Search results for "405"
showing 10 items of 3208 documents
Interpenetrated Luminescent Metal-Organic Frameworks based on 1H-Indazole-5-carboxylic Acid
2020
Herein we report the formation and characterization of two novel Zn-based multifunctional metal-organic frameworks (MOFs) based on 1H-indazole-5-carboxylic acid and bipyridine-like linkers, synthesized by soft solvothermal routes. These materials possess isoreticular 2-fold interpenetrated three-dimensional structures that afford a flexible character and allow porosity modulation of the MOFs as confirmed by CO2 sorption measurements. Apart from this attractive structural feature, the MOFs exhibit fascinating luminescent properties involving both luminescence thermometry and long-lasting phosphorescence.
Understanding the domino reactions of alkyne-tethered N-tosylhydrazones yielding fused polycyclic pyrazoles. An MEDT study
2019
Abstract The domino reactions of alkyne-tethered N-mesylhydrazones yielding fused polycyclic pyrazoles have been studied within the Molecular Electron Density Theory (MEDT). Analysis of the Gibbs free energies indicates that the more favourable reactive path is the one in which the elimination of mesylate anion takes place before the intramolecular [3 + 2] cycloaddition (IM32CA) reaction, which corresponds with the rate-determining step of these domino processes. ELF topological analysis of the bond formation along the IM32CA reaction indicates that in spite of the high activation energy associated to this intramolecular reaction, it shows a pmr-type mechanism characterised by the presence …
Structure and reactivity of a mononuclear gold(II) complex.
2017
Mononuclear gold(II) complexes are very rare labile species. Transient gold(II) species have been suggested in homogeneous catalysis and in medical applications, but their geometric and electronic structures have remained essentially unexplored: even fundamental data, such as the ionic radius of gold(II), are unknown. Now, an unprecedentedly stable neutral gold(II) complex of a porphyrin derivative has been isolated, and its structural and spectroscopic features determined. The gold atom adopts a 2+2 coordination mode in between those of gold(III) (four-coordinate square planar) and gold(I) (two-coordinate linear), owing to a second-order Jahn–Teller distortion enabled by the relativistical…
Distance Matters: Biasing Mechanism, Transfer of Asymmetry, and Stereomutation in N-Annulated Perylene Bisimide Supramolecular Polymers
2021
International audience; The synthesis of two series of N-annulated perylene bisimides (PBIs), compounds 1 and 2, is reported, and their self-assembling features are thoroughly investigated by a complete set of spectroscopic measurements and theoretical calculations. The study corroborates the enormous influence that the distance between the PBI core and the peripheral groups exerts on the chiroptical properties and the supramolecular polymerization mechanism. Compounds 1, with the peripheral groups separated from the central PBI core by two methylenes and an ester group, form J-type supramolecular polymers in a cooperative manner but exhibit negligible chiroptical properties. The lack of cl…
New hexanuclear FeIII clusters with the gem-diol hydrated form of di(2-pyridyl)ketone and carboxylato ligands: Crystal structures and magnetic proper…
2019
Abstract The hexanuclear compounds [Fe6O2Cl2{(py)2CO2}2(pyOH)2(pyCOO)2(ButCOO)6] (1) and [Fe6O2{(py)2CO2}2(pyCOO)4(ButCOO)6] (2) were obtained by condensation of the trinuclear μ3-oxo-centered iron(III) pivalate [Fe3O(ButCOO)6(H2O)3]+ in the presence of di(2-pyridyl)ketone [(py)2CO] in MeCN at ambient temperature. Both complexes contain an analogous core which can be described as two {Fe3O}7+ units joined by gem-diolato (py)2CO22− bridges. Variable-temperature magnetic susceptibility measurements in polycrystalline samples of 1 and 2 reveal strong antiferromagnetic couplings between the iron(III) ions leading to S = 0 ground states.
Structural and magnetic properties of polynuclear oximate copper complexes with different topologies
2017
Abstract Two new copper(II) complexes containing the methyl(2-pyridyl)ketone oxime ligand (mpkoH) [Cu3(OH)(ClO4)2(mpko)3]·CH3OH (1) and [Cu(ClO4)(mpko)(mpkoH)]n (2) have been prepared from Cu(ClO4)2 and mpkoH in different metal-to-ligand molar ratios. In addition, the compound [Cu{(mpko)2BF2}(H2O)](BF4) (3) [(mpko)2BF2 is the fluoroboration product of the oxime] has been obtained when replacing Cu(ClO4)2 by Cu(BF4)2. Compound 1 is an isolated triangle with a {Cu3(µ3-OH)}5+ core, whereas 2 is a chain of CuII ions linked by anionic mpko− bridges. 1 exhibits strong antiferromagnetic competing interactions, as well as antisymmetric exchange. On the other hand, very weak ferromagnetic interactio…
Carbonylmolybdenum complexes with di(imino)pyridine and related ligands: Reduction of a di(imino)pyridine to an aminoiminopyridine system under mild …
2006
Abstract The reactions of [Mo(CO) 6 ] towards a 2,6-di(imino)pyridine L 1 and related ligands were studied. The reaction with L 1 afforded two new complexes, [Mo(CO) 4 L 1 ] ( 1 ) and [Mo(CO) 4 L 2 ] ( 2 ), where L 2 is the 2-amino-6-iminopyridine ligand arising from the hydrogenation of one imine function of L 1 ; similar reaction with a 2-acetyl-6-iminopyridine ligand L 3 afforded [Mo(CO) 4 L 3 ] ( 3 ). Compounds 1 , 2 and 3 have been fully characterised by IR, 1 H NMR and X-ray crystallography; they present a metal ion in a pseudo-octahedral environment, the three organic ligands acting with bidentate N 2 coordination modes. One of the imine functions in 1 , the amine function in 2 , and…
Hantzsch Ester-Mediated Photochemical Transformations in the Ketone Series: Remote C(sp3)–H Arylation and Cyclopentene Synthesis through Strain Relea…
2021
A metal-free Hantzsch ester-mediated synthesis of cyclopentenylketones as well as γ-hetarylketones starting from ketocyclopropanes under eco-friendly conditions was developed. The versatility of the developed conditions is shown by reacting ketocyclopropanes in both a formal [3 + 2] cycloaddition with terminal alkynes (further investigated using theoretical calculations) and a radical C-C-coupling with cyanopyridines. The newly developed methodologies were later on utilized as a downstream reaction for photogenerated cyclopropanes combining UV and visible light photochemistry. Following this procedure, a UV-driven Norrish-Yang-type reaction induces the ring strain of the intermediates, whic…
Are Heme-Dependent Enzymes Always Using a Redox Mechanism? A Theoretical Study of the Kemp Elimination Catalyzed by a Promiscuous Aldoxime Dehydratase
2020
The design of biocatalysts is a goal to improve the rate, selectivity and environmental friendship of chemical processes in biotechnology. In this regard, the use of computational techniques has provided valuable assistance in the design of enzymes with remarkable catalytic activity. In this paper, hybrid QM/MM simulations have allowed getting an insight into the mechanism of a promiscuous aldoxime dehydratase (OxdA) for the Kemp elimination. We first demonstrate that, based on the use of linear response approximation (LRA) methods, the lowest energy electronic state of the benzisoxazole placed in the active sit of OxdA corresponds to a singlet state, being the triplet and the quintet state…
Sublimable Single Ion Magnets Based on Lanthanoid Quinolinate Complexes: The Role of Intermolecular Interactions on Their Thermal Stability
2018
We report the design, preparation, and characterization of two families of thermally robust coordination complexes based on lanthanoid quinolinate compounds: [Ln(5,7-Br2q)4]− and [Ln(5,7-ClIq)4]−, where q = 8-hydroquinolinate anion and Ln = DyIII, TbIII, ErIII, and HoIII. The sodium salt of [Dy(5,7-Br2q)4]− decomposes upon sublimation, whereas the sodium salt of [Dy(5,7- ClIq)4]−, which displays subtly different crystalline interactions, is sublimable under gentle conditions. The resulting film presents low roughness with high coverage, and the molecular integrity of the coordination complex is verified through AFM, MALDI-TOF, FT-IR, and microanalysis. Crucially, the single-molecule magnet …