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Prediction for eta(') -> pi+ pi- pi0 gamma signal.Gül, Alpaslan January 2016 (has links)
The branching ratios of the radiative decays η(')→ π+π-π0γ are still unknown. Only an upper limit for η has been established and η' has not been observed. In this thesis the decays of η and η' into the final state π+π-π0γ are studied through the dominant contributions from bremsstrahlung and intermediate vector meson states respectively. Simulations have been done using ROOT, a framework based on C++ language, to determine if the decay to the final state can be observed. Based on theories describing the dominant contributions to the final state signal, event generators have been designed in this thesis to produce particle distributions for the mentioned decay branches. The process η' → ωγ, ω → π+π-π0 is 6.16±0.83 more likely than η'→ π+π-π0 decay. Probabilities for the η → π+π-π0γ contributions are presented as a function of different photon energies. / Den bakomliggande dynamiken hos de radiativa sönderfallen η(')→ π+π-π0γ är fortfarande okänd. I nuläget finns bara en övre gräns för η och η' har ännu inte fastställts. I detta projekt studeras sönderfallen av η och η' till sluttillståndet π+π-π0γ genom de dominanta bidragen från bromsstrålning av η och ett mellantillstånd där η' först sönderfaller till ωγ och ett ytterligare sönderfall av ω till π+π-π0. Simulationer har genomförts med hjalp av ROOT, som är ett program baserat pa C++, for att avgöra om sönderfallen kan observeras. Händelsegeneratorn baseras på tidigare arbeten som beskriver sönderfallsprocesserna och resultaten presenteras i from av Dalitz-grafer. Sannolikheten for processen η' → ωγ, ω → π+π-π0 är 6.16±0.83 gånger mer trolig än η'→ π+π-π0. Sannolikheten för η → π+π-π0γ presenteras i resultatdelen av rapporten för olika energier av fotonen som avges genom bromsstrålning.
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Computational Study of Pi-Pi Stacking Interactions in Large Curved and Planar Polycyclic Aromatic HydrocarbonsKarunarathna, A A Sasith N 14 December 2013 (has links)
Theoretical studies of pi-pi interactions on several dimers of curved polycyclic aromatic systems have been carried out. In the first part, dispersion corrected density functional theory methods (DC-DFT) were used to evaluate the basis set superposition errors (BSSE) in dispersion interactions of the corannulene dimer, and the accuracy of the calculations using DC-DFT methods was compared with high level benchmark calculations. In these calculations, Grimme’s B97D DC-DFT method provided reasonably accurate results with the benchmark calculations. In addition, BSSE obtained with the B97D method along with cc-pVQZ basis set was negligible. Furthermore, a series of calculations were carried out to obtain the pi-pi interaction energy and most stable conformation for the sumanene dimer system. In these calculations, Grimme’s B97D method was used. The potential energy minimum of the sumanene dimer was determined as the concave-convex stacked arrangement with one monomer unit rotated to 60°. The binding energy of the dimer was found to be 19.34 kcal/mol with a 3.72 angstrom distance between two monomer units. Dimers of three different heterosumanenes along with the parent sumanene were also studied. In this set of calculations, two different concave-convex dimer motifs were chosen, eclipsed and staggered (60° rotated). For all the heterosumanenes, as well as the parent sumanene, the staggered conformation is the most stable geometry. The parent sumanene had the highest binding energy. The –NH substituted sumanene produced the second highest binding energy, while the –O analog was the weakest bonded dimer. Finally, dispersion calculations were carried out for the planar aromatic compound of triphenylene. The pi-system of the dimer was distorted by rotating one monomer unit around the principle axis and parallel displacing one monomer unit relative to the other one. Among the rotational dimers, the 39° rotated dimer was the minimum energy conformation. Interaction energy of that dimer was 14.42 kcal/mol with 3.40 angstrom separation between monomers at the B97D/cc-pVQZ level. The parallel displaced minimum energy dimer has a binding energy about 1.0 kcal/mol smaller than the rotational minimum energy geometry.
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Parametry uspořádání tříflavourové chirální symetrie z ππ rozptylu / Order parameters of three-flavour chiral symmetry from ππ scatteringŘíha, Jaroslav January 2021 (has links)
This thesis familiarizes the reader with the process behind the construction of ππ scattering amplitudes. Several representations and transformations nec- essary to pass from one to another are introduced. Then known solutions of Roy equations are employed to extract values of subthreshold parameters αππ and βππ from recent experimental data. As a second goal three-flavour chiral perturbation theory(χPT), which is a low energy effective field theory of quan- tum chromodynamics, is used to obtain theoretical predictions for αππ and βππ by applying a technique called resummed approach. A large statistical ensemble of predictions is numerically generated. Subsequently, Bayesian statistics is uti- lized to get more information about spontaneous symmetry breaking parameters X(3), Y (3), Z(3), which are related to the leading order low energy coupling constants of three-flavour χPT. These results are then compared to several other recent determinations. Significant shifts in probability distributions compared to Descotes-Genon et al. [2004] are observed. The new results are more consistent with theoretical expectations. 1 Bibliography S. Descotes-Genon, N. H. Fuchs, L. Girlanda, and J. Stern. Resumming qcd vac- uum fluctuations in three-flavor chiral perturbation theory. The European Phys- ical Journal C,...
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Synthesis, properties and characterization of N-Alkyl substituted b-Diketiminato copper(I) ComplexesOguadinma, Paul O. 04 1900 (has links)
Le ligand nacnacxylH (xyl = C6Me2H3) et les ligands dikétimines N-alkyle substitués (nacnacCH(Me)PhH, nacnacBnH and nacnaciPrH) ont été préparés avec de bons rendements à l’exception du nacnaciPrH (23%) en utilisant un protocole en une étape et à l’aide d’un montage Dean-Stark. La réaction du S,S-nacnacCH(Me)PhH et du nacnacBnH avec le nBuLi dans le THF conduit au S,S-nacnacCH(Me)PhLi(THF) et au nacnacBnLi(THF). Les tentatives de bromation de ces composés par le N-bromosuccinimide conduisent plutôt aux ligands S,S-succnacnacCH(Me)PhH et succnacnacBnH (succ = succinimido) substitués par un groupement succinimido sur le carbone La chloration par le N-chlorosuccinimide conduit au produit désiré, mais avec des impuretés.
La réaction de ces ligands avec le CuOtBu (ou bien MesCu, où Mes = C6Me3H2, et une quantité catalytique de CuOtBu) en présence de bases de Lewis donne les (nacnacxylCu)2(-toluène), nacnacxylCuCNC6H3(Me)2, nacnacCH(Me)PhCuL (L = PPh3, PMe3, CNC6H3(Me)2, DMAP, lutidine, Py, MeCN), nacnacBnCuL (L = PPh3, CNC6H3(Me)2, styrène, trans-stilbene, phenylvinylether, acrylonitrile, diphenylacetylène), nacnaciPrCuL (L = PPh3, CNC6H3(Me)2, MeCN) et le succnacnacCH(Me)PhCuL (PPh3, CNC6H3(Me)2, pyridine). Tous ces complexes sont jaunes et sensibles à l’air et à l’humidité. En l’absence de fortes bases de Lewis, on n’observe pas de réaction entre les précurseurs de cuivre et les ligands N-alkyle substitués.
Les études RMN des complexes dans le C6D6 ne présentent pas de complexe de toluène mais un mélange à l’équilibre du (nacnacxylCu)2(-C6D6) et nacnacxylCu(C6D6) dans une proportion de 2 pour 1. Alors que l’addition de plus de cinquante équivalents soit de THF, soit de toluène n’induit aucun changement des spectres RMN, l’addition de 2 équivalents de MeCN conduit instantanément au complexe nacnacxylCu(MeCN). De plus, le (nacnacxylylCu)2(-C6D6) ne se coordone ni ne réagit avec le N2O, même après avoir été chauffé à 60°C pendant treize jours.
En présence de DPA (diphenylacétylène), la réaction du nacnacBnH avec le CuOtBu conduit au dimère ponté (nacnacBnCu)2(µ-DPA). L’addition d’un excès de DPA (10-12 équivalents) transforme le dimère ponté en complexe lié en position terminale nacnacBnCuDPA. Les nacnacRH (R = CH(Me)Ph et i-Pr) ne forment pas de complexe ni avec les oléfines ni avec le DPA. Une réactivité similaire a été observée avec les complexes de nacnacCH(Me)PhCu(NCMe) et nacnaci-PrCu(NCMe). Tandis que le complexe lié en position terminale par MeCN a été isolé et caractérisé, l’équilibre en solution nous laisse suspecter la formation d’un complexe d’acétonitrile ponté.
Des études de réactivité comparatives ont été menées sur quelques complexes de cuivre. La Morpholine ne réagit pas avec le nacnacBnCu(acrylonitrile) contrairement à l’acrylonitrile libre. L’expérience de l’échange d’oléfine montre que l’acrylonitrile (une oléfine électro-attractrice) se lie plus fortement que les autres oléfines, mettant ainsi en évidence l’importance de la rétrodonation face à la donation La rétrodonation est cependant faible comparée aux autres complexes de styrène structurellement caractérisés. Les complexes nacnacCH(Me)PhCuL (L = PPh3 et MeCN) ont été employés dans la cyclopropanation catalytique du styrène et dans l’addition conjuguée du ZnEt2 sur la 2-cyclohexénone, mais les résultats indiquent que le ligand dikétimine est éliminé avant son entrée dans le cycle catalytique. Par conséquent, il n’y a pas d’induction chirale.
Les complexes tétra coordinées de cuivre avec les nacnacRCu(phen) (R = Bn, CH(Me)Ph et Phen = 1,10-phenanthroline, 2-Mes-1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline (dmp) et 2,9-diphenyl-1,10-phenanthroline (dpp)) ont été synthétisés. Ces complexes sont d’une intense couleur bleue et des interactions d’empilement entre l’un des cycles phényle des ligands nacnac et la phénanthroline ont été observées dans les structures à l’état solide. Les mesures en absorption UV-visible ont été effectuées dans le toluène et les bandes MLCT sont déplacées vers le rouge par rapport à celles des complexes de cuivre et bisphénanthroline. Tous ces composés émettent à l’état solide mais les complexes 1,10-phenanthroline et 2-Mes-1,10-phenanthroline n’émettent pas en solution.
Pour renforcer les interactions d’empilement , les nouveaux ligands nacnacRH (R = CH2C6H2(OMe)3, CH2C6F5) et leurs complexes de cuivre respectifs ont été préparés avec du dmp et dpp. Afin de permettre la comparaison, le nacnaciBuCu(dmp) a été synthétisé. Alors que les complexes dmp montrent une augmentation des interactions intramoléculaires - avec les substituants phényle du ligand dikétimine et de la phénanthroline, les complexes dpp ne révèlent pas de telles interactions. Les complexes perfluorés montrent, en absorption et en émission, un déplacement significatif vers le bleu, alors que les complexes substitués par un groupements isobutyle présentent des transitions déplacées vers le rouge. Alors que les intensités de luminescence et les durées de vie sont faibles, les déplacements réduits de Stokes et les pics étroits de luminescence comparables indiquent une réduction des distorsions de l’état excité. / The ligand nacnacxylH (xyl = C6Me2H3) and the N-alkyl substituted diketimine ligands (nacnacCH(Me)PhH, nacnacBnH and nacnaciPrH) have been prepared in good yields except nacnaciPrH (23%) using a one-step procedure with the help of a Dean-Stark apparatus. Reaction of S,S-nacnacCH(Me)PhH and nacnacBnH with nBuLi in THF gave S,S-nacnacCH(Me)PhLi(THF) and nacnacBnLi(THF). Attempts to brominate these THF adducts with N-bromosuccinimide gave instead the -carbon substituted succinimido ligands S,S-succnacnacCH(Me)PhH and succnacnacBnH (succ = succinimido). Chlorination with N-chlorosuccinimide, afforded the desired product albeit with significant amounts of impurities.
Reaction of these ligands with CuOtBu (or MesCu and catalytic amounts of CuOtBu, Mes = C6Me3H2) in the presence of Lewis bases gave (nacnacxylCu)2(-toluene), nacnacxylCuCNC6H3(Me)2, nacnacCH(Me)PhCuL (L = PPh3, PMe3, CNC6H3(Me)2, DMAP, lutidine, Py, MeCN), nacnacBnCuL (L = PPh3, CNC6H3(Me)2, styrene, trans-stilbene, phenylvinylether, acrylonitrile, diphenylacetylene), nacnaciPrCuL (L = PPh3, CNC6H3(Me)2, MeCN) and succnacnacCH(Me)PhCuL (PPh3, CNC6H3(Me)2, pyridine). All complexes are yellow and sensitive to air and moisture. There was no reaction between the copper precursors and the N-alkyl substituted ligands in the absence of strong Lewis bases.
NMR studies of the complex (nacnacxylCu)2(-toluene) in C6D6, showed no toluene adduct but an equilibrium mixture of (nacnacxylCu)2(-C6D6) and nacnacxylCu(C6D6) in a ratio of 2:1. While addition of up to 50 equiv of either toluene or THF did not cause any significant change in the 1H NMR spectrum, addition of 2 equiv MeCN gave instantaneously the nacnacxylCu(MeCN) complex. In addition, (nacnacxylylCu)2(-C6D6) did not coordinate or react with N2O even after heating at 60 oC for thirteen days.
In the presence of DPA (diphenylacetylene), reaction of nacnacBnH with CuOtBu yields the bridged dimer (nacnacBnCu)2(µ-DPA). Addition of excess DPA (10-12 equiv) converts the bridged dimer to the terminally bound complex nacnacBnCuDPA. NacnacRH (R = CH(Me)Ph and i-Pr) did not form complexes with olefins or with DPA. Similar reactivity was observed in nacnacCH(Me)PhCu(NCMe) and nacnaci-PrCu(NCMe) complexes. While the terminally bound MeCN complex was isolated and characterized, equilibrium in solution led us to suspect the formation of a bridged acetonitrile adduct.
Reactivity and comparative studies were performed with several copper complexes. Morpholine did not react with nacnacBnCu(acrylonitrile) while free acrylonitrile does. Olefin exchange experiment showed that acrylonitrile (an electron withdrawing olefin) binds stronger than the other olefins examined, showing the importance of -backbonding relative to -donation. -Backbonding is, however, still low when compared other structurally characterized transition metal styrene complexes. Complexes nacnacCH(Me)PhCuL (L = PPh3 and MeCN) have been employed in catalytic cyclopropanation of styrene and the conjugate addition of ZnEt2 to 2-cyclohexenone, but results indicate that the diketimine ligand is lost before it enters the catalytic cycle. Hence, there was no chiral induction.
Four-coordinate copper(I) complexes of the form nacnacRCu(phen) (R = Bn, CH(Me)Ph and Phen = 1,10-phenanthroline, 2-Mes-1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline (dmp) and 2,9-diphenyl-1,10-phenanthroline (dpp)) were also prepared. The complexes are intensely blue in colour and intramolecular -stacking interactions between one of the phenyl rings of nacnac ligand with the phenanthroline were observed in the solid state structures. UV-vis absorption measurements were performed in toluene and the MLCT bands are red-shifted relative to those of bisphenanthroline copper complexes. All compounds are emissive in the solid state, but 1,10-phenanthroline and 2-Mes-1,10-phenanthroline complexes do not emit in solution.
To buttress the -stacking interactions, the new ligands nacnacRH (R = CH2C6H2(OMe)3, CH2C6F5) and their respective copper complexes with dmp and dpp were prepared. For the sake of comparison, nacnaciBuCu(dmp) was prepared. While the dmp complexes showed enhanced -intramolecular interactions with both phenyl substituents of the diketimine ligand and the phenanthroline, dpp revealed no such interactions. The perfluorinated complex showed a significant blue-shift in absorption and emission spectra when compared to the other complexes, while the isobutyl substituted complex displayed red-shifted transitions. While luminescence intensities and lifetimes were low, reduced Stoke shifts and comparable sharp luminescence peaks indicate reduced distortions in the excited state.
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Synthesis, properties and characterization of N-Alkyl substituted b-Diketiminato copper(I) ComplexesOguadinma, Paul O. 04 1900 (has links)
Le ligand nacnacxylH (xyl = C6Me2H3) et les ligands dikétimines N-alkyle substitués (nacnacCH(Me)PhH, nacnacBnH and nacnaciPrH) ont été préparés avec de bons rendements à l’exception du nacnaciPrH (23%) en utilisant un protocole en une étape et à l’aide d’un montage Dean-Stark. La réaction du S,S-nacnacCH(Me)PhH et du nacnacBnH avec le nBuLi dans le THF conduit au S,S-nacnacCH(Me)PhLi(THF) et au nacnacBnLi(THF). Les tentatives de bromation de ces composés par le N-bromosuccinimide conduisent plutôt aux ligands S,S-succnacnacCH(Me)PhH et succnacnacBnH (succ = succinimido) substitués par un groupement succinimido sur le carbone La chloration par le N-chlorosuccinimide conduit au produit désiré, mais avec des impuretés.
La réaction de ces ligands avec le CuOtBu (ou bien MesCu, où Mes = C6Me3H2, et une quantité catalytique de CuOtBu) en présence de bases de Lewis donne les (nacnacxylCu)2(-toluène), nacnacxylCuCNC6H3(Me)2, nacnacCH(Me)PhCuL (L = PPh3, PMe3, CNC6H3(Me)2, DMAP, lutidine, Py, MeCN), nacnacBnCuL (L = PPh3, CNC6H3(Me)2, styrène, trans-stilbene, phenylvinylether, acrylonitrile, diphenylacetylène), nacnaciPrCuL (L = PPh3, CNC6H3(Me)2, MeCN) et le succnacnacCH(Me)PhCuL (PPh3, CNC6H3(Me)2, pyridine). Tous ces complexes sont jaunes et sensibles à l’air et à l’humidité. En l’absence de fortes bases de Lewis, on n’observe pas de réaction entre les précurseurs de cuivre et les ligands N-alkyle substitués.
Les études RMN des complexes dans le C6D6 ne présentent pas de complexe de toluène mais un mélange à l’équilibre du (nacnacxylCu)2(-C6D6) et nacnacxylCu(C6D6) dans une proportion de 2 pour 1. Alors que l’addition de plus de cinquante équivalents soit de THF, soit de toluène n’induit aucun changement des spectres RMN, l’addition de 2 équivalents de MeCN conduit instantanément au complexe nacnacxylCu(MeCN). De plus, le (nacnacxylylCu)2(-C6D6) ne se coordone ni ne réagit avec le N2O, même après avoir été chauffé à 60°C pendant treize jours.
En présence de DPA (diphenylacétylène), la réaction du nacnacBnH avec le CuOtBu conduit au dimère ponté (nacnacBnCu)2(µ-DPA). L’addition d’un excès de DPA (10-12 équivalents) transforme le dimère ponté en complexe lié en position terminale nacnacBnCuDPA. Les nacnacRH (R = CH(Me)Ph et i-Pr) ne forment pas de complexe ni avec les oléfines ni avec le DPA. Une réactivité similaire a été observée avec les complexes de nacnacCH(Me)PhCu(NCMe) et nacnaci-PrCu(NCMe). Tandis que le complexe lié en position terminale par MeCN a été isolé et caractérisé, l’équilibre en solution nous laisse suspecter la formation d’un complexe d’acétonitrile ponté.
Des études de réactivité comparatives ont été menées sur quelques complexes de cuivre. La Morpholine ne réagit pas avec le nacnacBnCu(acrylonitrile) contrairement à l’acrylonitrile libre. L’expérience de l’échange d’oléfine montre que l’acrylonitrile (une oléfine électro-attractrice) se lie plus fortement que les autres oléfines, mettant ainsi en évidence l’importance de la rétrodonation face à la donation La rétrodonation est cependant faible comparée aux autres complexes de styrène structurellement caractérisés. Les complexes nacnacCH(Me)PhCuL (L = PPh3 et MeCN) ont été employés dans la cyclopropanation catalytique du styrène et dans l’addition conjuguée du ZnEt2 sur la 2-cyclohexénone, mais les résultats indiquent que le ligand dikétimine est éliminé avant son entrée dans le cycle catalytique. Par conséquent, il n’y a pas d’induction chirale.
Les complexes tétra coordinées de cuivre avec les nacnacRCu(phen) (R = Bn, CH(Me)Ph et Phen = 1,10-phenanthroline, 2-Mes-1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline (dmp) et 2,9-diphenyl-1,10-phenanthroline (dpp)) ont été synthétisés. Ces complexes sont d’une intense couleur bleue et des interactions d’empilement entre l’un des cycles phényle des ligands nacnac et la phénanthroline ont été observées dans les structures à l’état solide. Les mesures en absorption UV-visible ont été effectuées dans le toluène et les bandes MLCT sont déplacées vers le rouge par rapport à celles des complexes de cuivre et bisphénanthroline. Tous ces composés émettent à l’état solide mais les complexes 1,10-phenanthroline et 2-Mes-1,10-phenanthroline n’émettent pas en solution.
Pour renforcer les interactions d’empilement , les nouveaux ligands nacnacRH (R = CH2C6H2(OMe)3, CH2C6F5) et leurs complexes de cuivre respectifs ont été préparés avec du dmp et dpp. Afin de permettre la comparaison, le nacnaciBuCu(dmp) a été synthétisé. Alors que les complexes dmp montrent une augmentation des interactions intramoléculaires - avec les substituants phényle du ligand dikétimine et de la phénanthroline, les complexes dpp ne révèlent pas de telles interactions. Les complexes perfluorés montrent, en absorption et en émission, un déplacement significatif vers le bleu, alors que les complexes substitués par un groupements isobutyle présentent des transitions déplacées vers le rouge. Alors que les intensités de luminescence et les durées de vie sont faibles, les déplacements réduits de Stokes et les pics étroits de luminescence comparables indiquent une réduction des distorsions de l’état excité. / The ligand nacnacxylH (xyl = C6Me2H3) and the N-alkyl substituted diketimine ligands (nacnacCH(Me)PhH, nacnacBnH and nacnaciPrH) have been prepared in good yields except nacnaciPrH (23%) using a one-step procedure with the help of a Dean-Stark apparatus. Reaction of S,S-nacnacCH(Me)PhH and nacnacBnH with nBuLi in THF gave S,S-nacnacCH(Me)PhLi(THF) and nacnacBnLi(THF). Attempts to brominate these THF adducts with N-bromosuccinimide gave instead the -carbon substituted succinimido ligands S,S-succnacnacCH(Me)PhH and succnacnacBnH (succ = succinimido). Chlorination with N-chlorosuccinimide, afforded the desired product albeit with significant amounts of impurities.
Reaction of these ligands with CuOtBu (or MesCu and catalytic amounts of CuOtBu, Mes = C6Me3H2) in the presence of Lewis bases gave (nacnacxylCu)2(-toluene), nacnacxylCuCNC6H3(Me)2, nacnacCH(Me)PhCuL (L = PPh3, PMe3, CNC6H3(Me)2, DMAP, lutidine, Py, MeCN), nacnacBnCuL (L = PPh3, CNC6H3(Me)2, styrene, trans-stilbene, phenylvinylether, acrylonitrile, diphenylacetylene), nacnaciPrCuL (L = PPh3, CNC6H3(Me)2, MeCN) and succnacnacCH(Me)PhCuL (PPh3, CNC6H3(Me)2, pyridine). All complexes are yellow and sensitive to air and moisture. There was no reaction between the copper precursors and the N-alkyl substituted ligands in the absence of strong Lewis bases.
NMR studies of the complex (nacnacxylCu)2(-toluene) in C6D6, showed no toluene adduct but an equilibrium mixture of (nacnacxylCu)2(-C6D6) and nacnacxylCu(C6D6) in a ratio of 2:1. While addition of up to 50 equiv of either toluene or THF did not cause any significant change in the 1H NMR spectrum, addition of 2 equiv MeCN gave instantaneously the nacnacxylCu(MeCN) complex. In addition, (nacnacxylylCu)2(-C6D6) did not coordinate or react with N2O even after heating at 60 oC for thirteen days.
In the presence of DPA (diphenylacetylene), reaction of nacnacBnH with CuOtBu yields the bridged dimer (nacnacBnCu)2(µ-DPA). Addition of excess DPA (10-12 equiv) converts the bridged dimer to the terminally bound complex nacnacBnCuDPA. NacnacRH (R = CH(Me)Ph and i-Pr) did not form complexes with olefins or with DPA. Similar reactivity was observed in nacnacCH(Me)PhCu(NCMe) and nacnaci-PrCu(NCMe) complexes. While the terminally bound MeCN complex was isolated and characterized, equilibrium in solution led us to suspect the formation of a bridged acetonitrile adduct.
Reactivity and comparative studies were performed with several copper complexes. Morpholine did not react with nacnacBnCu(acrylonitrile) while free acrylonitrile does. Olefin exchange experiment showed that acrylonitrile (an electron withdrawing olefin) binds stronger than the other olefins examined, showing the importance of -backbonding relative to -donation. -Backbonding is, however, still low when compared other structurally characterized transition metal styrene complexes. Complexes nacnacCH(Me)PhCuL (L = PPh3 and MeCN) have been employed in catalytic cyclopropanation of styrene and the conjugate addition of ZnEt2 to 2-cyclohexenone, but results indicate that the diketimine ligand is lost before it enters the catalytic cycle. Hence, there was no chiral induction.
Four-coordinate copper(I) complexes of the form nacnacRCu(phen) (R = Bn, CH(Me)Ph and Phen = 1,10-phenanthroline, 2-Mes-1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline (dmp) and 2,9-diphenyl-1,10-phenanthroline (dpp)) were also prepared. The complexes are intensely blue in colour and intramolecular -stacking interactions between one of the phenyl rings of nacnac ligand with the phenanthroline were observed in the solid state structures. UV-vis absorption measurements were performed in toluene and the MLCT bands are red-shifted relative to those of bisphenanthroline copper complexes. All compounds are emissive in the solid state, but 1,10-phenanthroline and 2-Mes-1,10-phenanthroline complexes do not emit in solution.
To buttress the -stacking interactions, the new ligands nacnacRH (R = CH2C6H2(OMe)3, CH2C6F5) and their respective copper complexes with dmp and dpp were prepared. For the sake of comparison, nacnaciBuCu(dmp) was prepared. While the dmp complexes showed enhanced -intramolecular interactions with both phenyl substituents of the diketimine ligand and the phenanthroline, dpp revealed no such interactions. The perfluorinated complex showed a significant blue-shift in absorption and emission spectra when compared to the other complexes, while the isobutyl substituted complex displayed red-shifted transitions. While luminescence intensities and lifetimes were low, reduced Stoke shifts and comparable sharp luminescence peaks indicate reduced distortions in the excited state.
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Non-covalent interactions in solutionYang, Lixu January 2013 (has links)
Non-covalent interactions taking place in solution are essential in chemical and biological systems. The solvent environment plays an important role in determining the geometry and stability of interactions. This thesis examines aromatic stacking interactions, alkyl-alkyl interactions, edge-to-face aromatic interactions, halogen bonds and hydrogen…hydrogen interactions in solution. Chapter 1 briefly introduces the different classes of non-covalent interactions, in addition to the state-of-the-art models and methods for investigating these weak interactions. The chapter finishes with a focus on dispersion interaction in alkanes and arenes. Chapter 2 investigates dispersion interactions between stacked aromatics in solution using a new class of complexes and thermodynamic double mutant cycles (DMCs). In extended aromatics, dispersion was detected as providing a small but significant contribution to the overall stacking free energies. Chapter 3 concerns the experimental measurement of alkyl-alkyl dispersion interactions in a wide range of solvents using Wilcox torsion balances. The contribution of dispersion interactions to alkyl-alkyl association was shown to be very small, with DMC, QSPR method and Hunter's solvation model. Chapter 4 studies edge-to-face aromatic interactions in series of solvents. In the open system, edge-to-face aromatic interactions were found to be sensitive to the solvent environment. The solvent effects were complicated and cannot be rationalised by a single parameter. Further analysis is needed. Chapter 5 describes a preliminary approach to investigate organic halogen…π interactions in solution using supramolecular complexes and torsion balances. Chapter 6 is a preliminary investigation of the ability of hydrogen atoms to act as H bond acceptors in silane compounds. Computations and 1H NMR demonstrated a weak interaction between silane and perfluoro-tert-butanol.
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SYNTHESIS AND CHARACTERIZATION OFSELF-ASSEMBLY BUILDING BLOCK CONTAINING PORPHYRIN RING AND BULKY BPOSS NANOPARTICLESHuang, Xin January 2017 (has links)
No description available.
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Precision measurement of the e+e− → π + π−(γ ) cross-section with ISR methodWang, L.-L. 26 May 2009 (has links) (PDF)
Vacuum polarization integral involves the vector spectral functions which can be experimentally determined. As the dominant uncertainty source to the integral, the precision measurement of the %born cross section of $e^+e^-\rightarrow\pi^+\pi^-(\gamma)$ as a function of energy from $2\pi$ threshold to 3GeV is performed by taking the ratio of $e^+e^-\rightarrow\pi^+\pi^-(\gamma)$ cross section to $e^+e^-\rightarrow\mu^+\mu^-(\gamma)$ cross section which are both measured with {\babar\ }data using ISR method in one analysis. Besides that taking the ratio of the cross sections of the two processes can cancel several systematic uncertainties, the acceptance differences between data and MC are measured using the same data, and the corresponding corrections are applied on the efficiencies predicted by MC which can control the uncertainties. The achieved final uncertainty of the born cross section of $e^+e^-\rightarrow\pi^+\pi^-(\gamma)$ in $\rho$ mass region ($0.6\sim0.9$GeV) is 0.54\%. As a consequence of the new vacuum polarization calculation using the new precision result of the $e^+e^-\rightarrow\pi^+\pi^-(\gamma)$ cross section, the impact on the SM prediction of muon anomalous magnetic moment $g-2$ is presented, which is also compared with other data based predictions and direct measurement.
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Copolymerization and Characterization of Vinylaromatics with Fluorinated StyrenesTang, Chau N. 12 May 2008 (has links)
No description available.
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A Study of Weak Noncovalent InteractionsXue, Xiaowen 20 September 2005 (has links)
No description available.
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