Theoretical Study on Reaction Mechanism of Curing Reaction of Epoxy-Imidazole Resin

Scalable Room-Temperature Synthesis of Multi-shelled Na3(VOPO4)2F Microsphere Cathodes

This dissertation focuses on the assessment and development of heterogeneous catalysts for the deperoxidation of cyclohexyl hydroperoxide and oxidation of cyclohexane, which will be based in metal oxides and gold nanoparticles. For this endeavour a multidisciplinary approach will be used combining theoretical chemistry, kinetic studies and synthesis and characterisation of materials.\nThe starting choice for the catalyst to carry out the process is supported gold nanoparticles. The approach of this dissertation is to first model the mecha- nism of cyclohexyl hydroperoxide decomposition and oxidation of cyclohexane on gold nanoparticles by theoretical calculations, and use these findings to synthesise efficient heterogeneous catalysts which will be subsequently tested and optimised experimentally. But as it will be seen, some metal oxides are active rather than acting as mere supports, which will also be studied both theoretical and experimentally.\n\nEach chapter has a specific focus and constitutes a strand of the overall goal:\n\nChapter 1 provides an introductory background on the topics that this dissertation lies upon: oxidation of cyclohexane, heterogeneous catalysis and catalysis by gold and metal oxides.\n\nChapter 2 outlines the objectives of the thesis, formulating the relevant hypotheses of this research and the subsequent validation tests.\n\nChapter 3 exposes the methodology with a brief conceptual background that has been used to carry out this work.\n\nChapter 4 is the first chapter dealing with results. It consists in a theoretical study using density functional theory of the reaction mechanism over different models of gold nanoparticles, in order to study the influence of several parameters on their catalytic activity: the particle size, atom coordination, and presence of additional species like oxygen atoms and water.\n\nChapter 5 uses the findings found in chapter 4 to drive the synthesis of supported gold nanoparticles. It consists in a experimental study of gold-based catalysts, which is combined with a theoretical study which takes into account an additional variable: the support.\n\nChapter 6 exploits one of the findings of chapter 5. One of the supports used for anchoring the gold nanoparticles is active by itself, namely cerium oxide. This chapter comprises an experimental work about its activity, studying parameters like particle size, morphology and the effect of doping.\n\nChapter 7 continues with the catalytic activity of cerium oxide-based materials, but now from a theoretical point of view. It first presents a systematic study of the parameters relevant for the proper quantum mechanical description of cerium oxide, which is followed by a mechanistic study on different models.\n\nChapter 8 outlines the conclusions obtained in this dissertation, present- ing them in a summarised way. Even though each chapter presents its corresponding conclusions at its end, this chapter groups them all in a structured way for the reader's convenience, so a global view of the project can be swiftly grasped.\n\nThe results herein further the knowledge of heterogeneous catalysis for the oxidation of cyclohexane, one of the most important industrial reactions, and which continues to be a challenge. Although the ultimate goal is to develop an industrial catalyst, the dissertation also aims to show how computational chemistry can drive the design of novel materials, and how it can help to understand catalytic reactions at the atomic level.

Circular dichroism and optical absorption spectra of mononuclear and trinuclear chiral Cu(II) amino-alcohol coordinated compounds: A combined theoretical and experimental study

Theoretical studies of Pygmy Resonances

Reactions of neutral cobalt oxide clusters (Co(m)O(n), m = 3-9, n = 3-13) with CO, NO, C(2)H(2), and C(2)H(4) in a fast flow reactor are investigated by time of flight mass spectrometry employing 118 nm (10.5 eV) single photon ionization. Strong cluster size dependent behavior is observed for all the oxidation reactions; the Co(3)O(4) cluster has the highest reactivity for reactions with CO and NO. Cluster reactivity is also highly correlated with either one or more following factors: cluster size, Co(iii) concentration, the number of the cobalt atoms with high oxidation states, and the presence of an oxygen molecular moiety (an O-O bond) in the Co(m)O(n) clusters. The experimental cluster observations are in good agreement with condensed phase Co(3)O(4) behavior. Density functional theory calculations at the BPW91/TZVP level are carried out to explore the geometric and electronic structures of the Co(3)O(4) cluster, reaction intermediates, transition states, as well as reaction mechanisms. CO, NO, C(2)H(2), and C(2)H(4) are predicted to be adsorbed on the Co(ii) site, and react with one of the parallel bridge oxygen atoms between two Co(iii) atoms in the Co(3)O(4) cluster. Oxidation reactions with CO, NO, and C(2)H(2) on the Co(3)O(4) cluster are estimated as thermodynamically favorable and overall barrierless processes at room temperature. The oxidation reaction with C(2)H(4) is predicted to have a very small overall barrier (<0.23 eV). The oxygen bridge between two Co(iii) sites in the Co(3)O(4) cluster is responsible for the oxidation reactions with CO, NO, C(2)H(2), and C(2)H(4). Based on the gas phase experimental and theoretical cluster studies, a catalytic cycle for these oxidation reactions on a condensed phase cobalt oxide catalyst is proposed.

A green synthesis of functionalized 4H‐chromenes using one‐pot, three‐component reaction of salicylaldehyde (1), active methylene (2), and carbon‐based nucleophile (3) using Fe3O4@CONa nanoparticles in water has been performed at 60°C. The Fe3O4@CONa nanoparticle as an efficient, green, and magnetically reusable heterogeneous catalyst was applied in these reactions up to the nine runs. Green catalyst and solvent, short reaction time, high product yields, as well as simple work‐up procedure were found as some advantages of this methodology. The density functional theory calculations were applied to all‐inclusive perception of the one‐pot, three‐component reaction mechanism. The most reactions progressed through the following route: (a) nucleophilic addition of 2 to 1; (b) ring closing, dehydration; (c) nucleophilic substitution of 3 (2‐naphtol, 4‐hydroxycumarin) to intermediate. Sometimes mechanism mutated to: (a) nucleophilic addition of 3 (indole, 2‐methylindole) to 1, and dehydration; (b) nucleophilic addition of 2 to intermediate; and (c) ring closing, and dehydration. The frontier molecular orbitals, NBO analyses, molecular electrostatic potential of reactants, and intermediates confirmed the proposal mechanisms. Theoretical study could be so helpful to pick out suitable reactants of the reaction.

Thomas C. Maier's group has reported a synergistic Ir/Ni catalysis method for the synthesis of C(sp2)-C(sp3) bonds through an amino radical transfer (ART) strategy to generate alkyl radicals. This work employed density functional theory (DFT) to investigate the reaction mechanism, including the redox mechanism of Ir complexes in the generation process of amino radicals, analyzed the role and rationale behind alkyl boronic esters becoming dominant reaction pathways in the ART process, and discussed the competitive reaction mechanisms between oxidative addition and radical capture during C(sp2)-C(sp3) cross-coupling with Ni complexes. Through this theoretical calculation study, we aim to provide a theoretical foundation for constructing key carbon radical intermediates using ART and Ni-complex catalyzed free-radical-involved C(sp2)-C(sp3) cross-coupling reactions.

Kinetics and mechanism of reactive radical mediated fluconazole degradation by the UV/chlorine process: Experimental and theoretical studies

Mechanism of the complexation reaction of aluminum chloride with o-hydroxy-benzophenone

As one of the most fundamental processes, excited-state proton transfer (ESPT) plays a major role in both chemical and biological systems. In the past several decades, experimental and theoretical studies on ESPT systems have attracted considerable attention because of their tremendous potential in fluorescent probes, biological imaging, white-light-emitting materials, and organic optoelectronic materials. ESPT is related to fluorescence properties and usually occurs on an ultrafast time scale at or below 100 fs. Consequently, steady-state and femtosecond time-resolved absorption, fluorescence, and vibrational spectra have been used to explore the mechanism of ESPT. However, based on previous experimental studies, direct information, such as transition state geometries, energy barrier, and potential energy surface (PES) of the ESPT reaction, is difficult to obtain. These data are important for unravelling the detailed mechanism of ESPT reaction and can be obtained from state-of-the-art ab initio excited-state calculations. In recent years, an increasing number of experimental and theoretical studies on the detailed mechanism of ESPT systems have led to tremendous progress. This Account presents the recent advances in theoretical studies, mainly those from our group. We focus on the cases where the theoretical studies are of great importance and indispensable, such as resolving the debate on the stepwise and concerted mechanism of excited-state double proton transfer (ESDPT), revealing the sensing mechanism of ESPT chemosensors, illustrating the effect of intermolecular hydrogen bonding on the excited-state intramolecular proton transfer (ESIPT) reaction, investigating the fluorescence quenching mechanism of ESPT systems by twisting process, and determining the size of the solute·(solvent) n cluster for the solvent-assisted ESPT reaction. Through calculation of vertical excitation energies, optimization of excited-state geometries, and construction of PES of the ESPT reactions, we provide modifications to experimentally proposed mechanisms or completely new mechanism. Our proposed new and inspirational mechanisms based on theoretical studies can successfully explain the previous experimental results; some of the mechanisms have been further confirmed by experimental studies and provided guidance for researchers to design new ESPT chemosensors. Determination of the energy barrier from an accurate PES is the key to explore the ESPT mechanism with theoretical methods. This approach becomes complicated when the charge transfer state is involved for time-dependent density functional theory (TDDFT) method and optimally tuned range-separated TDDFT provides an alternative way. To unveil the driving force of ESPT reaction, the excited-state molecular dynamics combined with the intrinsic reaction coordinate calculations can be employed. These advanced approaches should be used for further studies on ESPT systems.

Smog chamber/GC techniques were used to investigate the atmospheric degradation of two unsaturated alcohols, 1-penten-3-ol and (Z)-2-penten-1-ol, by oxidation with chlorine atoms at atmospheric pressure of N(2) or air, as a function of temperature. The rate coefficients at 298 K were (units in cm(3) molecule(-1) s(-1)): (2.35 ± 0.31) × 10(-10) and (3.00 ± 0.49) × 10(-10) for 1-penten-3-ol and (Z)-2-penten-1-ol, respectively. The identified and quantified gas-phase products (with molar yields in brackets) were carbonyl compounds such as chloroacetaldehyde (33 ± 1%), propionaldehyde (39 ± 1%), acetaldehyde (8 ± 3%) and 1-penten-3-one (2%) from 1-penten-3-ol; and chlorobutyraldehyde (19 ± 1%), propionaldehyde (27 ± 1%), acetaldehyde (18 ± 2%) and (Z)-2-pentenal (36 ± 1%) from (Z)-2-penten-1-ol. A parallel theoretical study at the QCISD(T)6-311G**//MP2/6-311G** level was carried out to facilitate understanding of the reaction mechanism. Both the theoretical and experimental studies indicated that addition of Cl to the double bond of the unsaturated alcohol is the dominant reaction pathway, although the H-abstraction channel cannot be excluded. The atmospheric lifetimes of those unsaturated alcohols were calculated and the results are discussed.

Theoretical Study on Photodecarboxylation Reaction of Acrylic Acid in Gas Phase

Theoretical study on the stabilities, electronic structures, and reaction and formation mechanisms of fullerenes and endohedral metallofullerenes

Monoamine Oxidase B (MAO B) is a flavoenzyme that regulates and oxidizes monoamine neurotransmitters such as adrenaline, noradrenaline and dopamine. The oxidation reaction also produces hydrogen peroxide that can be harmful to dopaminergic neurons leading to neurological disorders such as Alzheimer’s disease and Parkinson’s disease. MAO B inhibitor is consequently used for preventing those neurological disorders. The structural details insight into the oxidation reaction mechanism of MAO B are vital to design specific inhibitors. A theoretical study is used to explain structural details of theoretical states in molecular level. In this work, the deamination reaction of adrenaline by MAO B was carried out to gain molecular-level details via ONIOM technique at M062X/6–31+G(d,p):PM6 level of theory. According to ONIOM calculation results, there are 4 key MAO B active site residues which are Leu171, Phe343, Tyr398 and Tyr435. Residues that bind adrenaline via hydrophobic interactions are Leu171, Phe343 and Tyr398 while Tyr435 binds via hydrogen bond. Additionally, NBO analysis suggests that the mechanism of this reaction is a hybrid between hydride transfer and polar nucleophilic characters. HIGHLIGHTS The structural properties along the adrenaline deamination reaction by MAO B have been revealed by ONIOM technique Key MAO B active site residues for designing more specific MAO B inhibitors have been identified in this study The mechanism of adrenaline deamination reaction by MAO B is a mixture between hydride transfer mechanism and polar nucleophilic mechanism GRAPHICAL ABSTRACT

The reaction mechanism of living radical polymerization using organic catalysts, a reversible complexation mediated polymerization (RCMP), was studied using both theoretical calculations and experiments. The studied catalysts are tetramethylguanidine (TMG), triethylamine (TEA), and thiophene. Methyl 2-iodoisobutyrate (MMA-I) was used as the low-molar-mass model of the dormant species (alkyl iodide) of poly(methyl methacrylate) iodide (PMMA-I). For the reaction of MMA-I with TEA to generate MMA• and •I-TEA radicals (activation process), the Gibbs activation free energy for the inner-sphere electron transfer mechanism was calculated to be 39.7 kcal mol–1, while the observed one was 25.1 kcal mol–1. This difference of the energies suggests that the present RCMP proceeds via the outer-sphere electron transfer mechanism, i.e., single-electron transfer (SET) reaction from TEA to MMA-I to generate MMA• and •I-TEA radicals. The mechanism of the deactivation process of MMA• to generate MMA-I was also theoretically studied. For the studied three catalysts, the theoretical results reasonably elucidated the experimentally observed polymerization behaviors.