L'utilisation de ligands stéréochimiquement dynamiques en catalyse asymétrique est récente et des résultats marquants ont déjà été obtenus.<br />Le BIPHOS, diphosphine stéréodynamique, est efficace en alkylation allylique asymétrique, après dédoublement spontané par cristallisation et complexation.<br />Ces résultats nous ont amenés à développer une méthode générale d'accès aux 2,2'-biphospholes fondée sur un processus de contrôle des chiralités en deux étapes.<br />Grâce à l'introduction d'un lien chiral pontant les deux atomes de phosphore, le contrôle partiel a été obtenu puisque trois diastéréoisomères sont obtenus sur les six attendus. Ces derniers sont en équilibre en solution, l'interconversion se produit par inversion du phosphore, induisant l'atropoinversion.<br />Le contrôle total est réalisé lors du dédoublement dynamique par complexation. Des complexes énantio- et diastéréo- purs ont pu être isolés et testés en catalyse asymétrique.

Reproduction de : Thèse de doctorat : Cancérologie : Toulouse 3 : 2007. / Titre provenant de l'écran-titre. Bibliogr. p. 196-238.

Thèse de doctorat : Chimie analytique : Strasbourg 1 : 2007. / Titre provenant de l'écran-titre. Notes bibliogr.

Thesis (Ph. D.)--Open University. BLDSC no. DXN033657.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 80-85).

Thesis (M. S.)--Biomedical Engineering, Georgia Institute of Technology, 2006. / Committee Chair: Zhu, Cheng; Committee Member: Babensee, Julia; Committee Member: Dustin, Michael; Committee Member: Garcia, Andres; Committee Member: Jo, Hanjoong; Committee Member: van der Merwe, Anton. Part of the SMARTech Electronic Thesis and Dissertation Collection. Non-Latin script record

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Semiconductor nanocrystal-based photovoltaics are an interesting new technology with the potential to achieve high efficiencies at low cost. CuInSe2 nanocrystals have been synthesized in solution using arrested precipitation and dispersed in solvent to form a “solar ink”. The inks have been deposited under ambient conditions to fabricate photovoltaic devices with efficiency up to 3%. Despite the low cost spray coating deposition technique, device efficiencies remain too low for commercialization. Higher efficiencies up to 7% have been achieved using a high temperature selenization process, but this process is too expensive. New nanocrystal film treatment processes are necessary which can improve the device efficiency at low cost. To this end, CuInSe2 nanocrystals were synthesized using a diphenyl phosphine:Se precursor which allows for precise control over the nanocrystal size. The size is controlled by changing the temperature of the reaction. The smallest size nanocrystals demonstrated extremely high device open circuit voltage. Ligand exchange procedures were used to replace the insulating oleylamine capping ligand used during synthesis with more conductive halide ions or inorganic chalcogenidometallate cluster (ChaM) ligands. These ligands led to improved charge transport in the nanocrystal films. A high-intensity pulsed light processing technique known as photonic curing was used which allows for high temperature sintering of nanocrystal films on temperature-sensitive substrates. High energy pulses cause the nanocrystals to sinter into large grains, primarily through melting and resolidification. The choice of metal back contact has a dramatic effect on the final film morphology, with Au and MoSe2 back contacts providing much better adhesion with the CuInSe2 than Mo back contacts. Nanocrystal sintering without melting can be achieved by replacing the oleylamine ligands with ChaM ligands prior to photonic curing. Low energy photonic curing pulses vaporize the oleylamine ligands without inducing sintering or grain growth. This greatly improved nanocrystal coupling and interparticle charge transport. Multiexcitons were successfully extracted from these nanocrystal films and external quantum efficiencies over 100% were observed. Transient absorption spectroscopy was used to study the multiexciton generation process in CuInSe2 nanocrystal films and colloidal suspensions. The multiexciton generation efficiency, threshold, and Auger lifetimes for CuInSe2 compare well with other nanocrystal materials. / text

Not available / text

High spin has been shown to be necessary for optimal reactivity of transition metal complexes toward the activation and functionalization of C-H bonds. This thesis presents our examination of the weak-field, tripodal, trianionic tris(pyrrolyl)ethane (tpe) ligand and its complexes. Outer-sphere oxidation of the manganese, iron, cobalt, nickel and zinc complexes of tpe were performed by electrochemical and chemical methods. Electrochemical oxidation occurred at the same potential for each species, suggesting a ligand-based oxidation. The reaction product of chemical oxidation of iron showed oxidation of a pyrrole unit followed by H-atom abstraction to form a dichelated species. Density functional theory calculations confirm these results, and in silico oxidation of the complexes is entirely ligand-based. These results establish that tpe complexes are oxidized at the pyrrolide subunits in outersphere electron transfers, and elucidate minimal metal-ligand electronic communication. The more reactive \([(tpe)Fe(THF)]^−\) anion exhibits rapid binding of three equivalents of tert-butyl isonitrile, while reaction with excess carbon monoxide induces ligand fragmentation to form a species wherein two molecules of carbon monoxide have been reductively coupled. A mechanism based on the observed isonitrile species is proposed. The use of inner-sphere oxidant reagents allows for several stable iron (III) complexes of tpe to be isolated and characterized. Alkyl peroxides and alkyl disulfides, organic azides, and diphenyldiazomethane are all shown to oxidize iron by a single electron. Reaction with organic azides results in the formation of iron (III) amide species, likely as a result of Hatom abstraction. The weak-field of tpe creates a high propensity for forming high-spin iron (III) complexes, to the extent that diphenyldiazoalkane acts as a redox-active ligand and provides a one-electron reservoir to reveal a high-spin \(Fe^{3+}\). Spectroscopic and computational studies were undertaken to rigorously assign the physical oxidation state of iron in all cases. Given the outer-sphere redox liability of the tpe ligand, and the capability for inner-sphere oxidation local to iron, tpe complexes of iron represent a new class of metal-ligand redox activity, wherein the metal and ligand form two separate redox reservoirs, accessible via different mechanisms. / Chemistry and Chemical Biology