Browsing by Author "Szilvasi, Tibor"
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Item Accessing the main-group metal formyl scaffold through CO-activation in beryllium hydride complexes(Nature Portfolio, 2022) Hadlington, Terrance J.; Szilvasi, Tibor; Technical University of Munich; University of Alabama TuscaloosaCarbon monoxide (CO) is an indispensable C1 building block. For decades this abundant gas has been employed in hydroformylation and Pausen-Khand catalysis, amongst many related chemistries, where a single, non-coupled CO fragment is delivered to an organic molecule. Despite this, organometallic species which react with CO to yield C1 products remain rare, and are elusive for main group metal complexes. Here, we describe a range of amido-beryllium hydride complexes, and demonstrate their reactivity towards CO, in its mono-insertion into the Be-H bonds of these species. The small radius of the Be2+ ion in conjunction with the non-innocent pendant phosphine moiety of the developed ligands leads to a unique beryllium formyl complex with an ylidic P-C-CO fragment, whereby the carbon centre, remarkably, datively binds Be. This, alongside reactivity toward carbon dioxide, sheds light on the insertion chemistry of the Be-H bond, complimenting the long-known chemistry of the heavier Alkaline Earth hydrides. Stoichiometric carbon monoxide insertion processes leading to metal-formyl complexes are scarce, even for transition metals. Here, light is shed on the underexplored chemistry of beryllium hydrides leading to a stable example of a main group metal-formyl complex.Item Applications of Density Functional Theory and Machine Learning to Material Property Prediction and Solid-Liquid Interfaces(University of Alabama Libraries, 2025) Soyemi, Ademola Oluwole; Szilvasi, TiborComputational methods such as Density Functional Theory (DFT) in addition to machine learning (ML) methods have recently emerged as potential methods to accelerate the discovery of new materials. In order to provide more insights and show the capabilities of these methods, we use our calculations to explore high-throughput material property predictions and investigate the behavior of solvated ions in bulk water and at interfaces.We benchmarked the performance of semi-empirical quantum mechanical (QM) methods for the prediction of dipole moments of organic molecules against high-level coupled cluster (CC) predictions in the QM7b dataset (7211 molecules). We showed that the semi-empirical GFN2-xTB method offers the best balance of cost and accuracy in predicting the magnitude and direction of the total dipole moment. We also showed that GFN2-xTB can also provide geometries and electron density distributions that are comparable to those obtained at DFT level and can thus be used for downstream calculations. Building on this, we screened a virtual library of ~10,000 glycerol-derived via a workflow combining GFN2-xTB, DFT, machine-learning (ML), and empirical Hansen theory to predict key physicochemical properties and solvent-polymer interactions for sustainable plastic recycling. We also performed a comprehensive study on the performance of a directed message passing neural network in predicting the melting point of a diverse set of liquid crystals. Lastly, to break the usual cost-accuracy relationship of computational methods by providing DFT-level predictions at speed comparable to classical forcefields, we explore the application of ML interatomic potentials (MLIPs) to electrolytes, electrolyte-air, and solid-electrolyte interfaces and propose a simple method of maintaining constant chemical potential at these interfaces. Together, these studies establish versatile computational frameworks for simulating different materials and their properties, offering practical guidelines for selecting the appropriate computational approach across a range of applications.Item Design and Investigation of Bioinspired Reactivity Profiles of Synthetic Heme Peroxo Intermediate Complexes(University of Alabama Libraries, 2025) Rajapakse, Shanuk Ruvinda; Wijeratne, Gayan B.The activation and reduction of dioxygen (O₂) lie at the heart of aerobic life, driving essential processes in biological respiration and inspiring modern energy conversion systems such as fuel cells, where O₂ functions as a clean and efficient terminal electron acceptor. The stepwise transformation of O₂ into water is a highly exothermic process, and nature elegantly harnesses this chemistry utilizing transition metal centers. As the most abundant transition metal in the solar system, iron has been intricately woven into the fabric of biology, most notably through heme-containing enzymes. Heme enzymes are indispensable in physiology, orchestrating processes that span cellular respiration, detoxification, and the biosynthesis of signaling molecules. Yet, despite their ubiquity, the precise mechanistic details by which they mediate such reactions remain incomplete. Among the key species proposed in these catalytic cycles, ferric heme-peroxo (heme-PO) species have emerged as a crucial yet elusive intermediate, proposed to mediate a variety of pivotal biocatalytic transformations (e.g., conversion of L-arginine to L-citrulline in the concomitant formation of nitric oxide in nitric oxide synthase (NOS)). However, relative to other well-characterized heme intermediates such as high-valent iron-oxo adducts, the reactivities of heme-PO complexes remain severely underexplored. This knowledge gap is particularly striking given its potential significance in human pathology. Bioinorganic model chemistry provides a powerful framework for probing fundamental mechanistic questions by generating synthetic analogues that mimic essential features of enzymatic active sites, while allowing precise control over ligand environments, electronic structures, and reactivity. The central focus of this dissertation is the elucidation of structure-function relationships and reactivity patterns of heme-PO complexes. Synthetic heme-PO model systems featuring electronically diverse iron centers and varied axial ligation have been employed to systematically examine their reactivity landscapes toward biologically relevant substrates such as oximes (NOS model), aldehydes (aromatase model), and CO₂(g). These studies yield critical insights into the corresponding physiological transformations and address key gaps in the mechanistic understanding. Beyond advancing fundamental bioinorganic knowledge, the findings establish a conceptual foundation for the rational development of therapeutic strategies and the design of biomimetic catalytic systems inspired by nature's blueprint for key synthetic and energy applications.Item Development of Scalable and Sustainable Processes for Polymer Recycling, Upcycling, and Synthesis(University of Alabama Libraries, 2024) Al Alshaikh, Ali; Bara, Jason E.The circular economy is a concept often heard of in the context of the plastic waste crisis. Yet, chlorinated plastics, polyvinyl chloride (PVC) in specific, are often left out of the circularity conversation, despite PVC being the third most produced plastic worldwide. This dissertation discusses the challenges facing chlorinated plastics, but also the unique upcycling opportunities they provide. Inspired by the potential, this dissertation showcases new methods and processes contributing towards the circularity of PVC. Fractionation is a technique often used for lignin separation, but rarely used in plastics. Here, PVC is fractionated using solvent mixtures of incrementing PVC-dissolution performance. Using a weak solvent (acetone) - nonsolvent (methanol) mixture, low molecular weight PVC fraction can be obtained. These fractions show remarkable solubility in solvents previously unconsidered in PVC chemistry. This work illustrates this via homogenous catalytic hydrogenation of dehydrochlorinated PVC. Using this method to modify PVC yielded products with polyethylene-like characteristics, while maintaining PVC properties and solubility, a feat rarely achieved in PVC modification. The methods developed open the door for a wide range of PVC modification paths. This success inspired ways to enhance the yield of soluble low molecular weight chains from bulk PVC. Thus, a method for the depolymerization of PVC was developed. Ozonolysis, while an "ancient" process, was never deployed as an approach for PVC depolymerization, only as an analytical tool. In this work, a new safe and scalable procedure for the ozonolysis of PVC was developed, yielding PVC products that are around a third or fifth the molecular weight of the starting material. The products were readily soluble in weak PVC solvents like acetone, aspiring use in 3D printing and PVC chemistry. While these methods cover a diverse range of concepts, they mainly belong to a single side of the circular economy, the end-of-life management. This dissertation also touches on another side, production, albeit of a different class of monomer. Vinylimidazoles were long produced using hazardous, and in some cases expensive, techniques. The methods reported in this work were considerably "greener," covering nine out of the 12 principles of green chemistry. In totality, this dissertation diversly approached the end-of-life management of one of the most popular polymers, PVC, and the green production of a class of monomers previously produced using dangerous techniques.Item Electrodeposition of Superconducting Rhenium-Molybdenum Alloy(University of Alabama Libraries, 2025) Liu, Quanhong; Huang, QiangAs technological advancements progress, quantum computers are increasingly acknowledged for their potential to solve complex problems that surpass the capabilities of classical computing. Superconducting quantum computers offer significant advantages, including rapid processing speeds and prolonged coherence times, which contribute to enhanced computationalefficiency compared to other quantum systems. To further advance superconducting quantum computing technologies, the development of alternative superconducting metals with relatively higher superconducting transition temperatures is essential. This dissertation explores the electrodeposition of ReMo alloy thin films, emphasizing the development of novel chemical formulations, deposition processes, and film characterization for quantum device applications. The research background and motivation of this dissertation is introduced in Chapter 1. Chapter 2 systematically investigates the "water-in-salt" effect on metallic Mo electrodeposition, proposing a synergistic interaction between K⁺ and NH₄⁺ ions. Chapter 3 introduces a novel "water-in-acetate" system in the presence of citric acid, demonstrating, for the first time, its capability to enable the co-electrodeposition of ReMo alloys. The necessity of acetate for ReMo co-electrodeposition is established, and a hybrid citrate complex containing Re and Mo oxometallates is proposed to facilitate Mo reduction, where the induced electrodepositionmechanism is provided. Chapter 4 investigates the impact of Mo doping on electrodeposited nanocrystalline Re films, demonstrating that it preserves the enhanced superconducting Tc and improves the stability of Tc against thermal annealing at temperatures up to at least 200 ºC. This represents the first successful demonstration of Mo as a dopant to stabilize the enhanced Tc of electrodeposited Re films. Chapter 5 extends the study to alloys with higher Mo content, where a homogeneous Re3Mo phase alloy film with further enhanced Tc is achieved for the first time for electrodepositedfilms. As a summary for this dissertation study, a superconducting phase diagram of electrodeposited ReMo alloys as a function of Mo content is constructed, offering a systematic picture of the relationship between composition and superconductivity for the electrodeposited binary system.Item An Isolable Three-Coordinate Germanone and Its Reactivity(Wiley-VCH, 2021) Zhao, Xuan-Xuan; Szilvasi, Tibor; Hanusch, Franziska; Inoue, Shigeyoshi; University of Munich; Technical University of Munich; University of Alabama TuscaloosaA rare three-coordinate germanone [IPrN](2)Ge=O (IPrN=bis(2,6-diisopropylphenyl)imidazolin-2-imino) was successfully isolated. The germanone has a rather high thermal stability in arene solvent, and no detectable change was observed at 80 degrees C for at least one week. However, high thermal stability of [IPrN](2)Ge=O does not prevent its reactivity toward small molecules. Structural analysis and initial reactivity studies revealed the highly polarized nature of the terminal Ge=O bond. Besides, the addition of phenylacetylene, as well as O-atom transfer with 2,6-dimethylphenyl isocyanide make it a mimic of nucleophilic transition-metal oxides. Mechanism for O-atom transfer reaction was investigated via DFT calculations, which revealed that the reaction proceeds via a [2+2] cycloaddition intermediate.Item Isolation and Reactivity of Tetrylene-Tetrylone-Iron Complexes Supported by Bis(N-Heterocyclic Imine) Ligands(Wiley-VCH, 2022) Zhao, Xuan-Xuan; Szilvasi, Tibor; Hanusch, Franziska; Kelly, John A.; Fujimori, Shiori; Inoue, Shigeyoshi; Technical University of Munich; University of Alabama TuscaloosaThe germanium iron carbonyl complex 3 was prepared by the reaction of dimeric chloro(imino)germylene [IPrNGeCl](2) (IPrN=bis(2,6-diisopropylphenyl)imidazolin-2-iminato) with one equivalent of Collman's reagent (Na2Fe(CO)(4)) at room temperature. Similarly, the reaction of chloro(imino)stannylene [IPrNSnCl](2) with Na2Fe(CO)(4) (1 equiv) resulted in the Fe(CO)(4)-bridged bis(stannylene) complex 4. We observed reversible formation of bis(tetrylene) and tetrylene-tetrylone character in complexes 3 vs. 5 and 4 vs. 6, which was supported by DFT calculations. Moreover, the Li/Sn/Fe trimetallic complex 12 has been isolated from the reaction of [IPrNSnCl](2) with cyclopentadienyl iron dicarbonyl anion. The computational analysis further rationalizes the reduction pathway from these chlorotetrylenes to the corresponding complexes.Item Non-Thermal Plasma Assisted Dry Reforming of Methane Conversion by Ceria Supported Ni/Ru Based Catalysts(University of Alabama Libraries, 2024) Ahasan, Md Robayet; Wang, RuigangIncreasing rates of greenhouse gas emissions like CO2 & CH4 gases are responsible for the climate change. Additionally, excessive use of fossil fuels leads to an upcoming energy crisis due to the limited supply. A solution to capture and covert greenhouse gases into electricity, liquid fuels, hydrogen or other useful chemical compounds is always highly appreciable. Dry reforming of methane (DRM) is one of the top single step reactions that can convert major greenhouse gases into syngas, a crucial chemical reactant to produce value added chemicals and fuels using Fischer-Tropsch synthesis technology. However, DRM has a high operating temperature requirement (>750 °C) set by the thermodynamic barriers, and its side reactions cause carbon deposition and catalyst deactivation. Non-thermal plasma (NTP) is a powerful tool for surpassing the thermodynamic barriers of DRM. NTP or low-temperature plasma is a great source of generating highly reactive species such as energetic electrons, ions, and radicals that can replace the high temperature requirements of traditional thermal DRM as well as reduce the high temperature induced carbon deposition and side reactions. Catalytic materials in a plasma-catalysis reaction play a crucial role in plasma-catalysis synergism as well as the performance of gas conversion and energy efficiency in a plasma reactor. Processing of greenhouse gases by non-equilibrium plasma with catalytic reactions can have a global impact on energy conversion infrastructure such as small-scale reactors for chemical synthesis, power plants, gas-to-liquid technology, oil exploration, and fuel cells etc. The primary aim of this research is to explore the support shape effect of CeO2 supported NiO/RuOx-based catalysts on low-temperature plasma-assisted catalytic DRM conversion for production of syngas (H2, CO) and/or hydrocarbons. Understanding the shape effect (different shaped nanoparticles expose different crystal planes) of CeO2 (nanorods, nanocubes, and nanoctahedra) and SiO2 supports in plasma assisted DRM catalysis will open a new platform for CO2/CH4 capturing and production of value-added chemicals and fuels.Item Reversible metathesis of ammonia in an acyclic germylene-Ni-0 complex(Royal Society of Chemistry, 2021) Keil, Philip M.; Szilvasi, Tibor; Hadlington, Terrance J.; Technical University of Munich; University of Alabama TuscaloosaCarbenes, a class of low-valent group 14 ligand, have shifted the paradigm in our understanding of the effects of supporting ligands in transition-metal reactivity and catalysis. We now seek to move towards utilizing the heavier group 14 elements in effective ligand systems, which can potentially surpass carbon in their ability to operate via 'non-innocent' bond activation processes. Herein we describe our initial results towards the development of scalable acyclic chelating germylene ligands (viz.1a/b), and their utilization in the stabilization of Ni-0 complexes (viz.4a/b), which can readily and reversibly undergo metathesis with ammonia with no net change of oxidation state at the Ge-II and Ni-0 centres, through ammonia bonding at the germylene ligand as opposed to the Ni-0 centre. The DFT-derived metathesis mechanism, which surprisingly demonstrates the need for three molecules of ammonia to achieve N-H bond activation, supports reversible ammonia binding at Ge-II, as well as the observed reversibility in the overall reaction.Item Sustainable Valorization of Waste Plastics and Alternative Directions via Chemical Modification and Additive Manufacturing(University of Alabama Libraries, 2025) Bepari, Mousumi Rani; Bara, Jason E.The escalating accumulation of synthetic polymer waste necessitates sustainable plastic upcycling strategies that minimize risks to human health and ecosystems. This dissertation addresses this challenge and demonstrates several efficient depolymerization strategies for polyesters and polyurethanes, including a novel 'imidazolysis' approach alongside established 'glycolysis', 'alcoholysis', and 'aminolysis' methods, while driving new directions for the utilization of depolymerized products. Initially, this dissertation will demonstrate the catalyst-free depolymerization of polyethylene terephthalate (PET) using imidazoles termed "imidazolysis", which affords the bifunctional monomer 1,1'-terephthaloyl bisimidazoles (TBI) in high purity. Eight different imidazole derivatives were utilized, and it was observed that the reagents with electron-donating groups were more effective in the faster depolymerization of PET. TBIs were found to be versatile intermediates in transforming them into materials of increased value. Motivated by this outcome, we extend imidazolysis to polyurethane (PU), a ubiquitous polymer that is often neglected due to its cross-linked nature for recycling purposes. We achieved complete deconstruction of PU via imidazole, resulting in the product imidazole-carboxamide and the release of polyol. We then describe PET aminolysis to terephthalamide diols and their conversion to dichloro-terephthalamides, which serve as monomers for self-healing (SH) polyamide (PA) ionenes, compatible with fused-deposition (FDM) 3D printing. Ionenes are highly tunable materials having advantages for monomer selection from a vast library of di-(alkyl or aryl)-halides and tertiary diamines. Similarly, the dissertation demonstrates the glycolysis of PET with ethylene glycol, and further modification of this compound also led to the self-healing, tunable poly(ester-amide) ionene for 3D printing, noticeably different than the PA ionenes in terms of rigidity and self-recovery. In parallel, this dissertation presents the synthesis of novel terephthalates and carbamates (with and without allyl functional group), which were initially mass-produced from commercially available terephthaloyl chloride (TC) and methylene diphenyl diisocyanate (MDI), respectively. Subsequently, we aim to access the same products via organocatalyzed alcoholysis from waste PET and PU, enabling use in stereolithography (SLA) printing. Overall, these results highlight complementary depolymerization examples for PET and PU, demonstrating how careful reagent selection can allow us to produce commercially valuable products that link plastic circularity with additive manufacturing.Item Synthesis and Modification of Reverse Osmosis Membranes for the Enhanced Separation of Small Neutral Molecules(University of Alabama Libraries, 2023) Habib, Shahriar; Weinman, StevenThe focus of this dissertation is the modification and synthesis of reverse osmosis (RO) membranes for separating small, neutral molecules (SNMs) in water by using diamines and surfactants. While existing water treatment technologies such as coagulation, sedimentation, and filtration do well at treating large organic contaminants, SNMs, which can harm the environment and be toxic, such as urea and boric acid are still difficult to remove from water supplies. Because of its simple operation and minimal space requirements, RO has gained increased attention as a technique for removing SNMs from water. Despite excellent desalination performance, current RO membranes cannot reject SNMs sufficiently to produce potable water, especially at near-neutral pH levels, requiring the development of RO membranes with novel chemistries. Since IP reactions are fast and uncontrolled, the polyamide layer contains both network and aggregate free volume holes (pores). Because SNMs are not affected by the charge exclusion rejection mechanism that allows for high salt rejection, reducing the free volume to reduce the passage of SNMs through the membrane is needed. In this regard, the modification of RO membranes to increase the degree of cross-linking and altering the interfacial polymerization synthesis process of polyamide layers with new surfactants are ideal approaches. In this work, we modified polyamide layers of commercial RO membranes using m-phenylenediamine (MPD), numerous linear diamines, and a polyamine. The membranes were characterized using SEM, XPS, contact angle goniometry, and zeta potential. Membranes were performance tested for water permeance and NaCl, urea, and boric acid rejection using a dead-end stirred cell. We also investigated the effect of surfactants on MPD diffusion in the RO membrane synthesis process. We evaluated the MPD diffusion from a membrane support into n-dodecane in the presence of seven different surfactants and characterized the change in concentration of MPD into the organic phase when changing the surfactant, concentration of surfactant, and contact time. With the findings of these studies, we will be able to understand why surfactant addition, surface chemistry modification, and heat treatment affect the free volume, and further help us engineer RO membranes that can better separate SNMs.