Search results for "Catalysis"
showing 10 items of 5944 documents
Inside Cover: An Unusually Small Singlet-Triplet Gap in a Quinoidal 1,6-Methano[10]annulene Resulting from Baird’s 4nπ-Electron Triplet Stabilization…
2015
Dopamine interaction with a polyamine cryptand of 1H-pyrazole in the absence and in the presence of Cu(ii) ions. Crystal structure of [Cu2(H−1L](ClO4…
2000
The crystal structure of the binuclear Cu2+ complex [Cu2(H−1L)](ClO4)3 ·2H2O of the cryptand L = 1,4,7,8,11,14,17,20,21,24,29,32,33,36-tetradecaazapentacyclo[12.12.12.1 6,9.119,22,1,31,34]hentetraconta-6,9(41), 19(40), 21,31,34(39)-hexaene is presented; evidence for the formation in solution of binary L–dopamine and ternary Cu2+–L–dopamine complexes is presented.
HC-SCR of NOx over Ag/alumina: a combination of heterogeneous and homogeneous radical reactions?
2005
Matrix isolation combined with EPR and FT-IR technique at low temperature has been used to study the gas phase species involved in HC-SCR over a highly active Ag/alumina catalyst. A combination of heterogeneous and homogeneous (radical) reactions is proposed to take place over a Ag/alumina catalyst during HC-SCR. Radicals of low molecular weight were trapped in a growing argon matrix behind the Ag/alumina catalyst. In the same matrix, cyanogen isocyanate was detected and is suggested to be a key intermediate for the formation of amines and ammonia via the hydrolysis of isocyanate species.
Cover Feature: Highly Enantioselective Kinetic Resolution of Michael Adducts through N-Heterocyclic Carbene Catalysis: An Efficient Asymmetric Route …
2018
SBA-15/POSS-Imidazolium Hybrid as Catalytic Nanoreactor
2019
Supported imidazolium modified polyhedral oligomeric silsesquioxanes (POSS) on SBA-15 have been used as platform for Pd(II) species. The so-obtained material was firstly characterized by means of TGA, solid state NMR, TEM, XPS, SAXS, porosimetry and ICP-OES and it was successfully tested as pre-catalyst in C−C cross couplings, namely Suzuki-Miyaura and Heck reactions. In both cases, the solid proved to be highly efficient and easily recoverable from the reaction mixture. The recyclability was verified for up to seven cycles without showing any activity decrease. Interestingly, only Pd(II) was detected in the reused catalyst in the Heck reaction. Therefore, the versatility of the material w…
Solution Synthesis of a New Thermoelectric Zn1-xSb Nanophase and Its Structure Determination Using Automated Electron Diffraction Tomography
2010
Engineering materials with specific physical properties have recently focused on the effect of nanoscopic inhomogeneities at the 10 nm scale. Such features are expected to scatter medium- and long-wavelength phonons thereby lowering the thermal conductivity of the system. Low thermal conductivity is a prerequisite for effective thermoelectric materials, and the challenge is to limit the transport of heat by phonons, without simultaneously decreasing charge transport. A solution-phase technique was devised for synthesis of thermoelectric "Zn(4)Sb(3)" nanocrystals as a precursor for phase segregation into ZnSb and a new Zn-Sb intermetallic phase, Zn(1+delta)Sb, in a peritectoid reaction. Our …
Diffusion Control in Single-Site Zinc Reticular Amination Catalysts.
2020
Zn-containing metal-organic frameworks have been used for the first time as heterogeneous catalysts in the amination of C-Cl bonds. The use of extended bis(pyrazolate) linkers can generate highly porous architectures, which favor the diffusion of amines to the confined spaces with respect to other imidazolate frameworks with narrower pore windows. The N4Zn nodes of the Zn-reticular framework show comparable activity to state-of-the-art homogeneous Zn amination catalysts, avoiding the use of basic conditions, precious metals, or other additives. This is combined with long-term activity and stability upon several reaction cycles, without contamination of the reaction product. ispartof: INORGA…
Molecule Isomerism Modulates the Diradical Properties of Stable Singlet Diradicaloids
2019
Inclusion of quinoidal cores in conjugated hydrocarbons is a common strategy to modulate the properties of diradicaloids formed by aromaticity recovery within the quinoidal unit. Here we describe an alternative approach of tuning of diradical properties in indenoindenodibenzothiophenes upon anti → syn isomerism of the benzothiophene motif. This alters the relationship of the S atom with the radical center from linear to cross conjugation yet retains the same 2,6-naphtho conjugation pattern of the rearomatized core. We conduct a full comparison between the anti and syn derivatives based on structural, spectroscopic, theoretical, and magnetic measurements, showing that these systems are stabl…
A Tale of Two Isomers: Enhanced Antiaromaticity/Diradical Character versus Deleterious Ring‐Opening of Benzofuran‐fused s ‐Indacenes and Dicyclopenta…
2021
We examine the effects of fusing two benzofurans to s-indacene (indacenodibenzofurans, IDBFs) and dicyclopenta[b,g]naphthalene (indenoindenodibenzofurans, IIDBFs) to control the strong antiaromaticity and diradical character of these core units. Synthesis via 3-functionalized benzofuran yields syn-IDBF and syn-IIDBF. syn-IDBF possesses a high degree of paratropicity, exceeding that of the parent hydrocarbon, which in turn results in strong diradical character for syn-IIDBF. In the case of the anti-isomers, synthesized via 2-substituted benzofurans, these effects are decreased; however, both derivatives undergo an unexpected ring-opening reaction during the final dearomatization step. All th…
Operational Mechanism of Conjugated Polyelectrolytes
2014
Conjugated polyelectrolytes (CPEs) are versatile materials used in a range of organic optoelectronic applications. Because of their ionic/electronic nature, characterizing these materials is nontrivial, and their operational mechanism is not fully understood. In this work we use a methodology that combines constant-voltage-driven current-density transient measurements with fast current vs voltage scans to allow decoupling of ionic and electronic phenomena. This technique is applied to diodes prepared with cationic CPEs having different charge-compensating anions. Our results indicate that the operational mechanism of these devices is governed by electrochemical doping of the CPE. On the bas…