Yes / Sonochemistry, i.e., the application of mechanical energy in the form of sound waves, has recently been recognised for its similarity to mechanochemistry and is now included under the umbrella term of mechanochemistry. Typically, due to the hypothesised cavitation mechanism, a liquid medium is considered as a necessity for a process to take place as a result of ultrasonic irradiation. In view of this, condensation reactions between solid reagents in the complete absence of solvent were carried out successfully by ultrasonic irradiation with the importance of particle size being highlighted. This work increases the potential of sonochemistry in the drive towards a sustainable future. / EPSRC (EP/L019655/1)

No / Mechanochemical synthesis, i.e., reactions conducted by grinding solid reactants together with no or minimal solvent, has been demonstrated as an excellent technique for the formation of both organic and inorganic compounds. Mechanochemistry is viewed as an alternative approach to chemical synthesis and is not always considered when developing manufacturing processes of fine chemicals. Here, recent advances are highlighted regarding mechanochemical synthesis, by utilizing a well‐developed continuous technique – extrusion, and the advantages it offers to further support its use in the manufacturing of these chemicals. To put this work into context, it is shown how extrusion plays a vital role for manufacturing in the food, polymer, and pharmaceutical industries, and how the research carried out by these respective industrialists provides great insight and understanding of the technique, with the results being applicable in the chemical industry. The synthesis of metal–organic frameworks (MOFs) is highlighted herein as an excellent example showcasing the advantages that extrusion provides to the manufacture of these materials, one advantage being the exceptional space time yields (STYs) reported for these processes, at three orders of magnitude greater than conventional (solvothermal) synthesis. / EPSRC. Grant Number: EP/L019655/1

No / Mechanochemistry enabled the selective synthesis of the recherche´ orange polymorph of Wilkinson’s catalyst [RhCl(PPh3)3]. The mechanochemically prepared Rh-complex catalysed the solvent-free dehydrogenation of Me2NHBH3 in a ball mill. The in situ-generated hydrogen (H2) could be utilised for Rh-catalysed hydrogenation reactions by ball milling. / We thank the RWTH Aachen University for support from the Distinguished Professorship Program funded by the Excellence Initiative of the German federal and state governments, and the EPSRC for funding (EP/L019655/1).

This thesis describes applications in co-crystal reactivity, structure determination, and mechanochemical preparation. We also investigate the solution-phase reactivities of products derived from a template-directed synthesis. Specifically, we described the acid treatment of an achiral molecular ladder of C2h symmetry composed of five edge-sharing cyclobutane rings, or a [5]-ladderane, with acid results in cis- to trans- isomerization and/or oxidation of end pyridyl groups. Solution NMR spectroscopy and quantum chemical calculations support the isomerization to generate two diastereomers; namely, an achiral and a unique chiral ladderane. The NMR data, however, could not lead to unambiguous configurational assignments of the two isomers. Single-crystal X-ray diffraction was employed to determine each configuration. One isomer readily crystallized as a pure form and X-ray diffraction revealed the molecule as being achiral based on Ci symmetry. The second isomer resisted crystallization under a variety of conditions. Consequently, a strategy based on a co-crystallization was developed to generate single crystals of the second isomer. Co-crystallization of the isomer with a carboxylic acid readily afforded single crystals that confirmed a chiral ladderane based on C2 symmetry. We also demonstrate how the stereochemistry can be retained upon treatment with acid. It will be shown how a monocyclobutane can be used as a model system when investigating the reactivity of the [5]-ladderane. While investigating the reactivity of a diene diacid we determined that a bicyclobutyl that bears six carboxylic acid groups results from a trimerization of the solid in pure form in the solid state. Powder X-ray diffraction and a co-crystallization are used to solve the structure of the diene and elucidate the stereochemistry of the bicyclobutyl, respectively. Having established the reactivity of the diene diacid we used hydrogen-bond-acceptor (HBA) templates to assemble the diacid in the solid state in a photoactive solid for an intermolecular [2 + 2] photocycloaddition as well as a photostable solid. To enhance strategies to generate stereocontrolled products derived from reactive co-crystals mechanochemical methods were applied to eliminate or reduce the solvent used to prepare the co-crystal solids. In particular, we show how supermolecules with olefins organized by hydrogen-bond donor and acceptor templates that react in the solid state rapidly form co-crystals via solvent-free and liquid-assisted grinding.

Chemical reactions usually involve the conversion of reactants to products by overcoming an energetic barrier. Most commonly, this process can be assisted by adding energy through heat (thermochemistry), light (photochemistry) or electric current (electrochemistry). The fourth option is to overcome the reaction barrier through application of mechanical work, termed mechanochemistry. This method has received much attention from the scientific community in the last decade. Both theoretical and experimental studies have been performed, demonstrating the ability of mechanochemistry to activate reactions, with a strong focus on ringopening reactions. The vast majority of studies have focused on unimolecular reactions involving bond-rupture, which is very intuitively activated by the application of tensile stress. However, bimolecular reactions, which often involve bond formation as well as rupture, have received much less attention. In this thesis, we seek to change this by undertaking an in-depth study of mechanochemical activation of addition reactions to carbon-carbon double bonds, which involve the formation of two single bonds while the double bond becomes a single bond. We observe that large barrier changes can be induced by applying external force to reactions of this type, and the magnitude of these changes can be controlled by the choice of alkene substrate. By studying the changes induced in the geometry of the substrate, we are able to begin explaining the origins of the barrier reduction effect. In addition, by studying the contributions to the barrier change from mechanical work and the contributions from geometry changes, we discover that steric hindrance to a reaction can play a very significant role in the mechanochemical activation of the reaction. / Thesis (Master, Chemistry) -- Queen's University, 2010-11-29 10:43:04.945

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23025号 / 理博第4702号 / 新制||理||1674(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)准教授 齊藤 尚平, 教授 依光 英樹, 教授 時任 宣博 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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Traditional methods of synthesizing inorganic materials, such as hydrothermal, sol-gel, calcination and grinding steps, can typically require use of high temperatures, expensive precursors or use of solvents. Because of the energy-intensive nature or environmental impact these techniques, there is a push, especially from an industrial perspective, to move towards greener approaches. Mechanochemistry is a solvent-free alternative technique that can be used to synthesize a variety of materials under ambient conditions. Due to this, there is an increase in attention towards the use of this approach in both solid-state inorganic and organic chemistry. This dissertation reports the mechanochemical synthesis of a few inorganic materials without the need of using high temperatures or solvents. Additionally, examples are presented in which mechanochemistry is used in conjunction with a secondary technique. This mechanical activation of the precursors lead to a decrease in calcination temperature and reactions times, as well as alteration of properties or unique reaction products. The synthesis of kaolinite, vanadia nanostructures, and spinels were carried out in this fashion. Mechanical activation of the precursors allowed for reduced hydrothermal treatment times in case of both kaolinite and vanadia nanostructures and the spinels are calcined at lower temperature for shorter periods of time. In addition, we report alternative template agents than previously reported for the formation of vanadia nanotubes, and report the formation of nanorods. Choosing the appropriate amine template can alter the structure and size of the material. Isomorphously substituted mixed oxides, kaolinite and spinels (MgAl2O4 and ZnAl2O4) were synthesized through a mechanically assisted process. Kaolinites are treated hydrothermally iv for 1 week at 250 ºC to produce an X-ray pure crystalline material. The spinels undergo calcination as low as 500 ºC to produce a nanocrystalline material. Rare-earth metals and transition metals were used as the substitutional atom. The substituted kaolinites exhibit strong order along the c axis, but less ordering along the a and b axes. Trivalent chromium and trivalent rare-earth metals, such as La, Ce, Pr, Nd, Eu, Gd, Ho, and Er, are used to replace aluminum in the structure. Likewise, divalent and trivalent transition, such as Mn, Ni, Cu and Cr, are used as the substitutional atoms in MgAl2O4 and ZnAl2O4. Cathodoluminescence studies on the substituted Spinel structure show that Mn 2+ ions can occupy both the tetrahedral or octahedral holes to give a green and red emission, respectively. On the other hand, Cr3+ ions only occupy the octahedral holes to yield a red emission, similar to that in ruby. These isomorphously substituted materials may have potential applications in catalysis or glaze materials in ceramics. Oxidized graphite, an alternative to graphite oxide and graphene, can be synthesized rapidly by mechanochemical means. Grinding urea hydrogen peroxide adduct with graphite without the need of a solvent produces a product with an oxygen content of 5-15 wt%. The byproducts of this reaction are urea and water. This material is oxidized along the edges of the sheets, allowing it to be hydrophilic while retaining the conductivity. The material can suspend in water and processing allows for films of resistivities between 50 Ω cm-2 and 10 kΩ cm-2 . It was determined that the edges are fully oxidized to yield –COOH groups. This process offers a scalable, environmentally benign route to large quantities of oxidized graphite. An alternative method for the synthesis of nanostructured vanadia is reported. This process involves mechanical grinding of vanadium pentoxide, V2O5, with an amine template, v such as diphenylamine, theophylline, rhodamine 6G and rhodamine, prior to hydrothermal treatment. This allows for the synthesis of VOx nanotubes and nanorods dependent on which template is used. Diphenylamine, theophylline, and rhodamine B produce nanorods. Use of rhodamine 6G produces asymmetric VOx nanorods. In addition to the mixed metals oxides mentioned above, sodium and calcium tantalates are synthesized mechanically. This route does not require the need of elevated temperatures or expensive and hazardous materials. X-ray diffraction analysis of NaTaO3, Ca2Ta2O7, Ca4Ta2O9 and CaTa2O6 shows that these are the only phases detected after 4 h, 10 h, 27 h and 10 h of milling, respectively. During the synthesis of Ca2Ta2O7, an intermediate phase, Ca4Ta2O9, forms within 1 h, which reacts after 5 h to form the desired product. Reference Intensity Ratio analysis shows that the material synthesized mechanically is nanocrystalline Ca2Ta2O7. Nanocrystalline ZrSi2 can also be obtained through mechanochemical synthesis. This method allows for size control and results in crystallites ranging from 9 to 30 nm. Dilution with CaCl2 enables the size control process. A linear relationship exists between the concentration of CaCl2 and the crystallite size. Contrary to a typical self-propagating metathesis reaction, this process does not allow for self-propagation and requires continuous input of mechanical energy to continue. However, this method allows for non-passivated nanoparticles of ZrSi2, which can be incorporated into composites as a reinforcement material for several applications. Hard and ultra-compressible borides, such as ReB2 and OsB2, can be synthesized mechanically. The traditional synthesis of ReB2 requires excess boron due to treatment at high temperatures. This can lead to amorphous boron aggregating at the grain boundaries, which in vi turn, this would degrade the properties of the material. The mechanochemical approach requires mechanical treatment of Re and B powders in stoichiometric quantities for 80 h. Mechanical synthesis of OsB2 powders requires a 1:3 ratio of Os and B powders. After 12 h of milling time, h-OsB2 begins to form, and is the major phase present after 18 h. The lattice parameters corresponding to the hexagonal OsB2 were determined to be a = b = 2.9047 Å, c = 7.4500 Å, α = β = 90º, γ = 120º. Treatment of the OsB2 powder at 1050 ºC under vacuum for 6 days did not induce a phase change, suggesting the hexagonal phase is very stable. Mechanocatalysis of the depolymerization of cellulose and hydrogenation of olefins over BN are reported as well. Heterogeneous catalysis is difficult to apply to solids, such as cellulose. However, mechanical grinding of kaolin and cellulose allows for the catalysis to occur in the solid state. This process allows for a variety of different biomasses to be used as feedstock without inhibition. Kaolinite was found to be the best acid catalyst due to high surface acidity and its layered structure, allowing for up to 84% conversion of the cellulose to water-soluble compounds. This process allows for reduction of waste, insensitivity of feedstock, multiple product pathways and scalability. Hydrogenation reactions are carried out using transition-metals catalysts. These metals have desirable catalytic properties not seen in main group elements, but there is growing concern over their use. A metal-free heterogeneous hydrogenation catalyst based on frustrated Lewis pairs would significantly reduce the health, environmental, and economic concerns associated with these metal-based catalysts. We report the first metal-free heterogeneous hydrogenation catalyst. Hydrogenation of trans-cinnamic acid is carried out over defect-laden h-BN. The vii reactor we use is designed to maximize the defects produced in BN sheets. The introduction of defects in BN creates frustrated Lewis pairs. DFT calculations show that the carbon double bond is weakened over boron substitution for nitrogen sites, vacancies of both boron and nitrogen, and Stone-Wales defects. A new method for crystalline germanium deposition occurring at lower temperatures (210-260 ºC) is reported. This method involves mechanical treatment of the precursors to reduce the particle size. A ground mixture of Ge and CuI are heated under vacuum to synthesize GeI2. In situ disproportionation of this compound at 210 ºC allows for the deposition of polycrystalline Ge films onto a both glass and polymer substrates. The rate of deposition is found to be 25 ng min-1 . The byproducts of this process are GeI2, GeI4 and Cu3Ge, which are valuable precursors for the synthesis of germanium nanostructures and organogermanium compounds. Mechanochemistry is also utilized for the synthesis of trisubstituted pnictides. Mechanochemical treatment of bromobenzene with either Na3Sb or Na3Bi allows for the formation of triphenylstibine or triphenylbismuthine, respectively. The synthesis of the alkali metals pnictide precursors is reported as well. The synthesis of triphenylstibine produces SbPh3 as the major product from the reaction. The synthesis of triphenylbismuthine produces more Wurtz-type coupling products, which are due to the BiPh3 acting as a catalyst. Tributyl and triphenyl analogues are reported as well. The trialkylated analogues for both Sb and Bi produce more Wurtz type coupling products. This would allow for a more cost effective and scalable, alternative methods than what is currently in use today

No / Although mechanochemical synthesis is becoming more widely applied and even commercialised, greater basic understanding is needed if the field is to progress on less of a trial‐and‐error basis. We report that a mechanochemical reaction in a ball mill exhibits unusual sigmoidal feedback kinetics that differ dramatically from the simple first‐order kinetics for the same reaction in solution. An induction period is followed by a rapid increase in reaction rate before the rate decreases again as the reaction goes to completion. The origin of these unusual kinetics is found to be a feedback cycle involving both chemical and mechanical factors. During the reaction the physical form of the reaction mixture changes from a powder to a cohesive rubber‐like state, and this results in the observed reaction rate increase. The study reveals that non‐obvious and dynamic rheological changes in the reaction mixture must be appreciated to understand how mechanochemical reactions progress. / Engineering and Physical Sciences Research Council. Grant Number: EP/L019655/1