Synthesis and coordination chemistry of ferrocenyl-1,2,3-triazolyl ligands

"Click" reactions between ethynylferrocene and mono-, bis-, and tris-azido aromatic derivatives yielded mono-, bis-, and tris-1,2,3-ferrocenyltriazoles (1, 2, and 3, respectively) as orange crystals. The X-ray crystal structure of the monoferrocenyltriazole compound 1 was solved with two nearly identical molecules within the asymmetric unit. In both molecules, the two Cp rings make a tilt angle of 2.1(3) degrees [0.7(3) degrees], and they are roughly eclipsed with a twist angle of 2.4(3) degrees [1.8(3) degrees]. Reaction of 1 with [PdCl2(PhCN)2] in dimethylsulfoxide (DMSO) yielded orange crystals of [PdCl2L2] (4; L=1), for which the X-ray crystal structure shows trans coordination to the nitrogen atom close to the ferrocene substitution. The Pd atom is located on an inversion center and displays a nearly perfect square planar environment. In DMSO-d6, 4 reversibly dissociates to regenerate 1, whose (1)H NMR spectrum is then observed. The 1H NMR study also shows that progressive addition of PdCl2 or [PdCl2(NCR)2] (R=Me or Ph) to DMSO-d6 solutions of 1 reversibly leads to the formation of 4 and the addition of excess PdII is necessary to lead to the complete disappearance of the signals of 1. The cyclic voltammograms of 1, 2, and 3 show the reversible oxidation wave of the ferrocenyl group, and that of 4 shows that this wave appears with increased intensity tentatively attributable to redox-catalyzed oxidation.     

Mid/far-infrared photo-detectors based on graphene asymmetric quantum wells

We conducted a theoretical study on the electronic properties of a single-layer graphene asymmetric quantum well.Quantification of energy levels is limited by electron–hole conversion at the barrier interfaces and free-electron continuum.Electron–hole conversion at the barrier interfaces can be controlled by introducing an asymmetry between barriers and taking into account the effect of the interactions of the graphene sheet with the substrate.The interaction with the substrate induces an effective mass to carriers,allowing observation of Fabry–P′erot resonances under normal incidence and extinction of Klein tunneling.The asymmetry,between barriers creates a transmission gap between confined states and free-electron continuum,allowing the large graphene asymmetric quantum well to be exploited as a photo-detector operating at mid-and far-infrared frequency regimes.     

Dual role of price and myopia in a marketing channel

In this paper we study a dynamic two-player channel where the manufacturer controls the wholesale price and the investment in quality and the retailer chooses the retail price. We consider that the retail price affects both the demand and the perceived quality of the brand and that its variations contribute to the building of an internal reference price. One of the model’s distinctive features is that it accounts for the two meanings of price, i.e., its classical objective measure of the cost of acquiring a particular quantity of the product, and its subjective roles as an assessment of the quality of the product and an evaluation of gains or losses (deal vs. sacrifice) resulting from buying a “cheap” or an “expensive” product. This dual computation is done with respect to the internal reference price.     

Characterization and Catalytic Properties of Aerogel Chromium Oxide Supported by Alumina or Silica

Alumina or silica supported chromium oxide catalysts prepared by sol-gel technique have been investigated by X-ray diffraction, BET analysis, combined diffuse reflectance spectroscopy, EPR and reduction-extraction by ethane 1,2 diol. The results reveal the presence of Cr³⁺, Cr⁵⁺ and Cr⁶⁺ ions. Chromium species Cr⁶⁺ are isolated and atomically dispersed on the alumina support as free chromate CrO ₄ ^2– while on silica, dichromate or polychromate species like Cr₂O ₇ ^2– or Cr₃O ₁₀ ^2– predominate. Chromium oxide exhibits a better catalytic properties for paraxylene partial oxidation, when it is supported on alumina. The difference of oxidation states and degree of oligomerisation of chromium on the two supports affects the catalytic properties.     

An efficient one-pot synthesis of N-(substituted phenyl)-1,2,5-thiadiazolidine-2-carboxamide 1,1-dioxide derivatives

1,2,5-Thiadiazolidine-1,1-dioxide carboxamide derivatives 3a-3n are novel heterocyclic compounds synthesized by multicomponent condensation reaction in one pot of aniline, chlorosulfonyl isocyanate, and 2-chloroethylamine hydrochloride which is used as a useful precursor under mild conditions. This reaction is realized with high atom economy, at room temperature and in a short reaction time. Series of these desired products are obtained from good to excellent yields within 2 hours in all cases. All the synthesized compounds are characterized by ¹H, ¹³C NMR, MS, and HMBC/HSQC spectroscopy.     

Efficient solid-phase synthesis of sulfahydantoins

A novel solid-phase strategy allows the efficient preparation of "traceless" sulfahydantoins. A total of 28 derivatives, with crude purity generally higher than 85%, were prepared by parallel synthesis. Through reductive alkylations, Mitsunobu reactions, and sulfamoylation reactions on oxime resin, the synthetic strategy affords sulfahydantoin derivatives selectively substituted at N(2), N(5) and N(2), N(5) positions, although yields of disubstituted compounds are lower. The mild reaction conditions involved lead to sulfahydantoins without racemization.     

EPR and UV–visible spectroscopic studies of alumina-supported chromium oxide catalysts

The oxidation state, the mobility and the molecular structure of chromium species present on CrO_x–Al₂O₃ catalysts have been studied by combined diffuse reflectance spectroscopy, EPR and reduction–extraction by ethane 1,2 diol. CrO₄²⁻ species exist on the alumina surface in the form of loosely-interacting species on hydrated surface (species A) and in the form of strongly bonded species on dehydrated Al₂O₃ surface (species B). The CrO₄²⁻ species show high mobility and are probably responsible for the formation of CrO_x clusters.     

Hybrid excitons in organic–inorganic semiconducting quantum wells in a microcavity

We investigate theoretically the optical properties of composite organic–inorganic semiconductor quantum wells. These properties are dominated by hybrid Frenkel (or charge-transfer) and Wannier–Mott excitonic states. An important effect is the possibility of using the Stark shift to tune the resonance between Frenkel and Wannier–Mott excitons. This fact is very important from a practical point of view because it may be difficult to grow such a structure exactly at resonance. We also discussed the coupling of Frenkel or charge transfer and Wannier–Mott exciton through a microcavity photon. We evaluate the hybrid exciton-polariton Rabi splitting. In the strong coupling regime the Rabi splitting depends essentially on the oscillator strength of the Frenkel or charge-transfer exciton.     

Syntheses, X-ray structures, solid state high-field electron paramagnetic resonance, and density-functional theory investigations on chloro and aqua Mn(II) mononuclear complexes with amino-pyridine pentadentate ligands

The two pentadentate amino-pyridine ligands L5(2) and L5(3) (L5(2) and L5(3) stand for the N-methyl-N,N',N'-tris(2-pyridylmethyl)ethane-1,2-diamine and the N-methyl-N,N',N'-tris(2-pyridylmethyl)propane-1,3-diamine, respectively) were used to synthesize four mononuclear Mn(II) complexes, namely [(L5(2))MnCl](PF6) (1(PF6)), [(L5(3))MnCl](PF6) (2(PF6)), [(L5(2))Mn(OH2)](BPh4)2 (3(BPh4)2), and [(L5(3))Mn(OH2)](BPh4)2 (4(BPh4)2). The X-ray diffraction studies revealed different configurations for the ligand L5(n) (n = 2, 3) depending on the sixth exogenous ligand and/or the counterion. Solid state high-field electron paramagnetic resonance spectra were recorded on complexes 1-4 as on previously described mononuclear Mn(II) systems with tetra- or hexadentate amino-pyridine ligands. Positive and negative axial zero-field splitting (ZFS) parameters D were determined whose absolute values ranged from 0.090 to 0.180 cm(-1). Density-functional theory calculations were performed unraveling that, in contrast with chloro systems, the spin-spin and spin-orbit coupling contributions to the D-parameter are comparable for mixed N,O-coordination sphere complexes.     

Efficient Synthesis of Modified Sulfamides and Cyclosulfamides Containing Phosphonate Moieties

Abstract

The synthesis of two new series of functionalized phosphonates is described. A new entry for the synthesis of 5-phosphonoalkyl cyclosulfamides and bis(phosphonoalkyl) sulfamides starting from dihalogeno bis(amino) sulfone has been developed. These compounds have been synthesized in good yields. Triethylphosphite has been used to introduce the phosphonate moiety into sulfamides and cyclosulfamides via Arbuzov reaction.