Monthly Archives: September 2023

Cerium(IV) Nitrate Complexes With Bidentate Phosphine Oxides

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Cerium(IV) Nitrate Complexes With Bidentate Phosphine Oxides

The formation, structures and thermal and solution stability of cerium(IV) complexes with bidentate phosphine oxides are reported. Complexes with flexible ligand architecture tend to be less stable showing decomposition to Ce(III) in solution. The decomposition products of the thermal decomposition in the solid state have been identified by infrared spectroscopy.


Abstract

The reactions between ceric ammonium nitrate, (NH4)2Ce(NO3)6, (CAN) and the bidentate phosphine oxides, 4,5-bis(diphenylphosphine oxide)-9,9-dimethylxanthene (L1), oxydi-2,1-phenylene bis(diphenylphosphine dioxide) (L2), 1,2-bis(diphenylphosphino)ethane dioxide (L3) and 1,4-bis(diphenylphosphino)butane dioxide, L4 have been investigated. The crystal structures of the molecular Ce(NO3)4L1 (1), and ionic [Ce(NO3)3L3 2][NO3]⋅CHCl3 (3), [Ce(NO3)3L3 2][NO3] (4) and the polymeric [Ce(NO3)3L4 1.5] [NO3] (5) and the cerium(III) complex [Ce(NO3)2L1 2][NO3] (2) are reported. The thermal stability of the complexes has been examined by thermogravimetry with the gaseous decomposition products analysed by infrared spectroscopy. Evolution of CO2 is found for both Ce(III) and Ce(IV) complexes with the later also forming NO2. The formation of the complexes in solution has been studied by 31P NMR spectroscopy and further complexes [Ce(NO3)3L1 2]+[NO3]− and [Ce(NO3)2L1 3]2+2[NO3]− identified in CD3CN solution. The complex (1) exists as a single molecular species in solution and is stable in dichloromethane whilst (3) decomposes on standing in both CD2Cl2 and CD3CN to Ce(III) containing species. Complexes of L2 have been identified by solution 31P NMR spectroscopy and these decompose in solution to give Ce(NO3)3L2 2. This study represents the first structural characterisations of Ce(IV) complexes with bidentate phosphine oxides.

Smolyak Scheme for solving the Schrödinger equation: Application to Malonaldehyde in Full Dimensionality

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Smolyak Scheme for solving the Schrödinger equation: Application to Malonaldehyde in Full Dimensionality

A quantum dynamics approach that combines a Smolyak scheme and curvilinear coordinates is described. It is applied to the computation of malonaldehyde tunneling splitting in full dimensionality.


Abstract

In 1963 Smolyak introduced an approach to overcome the exponential scaling with respect to the number of variables of the direct product size [S. A. Smolyak Soviet Mathematics Doklady, 4, 240 (1963)]. The main idea is to replace a single large direct product by a sum of selected small direct products. It was first used in quantum dynamics in 2009 by Avila and Carrington [G. Avila and T. Carrington, J. Chem. Phys., 131, 174103 (2009)]. Since then, several calculations have been published by Avila and Carrington and by other groups. In the present study, and to push the limit to larger and more complex systems, this scheme is combined with the use of an on-the-fly calculation of the kinetic energy operator and a Block-Davidson procedure to obtain eigenstates in our home-made Fortran codes, ElVibRot and Tnum-Tana. This was applied to compute the tunneling splitting of malonaldehyde in full dimensionality (21D) using the potential of Mizukami et al. [W. Mizukami, S. Habershon, and D.P. Tew, J. Chem. Phys. 141, 1443–10 (2014)]. Our tunneling splitting calculations, 21.7±0.3 cm−1 and 2.9±0.1 cm−1, show excellent agreement with the experimental values, 21.6 cm−1 and 2.9 cm−1 for the normal isotopologue and the mono-deuterated one, respectively.

Fabrication of Hyperbranched Photomechanical Crystals Composed of a Photochromic Diarylethene

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Fabrication of Hyperbranched Photomechanical Crystals Composed of a Photochromic Diarylethene

The cover feature image shows the sublimation process of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene on a concave surface of a spherical glass substrate, on which the branched hollow crystals are densely produced. These crystals can make the roles in moving and releasing the minute object during the bending behaviors by the irradiation with UV light according to the number and size of units of the hollow structures in them, which depend on the substrate curvature. More information can be found in the Research Article by Seiya Kobatake and co-workers.


Response of the mechanical and chiral character of ethane to ultra‐fast laser pulses

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Response of the mechanical and chiral character of ethane to ultra-fast laser pulses

The ethane C1-C2 bond critical point (BCP) Hessian of ρ(r) eigenvector-trajectories T(s) for the for the clockwise (CW, [+1]) (red) and counter-clockwise (CCW, [−1]) (blue) circularly laser pulse polarized in yz plane 60 femtoseconds after the pulses are switched off. The end of each T(s) is denoted by a cube marker. The most (±e2) and least (±e1) preferred eigenvector directions of the total charge density accumulation ρ(rb). The inset is the view down the ethane C1-C2 BCP bond-path, showing the Cartesian yz axes, where the BCPs are represented by undecorated green spheres.


Abstract

A pair of simulated left and right circularly polarized ultra-fast laser pulses of duration 20 femtoseconds that induce a mixture of excited states are applied to ethane. The response of the electron dynamics is investigated within the next generation quantum theory of atoms in molecules (NG-QTAIM) using third-generation eigenvector-trajectories which are introduced in this work. This enables an analysis of the mechanical and chiral properties of the electron dynamics of ethane without needing to subject the C-C bond to external torsions as was the case for second-generation eigenvector-trajectories. The mechanical properties, in particular, the bond-flexing and bond-torsion were found to increase depending on the plane of the applied laser pulses. The bond-flexing and bond-torsion, depending on the plane of polarization, increases or decreases after the laser pulses are switched off. This is explainable in terms of directionally-dependent effects of the long-lasting superpositions of excited states. The chiral properties correspond to the ethane molecule being classified as formally achiral consistent with previous NG-QTAIM investigations. Future planned investigations using ultra-fast circularly polarized lasers are briefly discussed.

Recent Advances in Base‐Metal‐Catalyzed Carbonylation of Unactivated Alkyl Electrophiles

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Recent Advances in Base-Metal-Catalyzed Carbonylation of Unactivated Alkyl Electrophiles†

This review summarizes the recent advances in base-metal-catalyzed carbonylative C—C, C—N, C—O, C—X coupling and other carbonylation reactions of unactivated alkyl electrophiles using CO as C1 source, providing efficient methods for the synthesis of diverse alkyl-substituted carbonyl compounds or their derivatives including ketones, amides, esters, acylsilanes, acylborons, acyl chlorides and alcohols.


Comprehensive Summary

Transition metal-catalyzed carbonylation reactions represent a direct and atom-economical approach to synthesize carbonyl compounds or their derivatives by using CO as a cheap and readily available C1 feedstock. While carbonylation of C(sp2)-hybridized electrophiles (e.g., aryl halides) is well developed, carbonylation of less reactive unactivated alkyl electrophiles remains challenging. Recently, the use of earth-abundant base metals including Cu, Co, Mn, Fe, Ni as catalysts has enabled advances in carbonylative coupling of alkyl electrophiles for approaching diverse carbonyl compounds or their derivatives, notably, some of which are of synthetic importance but difficult to be synthesized through previous reported methods. Herein, we have summarized and discussed these recent achievements in base-metal-catalyzed carbonylative C—C, C—N, C—O, C—X coupling and other carbonylation reactions of unactivated alkyl electrophiles using CO as C1 source.

Elastic and Conductive Cross‐linked Anion Exchange Membranes Based on Polyphenylene Oxide and Poly(vinyl alcohol) for H2‐O2 Fuel Cells

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A series of cross-linked AEMs (c-DQPPO/PVA) are synthesized by using rigid polyphenylene oxide and flexible poly(vinyl alcohol) as the backbones. Dual cations are grafted on the PPO backbone to improve the ion exchange capacity (IEC), while glutaraldehyde is introduced to enhance compatibility and reduce swelling ratio of AEMs. In addition to the enhanced mechanical properties resulting from the rigid-flexible cross-linked network, c-DQPPO/PVA AEMs also exhibit impressive ionic conductivity, which can be attributed to their high IEC, good hydrophilicity of PVA, and well-defined micro-morphology. Additionally, due to confined dimension behavior and ordered micro-morphology, c-DQPPO/PVA AEMs demonstrate excellent chemical stability. Specifically, c-DQPPO/PVA-7.5 exhibits a wet-state tensile strength of 12.5 MPa and an elongation at break of 53.0% at 25 oC. Its OH− conductivity and swelling degree at 80 oC are measured to be 125.7 mS cm-1 and 8.2%, respectively, with an IEC of 3.05 mmol g-1. After 30 days in a 1 M NaOH solution at 80 oC, c-DQPPO/PVA-7.5 experiences degradation rates of 12.8% for tensile strength, 27.4% for elongation at break, 14.7% for IEC, and 19.2% for ion conductivity. With its excellent properties, c-DQPPO/PVA-7.5 exhibits a peak power density of 0.751 W cm-2 at 60 oC in an H2-O2 fuel cell.

High‐Intensity Microwave‐Assisted Pyrolysis Liquid Subjected to Supercritical Fluid Extraction with Carbon Dioxide (Case Study: Bio‐phenol)

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High-Intensity Microwave-Assisted Pyrolysis Liquid Subjected to Supercritical Fluid Extraction with Carbon Dioxide (Case Study: Bio-phenol)

Extraction with supercritical carbon dioxide (scCO2) was studied for separating value-added chemicals from crude bio-oil produced by pyrolysis of oil palm shell. Organic acids were the dominant group of chemicals enriched by scCO2 extraction. Phenol was considered as a specific value-added chemical for estimating the production costs, which were compared with the price of a commercial-grade product.


Abstract

A crude bio-oil from high-intensity microwave-assisted pyrolysis of oil palm shell was subjected to an attractive, environmentally friendly separation process, namely supercritical fluid extraction with carbon dioxide (scCO2), to study the value-added chemicals such as bio-phenol. The operating parameters temperature and pressure were examined above the critical point of carbon dioxide. The yield of scCO2-oil extract tended to increase significantly with these two parameters according to one-way ANOVA. The extract yield was within 63.09–67.72 %. The scCO2-oils were characterized for value-added chemical components by GC-MS and compared with the crude bio-oil. Acids, as the dominant group of chemicals, were enriched by scCO2, and included dodecanoic acid, n-hexadecanoic acid, and octadecanoic acid. The thermal behavior of scCO2-oil was studied by thermogravimetry. The production cost of bio-phenol extracted from scCO2-oil was estimated and compared with a commercial phenol product.

Exploring the Sequence Space of Antimicrobial Peptide Dendrimers

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Exploring the Sequence Space of Antimicrobial Peptide Dendrimers


Abstract

There is an urgent need to develop new antibacterial agents against multidrug resistant bacteria. Herein we report our investigation of antimicrobial peptide dendrimers (AMPDs) active against Gram-negative bacteria, whose sequences were designed using a genetic algorithm optimizing molecular similarity to the previously reported AMPD T7 with sequence (KL)8(KKL)4(KKLL)2 KKKL. Our computational approach selected analogues unlikely to emerge from a systematic study, including AMPD X66 with a non-conservative Leu→Glu mutation at the dendrimer core which proved compatible with antibacterial effects. Circular dichroism showed that this AMPD is α-helical. Molecular dynamics suggest that its α-helical structure is stabilized by an intramolecular salt bridge involving the core glutamate side chain and a lysine side chain in the dendrimer branches. More substantial variations at the dendrimer core were also tolerated such as the installation of the dianionic pegylated fatty acid side chain of the drug semaglutide potentially useful for in vivo studies.