Search results for "405"
showing 10 items of 3208 documents
Synthesis, characterization and magnetic study of two new octahedral iron(III) complexes with pendant zwitterionic Schiff bases
2016
Two Schiff bases, HL1 [2-((3-(dimethylamino)propylimino)methyl)-5-bromophenol] and HL2 [2-((2-(diethylamino)ethylimino)methyl)-6-methoxyphenol], have been employed to prepare two new octahedral iron(III) complexes, [Fe(HL1)2(N3)2]ClO4·2H2O (1) and [Fe(HL2)2(NCS)2]ClO4·H2O (2). Both complexes are characterized by spectral and elemental analyses. Single crystal X-ray diffraction studies confirm their structures. In both complexes, Schiff bases are trapped in their zwitterionic forms and coordinated to iron(III) only through the imine nitrogen and phenoxo oxygen, i.e., they behave as bi-dentate ligands, keeping the remaining potential donor sites pendant. The measurement of χM vs. T for both c…
Spontaneous Resolution of an Electron‐Deficient Tetrahedral Fe4L4cage
2015
A highly electron-deficient C3-symmetric tris(bipyridyl) ligand was prepared in four steps and used for the coordination of Fe(OTf)2, thereby resulting in the homochiral assembly of a new family of robust tetrahedral M4L4 cages. This homochiral T-symmetric cage containing a relatively large cavity of 330 A(3) is capable of encapsulating an anionic guest, as was determined by mass spectrometry, (19)F NMR spectroscopy, and finally shown from its crystal structure. Moreover, crystallization of the cage from CH3CN led to crystals containing both (ΔΔΔΔ and ΛΛΛΛ) enantiomers, while crystallization from CH3 OH resulted in crystals containing only the right-handed (ΔΔΔΔ) cage. The difference in the…
Mono‐ and Bis(imidazolidinium ethynyl) Cations and Reduction of the Latter To Give an Extended Bis‐1,4‐([3]Cumulene)‐p-carboquinoid System
2017
An extended π-system containing two [3]cumulene fragments separated by a p-carboquinoid and stabilized by two capping N-heterocyclic carbenes (NHCs) has been prepared. Mono- and bis(imidazolidinium ethynyl) cations have also been synthesized from the reaction of an NHC with phenylethynyl bromide or 1,4-bis(bromoethynyl)benzene. Cyclic voltammetry coupled with synthetic and structural studies showed that the dication is readily reduced to a neutral, singlet bis-1,4-([3]cumulene)-p-carboquinoid as a result of the π-accepting properties of the capping NHCs. peerReviewed
A new member of the fusaricidin family – structure elucidation and synthesis of fusaricidin E
2017
Two hitherto unknown fusaricidins were obtained from fermentation broths of three Paenibacillus strains. After structure elucidation based on tandem mass spectrometry and NMR spectroscopy, fusaricidin E was synthesized to confirm the structure and the suggested stereochemistry. The synthesis was based on a new strategy which includes an efficient access to the 15-guanidino-3-hydroxypentadecanoyl (GHPD) side chain from erucamide.
An easy access to fused chromanones via rhodium catalyzed oxidative coupling of salicylaldehydes with heterobicyclic olefins
2016
Abstract Herein we describe a detailed study on the rhodium catalyzed oxidative coupling of salicylaldehydes with heterobicyclic olefins such as diazabicyclic olefins and urea-derived bicyclic olefins. The developed method provides an ideal route to fused chromanone systems in a single synthetic step. Moreover, the scope of this methodology was extended to different oxa/aza-bridged bicyclic urea derivatives.
Efficient photoinduced electron transfer in a porphyrin tripod-fullerene supramolecular complex via pi-pi interactions in nonpolar media.
2010
A novel porphyrin tripod (TPZn(3)) was synthesized via "click chemistry". Three porphyrin moieties of TPZn(3) are geometrically close and linked by a flexible linker. The electron-transfer oxidation of TPZn(3) results in intramolecular pi-dimer formation between porphyrin moieties as indicated by electrochemical, vis-NIR, and ESR measurements. The cyclic voltammogram of TPZn(3) exhibited stepwise one-electron oxidation processes of three porphyrin moieties in the range from 0.58 to 0.73 V (vs SCE in CH(2)Cl(2)). When TPZn(3) was oxidized by tris(2,2'-bipyridyl)-ruthenium(III) ([Ru(bpy)(3)](3+)), the oxidized species (TPZn(3))(n+) (0n/= 3) exhibited a charge resonance band in the NIR region …
Special Issue: Improvements for Resveratrol Efficacy
2017
International audience; Resveratrol is a well-known phenolic stilbene because of its presence in several edible plants and its proposed properties that are beneficial to human health [...].
Structural, thermal and photomagnetic properties of spin crossover [Fe(bpp)2]2+ salts bearing [Cr(L)(ox)2]- anions
2009
International audience; This paper is divided into two parts: in the first part, the influence of solvate molecules on the magnetic properties of spin crossover salts of [Fe(bpp)(2)][Cr(L)(ox)(2)]ClO(4) x nS (bpp = 2,6-bis(pyrazol-3yl)pyridine; L = 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen); ox = oxalate dianion; S = solvent) is analyzed. The second part is devoted to the photomagnetic properties of the previously reported [Fe(bpp)(2)][Cr(L)(ox)(2)](2) family of compounds. The study describes the crystal structure, differential scanning calorimetry (DSC) and magnetic properties of [Fe(bpp)(2)][Cr(bpy)(ox)(2)]ClO(4) x EtOH x 4 H(2)O (1) and [Fe(bpp)(2)][Cr(phen)(ox)(2)]ClO(4) x 1.5 …
Substituent effects of nitro group in cyclic compounds
2020
AbstractNumerous studies on nitro group properties are associated with its high electron-withdrawing ability, by means of both resonance and inductive effect. The substituent effect of the nitro group may be well described using either traditional substituent constants or characteristics based on quantum chemistry, i.e., cSAR, SESE, and pEDA/sEDA models. Interestingly, the cSAR descriptor allows to describe the electron-attracting properties of the nitro group regardless of the position and the type of system. Analysis of classical and reverse substituent effects of the nitro group in various systems indicates strong pi-electron interactions with electron-donating substituents due to the re…
Syntheses of Trifluoroethylated N-Heterocycles from Vinyl Azides and Togni’s Reagent Involving 1,n-Hydrogen-Atom Transfer Reactions
2020
2,2,2-Trifluoroethyl-substituted 3-oxazolines, 3-thiazolines, and 5,6-dihydro-2H-1,3-oxazines have been obtained by reacting substituted vinyl azides with a combination of Togni’s reagent and substoichiometric amounts of iron(II) chloride. The results of density functional theory calculations support the proposed mechanism involving 1,n-hydrogen-atom transfer reactions. peerReviewed