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Item A computational study of a high-spin iron(I) complex for possible dinitrogen reduction to ammonia(Montana State University - Bozeman, College of Letters & Science, 2023) Pollock, Charlie Jeananne; Chairperson, Graduate Committee: Martin A. MosqueraA series of high-spin, low coordinate, paramagnetic iron complexes bearing a phenyltris((tert- butylthio)methyl)borate ligand were computationally modeled with density functional theory (DFT) and complete active space self-consistent field theory (CASSCF). The iron complexes examined in this research were inspired by nitrogenase, a naturally occurring, dinitrogen- fixating, iron-containing metalloenzyme. DFT and CASSCF offer a convenient way to explore reactions, complexes, and molecular orbitals without an immediate need to perform synthetic experiments. Our computational work can be used to guide synthetic efforts as well as urge future theoretical work in related research. DFT was utilized to compute two different thermodynamic properties: bond dissociation free energy (BDFE N-H) and Gibb's free energy. The conductor-like polarizable continuum model (CPCM) was applied to examine the solution phase of the system, and all BDFE and DeltaG values found were endothermic in tetrahydrofuran (THF). The methods, BP86 and BP86 ZORA, examined the gas phase of the system. The BDFE and DeltaG values calculated when using those two methods were largely inconsistent, which lead to the conclusion that the solution phase model is the most appropriate method for computing values of the dinitrogen complex ([Fe] 2(Mu-N 2)) and its related complexes. An N 2 vibrational mode was found (1915.30 cm -1) for [Fe] 2(Mu-N 2), which reflects a strongly coordinated dinitrogen bridge (Fe-N identical to N-Fe). Broken symmetry DFT (BSDFT) was used to examine the exchange coupling, which was found to have positive values (JAB =82.51 cm -1, 61.88 cm -1, 81.36 cm -1), and implied that [Fe] 2(Mu-N 2) is ferromagnetically coupled. Lastly, CASSCF and DFT were applied to plot and characterize certain molecular orbitals of [Fe] 2(Mu-N 2). The plotted and characterized molecular orbitals reflected moderate (DFT) to strong (CASSCF) covalent bonding between iron and dinitrogen. All this data reflected the synthetic plausibility of dinitrogen coordination to the bridged, Fe(I) complex ([Fe] 2(Mu-N 2)) that can be reduced through the dinitrogen cleavage mechanism.Item Ultrafast photochemistry of aqueous iron(III) complexes(Montana State University - Bozeman, College of Letters & Science, 2017) Danforth, Rebecca Ann; Chairperson, Graduate Committee: Erik Grumstrup; Bern Kohler was a co-author of the article, 'Ultrafast photochemical dynamics of hexaaqua iron(III) ion' in the journal 'Chemical physics letters' which is contained within this thesis.The ultrafast photochemical dynamics of aqueous iron(III) solutions were measured utilizing ultrafast pump probe spectroscopy. Aqueous solutions of iron(III) were prepared at low pH (<4.5) and low iron(III) concentration (<5 mM) to allow for small aquairon(III) complexes and ferrihydrite to be studied. Small monomeric and dimeric aquairon(III) complexes were studied to elucidate the mechanisms involved in the formation of OH ° after UV excitation which were previously known to generate OH ° in vastly different quantities. Upon excitation of Fe 3+, a proton is released from a coordinated water molecule to generate FeOH 2+ in less than 200 fs. The newly generated FeOH 2+ can then undergo numerous recombination pathways to regenerate the Fe 3+. Approximately 10% of the excited Fe 3+ undergoes photoreduction and subsequent release of OH ° and Fe 2+ within 20 ps. Exciting FeOH 2+, results in homolysis to form Fe 2+ and OH ° with a wavelength dependent yield with a lifetime of 20 ps. Fe 2(OH) 2 4+ does not appear to generate significant quantities of OH ° however, the dimer is photostable in comparison to Fe 3+ and FeOH 2+. To further the understanding of the primary kinetics of iron(III) in aqueous solutions, ferrihydrite nanoparticles were studied. Ferrihydrite exhibits similar dynamics to hematite in which electrons are excited into the conduction band of ferrihydrite. The electrons can then relax to the bottom of the conduction band within 390 fs before undergoing various recombination process. This limits the amount of iron(III) converted into iron(II) in ferrihydrite. All iron(III) systems studied show unique kinetics after excitation that elucidate the mechanisms behind the generation of OH °.Item Part 1: study toward the total synthesis of acutumine ; : Part 2: asymmetric intramolecular hydroamination catalyzed by group 3 metal complexes(Montana State University - Bozeman, College of Letters & Science, 2014) Huynh, Khoi Quang; Chairperson, Graduate Committee: Thomas S. Livinghouse; Tao Jiang and Tom Livinghouse were co-authors of the article, 'Substrate structural effect in Y(III)-catalyzed hydroamination/cyclization of 1,2-disubstituted and 1,1,2-trisubstituted aminoalkenes terminated by 2-(2-heteroarenyl) groups' in the journal 'Synlett' which is contained within this thesis.; Tom Livinghouse and Helena Lovick were co-authors of the article, 'N,N'-dibenzosuberyl-1,1'binaphthyl-2,2'-diamine. A highly effective supporting ligand for the enantio-selective cyclization of aminoalkenes catalyzed by chelating diamide complexes of La(III) and Y(III)' in the journal 'Synlett' which is contained within this thesis.Acutumine 1 is a tetracylic alkaloid isolated from Menispermum daurcum, which exhibits selective T-Cell cytotoxicity. It is potentially useful for specific therapy T-Cell related Leukemia and lymphoma. Acutumine is a highly functionalized tetracyclic natural product, containing a [4.3.3]-propellane core and a 5,5-spirocycle. The synthesis of the 5,5-spirocycle is prepared via enantioselective Pd II/IV catalyzed chloro-induced semi pinacol rearrangment. However, studies showed Pd catalyst functioned as Lewis acid to oxidant, PhI(OAc) 2 rather than forming a Pi-complex with the substrate as proposed. Fortunately, the preparation of the spirocycle can be accomplished from an asymmetric Pd II /Brønsted acid cocatalyzed semi pinacol rearrangement via direct allylic C-H activation. [4.3.3] propellane core was concisely synthesized in eight step sequences featuring a phosphoric Brønsted acid catalyzed aldol condensation and radical N-cyclization as the key transformations. Hydroamination, the addition of an amine N-H bond across an unsaturated carbon-carbon linkage, allows a highly atom economical access to industrial and pharmaceutical important alkaloids. The hydroamination of alkene by early transition metal has seen significant process. Herein, we reported the substrate structural effect in Yttrium(III)-catalyzed intramolecular hydroaminations. Aminoalkenes possessing a terminal 2- (5-trimethylsilyl)thienyl group exhibited substantially enhanced reactivity. Cyclization efficiency for a representative aminoalkene possessing a Z-configured 2-(phenyl)ethenyl group is considerably higher than that observed for the corresponding E-isomer. Enantioselective hydroamination/cyclization of representative aminoalkenes catalyzed by chelating diamide complexes of La(III) and Y(III) are described. The La(III) complex derived from the sterically demanding (R)-N,N'-dibenzosuberyl-1,1'-binaphthyl-2,2'-diamine proligand provides enantioselectivities that are in many cases significantly higher than those obtained with the corresponding Y(III) analog.