Chemistry

Permanent URI for this collectionhttps://hdl.handle.net/10315/26546

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Access status: Open Access ,
Lewis Acid-Catalyzed Carbofluorination Reactions Via Fluoride Recycling
(2026-07-24) McKnight, Elena; Le, Christine
Fluorinated compounds are widely employed as pharmaceuticals, agrochemicals, and polymer materials. As a result, there is a strong interest in developing more sustainable ways to make fluorinated molecules, as well as exploring their fundamental reactivity and stability. This dissertation focuses on the development of carbonyl fluorides derivatives—namely carbamoyl fluorides, acyl fluorides, and fluoroformates— as dual-function reagents that serve both as carbonyl fragments and as fluoride sources. These fluorinated building blocks were applied in the intramolecular carbofluorination of π bonds and in fluorine retentive rearrangement reactions under Lewis acid–catalyzed “fluoride shuttling” conditions. Chapter 1 provides background on fluorination chemistry, introducing common fluorinating reagents and then transitions into strategies that combine fluorine incorporation with carbon–carbon bond formation, namely the fluorinative difunctionalization of π-bonds (carbofluorination), which enables efficient construction of complex organofluorine compounds. Chapter 2 identifies a range of borane and borate-based catalysis that can activate acyl fluorides to acts as dual-function reagents. Trityl tetrafluoroborate was identified as the optimal catalyst for the synthesis of 1-(fluoromethylene)indan-2-ones from alkyne-tethered acyl fluorides, affording products with exceptional stereoselectivity under mild conditions. This method also enabled access to fluorinated scaffolds that had only been reported previously under harsher, transition metal–catalyzed conditions. Chapter 3 expands the use of Lewis acid catalyzed carbofluorination reactions to the stereoselective synthesis of 3-fluoromethylene oxindoles and γ-lactams from alkyne-tethered carbamoyl fluorides. Inexpensive, commercially available BF₃·OEt₂ identified as the optimal catalyst. Combined experimental and computational studies suggest that the reaction is initiated through oxophilic activation of the carbonyl group. This chapter also demonstrates that fluorinated secondary oxindoles can be accessed directly through a fluorocarbonylative annulation of o-alkynyl anilines. Finally, Chapter 4 details a mild and practical synthesis of fluoroformates from alcohols, employing a commercially available oxidant and a difluorocarbene source as an in situ difluorophosgene surrogate. These reaction conditions can also be applied to the synthesis of fluoro(thio)formates, carbamoyl fluorides, and acyl fluorides, providing a unified strategy for the synthesis of diverse (heteroatom)carbonyl fluoride derivatives. Preliminary studies exploring the use of fluoroformates as dual-function reagents are also presented, focusing on the fluorinative rearrangement of cyclopropylmethyl fluoroformates to fluorinated cyclobutanes.
Access status: Open Access ,
Measurement of Gas-Phase Perfluoroalkyl Carboxylic Acids (PFCAs) Using Nylon Passive Air Samplers
(2026-07-24) Nistorescu, Irina Andreea; VandenBoer, Trevor
Perfluoroalkyl carboxylic acids (PFCAs) are persistent anthropogenic compounds widely detected in environmental media. Few studies have measured ultrashort-chain PFCAs in air, despite their higher abundance compared to longer chains. Nylon passive air samplers (PAS) provide a cost-effective, low-labour technique to measure ultrashort- and short-chain gas-phase PFCAs. Method quality control and quality assurance parameters were optimized, including the calibration of perfluorobutanoic acid (PFBA), thereby improving confidence in reported mixing ratios. In a novel intercomparison with sorbent-impregnated polyurethane-foam (SIP) PAS at a wastewater treatment plant, good agreement between measurements was observed, with ultrashort-chain PFCAs dominating emissions. Nylon PAS were deployed in multiple Toronto locations, revealing Pearson International Airport to be a potential point source of perfluoropropanoic acid (PFPrA). Large-scale regional sampling along the St. Lawrence River, Quebec showed positive correlations between PFBA concentration and population size. These measurements have provided valuable insights into the sources and spatial distribution of PFCAs.
Access status: Open Access ,
Quantitative Analysis of Reduced Nitrogen Processing in Marine Aerosols by Fog and the Indoor Air of New Canadian Homes
(2026-07-24) Salehpoor, Leyla; VandenBoer, Trevor
Reduced nitrogen species, including ammonia (NH3) and alkylamines (NR3), are ubiquitous in the atmosphere and play important roles in new particle formation, aerosol growth, multiphase chemical processing, and air quality. However, their quantitative analysis across aerosol and gas phases remains analytically challenging. This thesis develops and applies ion chromatographic (IC) methods to quantify reduced nitrogen to investigate its processing in marine aerosols during fog events and in the indoor air of newly built Canadian homes. An IC method was developed to separate and quantify NH3 and the ten most abundant atmospheric NR3 with high selectivity and separation efficiency using 4 µm packed columns and resin-based suppressors, alongside stabilized NR3 calibration standards. Suppressor performance was improved by stepped-current operation and an external water supply, resulting in enhanced linearity, accuracy, precision, and lower detection limits than conventional suppression modes. The optimized IC method was applied to marine aerosol samples collected during the Fog and Turbulence Interactions in the Marine Atmosphere (Fatima) 2022 campaign over the Northwest Atlantic Ocean. Aerosol chemistry, microphysics, physical processing, and meteorological conditions were analyzed to investigate fog–aerosol interactions. Size-resolved chemical measurements showed a reduction in coarse mode sea salt ions during fog, attributed to their growth into fog droplets, while fine mode processed-S (e.g., nss-SO42- and MSA-) and reduced-N species increased due to enhanced aqueous-phase processing. Consistent reductions in coarse sea salt mass loading across more than a dozen fog events confirm their role as effective fog condensation nuclei and demonstrate the impact of fog processing on aerosol mass loading. The developed IC method was further applied to quantify indoor gas-phase reduced nitrogen in 48 newly built Canadian homes as part of the New Home Air Quality Study (NHAQS) from 2019 to 2024. Indoor NH3 mixing ratios decreased from pre- to post-occupancy and remained relatively stable over 12 months following, consistent with reduced emissions from new materials and increased partitioning surface area upon occupancy. Overall, this thesis develops a new analytical method to quantify reduced nitrogen in marine fog aerosols and indoor air, improving understanding of aerosol–fog chemistry, fog forecasting models, and indoor air quality.
Access status: Open Access ,
Characterizing the Evolution of Fresh and Aged Water-Soluble Brown Carbon Chromophores in Wildfire Smoke
(2026-07-24) Azzarello, Lisa; Young, Cora
Wildfires are an important source of carbonaceous aerosol that impact air quality and the Earth’s radiative budget. Organic aerosol that is partially water soluble and absorbs in the ultraviolet to visible spectral range is referred to as “brown carbon” (BrC). There remains uncertainty regarding BrC’s optical properties and atmospheric evolution. This dissertation investigates BrC across laboratory, airborne, and ground-based measurements. Chapter two examines airborne measurements of western U.S. wildfire smoke aged 0-5 hrs during FIREX-AQ. Brown carbon absorption was measured online using a particle-into-liquid sampler (PILS) and aqueous samples were collected for offline SEC-UV analysis. Absorption was dominated by low molecular weight (MW) (< 500 Da) species and exhibited variable trends with plume age. Comparisons between the online PILS and offline SEC-UV absorption measurements revealed differences between absolute absorption and wavelength dependence. These results emphasized the importance of intercomparison between measurement techniques when investigating BrC absorption. Chapter three focuses on controlled combustion experiments from the FIREX FireLab study. Western U.S. fuels were pyrolyzed and BrC absorption, total aerosol absorption, and aerosol composition was investigated online and offline at ambient and thermal denuded conditions. Offline filters were characterized using SEC-UV, a volatility basis set framework, and the octanol water partitioning coefficient log(Kow) was estimated. At ambient conditions, absorption was dominated by low volatility compounds of low MW. After thermal denuding, a fraction of BrC persisted, where the absorption contribution by high MW species increased. The log(Kow) values indicated moderately hydrophobic (log(Kow) >3) species which provided insight into their atmospheric persistence. Chapter four investigates aged wildfire emissions during a smoke intrusion in Toronto. Size-resolved aerosols were collected for offline chromatographic analyses. Absorption was dominated by high MW species with moderate hydrophobicity, and elevated levels of alkylamines (NR3H+/NH4+ of 0.3-3.6) were observed. Alkylamines were not detected in fresh FIREX FireLab emissions, suggesting the ratios observed in Toronto reflect atmospheric aging and mixed urban biomass burning influences rather than direct wildfire emissions. This work demonstrates that BrC chemical and absorption properties evolve after emission, and highlights the importance of integrating chromatographic methods, laboratory experiments, and field measurements to constrain the evolution of BrC.
Access status: Open Access ,
From Oxidation to Deposition: Novel Tools for Measuring Atmospheric Per- and Polyfluoroalkyl Substances
(2026-07-24) Colussi, Alessia Alessandra; Young, Cora; VandenBoer, Trevor
Per- and polyfluoroalkyl substances (PFAS) are a group of persistent, bioaccumulative, and toxic compounds characterized by strong carbon-fluorine bonds and their resulting environmental stability. Volatile and semi-volatile neutral PFAS and their precursors can undergo gas-phase oxidation to form perfluoroalkyl acids (PFAAs), including perfluorocarboxylic acids (PFCAs), which are widely detected in environmental matrices. Although long-chain PFAS have been phased out over the past two decades, increased production and degradation of precursor compounds have led to growing concern over the persistence, mobility, and expanding global distribution of ultrashort- and short-chain PFAAs. Chapter 2 investigates the hydroxyl (OH)-initiated oxidation of 4:2 fluorotelomer alcohol, a PFCA precursor, under low-NOx conditions at atmospherically relevant relative humidities (22%, 44%, and 60%). Using an oxidation flow reactor coupled to proton transfer reaction time-of-flight mass spectrometry, we detected the 4:2 fluorotelomer aldehyde and carboxylic acid, confirming proposed mechanisms and providing initial constraints on humidity-dependent OH kinetics. This technique provides an alternative to traditional dry smog chamber experiments with improved representation of ambient atmospheric conditions. Chapter 3 presents an open-source, modular, and affordable automatic wet deposition sampler capable of off-grid operation. The system was deployed across the Newfoundland and Labrador Boreal Ecosystem Latitudinal Transect and operated continuously using solar-assisted battery power. Performance was evaluated under summer and winter conditions, and proof-of-concept validation included routine rainwater chemistry measurements. Chapter 4 describes the development and validation of an artifact-minimized denuder sampling method to measure gas-phase perfluoropropionic acid (PFPrA), achieving 99.83 ± 0.03% capture efficiency. Additionally, year-long deposition and denuder sampling in regions home to endangered Canadian whale populations, at Tadoussac, Québec and Saturna Island, British Columbia, showed trifluoroacetic acid (TFA) and PFPrA as dominant PFCAs and demonstrated site-specific differences in wet versus dry deposition. A concurrent intercomparison with passive air samplers showed consistent seasonal trends for TFA, supporting the consistency of the denuder sampling. These measurements establish baseline levels in the two whale habitats and show that atmospheric deposition is an important source of ultrashort-chain PFCAs there. Together, these results present novel tools and foundational data to better understand atmospheric PFAS oxidation, transport, and deposition, while developing monitoring capabilities in remote and sensitive environments.
Access status: Open Access ,
Practical Synthesis Of 4-Pyridyl Phosphonates
(2026-07-24) Marques Neto, Abel; Orellana, Arturo
Pyridyl phosphonates are valuable motifs in medicinal chemistry, catalysis, and materials science. Common routes for their synthesis often rely on prefunctionalized pyridines, transition-metal-catalyzed cross-coupling reactions, special free radical conditions or photochemical reactions. Herein, we report a mild, one-pot, and regioselective method to access 4-pyridyl phosphonates from simple pyridines via chloroformate-mediated pyridine activation, nucleophilic phosphite addition, and oxidative rearomatization using molecular oxygen. The method shows broad tolerance toward 3-substituted pyridines, while challenges associated with 2-substitution were addressed through a complementary post-functionalization strategy enabling access to 2-substituted pyridyl phosphonate scaffolds.
Access status: Open Access ,
Understanding the Spatial and Temporal Distribution of Per- and Polyfluorinated Compounds in Atmospheric Deposition
(2026-07-24) Persaud, Daniel; Young, Cora
Per-and polyfluoroalkyl substances (PFAS) are persistent anthropogenic compounds that are distributed globally. However, uncertainties remain regarding dominant sources, long-range transport pathways, and atmospheric deposition mechanisms. This thesis advances the understanding of the spatial and temporal distribution of PFAS by analyzing atmospheric deposition across Arctic, boreal, urban, and tropical environments. To elucidate temporal trends, a 16 meter ice core from the Mt. Oxford icefield, Ellesmere Island provided a continuous 50-year deposition record (1967–2016). Analysis revealed an increase in PFCA deposition after the 1990s. Homologue correlations, molar concentration ratios, and model comparisons suggest that PFCAs are primarily formed through oxidation of volatile precursors. In contrast, PFSAs showed no discernible trend, with episodic deposition observed before 1990, which may be linked to historical Arctic military activities. Spatial patterns in PFAS deposition were examined across the Newfoundland and Labrador Boreal Ecosystem Latitudinal Transect using integrated atmospheric deposition samples collected between 2013–2016. We also quantitively separate wet and dry deposition fluxes for perfluorobutanoic acid (PFBA), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA). We found that the dry deposition contribution was equal to or greater than the wet deposition flux. This research also specifically focused on trifluoroacetic acid (TFA), a highly persistent and mobile ultrashort chain PFAS. We quantified TFA in total, wet and dry deposition samples in Toronto, Canada between 2018–2024. Seasonal variations showed fluxes peaking in summer months and a decrease in 2020, coinciding with COVID-19 lockdown measures. This work provided the first field-based quantification of TFA in dry deposition, demonstrating that it is a significant and previously underrepresented removal pathway. Finally, a novel hemispheric comparison found substantial TFA deposition at both a tropical site in Georgetown, Guyana (1014–6641 µg m-2 a-1) and a temperate residential site in Lambton County, Canada (1969–5863 µg m-2 a-1), confirming the global reach of TFA. Collectively, this thesis demonstrates that PFAS distribution by the atmosphere is governed by complex interactions between direct emissions, atmospheric transformation of precursors, and seasonally variable deposition processes.
Access status: Open Access ,
Elucidating the Conformational Dynamics of YTH Domain Containing Family of Proteins
(2026-03-10) Tahir, Iqra; Wilson, Derek J.
Hydrogen-Deuterium Exchange Mass Spectrometry (HDX-MS) has emerged as a powerful and time-efficient technique for capturing ‘breathing motions’ and intricate conformational dynamics of proteins. Here, we conduct HDX-MS to elucidate the conformational dynamics of the YTHDF proteins. The function of the three YTHDF proteins has been debated in the scientific community. According to the prevailing model, the three YTHDF proteins (YTHDF1, YTHDF2, and YTHDF3) have different functions, while the unified model proposes shared functions. We aimed to detect whether the observed conformational dynamics between the three YTHDFs are redundant or different for the fate of the m6A-modified RNA ligand. We observed that all three YTHDFs showed significant stabilization in the bound state relative to the unbound state. However, the conformational dynamics of YTHDF2 were most different, particularly in the α2–β3 region. HDX-MS was useful in detecting unique conformational dynamics in areas influenced by allostery, such as the α2–β3 region.
Access status: Open Access ,
Conformational Analysis of Astrochemically Relevant Molecules Using Rotational Spectroscopy
(2026-03-10) Chaudhary, Aadya; van Wijngaarden, Jennifer
Rotational spectroscopy was employed to investigate the conformational preferences and internal dynamics of two sulfur-containing organic molecules, allyl phenyl sulfide (APS) and 2-methylthioethylamine (2-mtea). Supersonic jet-cooled Fourier transform microwave (FTMW) Spectroscopy, supported by quantum chemical calculations, enabled the identification and characterization of low-energy conformers for both systems. The analysis of hyperfine structure due to the 14N nuclear quadrupole coupling and internal methyl rotation in 2-mtea provided detailed insights into the electronic and structural effects of sulfur and nitrogen substitution. Natural bond orbital (NBO) analysis revealed key orbital interactions between the lone pairs of sulfur and nitrogen, and the various organic side chains that govern conformational stability. These findings contribute to a deeper understanding of the conformational behavior of S and N containing organic molecules, which are of growing interest in astrochemical contexts.
Access status: Open Access ,
Dissecting Protein Interactions, Ligand Binding and Conformational Regulation using Hydrogen Deuterium Exchange Mass Spectrometry
(2026-03-10) Chow, Vimanda; Wilson, Derek J.
Understanding protein interactions and structural dynamics is fundamental to elucidating biological function, disease mechanisms, and therapeutic design. Proteins rarely act in isolation; their activities are mediated through transient or stable interactions with ligands, other proteins, nucleic acids, and membranes. Capturing these dynamic events requires biophysical tools capable of resolving structural changes at high temporal and spatial resolution. Among these, hydrogen-deuterium exchange mass spectrometry (HDX-MS) has emerged as a powerful technique for probing conformational flexibility and interaction interfaces under near-physiological conditions. In this work, we employed HDX-MS, including millisecond-to-second timescales, as a structural biology tool to investigate conformational dynamics and interaction landscapes across a diverse range of protein systems. HDX-MS enabled detailed characterization of cytochrome c (cyt c) binding to phospholipid membranes, revealing that cardiolipin (CL) and the model lipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1’-rac-glycerol)(POPG) both induce similar protection in specific interaction sites, particularly the adjacent “L” and “A” regions, while leaving others unperturbed. Expanding to nuclear receptors, HDX-MS provided mechanistic insights into the ligand-induced conformational plasticity of Constitutive Androstane Receptor (CAR) and Pregnane X Receptor (PXR). In CAR, transcriptional activation correlated with stabilization of helix 11 (H11) and can be independent of helix 12 (H12), and distinct structural responses were observed between full agonist and partial agonist. In the CAR: Retinoid X Receptor alpha (RXRα) heterodimer, we uncovered ligand-driven allosteric communication across the dimer interface, with dual ligands producing cooperative stabilization of the CAR ligand-binding domain. In PXR, cooperative binding of furanodienone (FDN) with estrogenic steroids (E2 and EE2) led to enhanced stabilization of helices H3 and H12, promoting full agonist-like activity. Finally, in the lipid hydrolase (ABHD2), HDX-MS enabled mapping of binding interfaces for inhibitors 191R and 192. Dynamic comparison with the catalytically inactive S207A mutant revealed mutation-induced stabilization and altered ligand responsiveness in the absence of crystallographic data. Together, these findings highlight HDX-MS as an effective and versatile technique for elucidating protein-ligand and protein-lipid interactions and highlighting its growing utility in guiding therapeutic development across diverse biological systems.
Access status: Open Access ,
Design, Synthesis, and Characterization of Novel Phosphorus-Containing Conjugated Materials Based on Vat Orange 3
(2025-11-11) Dadgaryeganeh, Reza; Baumgartner, Thomas
As the global production and diversification of electronic devices—ranging from energyconversion to energy-storage applications—continues to surge, enhancing their efficiency has become a critical objective. While the well-built metal-based technology of these devices warrants recognition, the associated sustainability and toxicity issues must not be overlooked. This is where π-conjugated organic materials play a pivotal role. Research in the new millennium has provided numerous types of conjugated materials possessing properties that offer clear paths towards integrated electronic devices (e.g., Organic Light-Emitting Devices (OLEDs), Organic Solar Cells (OSCs), Organic Field-Effect Transistors (OFETs), organic batteries) with performances approaching those of their metal-based counterparts. Accordingly, a multitude of developed compounds such as Polycyclic Aromatic Hydrocarbons (PAHs) or strategies that embed main group elements into carbon-based synthons, have all been aimed at this common goal. However, the development of PAHs and incorporation of heaver main group elements such as phosphorus have rarely intersected until recently. This marriage is facilitated by the emergence of vat dyes as cost-effective precursors for organic semiconductors as their scaffolds provide a convenient route to PAH cores, such as anthanthrene and chrysene. Therefore, this thesis is focused on methods of merging phosphacycles with Vat Orange 3, along with investigating the photophysics of these functional materials, their capacity and ease of undergoing redox processes, and the role of phosphorus in modulating the systems’ electronics and impact on the overall functional properties. Through bridging heavier main group elements and large conjugated scaffolds, the emerging platform also attempts to overcome long-standing limitations in the literature, such as inefficient low-energy luminescence, restoration of the original keto groups in the vat dye-based frameworks, and doublet emission from phosphorus-containing conjugated materials.
Access status: Open Access ,
Synthesis and Characterization of Model Compounds For Self-Assembled Dithienophosphole-Based Phosphamides
(2025-11-11) Odagwe, Mary Ibukunola; Baumgartner, Thomas
On the path to synthesizing classes of dithienophosphole soft materials, this thesis documents the synthesis and characterization of model compounds for self-assembled dithienophosphole-based phosphinamides. Expanding upon the blue-emitting series within this class of compounds and targeting applications in white OLEDs, green and orange emitters, along with their corresponding model compounds, are reported. Taking advantage of the ease of functionalizing the α-position of the dithienophosphole core, the emitter compounds were synthesized via Suzuki cross-coupling reactions. The model compounds, incorporating hydrogen-bonding moieties, were prepared through substitution at the phosphorus center. Comprehensive characterization was performed, including optical and spectroscopic analyses, and full synthetic details are provided.
Access status: Open Access ,
A Modified Commercial Dynamic Chamber System for Measuring Soil Reactive Nitrogen Fluxes
(2025-11-11) Shah, Moxy Hemantkumar; VandenBoer, Trevor
Reactive nitrogen compounds (NO, NO2, HONO, and NH3; Nr) play an important role in atmospheric processes and pose environmental and health risks. Though studied individually, their interactions at the surface–atmosphere interface remain unexplored. To address this issue, a comprehensive Nr dynamic chamber setup was developed by modifying a commercially available system for GHGs. System modifications to minimize surface loss for Nr were implemented. Proof-of-concept measurements under controlled lab conditions demonstrated that NO, NO2, HONO, NH3, and N2O emissions can be quantified simultaneously. The p-values for the NO, NO2 and HONO within a specific soil volumetric water content range (20-24%) revealed heterogeneity, suggesting a need to reconsider the soil sampling and handling techniques used in laboratory studies. Emission trends from urea and synthetic magnesium/zinc ammonium carbonate fertilizers provide preliminary insights into Nr release from fertilized soils.
Access status: Open Access ,
Synthesis and Lewis Base-Catalyzed Functionalization of Carbamoyl Fluorides
(2025-11-11) Cadwallader, Dusty James; Le, Christine
Amides are extremely prevalent in the pharmaceutical, agrochemical and materials industries. Typically, amides are prepared by the combination of amines and carboxylic acids in the presence of an amide-coupling reagent. This dissertation describes the synthesis and reactivity of carbamoyl fluorides, a unique electrophilic class of molecules that form amides when treated with carbon-based nucleophiles. A synthesis of carbamoyl fluorides directly from secondary amines is described. This method relies on the reaction of difluorocarbene with an oxidant to generate difluorophosgene (COF2) in-situ. Several carbamoyl fluorides were prepared with this method, and the mechanism was supported by kinetic analysis and nuclear magnetic resonance (NMR) spectroscopy experiments. To prepare alkynamides, carbamoyl fluorides were paired with alkynyl silanes and the common laboratory reagent tetrabutylammonium fluoride (TBAF) was found to be the optimal catalyst. This reaction proceeded efficiently due to the thermodynamic driving force of forming extremely strong Si-F bonds in the by-products. A selection of alkynamides were synthesized using this method, including those bearing functional groups that may be problematic in other modern alkynamide syntheses. Using silyl ketene imine nucleophiles, α-cyanoamides were prepared from carbamoyl fluorides using either fluoride, phenanthrolines or P(V) compounds as catalysts. As the amide produced in this method contains a chiral quaternary carbon centre, this project was focused on identifying a chiral Lewis base for asymmetric catalysis. It is suspected that the fluoride released in this reaction acts as the active catalyst, outcompeting the chiral compounds and limiting asymmetric induction.
Access status: Open Access ,
Group 4 and 12 Complexes Bearing Guanidine-Phenolate or Amidine-Phenolate Ligands: Coordination Chemistry and Polymerization Studies
(2025-11-11) Flores Romero, Victor; Lavoie, Gino
This dissertation explored the synthesis of Group 4 and Zn catalysts bearing guanidine–phenolate or amidine–phenolate ligands and their ability to catalyze chemical transformations. Group 4 diisopropoxide and Zn complexes were evaluated for the homopolymerization of lactide, while titanium dichloride complexes were assessed for their ability to polymerize ethylene. Group 4 diisopropoxide catalysts were active towards the ring-opening polymerization (ROP) of lactide, in the absence of any solvent, at 130°C. All Zr complexes were more active than the corresponding titanium homologues. The rate constant of the bis(guanidine–phenolate) group 4 systems (1.17––3.21 × 10-4 s–1) were higher than those displayed with Ti(OiPr)4 (5.34 × 10-5 s–1), and Zr(OiPr)4·iPrOH (2.79 × 10-5 s–1 ). Polylactic acid produced by guanidine-based catalysts exhibited similar molecular weights and dispersity (Ð) values to those of the industrial standard catalyst Sn(Oct)2, as well as to the precursors Ti(OiPr)4 and Zr(OiPr)4. The guanidine–phenol ligand proved to be active for the ROP of lactide with a larger rate constant than the most active Zr-based catalysts. The bis(guanidine–phenolate) titanium dichloride complexes were successfully synthesized and evaluated for the homopolymerization of ethylene. The low activity (up to 1.1 kgPE mol–1h–1) of the titanium dichloride complexes was ascribed to the electron-donating ability of the guanidine fragment and the stereoarrangement imparted by the guanidine–phenolate ligand about the Ti center. Zn catalysts bearing guanidine– and amidine–phenolate ligands were synthesized and evaluated for the ROP of lactide under solvent-free conditions at 130°C. The catalyst with the best performance was only 3 times slower than the industrial standard Sn(Oct)2 when a 100 to 1 monomer to catalyst ratio was used. Most catalysts displayed heterotactic bias in the polylactic acid generated with molecular weights up to 4900 Da. Dispersity values (Ð) ranged from 1.2 to 2.3 and were considered acceptable. Proligands were tested for the ROP of lactide, proving that their participation in the polymerization process cannot be ruled out. This new class of ligands and the corresponding complexes offer great potential and have a great deal of room for improvement.
Access status: Open Access ,
Properties of Crystalline and Amorphous Transition Metal Oxides with Enhanced Fe Content as OER Electrocatalysts
(2025-11-11) Rezaee, Bibisomaia; Morin, Sylvie
This work investigates the design of electrocatalysts for the oxygen evolution reaction (OER) using binary iron-cobaltites and ternary cobaltites containing Fe, Ni, and/or Cu, all synthesized by thermal decomposition in both the amorphous and spinel phases. The catalysts were characterized by numerous characterization methods to study their structure, composition, and morphology, while their surface area and electrochemical properties were also examined and corrected for the ohmic drop and film surface area. The catalytic activity and OER kinetics were also evaluated. Structural analysis confirmed the successful formation of amorphous and spinel oxides, where for the latter the crystallite sizes were in agreement across techniques. Electron microscopy and composition analysis demonstrated textural differences and stoichiometric consistency, while X-ray photoelectron Spectroscopy revealed distinct surface species and oxidation states. Overall, Fe incorporation enhanced the catalytic activity, whereas Ni-doping reduced the catalyst performance.
Access status: Open Access ,
Replacing Sp2 Hybridized Carbon Centers with Phosphorus
(2025-11-11) Torres, Lucas Christian; Caputo, Christopher
The striking parallels between the chemistry of molecular carbon and phosphorus compounds has fascinated chemists for decades and has even led to phosphorus being coined “the Carbon Copy.” A guiding tenet in organic chemistry is that carbon can be bonded to a maximum of four other atoms to satisfy the octet rule. By comparison, phosphorus, a heavier p-block element, can exist in hypervalent states and can form bonds with up to six other atoms. Apparent patterns in the bonding and reactivity of carbon and phosphorus compounds typically manifest when these elements are in lower coordination environments (bonded to few other atoms). Molecules featuring low-coordinate earth abundant p-block elements (C, P, Si, Al, etc) have generated considerable research interest as of late, with pivotal discoveries showing these systems can facilitate processes more traditionally distinctive of transition metal complexes. Such behavior includes the activation of thermodynamically strong chemical bonds, which in some cases is reversible, and the ability to directly perform catalytic transformations on organic molecules, overall pushing the needle towards more sustainable and cost-conscious chemistry. Low-coordinate phosphorus cations are one general group of compounds that show great promise in these domains. This thesis delineates the synthesis of cations that distinctly feature a sp2 hybridized phosphorus atom and are principally inspired from classic carbon motifs. Firstly, we explore a synthetic route to a phosphorus analog of a [3]cumulene (R2C=C=C=CR2). We found our target phospha-cumulene, also known as an allenylidene phosphonium cation, to be uniquely accessible when harnessing electron rich substituents known as N-heterocyclic imines (NHIs). The properties and reactivity of the allenylidene phosphonium cation are investigated, with one interesting reactivity pathway being a thermally reversible [2+2] cycloaddition which occurs between a P=C and C=C bond. This process is remarkable given that comparable [2+2] cycloadditions between two C=C functional groups typically requires photoexcitation. The NHI substituent platform is also used to prepare a series of phosphenium cations (the phosphorus analog of carbenes) and the reactivity of these species is subsequently disclosed.
Access status: Open Access ,
Vertical Structure And Surface Interactions Of Nitrous Acid Using A 1D Model
(2025-11-11) Ebrahimi-Iranpour, Yashar; VandenBoer, Trevor
This study was undertaken in order to study the vertical distribution and surface interactions of gas-phase HONO under non-ideal mixing conditions during the 2011 NACHTT campaign using the Platform for Atmospheric Chemistry and vertical Transport in One Dimension (PACT-1D) model. This work builds on a previous 0D modelling study from the NACHTT campaign, where the greatest unknown source rate of HONO was found during the early morning when a morning burst of HONO were observed and a stable nocturnal boundary layer formed. The 48-hour model was initialized using observational constraints selected during periods where a morning burst of HONO were observed and a stable nocturnal boundary formed. The modelled HONO showed excellent agreement with observations when heterogeneous ground surface processes of HONO, surface water, and vertical mixing were accounted for without the need to apply additional daytime sources of HONO.
Access status: Open Access ,
Forensic Applications of Sandpaper Spray Ionization Mass Spectrometry (SPS-MS): Detection and Chemometric Profiling of Small Molecules for Prohibited Practices
(2025-11-11) Rodrillo, Karl Angelo Morales; Ifa, Demian Rocha
The illicit trade of pharmaceuticals and wood presents threats to public health, ecological stability, and global markets. This thesis examines Sandpaper Spray Ionization Mass Spectrometry (SPS-MS) as a rapid, field-deployable technique for direct analysis of solid samples in two distinct forensic applications. (1) SPS-MS was used to detect and identify active pharmaceutical ingredients (APIs) and excipients in pharmaceuticals, assessing product authenticity. (2) SPS-MS was further developed for direct sampling and analysis, obtaining chemical fingerprints for classification and origin tracing of Canadian and Brazilian wood samples, in the context of forestry crimes. Chemometric analysis using PCA revealed clear species differentiation, supporting its use in species-level classification. SPS-MS thus offers a versatile, cost-effective, and operationally simple screening method to supplement current MS techniques. Its portability, minimal reagent use, and possible integration into current analytical workflows make it well-suited for remote or resource-limited settings for frontline testing of fraudulent drugs and trafficked wood.
Access status: Open Access ,
Exploring the Versatility of Dithieno[2,3-b;3?,2?-e]-4-keto-1,4-dihydrophosphinines
(2025-11-11) Hussein, Amaar; Baumgartner, Thomas
A less studied alteration of the dithienophosphole is the dithieno[2,3-b;3’,2’-e]-4-keto-1,4-dihydrophosphinine. Its relatively untouched chemistry and various sites for functionalization, makes it an appealing scaffold that can be tailored to the needs of various applications. Herein we report a range of targeted approaches to functionalizing each site of the dithienoketophosphinine with an emphasis on understanding the resulting properties. Based on the innate ability of phosphorus to be functionalized and alter the properties of entire molecular scaffolds, the first series of compounds focuses on phosphorus functionalization. The second series is derived from the synthetic versatility of carbonyl groups wherein Knoevenagel condensation was performed to create a series of dicyanomethylene-dithienophosphinines with enhanced acceptor character. Finally, a third series focusing on extending the conjugation of the dithienoketophosphinine by various aryl groups differing in their donor/acceptor behaviour and unlocking emission are presented. For each of the three series we report the optical, electrochemical, structural and synthetic details.

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