The side-on dioxygen adducts of N-heterocyclic carbene (NHC) containing rhodium complexes, [ClRh(IPr)2(O2)] and [ClRh(IMes)2(O2)], previously synthesized in our laboratories possess a square planar geometry and O-O bond lengths of 1.323(3) and 1.341(4) Å, respectively. Both of these attributes are uncharacteristic of Rh(O2) complexes, which are typically octahedral and possess O-O bond lengths of approximately 1.45 Å. Full characterization by NMR, IR, Raman, DFT and XAS confirmed the short O-O bond lengths of these structures and revealed that they were rhodium(I) coordination complexes of singlet oxygen with no net oxidation/reduction process having taken place. The unique bonding mode appears to result from the interaction of a filled Rh d orbital with one of the two degenerate O2 * orbitals, which causes splitting of the O2 * orbitals, favoring spin pairing in the O2 HOMO, and the inability of Rh to donate electron density to the empty * orbital. Initial investigations of these complexes as catalysts for the reduction and oxidation of C-O bonds, as well as singlet oxygen generation were also undertaken. Rh(IPr)2 coordination complexes of N2, H2 and CO were also synthesized and characterized by X-ray crystallography, NMR and elemental analysis. Interestingly, the addition of hydrogen gas to rhodium did result in oxidation of the metal. A Rh(NHC) complex featuring an anionic acetate ligand, [(AcO)Rh(IPr)(CO)2], was synthesized and characterized by NMR, IR and X-ray crystallography. This complex proved to be an effective catalyst for the regioselective hydroformylation of aliphatic and aromatic alkenes, which occurred without isomerization of the alkene. Initial rates of hydroformylation with our catalyst were compared to the chloride analogue, [ClRh(IPr)(CO)2], and demonstrated the beneficial nature of replacing the halide with a carboxylate ligand, which is less inhibiting of the reaction. The synthesis of a bifunctional hydrogenation catalyst featuring a protic-NHC was attempted by addition of benzimidazoles to [Cl2Ru(diphosphine)]. Although these attempts were unsuccessful, a large number of complexes of the formula [Cl2Ru(diphosphine)(-N3-benzimidazole)2] were synthesized and proved to be effective catalysts for the chemoselective hydrogenation of ketones versus alkenes. Use of chiral diphosphines and 1-triphenylmethylbenzimidazole yielded catalysts capable of producing secondary alcohols with moderate enantioselectivity. / Thesis (Ph.D, Chemistry) -- Queen's University, 2010-09-17 12:44:52.686

Aldehyde oxidase catalysed oxidation of various quinolinium and related cations has been studied in vitro. Oxidation products were identified by comparison of their spectral and chromatographic characteristics with those of authentic compounds. The N-heterocyclic cations and quinolones used required synthesis. Incubation of N-methylquinolinium, N-methyl-7,8-benzoquinolinium and N-phenylquinolinium yielded the corresponding 2- and 4-quinolones simultaneously. The ratio of 2- to 4-quinolone formation was found to be species dependent; the proportion of 4-quinolone was greater with guinea pig enzyme than with rabbit enzyme. Incubation of N-methyl-4-methylquinolinium, N-methyl-4-phenylquinolinium and N-methylphenanthridinium produced the expected 2-quinolones. Cations substituted adjacent to the ring nitrogen, i. e. N-methyl-2- methylquinolinium, N-methyl-2-phenylquinolinium and N-phenyl-2-phenylquinolinium, were oxidised to the corresponding 4-quinolones. Kinetic constants were determined spectrophotometrically. The Km values obtained with rabbit enzyme ranged from 1.6 x 10-3 M for N-methylquinolinium to <10-5 M for N-phenyl-2-phenylquinolinium. Quaternary compounds were found to be better substrates than their non-quaternary counterparts, except for N-methylisoquinolinium and N-methylphenanthridinium. In general, guinea pig aldehyde oxidase was shown to have a greater affinity for N-heterocyclic cations than rabbit enzyme. The substrate binding site has been discussed in the light of the results outlined below. Oxidation of N-methyl-4-phenylquinolinium (to the 2-quinolone) was competitively inhibited by N-methyl-2-phenylquinolinium (which yields the 4-quinolone), indicating that both these cations interact at the same active site. The ratio of 2- to 4-quinolone production from N-methylquinolinium was constant under various conditions, including purification of the enzyme but changed at high pH or in the presence of N-methylphenanthridinium. Inhibition studies indicated that both quaternary and non-quaternary compounds act at the same site on the enzyme. Km and Vmax values for phthalazine, N-methyl-2-phenylquinolinium and N-methylquinolinium were determined over the pH range 5.4 to 10.2. In each case, results indicated that the enzyme has an ionisable group at the active site with a pK ca. 8. Aldehyde oxidase was shown to catalyse the dehydrogenation of the pseudobases 3,4-dihydro-4-hydroxy-3-methyl-2-quinazolinone and 3,4-dihydro- 4-hydroxy-3-methylquinazoline.

Despite previous extensive study of the widely-employed ruthenium-catalysed olefin metathesis reaction, the finer mechanistic details have not been elucidated. An area that is noticeably lacking is spectroscopic exploration of the relevant complexes. In this work, organometallic ruthenium complexes of importance to olefin metathesis have been investigated using Ru K-edge X-ray absorption spectroscopy. The lowest energy feature in the Ru K-edge spectrum has been unambiguously assigned as due to Ru 4d←1s transitions. These electric-dipole-forbidden transitions are extremely sensitive to geometry. For centrosymmetric complexes, the pre-edge feature has very low intensity because it is limited by the weak electric quadrupole mechanism. By contrast, non-centrosymmetric complexes exhibit a substantial increase in pre-edge intensity because Ru 5p-4d mixing introduces electric-dipole-allowed character to the Ru 4d←1s transitions. The energy of the edge feature in the Ru K-edge spectrum corresponds to ionisation of 1s electrons and is a good indicator of the charge on the metal centre. Unexpectedly, we found that the first-generation (L = PCy₃) Grubbs precatalyst (1) has a higher 1s ionisation energy than the second-generation (L = H₂IMes) complex (2). This effect provides a compelling rationale for the unexplained differences in phosphine dissociation kinetics for complexes 1 and 2: the phosphine dissociation rate of 2 is slower than 1 because the metal centre is more electron-deficient in 2. Density functional theory calculations confirm the charge differences and offer some insight into the nature of bonding in these complexes, particularly with regard to the N-heterocyclic carbene and trialkylphosphine ligands. On the basis of these results, we propose that, for this system, the NHC ligand is a weaker σ-charge donor than the phosphine ligand, and that the NHC accepts significant π-electron density from the metal; both interactions function to reduce the electron density on the ruthenium centre. An ultimate goal is to investigate reactive species in the olefin metathesis mechanism; accordingly, we have made considerable progress toward collecting XAS data for a metallacyclobutane species, and we are pursuing methods to trap the four-coordinate intermediate in the metathesis cycle.

Despite previous extensive study of the widely-employed ruthenium-catalysed olefin metathesis reaction, the finer mechanistic details have not been elucidated. An area that is noticeably lacking is spectroscopic exploration of the relevant complexes. In this work, organometallic ruthenium complexes of importance to olefin metathesis have been investigated using Ru K-edge X-ray absorption spectroscopy. The lowest energy feature in the Ru K-edge spectrum has been unambiguously assigned as due to Ru 4d←1s transitions. These electric-dipole-forbidden transitions are extremely sensitive to geometry. For centrosymmetric complexes, the pre-edge feature has very low intensity because it is limited by the weak electric quadrupole mechanism. By contrast, non-centrosymmetric complexes exhibit a substantial increase in pre-edge intensity because Ru 5p-4d mixing introduces electric-dipole-allowed character to the Ru 4d←1s transitions. The energy of the edge feature in the Ru K-edge spectrum corresponds to ionisation of 1s electrons and is a good indicator of the charge on the metal centre. Unexpectedly, we found that the first-generation (L = PCy₃) Grubbs precatalyst (1) has a higher 1s ionisation energy than the second-generation (L = H₂IMes) complex (2). This effect provides a compelling rationale for the unexplained differences in phosphine dissociation kinetics for complexes 1 and 2: the phosphine dissociation rate of 2 is slower than 1 because the metal centre is more electron-deficient in 2. Density functional theory calculations confirm the charge differences and offer some insight into the nature of bonding in these complexes, particularly with regard to the N-heterocyclic carbene and trialkylphosphine ligands. On the basis of these results, we propose that, for this system, the NHC ligand is a weaker σ-charge donor than the phosphine ligand, and that the NHC accepts significant π-electron density from the metal; both interactions function to reduce the electron density on the ruthenium centre. An ultimate goal is to investigate reactive species in the olefin metathesis mechanism; accordingly, we have made considerable progress toward collecting XAS data for a metallacyclobutane species, and we are pursuing methods to trap the four-coordinate intermediate in the metathesis cycle. / Science, Faculty of / Chemistry, Department of / Graduate

For the preparation of semiconducting polymers often ‘standard’ catalytic systems are used without further optimisation. New ligands, such as N-heterocyclic carbenes have shown excellent activity in cross-coupling reactions (e.g. Suzuki-Miyaura reaction, or Hartwig-Buchwald amination). These systems show excellent conversions under mild conditions and even allow the use of aryl chlorides as reagents. Nevertheless, previously no system has been reported for the synthesis of conjugated polymers, e.g. the Suzuki polycondensation or Buchwald-Hartwig type polycondensation using these catalysts. A NHC-Pd based catalytic system was optimised for a polyamination reaction and the catalyst [(IPr)Pd(allyl)Cl] was found to be the most active. Polytriarylamines were synthesised using the optimised catalytic system and tested in organic field-effect transistors. Mobilities found were low which was found to be attributed to the presence of high molecular weight fractions. Molecular weights were controlled using an in situ end-capping approach and polymers tested in the semiconducting layer of OFETs gave similar mobilities tothose reported earlier. Several polytriarylamines, which have not been reported previously, were synthesised using NHC-chemistry and the in situ end-cappingapproach, as well as polytriarylamines that have been reported previously using Pd/phosphine catalysts. One library containing polymers based on biphenyles andbridged biphenyles and another library containing polymers with bridged oligoarenes were synthesised. Suzuki polycondensation was also studied besides the polyamination protocol and low catalyst loadings and reaction temperatures could be realised using a NHC-Pd catalyst. Sulfur containing monomers that could not be polymerised using the polyamination were polymerised successfully. All polymers were fully characterised and studied as the active layer in organic field-effect transistors. The highest mobilities determined for these polymers (~10-2 cm2/Vs) is close to the highest reported for this class of polymer reported to date.

京都大学 / 0048 / 新制・課程博士 / 博士(薬科学) / 甲第21043号 / 薬科博第86号 / 新制||薬科||9(附属図書館) / 京都大学大学院薬学研究科薬科学専攻 / (主査)教授 高須 清誠, 教授 竹本 佳司, 教授 大野 浩章 / 学位規則第4条第1項該当 / Doctor of Pharmaceutical Sciences / Kyoto University / DFAM

No description available.

Aldehyde oxidase catalysed oxidation of various quinolinium and related cations has been studied in vitro. Oxidation products were identified by comparison of their spectral and chromatographic characteristics with those of authentic compounds. The N-heterocyclic cations and quinolones used required synthesis. Incubation of N-methylquinolinium, N-methyl-7,8-benzoquinolinium and N-phenylquinolinium yielded the corresponding 2- and 4-quinolones simultaneously. The ratio of 2- to 4-quinolone formation was found to be species dependent; the proportion of 4-quinolone was greater with guinea pig enzyme than with rabbit enzyme. Incubation of N-methyl-4-methylquinolinium, N-methyl-4-phenylquinolinium and N-methylphenanthridinium produced the expected 2-quinolones. Cations substituted adjacent to the ring nitrogen, i. e. N-methyl-2- methylquinolinium, N-methyl-2-phenylquinolinium and N-phenyl-2-phenylquinolinium, were oxidised to the corresponding 4-quinolones. Kinetic constants were determined spectrophotometrically. The Km values obtained with rabbit enzyme ranged from 1.6 x 10-3 M for N-methylquinolinium to <10-5 M for N-phenyl-2-phenylquinolinium. Quaternary compounds were found to be better substrates than their non-quaternary counterparts, except for N-methylisoquinolinium and N-methylphenanthridinium. In general, guinea pig aldehyde oxidase was shown to have a greater affinity for N-heterocyclic cations than rabbit enzyme. The substrate binding site has been discussed in the light of the results outlined below. Oxidation of N-methyl-4-phenylquinolinium (to the 2-quinolone) was competitively inhibited by N-methyl-2-phenylquinolinium (which yields the 4-quinolone), indicating that both these cations interact at the same active site. The ratio of 2- to 4-quinolone production from N-methylquinolinium was constant under various conditions, including purification of the enzyme but changed at high pH or in the presence of N-methylphenanthridinium. Inhibition studies indicated that both quaternary and non-quaternary compounds act at the same site on the enzyme. Km and Vmax values for phthalazine, N-methyl-2-phenylquinolinium and N-methylquinolinium were determined over the pH range 5.4 to 10.2. In each case, results indicated that the enzyme has an ionisable group at the active site with a pK ca. 8. Aldehyde oxidase was shown to catalyse the dehydrogenation of the pseudobases 3,4-dihydro-4-hydroxy-3-methyl-2-quinazolinone and 3,4-dihydro- 4-hydroxy-3-methylquinazoline.

No description available.

No description available.