Design and synthesis of (E)-4-((3-ethyl-2,4,4-trimethylcyclohex-2-enylidene)methyl)benzoic acid

(E)-4-((3-Ethyl-2,4,4-trimethylcyclohex-2-enylidene)methyl)benzoic acid, 6, was synthesized in 87% starting from β-cyclocitral. The target compound 6 was synthesized starting from 1 via a Grignard reaction to form alcohol 2. Compound 2 was converted to Wittig salt 3 by treatment with aldehyde 4 in butyllithium and hexane at −78 °C to form ester 5. Ester 5 was saponified and, following acidification, acid 6 was isolated as white solid yield 87%.     

Wurtzite CuGaS2 with an In-Situ-Formed CuO Layer Photocatalyzes CO2 Conversion to Ethylene with High Selectivity

We present surface reconstruction-induced C−C coupling whereby CO₂ is converted into ethylene. The wurtzite phase of CuGaS_2. undergoes in situ surface reconstruction, leading to the formation of a thin CuO layer over the pristine catalyst, which facilitates selective conversion of CO₂ to ethylene (C₂H₄). Upon illumination, the catalyst efficiently converts CO₂ to C₂H₄ with 75.1 % selectivity (92.7 % selectivity in terms of R_electron) and a 20.6 μmol g⁻¹ h⁻¹ evolution rate. Subsequent spectroscopic and microscopic studies supported by theoretical analysis revealed operando-generated Cu²⁺, with the assistance of existing Cu⁺, functioning as an anchor for the generated *CO and thereby facilitating C−C coupling. This study demonstrates strain-induced in situ surface reconstruction leading to heterojunction formation, which finetunes the oxidation state of Cu and modulates the CO₂ reduction reaction pathway to selective formation of ethylene.     

Vibrational phase relaxation of O–H stretch in bulk water: Role of large amplitude angular jumps and negative cross-correlations among the forces on the O–H bond

The ultrafast vibrational phase relaxation of O–H stretch in bulk water is investigated in molecular dynamics simulations. The dephasing time (T₂) of the O–H stretch in bulk water calculated from the frequency fluctuation time correlation function (C_ω(t)) is in the range of 70–80 femtosecond (fs), which is comparable to the characteristic timescale obtained from the vibrational echo peak shift measurements using infrared photon echo [W.P. de Boeij, M.S. Pshenichnikov, D.A. Wiersma, Ann. Rev. Phys. Chem. 49 (1998) 99]. The ultrafast decay of C_ω(t) is found to be responsible for the ultrashort T₂ in bulk water. Careful analysis reveals the following two interesting reasons for the ultrafast decay of C_ω(t). (A) The large amplitude angular jumps of water molecules (within 30–40 fs time duration) provide a large scale contribution to the mean square vibrational frequency fluctuation and gives rise to the rapid spectral diffusion on 100 fs time scale. (B) The projected force, due to all the atoms of the solvent molecules on the oxygen (F_O(t)) and hydrogen (F_H(t)) atom of the O–H bond exhibit a large negative cross-correlation (NCC). We further find that this NCC is partly responsible for a weak, non-Arrhenius temperature dependence of the dephasing rate.     

Heme peroxidase-catalyzed iodination of human angiotensins and the effect of iodination on angiotensin converting enzyme activity

The heme peroxidase-catalyzed iodination of human angiotensins I and II is described. It is observed that lactoperoxidase (LPO) can effectively and selectively iodinate the tyrosyl residues in angiotensin peptides. The thiourea/thiouracil-based peroxidase inhibitors effectively inhibit the iodination reactions, indicating that iodination is an enzymatic reaction and the mechanism of iodination is similar to that of peroxidase-catalyzed iodination of thyroglobulin. This study also shows that the monoiodo Ang I is a better substrate for the angiotensin converting enzyme than the native peptide.     

Influence of γ-ray-induced effects on dielectric dispersion of CuO-doped calcium fluoroborophosphate glass system

γ-Ray-induced dielectric dispersion in CaF₂–B₂O₃–P₂O₅ glasses doped with different concentrations of CuO was investigated. The glass samples were exposed to γ-rays with dose varying within the range 0–10 kGy. The dielectric dispersion and spectroscopic properties were measured before and after γ-ray treatment. Additionally, thermoluminescence studies were performed on post-irradiated glass samples. The results of dielectric properties and dielectric breakdown strength indicated a substantial increase in the insulating strength of CuO containing glasses due to γ-ray irradiation. The analysis of these results together with UV-vis optical absorption, IR spectra, and thermoluminescence studies have indicated a gradual increase in the concentration of mono-valent copper ions due to γ-ray treatment of the glass network. The additional studies have confirmed that these Cu⁺ ions occupy network-forming positions, increase the polymerization of the borophosphate glass network, and facilitates for the increase of insulating strength of the titled glass.     

Urchin-like α-MnO<Subscript>2</Subscript> formed by nanoneedles for high-performance lithium batteries

MnO₂ nanoneedles (NNs) were synthesized by sol-gel assisted by a redox reaction between ascorbic acid and KMnO₄. X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), Raman, far-infrared spectroscopy, and magnetic measurements confirm the tunnel structure of the tetragonal α-MnO₂ phase. The MnO₂ NNs prepared by sol-gel at moderate temperature (T ≈ 350 °C) aggregate with an urchin-like morphology observed by scanning electron (SEM) and high-resolution transmission electron (TEM) microscopy. Electrochemical investigations show an outstanding initial specific capacity ca. 230 mAh g^?1 and 45 % capacity retention at 100th cycle was obtained for these MnO₂ nanoneedles.     

Structures and energetics of complexation of metal ions with ammonia,water, and benzene: A computational study

Quantum chemical calculations have been performed at CCSD(T)/def2‐TZVP level to investigate the strength and nature of interactions of ammonia (NH₃), water (H₂O), and benzene (C₆H₆) with various metal ions and validated with the available experimental results. For all the considered metal ions, a preference for C₆H₆ is observed for dicationic ions whereas the monocationic ions prefer to bind with NH₃. Density Functional Theory–Symmetry Adapted Perturbation Theory (DFT‐SAPT) analysis has been employed at PBE0AC/def2‐TZVP level on these complexes (closed shell), to understand the various energy terms contributing to binding energy (BE). The DFT‐SAPT result shows that for the metal ion complexes with H₂O electrostatic component is the major contributor to the BE whereas, for C₆H₆ complexes polarization component is dominant, except in the case of alkali metal ion complexes. However, in case of NH₃ complexes, electrostatic component is dominant for s‐block metal ions, whereas, for the d and p‐block metal ion complexes both electrostatic and polarization components are important. The geometry (M⁺–N and M⁺–O distance for NH₃ and H₂O complexes respectively, and cation–π distance for C₆H₆ complexes) for the alkali and alkaline earth metal ion complexes increases down the group. Natural population analysis performed on NH₃, H₂O, and C₆H₆ complexes shows that the charge transfer to metal ions is higher in case of C₆H₆ complexes. © 2016 Wiley Periodicals, Inc.     

Spectroscopic study of association of a hemicyanine dye in mixed aqueous binary solvents

Electronic absorption and steady state emission properties of a hemicyanine dye [4-[4-(dimethylamino)styryl]-1-docosylpyridinium bromide], have been studied in several pure solvents and two mixed binary solvents (water+ethanol and water+acetonitrile). In pure solvents the band-width of the absorption spectrum correlates well with the Stoke's shift. In mixed aqueous solvents two different molecular forms of the solute, viz. the monomer and the dimer of the solute exists in equilibrium. Thermodynamic parameters (e.g. the Delta G degrees and Delta H degrees ) characterizing the equilibrium have been determined. While the value of Delta G degrees changes very slightly with the composition of the binary mixture, the value of Delta H degrees has been observed to depend significantly with solvent composition.     

Two-dimensional infrared investigation of N-acetyl tryptophan methyl amide in solution

The linear infrared and two-dimensional infrared (2D IR) spectra in the amide-I region of N-acetyl tryptophan methyl amide (NATMA) in solvents of varying polarity are reported. The two amide-I transitions have been assigned unambiguously by using 13C isotopic substitution of the carbonyl group. The amide unit at the amino end shows a lower transition frequency in CH2Cl2 and methanol, while the acetyl end has a lower transition frequency in D2O. Multiple conformers exist in CH2Cl2 and methanol, but only one conformer is evident in D2O. The 2D IR cross peaks from the intermode coupling yield off-diagonal anharmonicities 2.5 +/- 0.5, 3.25 +/- 0.5, and 3.0 +/- 0.5 cm(-1) in CH2Cl2, methanol, and D2O, respectively, which by simple matrix diagonalization yield the coupling constants 8.0 +/- 0.5, 8.0 +/- 1.0, and 5.5 +/- 1.0 cm(-1). The major conformer in CH2Cl2 corresponds to a C7 structure, in agreement with that found in the gas phase [Dian, B. C.; Longarte, A.; Mercier, S.; Evans, D. A.; Wales, D. J.; Zwier, T. S. J. Chem. Phys. 2002, 117, 10688-10702] with intramolecular hydrogen bonding between the acetyl end C=O and the amino end N-H. The backbone dihedral angles (phi, psi) are determined to be in the ranges of (-55 +/- 5 degrees , 30 +/- 5 degrees ), (120 +/- 10 degrees , -20 +/- 10 degrees ), and (+/-160 +/- 10 degrees , +/-75 +/- 10 degrees ) in CH2Cl2, methanol, and D2O, respectively.