Search results for "LTA"
showing 10 items of 5738 documents
Radical cation and dication of a 4H-dithieno[2,3-b:3′,2′-e][1,4]-thiazine
2017
A p-tert-butylphenyl substituted 4H-dithieno[2,3-b:3′,2′-e][1,4]thiazine was synthesized by twofold Buchwald–Hartwig coupling. The electronic properties (UV/Vis, cyclic voltammetry and spectroelectrochemistry) and the DFT- and TD DFT-calculated electronic structure reveal that the parent system and the radical cation and dication oxidation products are highly polarizable π-systems with strong charge transfer contributions. The radical cation and the dication were prepared by oxidation with antimony(V) pentachloride, giving stable deeply colored salts. EPR spectroscopy of the radical cation furnishes hyperfine coupling constants with the nitrogen nucleus and the α-thienyl protons. The dicati…
Synthesis, crystal structure and magnetic properties of [Co(bpcam)2]ClO4·dmso·H2O, [Co(bpcam)2]2[Co(NCS)4]·dmso·H2O and [Ni(bpcam)2]·H2O [Hbpcam = bi…
2017
The preparation, spectroscopic characterization, structural study and magnetic investigation of three new complexes of formula [Co(bpcam)2]ClO4·dmso·H2O (1), [Co(bpcam)2]2[Co(NCS)4]·dmso·H2O (2) and [Ni(bpcam)2]·H2O (3) [Hbpcam = bis(2-pyrimidylcarbonyl)amide] are reported. Each bpcam group in 1–3 acts as a tridentate ligand being coordinated to the cobalt(III) (1 and 2)/nickel(II) (3) ions through three nitrogen atoms in a mer-arrangement. Six-coordinate cobalt(III) and nickel(II) occur in 1 and 3 respectively, whereas six-coordinate cobalt(III) and four-coordinate cobalt(II) coexist in 2. Cyclic voltammetry of 1 in acetonitrile shows the occurrence of one quasi reversible CoIII ↔ CoII pro…
Mono‐ and Bis(imidazolidinium ethynyl) Cations and Reduction of the Latter To Give an Extended Bis‐1,4‐([3]Cumulene)‐ p ‐carboquinoid System
2018
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.
Structure and properties of a novel staircase-like decanuclear [CuII10] cluster supported by carbonate and carboxylate bridges
2018
This article describes a novel staircase-like decanuclear copper(II) cluster [CuII10(cpdp)4(CO3)4(CH3OH)2]·3.33CH3OH·7.83H2O (1) (H3cpdp = N,N′-bis[2-carboxybenzomethyl]-N,N′-bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol) composed of a pair of [CuII5] pentamers. In methanol, the reaction of H3cpdp with Cu(NO3)2·3H2O in the presence of K2CO3 leads to the isolation of complex 1. This complex has been characterized by various analytical techniques including single crystal X-ray crystallography. Structural analysis reveals that the two [CuII5] pentameric units are bridged together exclusively by two μ2:η2:η1 carbonate groups. Complex 1 shows a rare μ3:η2:η1:η1 bridging coordination mode of four b…
Synthesis, reactivity and structural studies of selenide bridged carboranyl compounds.
2006
Reaction of the lithium salt Li[1-R-1,2-closo-C(2)B(10)H(10)] with selenium under mild conditions, followed by hydrolysis gave the diselenide compound (1-Se-2-R-1,2-closo-C(2)B(10)H(10))(2) in contrast to the well-reported mercapto compounds 1-SH-2-R-1,2-closo-C(2)B(10)H(10) obtained using a similar synthetic procedure. Details for the preparation and X-ray structural characterisation of the new compounds (2-Me-1,2-closo-C(2)B(10)H(10))(2)Se, (1-Se-2-R-1,2-closo-C(2)B(10)H(10))(2) (R = Me, Ph, ) are specified. To further explore the mechanism of the dimerization reaction, the complex [Au(1-Se-2-Me-1,2-closo-C(2)B(10)H(10))(PPh(3))] was synthesized, confirming the existence of the intermedia…
Unexpected Scholl Reaction of 6,7,13,14-Tetraarylbenzo[k]tetraphene: Selective Formation of Five-Membered Rings in Polycyclic Aromatic Hydrocarbons
2016
Cyclodehydrogenation is a versatile reaction that has enabled the syntheses of numerous polycyclic aromatic hydrocarbons (PAHs). We now describe a unique Scholl reaction of 6,7,13,14-tetraarylbenzo[k]tetraphene, which "unexpectedly" forms five-membered rings accompanying highly selective 1,2-shift of aryl groups. The geometric and optoelectronic nature of the resulting bistetracene analogue with five-membered rings is comprehensively investigated by single-crystal X-ray, NMR, UV-vis absorption, and cyclic voltammetry analyses. Furthermore, a possible mechanism is proposed to account for the selective five-membered-ring formation with the rearrangement of the aryl groups, which can be ration…
Catalytic activity of biscobalt porphyrin-corrole dyads toward the reduction of dioxygen
2009
A series of biscobalt cofacial porphyrin-corrole dyads bearing mesityl substituents at the meso positions of the corrole ring were investigated as to their electrochemistry, spectroelectrochemistry, and CO binding properties in nonaqueous media and then applied to the surface of a graphite electrode and tested as electrocatalysts for the reduction of dioxygen to water or hydrogen peroxide in air-saturated aqueous solutions containing 1 M HClO(4). The catalytic reduction of O(2) with the same dyads was also investigated in the homogeneous phase using 1,1'-dimethylferrocene as a reductant in PhCN containing HClO(4). The examined compounds are represented as (PMes(2)CY)Co(2), where P = a porph…
A reinvestigation of compound CpMo(PMe3)2(CH3)2: Alkylation by single electron transfer and radical addition?
2001
International audience; The synthesis of the half-sandwich molybdenum(III) diphosphine dimethyl complex CpMo(PMe3)2(CH3)2 has been reinvestigated. The compound was obtained from the corresponding dichloro complex CpMo(PMe3)2Cl2 and methyllithium at low temperatures and isolated as a crystalline product by conducting all operations at temperatures lower than −10 °C. The complex is thermally unstable at room temperature but has been fully characterised by EPR spectroscopy, cyclic voltammetry and X-ray diffraction. The formation reaction is retarded by excess phosphine. On the basis of this and other related observations, a mechanism involving phosphine pre-dissociation followed by single elec…
Subarcsecond Location of IGR J17480-2446 with Rossi XTE
2012
On 2010 October 13, the X-ray astronomical satellite Rossi XTE, during the observation of the newly discovered accretion powered X-ray pulsar IGR J17480--2446, detected a lunar occultation of the source. From knowledge of lunar topography and Earth, Moon, and spacecraft ephemeris at the epoch of the event, we determined the source position with an accuracy of 40 mas (1{\sigma} c.l.), which is interesting, given the very poor imaging capabilities of RXTE (\sim 1\circ). For the first time, using a non-imaging X-ray observatory, the position of an X-ray source with a subarcsecond accuracy is derived, demonstrating the neat capabilities of a technique that can be fruitfully applied to current a…
The size, shape, density and ring of the dwarf planet Haumea from a stellar occultation
2017
Ortiz, José Luis et. al.