3 research outputs found
Graphene Oxide Promotes Site-Selective Allylic Alkylation of Thiophenes with Alcohols
The graphene oxide (GO) assisted allylic alkylation of thiophenes with alcohols is presented. Mild reaction conditions and a low GO loading enabled the isolation of a range of densely functionalized thienyl and bithienyl compounds in moderate to high yields (up to 90%). The cooperative action of the Bronsted acidity, epoxide moieties, and pi-surface of the 2D-promoter is highlighted as crucial in the reaction course of the present Friedel-Crafts-type protocol
A new copper(I) coordination polymer from 2,6-bis(1<i>H</i>-benzotriazol-1-ylmethyl)pyridine: Synthesis, characterization, and use as additive in transparent submicron UV filters
<p>The use of a new copper(I) coordination polymer (CP) as additive in transparent composite films of 190 nm of thickness for ultraviolet (UV) shielding is presented. The luminescent 1-D Cu(I) CP was easily synthesized through a self-assembly process between Cu(I) iodide and 2,6-bis(1<i>H</i>-benzotriazol-1-ylmethyl)pyridine (L). The CP, [Cu<sub>2</sub>(<i>μ</i> − I)<sub>2</sub>(<i>μ</i> − <b>L</b>)<sub>2</sub>]<sub><i>n</i></sub>, was structurally characterized by infrared, UV–visible diffuse reflectance and photoluminescence spectroscopy, elemental and thermogravimetric analyses, single-crystal and powder X-ray diffraction, and relativistic density functional theory calculations. The CP was dispersed and immobilized into a polymeric matrix in the presence of Sudan I, yielding a composite material that exhibits a reduction of 49% of the UV transmittance at 350 nm. Thus, the use of a new Cu(I) CP in polymeric composite films appears as a novel approach toward ultrathin and transparent UV shielding films, which have potential applications as protection layers of paints and coatings that tend to degrade when exposed to UV radiation.</p
[OSSO]-Type Iron(III) Complexes for the Low-Pressure Reaction of Carbon Dioxide with Epoxides: Catalytic Activity, Reaction Kinetics, and Computational Study
The
selective conversion of variously substituted epoxides into
the corresponding cyclic carbonates under mild reaction conditions
was achieved with mononuclear FeÂ(III) complexes bearing bis-thioether-diphenolate
[OSSO]-type ligands, in combination with tetrabutylammonium bromide
(TBAB). For example, propylene carbonate was obtained in 1 h at 35
°C (turnover frequency, TOF = 290 h<sup>–1</sup>), from
propylene oxide and 1 bar of CO<sub>2</sub> pressure, using 0.1 mol
% of the FeÂ(III) complex and 0.5 mol % of TBAB. Product divergence
is observed only for cyclohexene oxide toward the exclusive formation
of the aliphatic polycarbonate (TOF = 165 h<sup>–1</sup> at
80 °C and 1 bar of CO<sub>2</sub> pressure, using 0.1 mol % of
the FeÂ(III) complex and 0.1 mol % of tetrabutylammonium chloride).
Kinetic investigations indicated reaction orders of two and one, with
respect to the FeÂ(III) complex, for the production of propylene carbonate
and the polyÂ(cyclohexene carbonate), respectively. The enthalpy and
entropy of activation were determined using the Eyring equation [for
propylene carbonate: Δ<i>H</i><sup>‡</sup> =
8.4 ± 0.7 kcal/mol and Δ<i>S</i><sup>‡</sup> = −33 ± 3 cal/(mol·K); for polyÂ(cyclohexene carbonate):
Δ<i>H</i><sup>‡</sup> = 11.9 ± 0.3 kal/mol
and Δ<i>S</i><sup>‡</sup> = −36 ±
2.2 cal/(mol·K)]. Supported by density functional theory based
investigations, we propose a mechanistic scenario in which the rate-limiting
step is the bimetallic ring opening of the epoxide, in the case of
propylene carbonate, and the monometallic insertion of the epoxide
in the growing polymer chain, in the case of polyÂ(cyclohexene carbonate)