A series of tetravalent zirconium and hafnium complexes were supported by diarylamido-phosphino [PNP]- (bis(o-diisopropylphosphinophenyl)amide) ligand. The reaction of MCl4(THF)2 (M = Zr, Hf) with [PNP]Li in toluene at room temperature generates [PNP]MCl3 as solid in 60 % yield. Polyalkyl complexes which are lack of £]-hydrogen have been achieved in synthesis of [PNP]MR3 (R = Me, CH2SiMe3) or [PNP]M(CH2SiMe3)2(E) (E = Cl, Me) since we could control the desired product from steric effect. An X-ray diffraction study of [PNP]ZrCl3 showed it to be a chloride-bridged binuclear species {[PNP]MCl2(£g-Cl)}2 in which both metal atoms are 7-coordinate whereas that of [PNP]MCl3(THF) revealed a mononuclear, 7-coordinate core structure. The phosphine fluxional exchange were found in those complexes, monitoring variable temperature 31P NMR, their fluxionality were calculated by line shape analysis. By heating [PNP]M(CH2SiMe3)2(Cl) in solution, we can afford new alkylidene complexes [PNP]M(Cl)(=CHSiMe3) via intramolecular £\-abstraction. Through Eyring plot analysis, the activation energy of [PNP]Zr(CH2SiMe3)2(Cl) £\-abstraction is ∆H‡ = 16.49(19) kcal/mol and ∆S‡ = −25.64(19) cal/mol•K; [PNP]Hf(CH2SiMe3)2(Cl) £\-abstraction is ∆H‡ = 18.70(36) kcal/mol and ∆S‡ = −23.12(36) cal/mol•K. The mixture [PNP]Hf(=CHSiMe3)(Cl) could not isolate with any purification, but [PNP]Hf(=CHSiMe3)(CH2SiMe3) obtained through directly alkylation. Here we also identified multiple alkylidene derivatives of [PNP]M(=CHSiMe3)(X) (X = Cl, CH2SiMe3). The X-ray structured and solution NMR data of those alkylidene complexes can be ascribed to evidence of £\-agostic interaction with metal center. A novel zwitterionic complex [PNP]Zr(£g2-CHSiMe3)2(AlMe2) was characterized by X-ray and been received a bisalkylidene complex which was synthesized through addition Lewies acid (AlMe3) into [PNP]Zr(=CHSiMe3)(CH2SiMe3). Group 4 alkylidene was acting as catalyst to metathesize ethylene or norbornene. The complexes [PNP]M(=CHSiMe3)(Cl) have highly streotic selectivity catalyst for ring-opening metathesis polymerization (ROMP) of norbornene. It is important to emphasize the great significance of the catalyst discoveries and improvements for both academic research and industry.

The work reported herein describes efforts to create ring-opening metathesis block copolymers and homopolymers. The block copolymers were studied to gain insight into the local nanoscale environment of a block copolymer thin film. Additionally, perylene containing homopolymers were characterized in light of their possible use as an n-type material. In the first section of the thesis, the synthesis of diblock copolymers consisting of two blocks with very different dynamics is described. The covalent attachment of a molecular rotor which is sensitive to its local environment allowed the study of the dynamics of the polymers in thin films. The emissive intensity as a function of temperature allowed us to see discontinuity in the rates of change, indicating a change in the local environment corresponding to the transition of the polymer from a glassy to rubbery state. The corresponding temperature, to this event, is known as the glass transition temperature, Tg. Additionally, a polymer featuring a covalently bound n-type molecule, perylene diimide, was synthesized. The photophysical properties, including aggregation in dilute solution, are described. The material is expected to demonstrate the ability to efficiently transport negative charge, acting as n-type material in organic electronics. / text

Dicyclopentadiene (DCPD), a tricyclic olefin, is available from the C5 fraction of petroleum feedstocks. Owing to its high reactivity (due to the presence of a strained alkene), low cost, and lack of other commercial uses, DCPD has been extensively pursued as a monomer for use in ring-opening metathesis polymerization processes. The olefin metathesis reaction, for which Yves Chauvin, Robert H. Grubbs, and Richard R. Schrock received the 2005 Nobel prize, is among the most attractive approaches to polymerize olefins, allowing production of high-molecular weight polymers including linear macromolecules, block copolymers, and crosslinked materials. Polydicyclopentadiene (PDCPD), which can be produced using a variety of early- and late-transition metal catalysts, is a thermoset polymer with a highly crosslinked structure. PDCPD has excellent impact strength, high storage modulus, good chemical resistance, wide service temperature range, and low density. As a result, it has found broad commercial utility in industrial manufacturing. Additionally, the reaction injecting molding (RIM) process used for DCPD polymerization makes it possible to precisely control the shape and dimensions of PDCPD products. Owing to its lack of chemical functionality, however, polydicyclopentadiene has many limitations. Previously, our research group developed a modified dicyclopentadiene monomer by adding an electron withdrawing group – a methyl ester functional group – on the pendent cyclopentene ring of the monomer. Polymerization of this functionalized monomer led to a novel thermoset material – methyl ester functionalized polydicyclopentadiene (fPDCPD) – that exhibits tunable surface hydrophobicity. In experiments described in this dissertation, my collaborators and I confirmed the thermal crosslinking mechanism of fPDCPD using a combination of solution-state and solid-state NMR, FTIR, and Raman spectroscopy. We also explored the surface chemistry of our novel material, by harnessing the embedded functional group in order to exert finer control over hydrophobicity, and to control interactions with biological organisms through the conjugation of biologically relevant functional groups. To further extend the utility of our functionalized dicyclopentadiene monomer, we synthesized a series of statistical polymers: fPDCPD-stat-PDCPD. Once again, we used a wide range of characterization methods, and showed that we can both tune the surface hydrophobicity of the copolymers and manipulate the mechanical properties by adjusting the molar fractions of functionalized and non-functionalized monomers. Chemical structures of these copolymers were interrogated by NMR, FTIR, and Raman spectroscopy. Frontal ring-opening metathesis polymerization was applied in an effort to study the kinetics of (co)polymerization. Finally, to lay the groundwork for future fPDCPD manufacturing, we successfully optimized the production of fDCPD monomers to half-kilo scale and fPDCPD polymers at 20-gram scale, while developing a reaction-injection molding process that permitted the production of dimensionally controlled fPDCPD objects. This in turn allowed us to conduct a rigorous assessment of the mechanical properties of our fDCPD through dynamic mechanical analysis (DMA), which established for the first time that our functionalized material has a comparable storage modulus to that of the parent (unmodified) PDCPD. The development of fPDCPD is approaching a new stage where it is ready to be commercialized and mass produced. We hope that our novel fPDCPD material will soon play a crucial role in replacing traditional metallic components in vehicle design and engineering material manufacturing. / Graduate / 2021-12-14

This dissertation describes the synthesis of molecular machines designed to operate on surfaces (nanocars) or in the solution phase (nanosubmarines), and the study of their diffusion using fluorescence techniques. The design of these molecular machines is aimed to facilitate monitoring of their movement and incorporation of a source of energy for propulsion. To complement previous scanning tunneling microscopy studies of the translation of nanocars on surfaces, chapter 1 describes the synthesis of a family of fluorescently tagged nanocars. The nanocars were functionalized with a tetramethylrhodamine isothiocyanate (TRITC) fluorescent dye. Single-molecule fluorescence microscopy (SMFM) studies of one of these nanocars revealed that 25% of the nanocars moved on glass. The SMFM results also suggested that the dye hindered the mobility of the nanocars. Seeking to improve the mobility, chapter 2 presents the synthesis of a new set of fluorescent nanocars, featuring a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dye embedded in their axles. The mobility of these inherently fluorescent nanocars on glass was nearly double than that of their TRITC-tagged predecessors. Their diffusion was also studied on reactive-ion-etched glass, and amino-functionalized glass. The results showed that the mobility is affected by the substrate. To equip the nanocars with an energy input for propulsion, two nanocars functionalized with an olefin metathesis catalyst were synthesized, as described in chapter 3. The catalytic activity of these nanocars toward ring-opening metathesis polymerization (ROMP) in solution was similar to that of their parent catalysts. As an alternative approach to investigate if chemical propulsion through a ROMP process can be achieved at the molecular level, chapter 4 presents the synthesis of a fluorescent ROMP catalyst, termed a nanosubmarine, and the study of its diffusion using fluorescence correlation spectroscopy (FCS). FCS results showed an increase of 20 ± 7% in the diffusion constant of this nanosubmarine in presence of its fuel, cis,cis-1,5-cyclooctadiene. Overall, the work accomplished in this dissertation constitutes a step forward toward development of easily tracked and highly mobile nanocars, and paves the way for the synthesis of truly nanosized chemically propelled molecular machines that operate in the solution phase.

Compounds containing multiple metal-carbon bonds are now widely used as catalysts for organic and materials synthesis. Among such transformations, olefin metathesis (OM) occupies a position of pre-eminent significance. Alkyne metathesis holds great promise, but remains in a much lower state of development. The OM-directed work in this thesis sought to advance the state of the art in living, Ru-catalyzed ringopening metathesis polymerizations (ROMP). Currently, the first- and third-generation Grubbs initiators, which exhibit the ease of handling characteristic of the late metal ruthenium, dominate ROMP applications. These initiators are characterized by extremes of reactivity, however. We describe the first ruthenium initiator capable of living ROMP at RT, irrespective of monomer bulk. Polydispersity indices as low as 1.03 are routinely attainable, and excellent control is maintained in synthesis of diblock copolymers from sterically demanding and sterically unencumbered monomers. Work on alkyne metathesis sought to expand existing understanding of the features that influence stability and reactivity in ruthenium carbynes. A classification system was developed in which Class A carbynes were defined as those that readily undergo conversion into an M=C entity (e.g. vinylidene, allenylidene, or alkylidene); Class B carbynes those that have a stable carbyne functionality. Four Ru carbyne complexes, all initially regarded as prospective Class B carbynes, were selected for study. Investigation of their reactivity resulted in categorization of several as Class A species, and development of design criteria that may open the door to assembly of stable, well-defined carbyne complexes of ruthenium.

The mechanism of a conjugate addition of an alcohol to an alkynic acid ester using a phosphine catalyst was investigated using pressurized sample infusion electrospray ionization mass spectrometry (PSI-ESI-MS) and proton and phosphorus nuclear magnetic resonance (NMR) experiments. Since ESI-MS only detects charged species, and only the phosphonium intermediates and by-products were visible by ESI-MS, 1H NMR was used to track the disappearance of the starting alkyne and the appearance of the conjugate addition product over time. 31P NMR was used to quantify the ESI-MS results. By-product formation was shown to out-compete product formation upon fast addition of alkyne, but with dropwise addition of alkyne, product was shown to dominate. A detailed numerical model was developed using PowerSim software to test mechanistic hypotheses. The experimental results were shown to be consistent with the mechanism proposed by Inanaga, and the cycle was elaborated to account for by-product formation. Piers’catalyst, a ruthenium complex with a phosphonium-functionalized carbene ligand, is a fast-initiating living catalyst for a number of olefin metathesis reactions, including ring-opening metathesis polymerization (ROMP) and cross metathesis (CM). Catalyst speciation was monitored in real-time for the ROMP of norbornene and the CM of 1-hexene using PSI-ESI-MS. The expected mass distribution of charged polymer-catalyst species were not observed, but merely catalyst and decomposition species were visible by ESI-MS. NMR and gel permeation chromatography (GPC) were used to determine quantitatively the presence of polymer and the polydispersity index, respectively. The results suggest that while Piers’ catalyst is indeed fast-initiating, the propagation rate greatly outstrips the initiation rate. In a foray into the area of chemical education, a well-known pH-induced colour change exhibited by the anthocyanins in red cabbage was developed into a simple – and ingestible – classroom demonstration. / Graduate / 0485

Compounds containing multiple metal-carbon bonds are now widely used as catalysts for organic and materials synthesis. Among such transformations, olefin metathesis (OM) occupies a position of pre-eminent significance. Alkyne metathesis holds great promise, but remains in a much lower state of development. The OM-directed work in this thesis sought to advance the state of the art in living, Ru-catalyzed ringopening metathesis polymerizations (ROMP). Currently, the first- and third-generation Grubbs initiators, which exhibit the ease of handling characteristic of the late metal ruthenium, dominate ROMP applications. These initiators are characterized by extremes of reactivity, however. We describe the first ruthenium initiator capable of living ROMP at RT, irrespective of monomer bulk. Polydispersity indices as low as 1.03 are routinely attainable, and excellent control is maintained in synthesis of diblock copolymers from sterically demanding and sterically unencumbered monomers. Work on alkyne metathesis sought to expand existing understanding of the features that influence stability and reactivity in ruthenium carbynes. A classification system was developed in which Class A carbynes were defined as those that readily undergo conversion into an M=C entity (e.g. vinylidene, allenylidene, or alkylidene); Class B carbynes those that have a stable carbyne functionality. Four Ru carbyne complexes, all initially regarded as prospective Class B carbynes, were selected for study. Investigation of their reactivity resulted in categorization of several as Class A species, and development of design criteria that may open the door to assembly of stable, well-defined carbyne complexes of ruthenium.

Compounds containing multiple metal-carbon bonds are now widely used as catalysts for organic and materials synthesis. Among such transformations, olefin metathesis (OM) occupies a position of pre-eminent significance. Alkyne metathesis holds great promise, but remains in a much lower state of development. The OM-directed work in this thesis sought to advance the state of the art in living, Ru-catalyzed ringopening metathesis polymerizations (ROMP). Currently, the first- and third-generation Grubbs initiators, which exhibit the ease of handling characteristic of the late metal ruthenium, dominate ROMP applications. These initiators are characterized by extremes of reactivity, however. We describe the first ruthenium initiator capable of living ROMP at RT, irrespective of monomer bulk. Polydispersity indices as low as 1.03 are routinely attainable, and excellent control is maintained in synthesis of diblock copolymers from sterically demanding and sterically unencumbered monomers. Work on alkyne metathesis sought to expand existing understanding of the features that influence stability and reactivity in ruthenium carbynes. A classification system was developed in which Class A carbynes were defined as those that readily undergo conversion into an M=C entity (e.g. vinylidene, allenylidene, or alkylidene); Class B carbynes those that have a stable carbyne functionality. Four Ru carbyne complexes, all initially regarded as prospective Class B carbynes, were selected for study. Investigation of their reactivity resulted in categorization of several as Class A species, and development of design criteria that may open the door to assembly of stable, well-defined carbyne complexes of ruthenium.

<p>The controlled synthesis of functional low molecular weight polyethylene and polyethylene mimics is important in tuning polymer properties and is of great industrial interests. Living polymerization is a method that allows for precise control in polymer structure. Although high molecular weight polymers with controlled structures can be efficiently produced via living polymerization, the production of low molecular weight polymers faces the challenges of the use of large amounts of expensive catalyst and the broadening of polydispersity.</p> <p>The synthesis of well-defined functional low molecular weight polyethylene and polyethylene mimics is studied. Promising polymerization systems, including living ring opening metathesis polymerization (ROMP), living coordination polymerization, coordinative chain transfer polymerization (CCTP), and living C1 polymerization, are identified and are analyzed based on product properties, efficiency, cost, and safety.</p> <p>Within the identified systems, living ROMP is selected for study due to the industrial relevance of ROMP polymers, the availability of raw materials, and the ease of reaction setup. The efficiency of ROMP is challenged by polydispersity broadening resulting from slow initiation and poor reactor volume efficiency due to its implementation as a solution polymerization process. The challenges are addressed by the use of excess phosphine and the realization of ROMP as a bulk polymerization process.</p> <p>Experimental results demonstrate that bulk ROMP with and without phosphines yield product with similar or enhanced molecular weight distribution control as solution ROMP. Kinetic studies confirm living polymerization behaviour of bulk ROMP. A mathematical model is developed for the first time using method of moments to describe the kinetics and development of molecular weight distribution of ROMP. The model is a useful tool in preliminary research and commercialization of ROMP. The success of bulk ROMP and the development of a representative model yield ROMP as a promising method for the production of low molecular weight polymers with controlled architecture.</p> / Master of Applied Science (MASc)

Ring-opening metathesis polymerization (ROMP) is a robust synthetic technique for synthesizing complex polymer architectures (topologies). To achieve complex architectures, specifically bottlebrush polymers, using ROMP, attaining the highest degree of living character is essential. As the molecular weight of the side chain or backbone increases, the "livingness" of the polymerization suffers due to premature catalyst degradation. Attaining large, well-defined, bottlebrush polymers requires precision so it was our goal to determine how seemingly simple reaction variables could affect the rates of propagation and achievable conversion, as well as why these variables have these effects. We tested several reaction parameters to understand how they affect the rate of polymerization, the rate of catalyst degradation, and the conversion that can be reached. We performed a systematic study using six organic solvents to determine the propagation rate of three macromonomers (MMs), one polystyrene and two poly(n-butyl acrylate) MMs, in ROMP with varying side chain chemistries and end groups, as well as rate of catalyst degradation in each of the solvents. We determined that solvent affected that rate of propagation primarily by interacting with the catalyst, while there was some evidence of polymer sidechain chemistry affecting the rate. We found that ethyl acetate (EtOAc) and CH2Cl2 had the highest rates of propagation compared to the other solvents, while DMF and THF were the slowest. UV-Vis testing on the catalyst in each solvent revealed that DMF and THF had fast rates of catalyst decomposition, while toluene was much slower to decompose. From these experiments we learned that toluene, despite its slower propagation rate, has the most living character, due to its slower rate of decomposition. We also learned that purification greatly affects the propagation rate, with THF requiring purification to have any conversion to bottlebrush polymer, while purification of EtOAc slows the rate of propagation almost 2-fold. From the decrease in rate after purification, and the conclusion that it was due to an acetic acid impurity in the impure EtOAc, we decided to systematically test small molecule additives and found that acids can increase the propagation rate and the conversion of the polynorbornene backbone achievable in ROMP reactions. Notably, in reactions performed in DMF with added CF3COOH we were able to polymerize a norbornene-functionalized unprotected peptide, which was insoluble in most organic solvents, to a higher conversion than in DMF without the added acid. We learned from our research that changing reaction variables can lead to substantial changes in the rate of propagation as well as the achievable conversion in bottlebrush polymer synthesis. By understanding this we can further test other reaction variables and do systematic studies on atmosphere and temperature. We hope this research and future fundamental research can guide scientists toward synthesizing large, well-defined, complex polymer architectures using ROMP. / Doctor of Philosophy / Nature has shown that complex molecular architectures lead to unique material properties. This has inspired scientists to synthetically mimic nature to create these polymer architectures in an effort to obtain novel material properties. Ring-opening metathesis polymerization (ROMP) has become a powerful synthetic method for synthesizing complex polymer architectures. Specifically, ROMP has been used to synthesize bottlebrush polymers, so named due to the polymer backbone with long, densely grafted, polymer side chains attached. These materials exhibit very interesting properties compared to their linear polymer counterparts. Using ROMP to synthesize bottlebrush polymers is not uncommon; however, difficulties can arise if trying to use sidechains that are very long or bulky. We have worked to understand how manipulating some of the reaction parameters can allow us, and other researchers, to synthesize bottlebrush polymers that contain long and/or bulky polymer side chains. We tested the purity and type of solvent that the reaction was performed in on one polystyrene macromonomer and two poly(n-butyl acrylate) macromonomers, as well as adding small molecules, including acids, bases, and salts, to determine if these variables could improve the synthesis of bottlebrush polymers. What we found was that all of the tested variables, solvent, purity, additives, and combinations of all of these variables, did have an effect on the synthesis of these materials. This fundamental information will assist our lab, and many others, in efficiently synthesizing complex architectures, thus achieving unique material properties.