Chapter 1 constitutes a review of current methods of aromatic substitution focusing on Directed ortho Metalation (DoM) and Directed remote Metalation (DreM). The field of mesoporous silica is reviewed in Chapter 2, focusing on the preparation, characterization, and application of mesoporous silicates. Chapter 3 presents an introduction of phosphorus based Directed Metalation Groups (DMGs). The development of the directed ortho metalation (DoM) reaction of the tetraethyl phosphorodiamidate DMG is described. In addition to being one of the most powerful DMGs, migration of the OPO(NEt2)2 group to the ortho and remote positions is demonstrated, constituting new reactions as well as affording new organophosphorus compounds. Attempts to improve the synthetic utility of the DMG led to the discovery and optimization of a two new nickel-catalyzed cross coupling reactions, which is described in Chapter 4. Both the OPO(NEt2)2 and OCONEt2 DMGs are demonstrated to undergo cross coupling reactions with aryl boronic acids. By means of DoM and cross coupling tactics, the concise synthesis of a chiral binaphthol bridged silasesquioxane is described. Chapter 5 explores new methods to prepare chiral periodic mesoporous organosilica (PMO) materials using this monomer. PMOs are prepared by the co-condensation of a relatively small amount of chiral binaphthyl dopant which acts to twist the bulk prochiral biphenylene framework. / Thesis (Master, Chemistry) -- Queen's University, 2009-09-25 11:38:25.029

The field of mesoporous materials has been expanding rapidly in recent years, and has come to include a wide variety of different types of materials from organic to inorganic, as well as hybrid materials that encompass both worlds. The following account explores one type of mesoporous materials, specifically those consisting of silica with an attached organic group that have come to be known as periodic mesoporous organosilicas (PMOs). Much of the work here involves incorporating new types of organic groups into a mesoporous framework for the purpose of adding a useful functionality, either chemical or physical, to the material. Firstly it is shown that a borazine moiety can be successfully incorporated into a mesoporous material with a very high loading. It was further shown that once incorporated into the material many of the borazine moieties are available for further chemical reactions with acids and transition metals. Next, a new class of materials termed hybrid periodic mesoporous organosilicas (HPMOs) was developed that was able to circumvent many of the problems associated with PMO self-assembly. Now, using very simple techniques, virtually any type of silsesquioxane can be incorporated into a PMO, and the organic group can be specifically at the surface of the pores, thereby maximizing its accessibility. And finally, a PMO is made that incorporates buckyballs, and it is shown that, given the right synthetic conditions, the buckyballs are homogeneously distributed throughout the material.

The field of mesoporous materials has been expanding rapidly in recent years, and has come to include a wide variety of different types of materials from organic to inorganic, as well as hybrid materials that encompass both worlds. The following account explores one type of mesoporous materials, specifically those consisting of silica with an attached organic group that have come to be known as periodic mesoporous organosilicas (PMOs). Much of the work here involves incorporating new types of organic groups into a mesoporous framework for the purpose of adding a useful functionality, either chemical or physical, to the material. Firstly it is shown that a borazine moiety can be successfully incorporated into a mesoporous material with a very high loading. It was further shown that once incorporated into the material many of the borazine moieties are available for further chemical reactions with acids and transition metals. Next, a new class of materials termed hybrid periodic mesoporous organosilicas (HPMOs) was developed that was able to circumvent many of the problems associated with PMO self-assembly. Now, using very simple techniques, virtually any type of silsesquioxane can be incorporated into a PMO, and the organic group can be specifically at the surface of the pores, thereby maximizing its accessibility. And finally, a PMO is made that incorporates buckyballs, and it is shown that, given the right synthetic conditions, the buckyballs are homogeneously distributed throughout the material.

Student Number : 0107507J - PhD thesis - School of Chemistry - Faculty of Science / Periodic mesoporous organosilica (PMO) materials (consisting of ethane groups in the framework) and bifunctional periodic mesoporous organosilica materials (consisting of ethane groups in the framework and either glycidoxypropyl groups or aminopropyl groups in the channels) were synthesized by the sol-gel method under basic conditions. Ethanesilica materials were synthesized by condensation of 1,2-bistrimethoxysilylethane (BTME) and by co-condensation of BTME with tetraethylorthosilicate (TEOS). Bifunctional periodic mesoporous organosilica materials were synthesized by the co-condensation of BTME with either 3- glycidoxypropyltriethoxysilane (GPTS) or 3-aminopropyltriethoxysilane (APTS). Cetyltrimethylammonium bromide was used as the structure-directing template. Cobalt ion incorporated ethanesilica and modified ethanesilica materials were synthesized in situ by adding cobalt nitrate to the reaction mixture. Cobalt was also supported on ethanesilica materials and APTS-modified materials by using the incipient wetness impregnation method. Raman spectroscopy and diffuse reflectance infrared spectroscopy (DRIFTS) results confirmed the formation of organosilica materials and showed that the surfactant was removed by solvent extraction. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) showed that the ethane portion of the materials (originating from the bridging ethane group in BTME) only decomposed at temperatures > 400 oC. These techniques also showed that the surfactant is removed by solvent extraction. Cobalt ion incorporation was confirmed by Raman spectroscopy and UV-vis diffuse reflectance spectroscopy. Powder powder X-ray diffraction (XRD) and nitrogen adsorption data indicated that the mesophase and textural properties of the materials are dependent on the reaction conditions (i.e. ageing duration, ageing temperature, amount of silica precursor(s), amount of water and amount of base (NH4OH)). The periodicity of the materials was indicated by the presence of low angle diffraction peaks in powder X-ray diffraction patterns. Cubic and hexagonal mesophases were identified using powder X-ray diffraction. When solvent extraction is prolonged, the BET surface area and the pore volume increase, while the average pore diameter decreases. Materials with more dominant XRD structural features and larger d values, higher surface areas, lower pore volumes and average pore diameters are obtained when low ageing temperatures are used. For samples prepared from a mixture of BTME and TEOS at a given temperature, the surface area was found to increase with increasing amount of TEOS added. This trend was observed for materials with and without cobalt. Type IV isotherms, typical of mesoporous materials, were obtained for ethanesilica and modified ethanesilica materials prepared without cobalt. For cobalt incorporated periodic mesoporous ethanesilica materials, the XRD lattice parameter (d100) increased whereas surface area and pore volume decreased with increasing cobalt loading. Nitrogen gas adsorption on samples with varying ratios of BTME:GPTS or BTME:APTS revealed that increasing the amount of GPTS or APTS affects pore size, surface area and pore volume as well as shapes of the isotherms and hysteresis loops. The hysteresis loops of the Type IV isotherms obtained for GPTS-modified ethane silica materials (without cobalt) change from Type H3 to Type H4. There is a tendency for pore sizes to change from mesopore to micropore when the amount of GPTS is increased. Isotherms of cobalt incorporated GPTS-modified ethane silica materials changed from Type IV to Type I. The surface area, pore volume and pore diameter decreased with increasing loading of GPTS or APTS as well as after cobalt incorporation.

It is well established that cancer is one of the leading causes of death globally. Its complete eradication requires early detection and intensive drug treatment. In many cases it might also require surgery. Unfortunately, current medicine is still more focused on cancer treatment rather than elimination of its reason. The mechanism of tumor emergence and development is quite complicated, although, we are constantly advancing in this field. Nanomedicine is envisioned as the silver bullet against cancer. Thus, nanoscale systems with therapeutic and diagnostic modalities can simultaneously perform several functions: accurate detection of tumor site, precise targeting, and controlled drug release inside abnormal cells and tissues while being nontoxic to healthy ones. Moreover, surface modification of such nanoparticles allows them to be invisible to the immune system and have longer blood circulating time. The performed research in this dissertation is completely based on hybrid organicinorganic bridged silsesquioxane (also known as organosilica) nanomaterials, therefore comprising "soft" organic/bioorganic part which can imitate certain biorelevant structures and facilitates successful escape from the immune system for more efficient accumulation in cancer cells, while "hard" inorganic part serves as a rigid and stable basis for the creation of cargo nanocarriers and imaging agents. This dissertation discusses the 5 critical points of safe biodegradable nanoplatforms, delivery of large biomolecules, and cytotoxicity regarding the shape of nanoparticles. As a result novel fluorescent biodegradable oxamide-based organosilica nanoparticles were developed, light-triggered surface charge reversal for large biomolecule delivery was applied with hollow bridged silsesquioxane nanomaterials, and biocompatibility of periodic mesoporous organosilicas with different morphologies was studied. Furthermore, the current achievements and future perspectives of mesoporous silica organosilica, and silsesquioxane nanoparticles were considered in regards to their biomedical applications and summarized in two reviews.

The structuring of porous silica materials at the nanometer scale and their surface functionalization are important issues of current materials research. Many innovations in chromatography, catalysis and electronic devices benefit from this knowledge. The work at hand is dedicated to the targeted design of functional organosilica materials. In this context a new precursor concept based on boron-silanes is presented. These precursors combine the properties of a structure directing group and a silica source by covalent borane linkage. Formation of the precursor is easily realized by a sequential two-step hydroboration, firstly on bis(triethoxysilyl)ethene, and secondly on an unsaturated structure directing moiety such as alkenes or polymers. The so prepared precursors self-organize when hydrolysis of their inorganic moiety takes place via an aggregation of their organic side chains into hydrophobic domains. In this way, the additional use of a surfactant as a template is not necessary. Chemical cleavage of these moieties (e.g. by ammonolysis or oxidative saponification) yields an organosilica where all functionalities are exclusively located at the pore wall and therefore accessible. The accessibility of the functionalities is a vital point for applications and is not necessarily granted for common silica functionalization approaches. Further advantages of the boron-silane concept are the possibility to introduce a variety of surface functionalities by heterolytic cleavage of the boron linker and the control of the pore morphology. For that purpose the covalent linkage of different alkyl groups and polymers was studied. Another aspect is the access to chiral boron silane precursors yielding functionalized mesoporous organosilica with chiral functionalities exclusively located at the pore walls after condensation and removal of the structure directing moiety. These materials possess great potential for applications documented by preliminary investigations on chiral resolution of a racemic mixture by HPLC and asymmetric catalysis. In the course of this work valuable insights into the targeted structuring and surface functionalization of organosilicas were gained. A promising outlook for further investigations is the extension of this concept by altering the structure directing moieties of the precursor. That way the morphology of the final organosilica might be controlled by for example mesogens. Furthermore, the use of the boron linker enables the introduction of multiple functionalities into organosilicas, making the obtained material unique in its performance. / Die Nanostrukturierung von funktionalisierten porösen Materialien auf Silikatbasis steht im Brennpunkt der aktuellen Forschung. Anwendungen wie Chromatographie, Katalyse oder die Herstellung elektronischer Bauteile profitieren von den Erkenntnissen, die auf diesem Gebiet gewonnen werden. Die vorliegende Arbeit soll einen Beitrag zur gezielten Herstellung dieser Funktions-materialien leisten. Hierfür wurde ein neues Precursor-Konzept auf der Basis von Borsilanen vorgestellt. Diese Precursoren werden über eine sequentielle zweistufige Hydroborierung an Bis(triethoxysilyl)ethene und ein Alken oder ein ungesättigtes Polymer erhalten. Über den zweiten Schritt wird hierbei die so genannte strukturgebende Gruppe eingeführt und damit das Template kovalent gebunden. Dadurch entfällt im Vergleich zum bekannten Nanocasting-Mechanismus zum einen die Verwendung des herkömmlichen Templates für die Bildung der Porenstruktur und zusätzlich führt die Mikrophasenseparation während der Kondensation zu einer Anordnung der strukturgebenden Gruppen des Precursors an der Silikatphasengrenze. Nach der chemischen Abspaltung dieser Gruppen, die gleichzeitig zur Einführung funktioneller Gruppen führt, werden somit hochporöse Organosilikate erhalten, in denen sich die funktionellen Gruppen ausschließlich an der Porenoberfläche befinden. Ein Vorteil der Verwendung der Hydroborieung wird in der Vielfalt der funktionellen Gruppen deutlich, die eingeführt werden können. Die Zugänglichkeit der funktionellen Gruppen ist entscheidend für potentielle Anwendungen und bei herkömmlichen Organosilikaten nicht zwangsläufig gegeben. Ein herausragender Aspekt dieses Konzepts besteht in der Möglichkeit, sehr einfach chirale Precursoren und damit Organosilikate mit hoch funktionalisierten, chiralen Oberflächen herzustellen. Es konnte gezeigt werden, dass sich diese Materialien sowohl für die chromatographische Trennung von Racematen mittels HPLC als auch für die asymmetrische Katalyse eignen. Durch die in dieser Arbeit erhaltenen Ergebnisse konnten wertvolle Erkenntnisse zur Ober-flächenfunktionalisierung und Strukturierung von mesoporösen Silikaten gewonnen werden. Die Möglichkeit, das vorgestellte Konzept auf andere strukturgebende Gruppen wie zum Beispiel Mesogene zu übertragen und damit die Porenmorphologie gezielt zu steuern, eröffnet viele weitere interessante Materialeigenschaften.

Organosilica nanoparticles have attracted a lot of research interest in a variety of areas such as drug delivery and catalysis because of their properties which include high surface area as well as tunable particle and pore size. In particular, nanoparticles with large pore sizes are of great interest because of their potential to host large guest molecules such as proteins and as catalysts. The focus of the work in the thesis was to develop phosphonate functionalized organosilica nanoparticles for biomedical and catalytic applications. Raspberry textured phosphonatesilica nanoparticles denoted, RNPPME(2.5) (where the number in the brackets represents the moles of organophosphonate per gram), with large pore size (11–17 nm), uniform particle size (70 – 90 nm) and high surface area were produced through the use of template directed base catalysed synthesis, using tetraethylorthosilicate (TEOS) and dimethylphosphonatoethyltrimethoxysilane (DMPTMS) as the silica sources. The role of the reaction conditions such as temperature, surfactant concentration, pH, organosilane concentration and type were investigated and a mechanism for the raspberry nanoparticle formation was proposed. The particles were characterized using electron microscopy (SEM and TEM), Dynamic light scattering (DLS), silicon and phosphorus solid state NMR, and solution phase proton NMR of base digested particles, FT–IR, nitrogen adsorption porosimetry and thermal analysis (TGA). The ability of the particles to host protein molecules of the model protein, bovine serum albumin (BSA) was investigated and the particle–protein composite was characterized using circular dichroism (CD). Raspberry textured nanoparticles were found to host large quantities (26 wt%) of protein. Studies on other (small pore (3 nm) phosphonate functionalized nanoparticles NP_PME(0.2) and NP_PME(1.0)) and (3 nm pore) unfunctionalized mesoporous silica nanoparticles (MSN) revealed that phosphonate loading and the pore size influenced the protein uptake In addition to high protein uptake, the RNP_PME(2.5) particles also absorbed protein molecules rapidly (~ 20 minutes to maximum load). CD studies determined that the particle bound protein structure was not affected at physiological pH (7.40). The vast majority of the previously reported studies involving protein immobilization involved the use of bulk silica materials, which cannot be dispersed and hence those materials were unsuitable for in vivo protein delivery applications. The BSA@RNP_PME(2.5) particles showed good protein load and dispersion properties and hence are excellent protein delivery agents. Dispersions of nanoparticle composite BSA#@RNP*_PME(2.5) (where BSA# represents fluorescein isothiocyanate labelled BSA and RNP*_PME(2.5) represents rhodamine B isothiocyanate labelled RNP_PME(2.5)) was used to successfully deliver membrane impermeable protein BSA into HeLa cells. Intracellular protein delivery has attracted great interest due to its potential therapeutic applications and research tool value (e.g. for studying various cellular pathways). The toxicity of the guest free particles RNP*_PME(2.5) and the protein loaded particles BSA#@RNP*_PME(2.5) was studied using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The particles and the protein-particle composite were found to be non-toxic. The mechanism of the particle uptake by the cells was also studied. The unloaded (protein free) particles were found to be taken up by caveolar endocytosis pathway and the protein loaded particles were taken up by folic acid mediated pathway. The results indicated that the particles can successfully deliver membrane impermeable protein across the cell membrane. This result suggested that the particles can potentially be used for intracellular protein delivery applications. Raspberry textured nanoparticles RNP_PME(2.5) were also used to host the enzyme lipase. It was demonstrated that immobilization increased the maximum velocity and Michaelis constant of the enzyme and also that the particles offered protection against the denaturing agent, urea. Finally, in a chemical catalysis application, the RNP_PME(2.5) particles were used to synthesize the platform chemical HMF, through Brönsted acid catalysed dehydration of fructose. High yields of HMF (87 %) were achieved when 10 wt% fructose was used. The particles demonstrated good recyclability and also the ability to convert up to 50 wt% fructose into HMF (80 % yield). The particles therefore acted as protective agents for enzymes and can therefore be used as enzyme immobilizing agents. Additionally, they also acted as excellent Brönsted acid catalysts.

Synthesis and Applications of Novel Periodic Mesoporous Organosilicas by Chun Xiang (Cynthia) LIN Abstract This dissertation is concerned with the synthesis, functionalization, and applications of periodic mesoporous organosilica (PMO) with a unique hollow spherical morphology, with the main objectives as follows: • Developing new techniques to synthesize mesoporous silica and organosilica materials • Designing different approaches to modify PMO and silica materials to meet various applications • Developing innovative applications of novel PMO materials in biological fields. The key features that have been achieved in this work are highlighted as follows: • A series of studies has been carried out and resulted in a new strategy for the synthesis of PMO material with a novel hollow morphology. This new approach employs both hydrocarbon and fluorocarbon surfactants as mixed structure-directing-agents in alkaline medium. Moreover, a vesicle and liquid crystal "dual-templating" mechanism has been proposed. • Detailed observation on the formation mechanism of hollow PMO has revealed that the demixing temperature (Td) plays an important role on the formation of highly ordered mesostructure of PMO hollow spheres. Beside that, dissimilarity on the hydrophobic nature of silica - organic silica precursors has brought differences in the resulted materials. • Different approaches in the modification of PMO hollow spheres with several functional groups and commercial magnetic ferrite nanoparticles have shown some unique features of this material. It was found that different reactive sites of each functional group bring different disruptive effect on the mesopore geometry of hollow PMO. Furthermore, hollow PMO material show different behavior on encapsulating the commercial magnetic ferrite nanoparticles compared to superparamagnetic particles, where different techniques should be applied, which involved several factors that need to be carefully adjusted. • Applications of hollow PMO in biological field were performed on drug and DNA delivery. A comparison between periodic mesoporous silica (PMS) and PMO as drug carriers showed the differences in wall composition between pure silica and hybrid organic silica, also the morphology (hollow and solid spheres) play important roles in controlling adsorption capacity and drug release rate. In addition, different pH value of release medium also brings significant effect on release profile. As a carrier of DNA, magnetic modified hollow PMO material showed biocompatibility towards sugarcane callus. Moreover, this study has introduced a new innovative technique on delivering DNA into plant cell through the application of modified hollow PMO with barium magnetic core and enzyme digestion approach.

No description available.

Surfactant-templated, sol-gel based methodologies for the synthesis of tailored, nanostructured, hybrid inorganic–organic materials are incredibly powerful and versatile. Although growth in this field has been explosive in recent decades, a lot of room remains to contribute to the design and synthesis of new materials, as well as the development of advanced applications. In the work described herein, we firstly explored the synthesis of thick, mesoporous organosilica films and their application as functional coatings for solution-based, fibre-optic heavy metal sensors. Notably, sub-ppm level detection was observed for the detection of Pb(II) in mixed aqueous–organic media in short timeframes, and progress has been made toward synthesizing organotitania films that would allow for heavy metal sensing in purely aqueous solution. Furthermore, the utility of these types of surfactant-templated, organically-functionalized, mesostructured coatings has been preliminarily extended to other types of optical devices for heavy metal sensing. We have also explored the use of designer amphiphilic, alkyl oligosiloxane precursors for the tightly-controlled formation of thin, self-templated, hybrid nanostructured films. Moreover, films bearing uniaxial 2D hexagonal alignment over macroscopic length scales were obtained using polymer-treated substrates to control the interfacial interactions between the film precursors and the substrate surface. In addition, a relatively mild UV / ozone treatment was employed to remove the alkyl moieties from the films to yield porous materials without catastrophic loss of the as-synthesized, mesostructural order. Lastly, novel chiral, binaphthylene-based, periodic mesoporous organosilica (PMO) materials have been prepared. With the aim of demonstrating chiral recognition with such materials, porous, co-continuous capillary monoliths have been synthesized and applied as chiral stationary phases in nano-HPLC and CEC. Notably, enantioselective interactions between our materials and a chiral acetal-based analyte have been observed. Quantification of these enantioselective interactions in chiral PMOs by isothermal titration microcalorimetry is also being pursued. It has thus been demonstrated that a wide array of different functional materials may be accessed through template-based synthetic strategies. By varying parameters such the starting monomers, the sol composition, and the interfacial interactions between reacting species and a given substrate (to name a few), the resulting materials may be tailored to meet the demands of new and emerging technologies. / Thesis (Ph.D, Chemistry) -- Queen's University, 2011-05-24 19:50:17.478