Reactivity of a two heteroatom stabilized anionic chromium (0) carbene complex towards a mono- and a disubstituted alkyne: New synthesis of γ-aminobutenolides and formation of a novel oligomer chromium (0) complex

The reaction of the chromium anionic carbene complex 1 towards diphenylacetylene and phenylacetylene is reported. In the former case the synthesis of γ-functionalized butenolides results after demetallation of the chromium complex 2 and the latter leads to the formation of a novel oligomer chromium complex 5. These complexes were characterized by mass spectrometry, IR and ¹H and ¹³C NMR spectroscopies and their structures were confirmed by single-crystal X-ray analysis.     

Fullerenes as Key Components for Low‐Dimensional (Photo)electrocatalytic Nanohybrid Materials

An emerging class of heterostructures with unprecedented (photo)electrocatalytic behavior, involving the combination of fullerenes and low‐dimensional (LD) nanohybrids, is currently expanding the field of energy materials. The unique physical and chemical properties of fullerenes have offered new opportunities to tailor both the electronic structures and the catalytic activities of the nanohybrid structures. Here, we comprehensively review the synthetic approaches to prepare fullerene‐based hybrids with LD (0D, 1D, and 2D) materials in addition to their resulting structural and catalytic properties. Recent advances in the design of fullerene‐based LD nanomaterials for (photo)electrocatalytic applications are emphasized. The fundamental relationship between the electronic structures and the catalytic functions of the heterostructures, including the role of the fullerenes, is addressed to provide an in‐depth understanding of these emerging materials at the molecular level.     

Orchid flowers tolerance to gamma-radiation

Cut flowers are fresh goods that may be treated with fumigants such as methyl bromide to meet the needs of the quarantine requirements of importing countries. Irradiation is a non-chemical alternative to substitute the methyl bromide treatment of fresh products. In this research, different cut orchids were irradiated to examine their tolerance to gamma-rays. A 200 Gy dose did inhibit the Dendrobium palenopsis buds from opening, but did not cause visible damage to opened flowers. Doses of 800 and 1000 Gy were damaging because they provoked the flowers to drop from the stem. Cattleya irradiated with 750 Gy did not show any damage, and were therefore eligible for the radiation treatment. Cymbidium tolerated up to 300 Gy and above this dose dropped prematurely. On the other hand, Oncydium did not tolerate doses above 150 Gy.     

Expeditious selective synthesis of primary rim tri-differentiated α-cyclodextrin

An expeditious synthesis of a cyclodextrin with three pairs of functionalities on its primary rim is presented. Compared to the previous one, this improved synthetic route yields the product in four steps and 70% yield, instead of six steps and 35% yield; it also bypasses two metathesis reactions and avoids the use of tin reagent.     

Synthesis and spectral properties of 2‐[(o‐ and p‐substituted)aminophenyl] ‐3H‐5‐[(o‐ and p‐substituted)phenyl]‐7‐chloro‐1,4‐benzodiazepines

A series of twelve new 2‐[(o‐ and p‐substituted)aminophenyl]‐3H‐5‐[(o‐ and p‐substituted)phenyl]‐7‐chloro‐1,4‐benzodiazepines, which have possible pharmacological properties has been obtained. The synthesis was carried out following six steps. The structure of all products was corroborated by ir, ¹H nmr, ¹³C nmr and ms. In addition for the compound 2‐(o‐chloroaminophenyl)‐3H‐5‐(o‐fluorophenyl)‐7‐chloro‐1,4‐benzodiazepine 7, its structure was confirmed by X‐ray diffraction.     

Abraham Model Correlations for Triethylene Glycol Solvent Derived from Infinite Dilution Activity Coefficient,Partition Coefficient and Solubility Data Measured at 298.15 K

A gas chromatographic headspace analysis method was used to experimentally determine gas-to-liquid partition coefficients and infinite dilution activity coefficients for 29 liquid organic solutes dissolved in triethylene glycol at 298.15 K. Solubilities were also determined at 298.15 K for 23 crystalline nonelectrolyte organic compounds in triethylene glycol based on spectroscopic absorbance measurements. The experimental results of the headspace chromatographic and spectroscopic solubility measurements were converted to gas-to-triethylene glycol and water-to-triethylene glycol partition coefficients, and molar solubility ratios using standard thermodynamic relationships. Expressions were derived for solute transfer into triethylene glycol by combining our measured experimental values with published literature data. Mathematical correlations based on the Abraham model describe the observed partition coefficient and solubility data to within 0.16 log₁₀ units (or less).     

Intramolecular Carbonyl–Carbonyl Interaction as the Directing Motif of the Opposed Conformational Preferences Among [4?+?2] Cycloadducts of 3-Ethoxycarbonyl- and 3-Acetyl-Coumarins with 2,3-Dimethyl-1,3-Butadiene

Abstract  

In this work, the molecular structures of the Diels–Alder adducts: ethyl (6aR/S,10aR/S)-6a,7,10,10a-tetrahydro-8,9-dimethyl-6-oxodibenzo[b,d]pyran-6a-carboxylate C₁₈H₂₀O₄ 1 and (6aR/S,10aR/S)-6a-acetyl-6a,7,10,10a-tetrahydro-8,9-dimethyl-6-oxodibenzo[b,d]pyran C₁₇H₁₈O₃ 2; and the epoxide of this last (6aR/S,7aR/S,8aS/R,9aR/S)-6a-acetyl-6a,7,7a,8a,9,9a-hexahydro-7a,8a-dimethyl-6-oxo-6H-5,8-dioxacyclopropa[b]phenanthrene C₁₇H₁₈O₄ 3, are comparatively analyzed. Compound 1 is triclinic, space group P-1 with a = 7.7529(6) ?, b = 9.8625(8) ?, c = 11.3103(9) ?, α = 109.387(9)°, β = 95.484(1)°, γ = 99.753(1)°, Z = 2. Compound 2 is monoclinic, space group Cc, a = 7.7285(7) ?, b = 16.6813(15) ?, c = 11.3213(10) ?, β = 92.470(2)°, Z = 4. Compound 3 is monoclinic, space group P2 ₁ /c a = 11.2036(10), b = 15.8326(14), c = 8.3182(7), β = 90.600(2)°, Z = 4. The molecular structures of compounds 1–3 show conformational differences between lactone and 6a-acyl carbonyls. CO···CO dipolar interactions stabilize the less favoured syn conformation in 2–3, conclusions are supported on theoretical calculations. The molecular structure of compound 3 demonstrates that epoxidation of 2 leads to the stereo-selective addition of the oxygen atom.     

Temperature and pressure dependences of volumetric properties of two poly(propylene glycol) dimethyl ether lubricants

The densities at high pressures of two dimethoxy end-capped poly(propylene glycols), CH₃–O–[CH₂–CH(CH₃)–O]_m–CH₃, with average molar masses higher than 1300 g · mol^?1, were measured in the range (0.1 to 60) MPa at five different temperatures from (298.15 to 398.15) K. The measurements were performed in a high-pressure vibrating tube densimeter. A correction factor, due to the viscosity of the sample, was applied to the experimental density values. The pressure–volume–temperature behavior of these lubricants was evaluated accurately over wide temperature and pressure ranges and correlated successfully with the empirical Tammann–Tait equation. The experimental data and the correlations were used to study the behavior and the influence of temperature and pressure on the isothermal compressibility, the isobaric thermal expansivity, and the internal pressure, as well as the effect of the polyether molecular structure on these properties.     

Electronic and optical properties of Si and Ge nanocrystals: An ab initio study

First-principles calculations within density functional theory and many-body perturbation theory have been carried out in order to investigate the structural, electronic and optical properties of undoped and doped silicon nanostructures. We consider Si nanoclusters co-doped with B and P. We find that the electronic band gap is reduced with respect to that of the undoped crystals, suggesting the possibility of impurity based engineering of electronic and optical properties of Si nanocrystals. Finally, motivated by recent suggestions concerning the chance of exploiting Ge dots for photovoltaic nanodevices, we present calculations of the electronic and optical properties of a Ge₃₅H₃₆ nanocrystal, and compare the results with those for the corresponding Si₃₅H₃₆ nanocrystals and the co-doped Si₃₃BPH₃₆.