silicon. A proposed solution to this dilemma is molecular electronics. Within this field researchers are attempting to develop individual organic molecules and metal complexes that can act as molecular equivalents of electronic components such as wires, diodes, transistors and capacitors. In this work we have synthesized a number of new bi- and terdentate thiophenyl pyridine and pyridyl thienopyridine ligands and compared the electrochemical, structural and photophysical properties of their corresponding Ru(II) complexes with Ru(II) complexes of a variety of ligands based on 6-thiophen-2-yl-2,2'-bipyridine and 4-thiophen-2-yl-2,2'-bipyridine motifs. While the electrochemistry of the Ru(II) complexes were similar to that of unsubstituted [Ru(bpy)3]2+ and [Ru(tpy)2]2+, substantial differences in luminescence lifetimes were found. Our findings show that, due to steric interactions with the auxiliary bipyridyl ligands, luminescence is quenched in Ru(II) complexes that incorporate the 6-thiophen-2-yl-2,2'-bipyridine motif, while it was comparable with the luminescence of [Ru(bpy)3]2+ in the Ru(II) complexes of bidentate pyridyl thienopyridine ligands. The luminescence of the Ru(II) complexes based on the 4-thiophen-2-yl-2,2'-bipyridine motif was enhanced compared to [Ru(bpy)3]2+ which indicates that complexes of this category may be applicable for energy/electron-transfer systems. At the core of molecular electronics is the search for molecular ON/OFF switches. Based on the ability of the ligand 6-thiophen-2-yl-2,2'-bipyridine to switch reversibly between cyclometallated and non-cyclometallated modes when complexed with Ru(tpy) we have synthesized a number of complexes, among them a bis-cyclometallated switch based on the ligand 3,8-bis-(6-thiophen-2-yl-pyridin-2-yl)-[4,7]phenanthroline, and examined their electrochemical properties. Only very weak electronic coupling could be detected, suggesting only little, if any, interaction between the ruthenium cores.

This thesis reports progress in three major aspects of σ-bonded organometallic porphyrins that are described in the published papers found in chapters 4, 5 and 6. meso-Iodoporphyrins, which were prepared in a rapid, selective and high yielding methodology from the respective 1-palladioporphyrins or bromoporphyrins, are important starting materials for further functionalisations of porphyrins. Their utility was confirmed in a palladium-catalysed coupling reaction and this novel synthetic strategy could potentially be applied for iodine/bromine exchange on other organic substrates.. A 1-palladioporphyrin was also utilised to optimise the reaction conditions leading to the formation of porphyrinylphosphine oxides. This synthetic strategy simplified the challenging optimisation of the palladium-catalysed reaction and has great potential to be applied in other catalytic processes. Subsequently a suite of porphyrinylphosphine oxides was prepared under the optimised catalytic conditions. These macrocycles, which represent a new class of porphyrins, were isolated cleanly in very high yields. Detailed spectroscopic investigations as well as X-ray single crystal analysis demonstrated their structures unambiguously and established their potential as ligands for supramolecular chemistry. The coordinating properties of phosphine oxides in general and porphyrinylphosphine oxides in particular, towards Mg(II) centred porphyrins were examined in further experiments. Triphenylphosphine oxide showed a strong affinity towards Mg(II) porphyrins and the calculated displacement constant of 5.3 × 105 M-1 was two orders of magnitude larger than any other Mg(II) porphyrin-ligand binding constant reported thus far. Di- and triporphyrin arrays consisting of Mg(II) porphyrin coordinated to free base and Ni(II) porphyrinyl mono- and bis-phosphine oxides were also prepared in high yields. Spectroscopic studies indicated that these porphyrin oligomers exhibit strong inter-porphyrin electronic interaction. A Mg(II) porphyrinylphosphine oxide dimer was also isolated in a satisfactory yield. The large self-association constant of 5.5 × 108 M-1 confirmed the strong affinity of porphyrinylphosphine oxides towards Mg(II) porphyrins and established these complexes as the first strongly bound synthetic Mg(II) porphyrin analogues of the "special pair" of the photosynthetic reaction centre.

The earliest landmark in computer technology was construction of the Electronic Numerial Integrator and Computer, ENIAC. Computational switching was performed with vacuum tubes and relays, rather large in size, making this computer rather unwieldy. The next milestone came with the integration of transistors into computers as the switching component. Since then, transistors have been miniaturised dramatically, resulting in the amount of components integrated on a computer chip increasing logarithmically with time. The components are nowadays so small and so densely packed that problems with leak currents and cross-talk can arise and the lower limit for transistor size will soon be reached. In order to meet increasing demands on the size and performance of electronics, a new paradigm is due – the molecular electronics approach. Oligothiophenes have been shown to possess the physical and chemical characteristics required for electron/energy transport in molecular systems. However oligothiophenes must be electronically coupled to other components within a molecular circuit for them to be functional. In this work, different modes of incorporation of [2,2’]-bipyridinyl functionalities onto the ends of prototypic oligothiophene wires have been examined. The bipyridine connectors allow complexation to metal centres which can then function as a source or sink of electrons in the circuit. Ruthenium tris-bipyridine complexes, in particular, possess interesting electrochemical and photophysical characteristics, making them suitable for use in molecular electronics. This thesis reports synthetic strategies to a range of novel ligands based on the [2,2’]-bipyridinyl system, together with a study of the redox and fluorescence properties of their ruthenium tris-bipyridine complexes. The mode of connection between the chelating bipyridine and the first member of the oligothiophene chain was found to have a profound effect upon the fluorescence lifetimes and intensities of the resulting complexes. The discovery of complexes exhibiting long and intense fluorescence (a requirement for directed electron/energy transfer within molecular networks) thus forms an important design element in future prototypes.

According to the famous axiom known as Moore’s Law the number of transistors that can be etched on a given piece of silicon, and therefore the computing power, will double every 18 to 24 months. For the last 40 years Moore’s prediction has held true as computers have grown more and more powerful. However, around 2020 hardware manufac-turers will have reached the physical limits of silicon. A proposed solution to this dilemma is molecular electronics. Within this field researchers are attempting to develop individual organic molecules and metal complexes that can act as molecular equivalents of electronic components such as diodes, transistors and capacitors. By utilizing molecular electronics to construct the next generation of computers processors with 100,000 times as many components on the same surface area could potentially be created. We have synthesized a range of new pyridyl thienopyridine ligands and compared the electrochemical and photophysical properties of their corresponding Ru(II) complexes with that with the Ru(II) complexes of a variety of ligands based on 6-thiophen-2-yl-2,2´-bipyridine and 4-thiophen-2-yl-2,2´-bipyridine. While the electrochemistry of the Ru(II) complexes were similar to that of unsubstituted [Ru(bpy)3]2+, substantial differences in luminescence lifetimes were found. Our findings show that, due to steric interactions with the auxiliary bipy-ridyl ligands, luminescence is quenched in Ru(II) complexes that in-corporate the 6-thiophen-2-yl-2,2´-bipyridine motif, while it is on par with the luminescence of [Ru(bpy)3]2+ in the Ru(II) complexes of the pyridyl thienopyridine ligands. The luminescence of the Ru(II) com-plexes based on the 4-thiophen-2-yl-2,2´-bipyridine motif was en-hanced compared to [Ru(bpy)3]2+ which indicates that complexes of this category are the most favourable for energy/electron-transfer sys-tems. At the core of molecular electronics are the search for molecular ON/OFF switches. We have synthesized a reversible double cyclome-tallated switch based on the Ru(tpy) complex of 3,8-bis-(6-thiophen-2-yl-pyridin-2-yl)-[4,7]phenanthroline. Upon treatment with acid/base the complex can be switched between the cyclometallated and the S-bonded form. This prototype has potentially three different states which opens the path to systems based on ternary computer logic.

No description available.

Contemporary challenges in synthetic organic chemistry require innovative solutions. The discovery of highly-effective and readily accessible scaffolds drives the ever expanding scope of catalytic transformations. This dissertation outlines the repurposing of 1,5-Diaza-3,7-diphosphacyclooctanes (P₂N₂) ligands, commonly employed in inorganic or coordination chemistry, towards organic cross-coupling reactions. Despite their prominence in energy-storage applications, P₂N₂ ligands have been underexplored in catalytic C-C bond formation reactions. Chapter 1 provides a detailed introduction to late transition metal catalysis and the history of P₂N₂ ligands. Chapter 2 outlines the discovery of P^(Cy)₂N^(ArCF3)₂ as a powerful P₂N₂ ligand for the Ni-catalyzed reductive cross-coupling of aryl iodides with aldehydes. Chapter 3 details the extrapolation of the Ni/P^(Cy)₂N^(ArCF3)₂ catalyst system to the related, but less established, redox-neutral α-arylation of primary alcohols. Chapter 4 highlights the applicability of P₂N₂ ligands towards Ni- and Pd-catalyzed Mizoroki-Heck reactions. High-throughput experimentation (HTE) indicated a range of hits with P₂N₂ ligands compared to established ligands in Heck-type couplings. We discovered that absolute site selectivity of C-C bond formation could be controlled by simply altering the phosphorus substituent on the P₂N₂ ligand for the coupling of aryl triflates with styrenes. Notably, this degree of selectivity was not observed with conventional ligands. Chapter 5 focuses on the preparation of the P₂N₂ ligands. Finally, chapter 6 offers a perspective on future developments of P₂N₂ ligands and the prospective directions of their application in transition metal-catalyzed transformations.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24446号 / 理博第4945号 / 新制||理||1706(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 有賀 哲也, 教授 吉村 一良 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

<p>This thesis describes mechanistic studies, rational ligand design, and synthesis of asymmetric transition metal catalysts. The topics addressed concerned [Papers I-VII]:</p><p>[I] The asymmetric addition of diethyl zinc to <i>N</i>-(diphenylphosphinoyl)benzalimine catalyzed by bicyclic 2-azanorbornyl-3-methanols was studied. An efficient route to both diastereomers of new bicyclic 2-azanorbornyl-3-methanols with an additional chiral center was developed, in the best case 97% ee was obtained with these ligands. The experimental results were rationalized by a computational DFT-study.</p><p>[II] An aza-Diels-Alder reaction of cyclopentadiene with chiral heterocyclic imines derived from (<i>S</i>)-1-phenylethylamine and different heteroaromatic aldehydes was developed. The cycloaddition proved to be highly diastereoselective and offers a very rapid access to possible biologically active compounds and interesting precursors for chiral (<i>P,N</i>)-ligands. </p><p>[III] A convenient and high-yielding method for the preparation of (<i>R</i>)-tolterodine, utilizing a catalytic asymmetric Me-CBS reduction was developed. Highly enantio-enriched (<i>R</i>)-6-methyl-4-phenyl-3,4-dihydrochromen-2-one (94% ee) was recrystallized to yield practically enantiopure material (ee >99%) and converted to (<i>R</i>)-tolterodine in a four-step procedure. </p><p>[IV] The reaction mechanism of the iridium-phosphanooxazoline-catalyzed hydrogenation of unfunctionalized olefins has been studied by means of DFT-calculations (B3LYP) and kinetic experiments. The calculations suggest that the reaction involves an unexpected IrIII-IrV catalytic cycle facilitated by coordination of a second equivalent of dihydrogen. On the basis of the proposed catalytic cycle, calculations were performed on a full system with 88 atoms. These calculations were also used to explain the enantioselectivity displayed by the catalyst.</p><p>[V and VI] A new class of chiral (<i>P,N</i>)-ligands for the Ir-catalyzed asymmetric hydrogenation of aryl alkenes was developed. These new ligands proved to be highly efficient and tolerate a broad range of substrates. The enantiomeric excesses are, so far, the best reported and can be rationalized using the proposed selectivity model.</p><p>[VII] The complex formed between the quincorine-amine, containing both a primary and a quinuclidine amino function, and [Cp*RuCl]₄ catalyzes the hydrogenation of aromatic and aliphatic ketones in up to 90% ee approx. 24-times faster than previously reported Ru-diamine complexes. The reason for the lower but opposite stereoselectivity seen with the quincoridine-amine, as compared to the quincorine-amine, was rationalized by a kinetic and computational study of the mechanism. The theoretical calculations also revealed a significantly lower activation barrier for the alcohol mediated split of dihydrogen, as compared to the non-alchol mediated process. A finding of importance also for the diphosphine/diamine mediated enantioselective hydrogenation of ketones.</p>