Theoretical Investigation For The Circulation Reactions Of N₂O Catalyzed By Fe⁺, Then Respectively Oxidative H₂and CO In The Gas Phase

In recent years, the reaction of metal ion activation of small molecules werewidespread concerned in experimental and theoretical by chemists. Particularly, theelimination of atmospheric pollutants (N2O, CO2, NO, NO2) experimental studiesincreasingly were concerned by chemists, reaction were catalyzed by a metal ion (orionic compounds).1981Kappes’s landmark experiment for the first time discoveredby a transition metal ion catalyzed reaction catalytic cycle to eliminate N2O and CO.then, about the N2O and transition metal ions (or ionic compounds) reactions studiesgradually increased. Which, Lavrov and Blagojevic, using inductively coupled plasma/selected-ion flow tube (ICP/SLFT) tandem mass spectrometry, who surveyedreactions of N2O with59different atomic cations on the periodic table, and havethoroughly characterized the room temperature kinetics for the reduction of nitrousoxide by atomic metal. Then, Measurements of the kinetics of the second reaction stepof the catalytic cycle, the oxidation of hydrogen to water measured immediately bymetal cation.Speaking of the catalytic cycle reaction, the catalyst necessarily participate in thereaction, and the turnover frequency (TOF) is an important indicator of catalyticactivity evaluation. For a long time, catalyst selection has been an issue of concernchemists. Therefore, the turnover frequency (TOF) is calculated for a catalytic cycleof reactions is particularly important. In the2006, Kozuch reference Christiansenmultistep process using the steady state reaction rate constant (k-means) of themethods affect the overall reaction rate, according to the Eyring’s transition statetheory and Amatore’s energy span concept, the system established energy spantheoretical model by the reaction Gibbs free energy. Kozuch’s energy span model thatin a catalytic cycle, the total rate were affected by the Gibbs energy each of theintermediates and transition states, play a decisive role in the catalytic cycle of Gibbsfree energy of the rate-determining transition states (TDTS) and rate-determining intermediates (TDI).Based on the two-state reactivity theory, this thesis uses density functional theory(DFT), coupled cluster theory (CCSD), and quantum-chemical calculation programsincluding Gaussian-03program, Crossing2004, Gamess program, and NBO5.0tomake a thorough and detailed theoretical investigation on the reaction mechanism ofN2O, H2and CO were catalyzed by transitional metal ions Fe+the gas phase.The whole thesis consists of four chapters, Chapter1briefly describe thedevelopment and application of quantum chemistry as well as the development andtheory of TSR. Chapter2briefly introduce elementary theory and quantum chemistrycomputation methods. Including density functional theory, overview of the potentialenergy surface and the adiabatic approximation, transition state theory, overview ofthe natural bond orbital theory, reaction potential energy surfaces intersect withdisjoint rule, the basic theory of spin-orbit coupling as well as transition probabilitycalculation, and energy span model. These theoretical knowledge for our experimentalstudy in this paper provide a reliable theoretical basis of quantum chemistry.The chapter3, the mechanisms of the gas phase reactions between N2O and H2catalyzed by Fe+have been investigated using density functional theory (DFT)B3LYP functional and coupled cluster theory (CCSD) levels of theory in the quartetand sextet states. The potential energy surfaces (PESs) were characterized in detailusing molecular orbital theory and natural bonding orbital (NBO) analysis. Thepossibility of spin inversion and cross-section situation of potential energy surfaceswere discussed, by calculating spin-orbit coupling (SOC) constants and transitionprobability at the minimum energy crossing point (MECP). The use of Energetic SpanModel Kozuch proposed, the rate-determining transition states (TDTS) andrate-determining intermediates (TDI) were confrmed of the reaction. Finally, turnoverfrequency (TOF) were calculated, in order to evaluate the performance of the catalyst.The chapter4, the mechanisms of the gas phase reactions between N2O and COcatalyzed by Fe+have been investigated using density functional theory (DFT)B3LYP functional and coupled cluster theory (CCSD) levels of theory in the quartet and sextet states. We found that this reaction is a typical two-state reaction. Thepotential energy surfaces (PESs) were characterized in detail using molecular orbitaltheory and natural bonding orbital (NBO) analysis. Crossing seam were found of thequartet and sextet states by Yoshizawa’ single-point vertical excitation method, andstructures and relative energy of crossing point the potential energy surface weredetermined. The possibility of spin inversion and cross-section situation of potentialenergy surfaces were discussed, by calculating spin-orbit coupling (SOC) constantsand transition probability at the minimum energy crossing point (MECP). Finally, theoptimal reaction path, the rate-determining transition states (TDTS) andrate-determining intermediates (TDI) were confrmed of the reaction. In order toevaluate the performance of the catalyst, turnover frequency (TOF) were calculated byEnergetic Span Model Kozuch proposed.