Search results for "NHC"
showing 10 items of 10 documents
Miljoonat poissa kotoaan : YK:n pakolaisjärjestön toiminta itäisessä ja eteläisessä Afrikassa 1980- ja 1990-luvuilla
2002
Orbital Decomposition of the Carbon Chemical Shielding Tensor in Gold(I) N-Heterocyclic Carbene Complexes.
2020
The good performance of N‐heterocyclic carbenes (NHCs), in terms of versatility and selectivity, has called the attention of experimentalists and theoreticians attempting to understand their electronic properties. Analyses of the Au(I)–C bond in [(NHC)AuL]+/0 (L stands for a neutral or negatively charged ligand), through the Dewar–Chatt–Duncanson model and the charge displacement function, have revealed that NHC is not purely a σ‐donor but may have a significant π‐acceptor character. It turns out, however, that only the σ‐donation bonding component strongly correlates with one specific component of the chemical shielding tensor. Here, in extension to earlier works, a current density analysi…
Azolium and acetate ions in DMF: Formation of free N-heterocyclic carbene. A voltammetric analysis
2016
In order to reveal the possible formation of free N-heterocyclic carbene (NHC) in DMF-azolium and acetate solutions, the proton exchange equilibrium between azolium cations and CH3COO− was investigated (by cyclic voltammetry) by adding CH3COOH or tetrabutylammonium acetate to DMF solutions of imidazolium or thiazolium salts of different acidity.The voltammetric analysis confirms that the deprotonation of the azolium cation by CH3COO− (with the formation of free NHC) is significant in the case of the more acidic thiazolium cations, while it is not effective with the less acidic imidazolium ones.Accordingly, the NHC-catalyzed benzoin condensation was carried out in DMF solutions of azolium sa…
Complejos NHC–Metal en la funcionalización de hidrocarburos; procesos en batch y en flujo
2017
Desde hace muchos años, la catálisis juega un papel fundamental en distintas áreas, tanto del ámbito académico como del industrial, ya que facilita la síntesis de productos de gran impacto para la sociedad. Actualmente, industrias como la petroquímica, la farmacéutica, la cosmética, o la alimentaria, entre otras, dependen en gran medida de la catálisis. En la búsqueda de sistemas catalíticos óptimos que permitan llevar a cabo transformaciones eficientes, selectivas y que minimicen el costo energético y la producción de residuos, surgió la catálisis metálica, principalmente basada en complejos de metales de transición como catalizadores. Estos complejos han tenido una importante evolución, d…
The role of the International Organization for Migration and the UNHCR in the EU and Italy: Still entrapped by a securitization approach to Mediterra…
2019
Mediterranean migration flows have been managed, so far, by revitalizing the traditional remits, such as border control, of the state. Recent years have seen the growth of nationalist parties, able to exploit migrant flows to expand their support. Rescue operations have also received widespread criticism from several other actors, instead others have expressed anxiety about the lack of concern, on the part of state representatives, for the humanitarian dimension of the phenomenon. The EU has not been able to act as a counterweight and has shown all the difficulties involved in enhancing solidarity and responsibility-sharing between member states. Moreover, there is a lack of mutual trust af…
NHC-Based Iron Sensitizers for DSSCs
2018
International audience; Nanostructured dye-sensitized solar cells (DSSCs) are promising photovoltaic devices because of their low cost and transparency. Ruthenium polypyridine complexes have long been considered as lead sensitizers for DSSCs, allowing them to reach up to 11% conversion efficiency. However, ruthenium suffers from serious drawbacks potentially limiting its widespread applicability, mainly related to its potential toxicity and scarcity. This has motivated continuous research efforts to develop valuable alternatives from cheap earth-abundant metals, and among them, iron is particularly attractive. Making iron complexes applicable in DSSCs is highly challenging due to an ultrafa…
Bezvalstnieka termins ANO 1954. gada Konvencijā par bezvalstnieka statusu, tā norobežošana no valsts piederīgajiem: Latvijas nepilsoņa statuss
2017
Starptautiskajās tiesībās pastāv divi statusi, kuri tiek jaukti. Bezvalstnieka statuss, kuru izveidoja 1954. gadā, lai noregulētu to cilvēku statusu, kuri bija zaudējuši pilsonību pēc otrā pasaules kara. Nepilsoņa statuss, kuru izveidoja 1995. gadā, lai noregulētu to cilvēku statusu, kuri zaudēja pilsonību Padomju Sociālistiskās Republikas sabrukuma rezultātā. Darba mērķis noskaidrot vai starp šiem statusiem pastāv atšķirības. Darba rezultātā autore secina, ka nepilsoņa statuss ir pietuvināts pilsonībai, jo nepilsonim ir piešķirtas gandrīz visas pilsoņa tiesības. Līdz ar to, šie abi statusi nevar tikt uzskatīti par līdzīgiem, jo vienīgā līdzība, kura saista šos abus statusus ir pilsonības t…
Photophysical Investigation of Iron(II) Complexes Bearing Bidentate Annulated Isomeric Pyridine-NHC Ligands
2020
The possibility of achieving luminescent and photophysically active metal-organic compounds relies on the stabilization of charge transfer states and kinetically and thermodynamically blocking non-...
Crystal structure of 3-mesityl-1-[(pyridin-2-yl)methyl]-3,4,5,6-tetrahydropyrimidin-1-ium bromide monohydrate
2015
In the title hydrated salt, C19H24N3+·Br−·H2O, the values of the N—C bond lengths within the tetrahydropyrimidinium ring indicate delocalization of the N=C double bond. In the cation, the dihedral angle formed by the pyridine and benzene rings is 14.97 (12)°. In the crystal, ions and water molecules are linked by O—H...Br, O—H...N, C—H...Br and C—H...O hydrogen bonds into chains running parallel to thebaxis.
Palladium-NHC (NHC = N-heterocyclic Carbene)-Catalyzed Suzuki–Miyaura Cross-Coupling of Alkyl Amides
2022
We report the Pd-catalyzed Suzuki–Miyaura cross-coupling of aliphatic amides. Although tremendous advances have been made in the cross-coupling of aromatic amides, C–C bond formation from aliphatic amides by selective N–C(O) cleavage has remained a major challenge. This longstanding problem in Pd catalysis has been addressed herein by a combination of (1) the discovery of N,N-pym/Boc amides as a class of readily accessible amide-based reagents for cross-coupling and (2) steric tuning of well-defined Pd(II)-NHC catalysts for cross-coupling. The methodology is effective for the cross-coupling of an array of 3°, 2°, and 1° aliphatic amide derivatives. The catalyst system is user-friendly, sinc…