할로겐 원소들을 포함하는 화합물에서의 스핀-오비트 효과

학위논문(석사) - 한국과학기술원 : 화학과, 2004.2, [ vii, 55 p. ]The spin―orbit effects on the spectroscopic constants (bond lengths, dissociation energies and harmonic vibrational frequencies) for IX (X=F, Cl, Br and I) molecules have been studied using shape-consistent relativistic effective core potentials (RECPs) with effective one-electron spin―orbit operator at HF, MP2, CCSD and CCSD(T) levels. The spectroscopic constants calculated by our effective core potential (ECP) method are in good agreement with those from all-electron Dirac―Coulomb calculations at every level of calculation considered. The spin―orbit effects elongate the bond lengths, while reduce the harmonic vibrational frequencies and dissociation energies. From the spin―orbit effects on the dissociation energies, it is confirmed that the extent of spin―orbit effects increases in F < Cl < Br < I order. For the dissociation energies, the spin―orbit effects and electron correlation effects may not be additive, and may better be treated simultaneously. Two-component spin―orbit density functional theory (SODFT) calculations for spectroscopic constants of IX (X=F, Cl, Br and I) molecules have also been performed using several functionals. Our SODFT results obtained with the B3LYP functional are in very good accord with the results of two-component CCSD(T) calculations. BLYP and BP86 functionals overestimate the bond lengths and dissociation energies, while underestimate harmonic vibrational frequencies, when the results are compared with those of two-component CCSD(T) calculations. The two-component SODFT calculations imitate reported all-electron four-component relativistic DFT calculations and ZORA results well. In addition, the spectroscopic constants from three hybrid functionals, B3LYP, ACM and PBE0, give the best agreement with the experimental values. The spin―orbit effects from the SODFT calculations result in an increase of bond length, and decrease of harmonic vibrational frequency and dissociation energy. The spin―orbit effects from the SODFT calcula...한국과학기술원 : 화학과

금 촉매작용: 사이아노실릴레이션 반응.

학위논문(박사) - 한국과학기술원 : 화학과, 2008.2, [ xv, 207 p. ]I. Gold Catalysis: Cyanosilylation Reaction Gold had been considered to be an extremely inert metal, but recently it was found that nanometer-sized gold particles on metal oxide supports acted as catalysts for simple organic reactions, such as oxidation and hydrogenation, even at or below room temperature. In Chapter 1, we report that gold nanoparticles (AuNPs) of zero oxidation state $(Au^o)$ are catalytically active for a C-C bond forming reaction, cyanosilylation of aldehydes. Cyanosilylation is one of the most useful reactions for transforming carbonyl compounds into the corresponding α-hydroxy nitriles, which can be further manipulated to versatile building blocks, such as α-hydroxy acids, α-hydroxy carbonyl compounds, and β-amino alcohols. The AuNP-catalyzed cyanosilylation proceeded smoothly at room temperature with 0.2 wt% loading of AuNPs. The reactions of aromatic aldehydes were almost quantitative except benzaldehyde derivatives containing the electron-withdrawing $NO_2$ group, and α,β-unsaturated aromatic aldehydes were most reactive substrates for the reactions. The reactions also went smoothly for aliphatic aldehydes. Mechanistic studies indicate that the reactions proceeded both homogeneously and heterogeneously: homogenous catalysis by leached gold species and heterogeneous catalysis by the adsorption of the reactants (aldehydes and trimethylsilyl cyanide) onto AuNPs. The ratio of homogeneous and heterogeneous catalysis was estimated to be about 4 to 1. This mechanistic finding led us to examine the reaction catalyzed by homogeneous cationic gold species more thoroughly. In Chapter 2, we describe that gold(III) chloride was a highly efficient catalyst for cyanosilylation of various ketones and aldehydes. The reactions were complete within 30 min at room temperature with only 1 mol% AuCl_3, yielding the corresponding cyanohydrin trimethylsilyl ethers in very good yields. The isolated yields for ketones were up to 98%, and the reactions w...한국과학기술원 : 화학과