In situ monitoring of solid-state polymerization reactions in sodium chloroacetate and sodium bromoacetate by 23Na and 13C solid-state NMR spectroscopy

The thermally induced solidstate polymerization reactions in sodium chloroacetate and sodium bromoacetate, leading to poly(hydroxyacetic acid) (polyglycolide) and NaCl and NaBr, respectively, were studied by isothermal in situ solid-state NMR spectroscopy at 120, 130 and 140 degrees C with a time resolution of the order of 5 to 25 min. The nuclei probed were 23Na and 13C, allowing the parent compounds (sodium halogenoacetates) and both reaction products (polymer and alkali halide) to be monitored. For sodium chloroacetate, there is no evidence for the involvement of intermediate phases during the reaction whereas this cannot be excluded for sodium bromoacetate. The crystal structure of sodium bromoacetate was determined directly from powder diffraction data by the Monte Carlo method, and was found to be isostructural with sodium chloroacetate. The topochemical reaction mechanism proposed previously for sodium chloroacetate is thus also applicable for the polymerization reaction in sodium bromoacetate. The mechanistic and kinetic information obtained from our in situ solid-state NMR investigations is compared and contrasted with information obtained from other in situ probes of the polymerization reactions in these materials.     

Hierarchically structured polyglycolide – a biomaterial mimicking natural bone

Polyglycolide (poly(hydroxyacetic acid)) with wide variability of pore size can be prepared by combination of a solid-state polymerization reaction and addition of sodium chloride crystals. The solid state reaction leads to a composite of polyglycolide and NaCl. The latter can be washed out with water leaving behind porous polyglycolide with interconnected pores in the micrometer range. To achieve a higher porosity and to induce larger pores, additional coarse sodium chloride was added before polymerization. This opens a way to functionally graded polyglycolide resembling natural bone that should have a potential as bone substituting material.     

An in situ IR-spectroscopic study of the solid-state formation reaction of polyglycolide

The thermal elimination of NaCl from sodium chloroacetate, a polymerization reaction that takes place between 150 and 200C in the solid state, leads quantitatively to the simplest polyester, polyglycolide. Byin situ IR-spectroscopy, we have shown that the reaction proceeds smoothly and directly without intermediates or by-products. The endgroups of the polymeric product — ionised carboxylate groups (-COONa) and hydrogen-bonded alcohol groups (–COH) — are clearly detectable. It is therefore concluded that the polymer forms extended chains, not rings, during the course of this solid-state reaction. That corresponds well with the idea of a polymerization reaction in the solid state. However, this experiment does not exclude the formation of polyglycolide rings as further product because they do not contain any terminating groups.M. E. and H. K. thank Prof. A. Reller, Hamburg, for generous support. Dr. G. Sankar, London, is acknowledged for experimental assistance. This work was supported by the Deutsche Forschungsgemeinschaft (Bonn, Germany), the Fonds der Chemischen Industrie (Frankfurt/Main, Germany) and the Engineering and Physical Sciences Research Council (UK).     

solid-state reaction of a lead tetraacetate-metal halide system with naphthalene under mechanical activation

A mechanically activated solid-state reaction of halogenation of naphthalene with a Pb(OAc)₄—alkaline or alkaline-earth metal halide system was carried out to yield 1-halonaphthalene as the main reaction product and 1,4-dihalonaphthalene. The solid-state halogenation of naphthalene is more selective than a liquid-phase reaction.     

Oxidation of 1-alkylcycloalkanols with PbIV and MnIII compounds under mechanical activation

A mechanoactivated solid-state oxidative decyclization of 1-alkylcycloalkanols under the action of the Pb(OAc)₄?MX or Mn(OAc)₃?MX systems (MX is a metal halide) was carried out for the first time. The reaction affords exclusively ω-haloalkanones.     

Application of solid-state early-transition metal clusters as catalysts

Metal cluster compounds are expected to be catalysts for new reactions because of synergistic effect of the metal atoms. In solid-state halide clusters and sulfide clusters, metal cluster frameworks are linked in two- or three-dimensions to form a cluster network. Halogen- or sulfur-deficient metal sites in an octahedral metal cluster framework are retained intact and act as catalytically active sites even at high temperatures of 400–700?°C. This review reports recent advances in the development of coordinatively unsaturated metal atoms on solid-state clusters with an octahedral metal framework and their application to organic catalytic reactions.     

Morphology-Dependent Stability of Complex Metal Hydrides and Their Intermediates Using First-Principles Calculations

Complex light metal hydrides are promising candidates for efficient, compact solid-state hydrogen storage. (De)hydrogenation of these materials often proceeds via multiple reaction intermediates, the energetics of which determine reversibility and kinetics. At the solid-state reaction front, molecular-level chemistry eventually drives the formation of bulk product phases. Therefore, a better understanding of realistic (de)hydrogenation behavior requires considering possible reaction products along all stages of morphological evolution, from molecular to bulk crystalline. Here, we use first-principles calculations to explore the interplay between intermediate morphology and reaction pathways. Employing representative complex metal hydride systems, we investigate the relative energetics of three distinct morphological stages that can be expressed by intermediates during solid-state reactions: i) dispersed molecules; ii) clustered molecular chains; and iii) condensed-phase crystals. Our results verify that the effective reaction energy landscape strongly depends on the morphological features and associated chemical environment, offering a possible explanation for observed discrepancies between X-ray diffraction and nuclear magnetic resonance measurements. Our theoretical understanding also provides physical and chemical insight into phase nucleation kinetics upon (de)hydrogenation of complex metal hydrides.     

Hybrid perovskite resulting from the solid-state reaction between the organic cations and perovskite layers of alpha1-(Br-(CH(2))(2)-NH(3))(2)PbI(4)

The alpha1-(Br-(CH(2))(2)-NH(3))(2)PbI(4) hybrid perovskite undergoes a solid-state transformation, that is, the reaction between the organic cations and the perovskite layers to give the new hybrid perovskite (Br-(CH(2))(2)-NH(3))(2-x)(I-(CH(2))(2)-NH(3))(x)PbBr(x)I(4-x), based on mixed halide inorganic layers. This transformation has been followed by a conventional powder X-ray diffraction system equipped with a super speed detector, and both solid-state (13)C NMR and ESI/MS measurements have been adopted in the estimation of the rate of halide substitution. The first reaction step leads to the special composition of x approximately 1 (A phase), while the complete substitution is not achieved even at elevated temperature (x(max) approximately 1.85 (B phase)). This unprecedented solid-state reaction between organic and inorganic components of a hybrid perovskite can be considered as a completely new strategy to achieve interesting hybrid perovskites.     

The Kharasch type reaction of allylic halides with Grignard reagent in the presence of transition metal halides

The reaction of allylic halide with Grignard reagent in the presence of transition metal chloride has been investigated. Three reactions of allylic halide occurred competitively; (i) reduction to olefin, (ii) coupling with Grignard reagent to olefin (cross-coupling) and (iii) coupling with itself to 1,5-diene (homo-coupling). The relative importance of these reactions depends on both the structures of allylic halide and Grignard reagent, as well as on the transition metal salt utilized. The mechanism was discussed in terms of the allylic transition metal intermediate.     

Promoting non-transition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: VII. Additional details of the mechanism

Mechanism of metals alkylation with an organic halide in the presence of binary systems has been defined in more detail. It has been shown that the passivating film on the surface of zinc and cadmium is partially preserved in the course of the process, and the reaction in diethyl ether is decelerated due to the competitive adsorption of the organyl halide and diethyl ether on the surface of the reacting metal. The ratelimiting stages of the studied alkylation process have been elucidated basing on the experimental data on the effect of the reagents (organyl halide and alkylated metal) nature on the rate of the steady-state reaction and modeling of the suggested catalytic cycle.     

Evidence for the intermediacy of π-allylic metal complexes in the reaction of allylic halides with grignard reagent in the presence of transition metal halides

The reactions of allyl bromide and crotyl chloride with Grignard reagent catalyzed by π-allyl and crotyl metal complexes of nickel, cobalt, and iron, and the stoichiometric reaction of the complexes with the Grignard reagent have been examined. The similarity in catalytic behaviour of the complex and the corresponding metallic halide affords further evidence in support of the previous proposal that the π-allylic metal intermediate plays an important role in the catalytic reaction. The stoichiometric reaction suggests that the dependence of distribution of product in the catalytic process on the type of both allylic halide and metal is attributable to the facility of ligand exchange between the π-allylic complex and Grignard reagent.     

反溶剂法快速合成高效发光二维锡卤钙钛矿材料

铅卤钙钛矿材料由于其优异的光电性质而受到了广泛关注. 但是, 材料中铅的毒性问题极大地阻碍了其大规模应用. 因此, 寻找与铅卤钙钛矿具有相似光电性质的非铅卤化物钙钛矿材料十分重要. 其中, 锡基卤化物钙钛矿被认为是铅基钙钛矿材料最佳的替代材料之一. 本文通过简便的反溶剂方法, 合成了一系列新型二维(RNH₃)₂SnX₄(R为烷基链, X=Br^-, I^-)钙钛矿材料. 研究结果表明, 所合成的材料具有优异的荧光发射性质, 发光量子效率高达98.5%, 比三维ASnX₃[A=Cs⁺, 甲胺(MA⁺), 甲脒(FA⁺)等]型钙钛矿表现出更好的稳定性. 本文所采用的合成方法简单易行, 有利于实现金属卤化物钙钛矿材料的大规模合成及在固态照明器件和显示器件领域的工业应用.     

卤化物固态电解质研究进展

全固态电池因其高能量密度和高安全性而成为具有发展前景的下一代储能技术。开发具有高室温离子电导率、优异化学/电化学稳定性、良好正/负极兼容性的固态电解质是实现全固态电池实用化的关键。卤化物固态电解质因其优异的电化学窗口、高正极稳定性、可接受的室温锂离子电导率等优势,受到了广泛的关注。本文通过对近年来卤化物电解质的相关研究进行总结,综述了该类电解质的组成、结构、离子传导路径及制备方法,并分析了金属卤化物电解质的电导率、稳定性特点,归纳了近年来该电解质在全固态电池中具有代表性的应用,并基于以上总结和分析,指出了卤化物固态电解质的研究难点及发展方向。     

Synthesis of c-17 trans β-lactams of the androstane series

3,3′-Ethylenedioxyandrost-4-en-17β-ol 1 was converted into the ethyl ester 2 by reaction with potassium metal and ethyl chloroacetate. The ethyl ester 2 on reaction with hydrazine gave the hydrazide 3 . Condensation of 3 with aryl aldehydes gave the Schiff bases 4 . The reaction of Schiff bases 4 with mono-chloroacetyl chloride in the presence of triethylamine afforded the β-lactams 5 .     

A Team for the Development and Characterization of Next-Generation Hybrid Semiconductors

This invited Team Profile was created by the Spanopoulos group, University of South Florida, Tampa (USA) , the Guo group, Yale University, West Haven (USA) , the Trikalitis group, University of Crete, Heraklion (Greece) , the Zimbouche group, Lancaster University, Lancaster (UK) , and the Reddy group, University of Lille, Lille (France) . They recently published an article on the development of a new family of hybrid semiconductors, namely porous metal halide semiconductors (PMHS). The first member of this series was characterized by using a battery of techniques, shedding light on the corresponding structure–property relationships and its unparalleled water stability. This work provides a solution to address the stability deficiency of metal halide semiconductors and render them suitable for yet unexplored applications, such as solid-state batteries, photonic crystals, sensing and environmental remediation: “Porous and Water Stable 2D Hybrid Metal Halide with Broad Light Emission and Selective H₂O Vapor Sorption”, A. Azmy, S. Li, G. K. Angeli, C. Welton, P. Raval, M. Li, N. Zibouche, L. Wojtas, G. N. M. Reddy, P. Guo, P. N. Trikalitis, I. Spanopoulos, Angew. Chem. Int. Ed. Engl. 2023 , 62, e202218429 .     

Sequestering perrhenate with a borate-based coordination polymer: a model for pertechnetate separation

Crystals of the layered metal organic framework solid Pb[B(Im)4](NO3)(nH2O) can undergo exchange of the nitrate for perrhenate, a model for pertechnetate, forming Pb[B(Im)4](ReO4). We can monitor this reaction by 207Pb solid-state NMR and can isolate single crystals of the resultant material through growth in the presence of an excess of perrhenate. Such a synthetic metal-organic framework solid represents a new candidate for pertechnetate-sequestering materials.     

Reaction mechanism in crystalline solids: kinetics and conformational dynamics of the Norrish type II biradicals from α-adamantyl-p-methoxyacetophenone

In an effort to determine the details of the solid-state reaction mechanism and diastereoselectivity in the Norrish type II and Yang cyclization of crystalline α-adamantyl-p-methoxyacetophenone, we determined its solid-state quantum yields and transient kinetics using nanocrystalline suspensions. The transient spectroscopy measurements were complemented with solid-state NMR spectroscopy spin-lattice relaxation experiments using isotopically labeled samples and with the analysis of variable-temperature anisotropic displacement parameters from single-crystal X-ray diffraction to determine the rate of interconversion of biradical conformers by rotation of the globular adamantyl group. Our experimental findings include a solid-state quantum yield for reaction that is 3 times greater than that in solution, a Norrish type II hydrogen-transfer reaction that is about 8 times faster in crystals than in solution, and a biradical decay that occurs on the same time scale as conformational exchange, which helps to explain the diastereoselectivity observed in the solid state.     

Porous and Water Stable 2D Hybrid Metal Halide with Broad Light Emission and Selective H2O Vapor Sorption

In this work we report a strategy for generating porosity in hybrid metal halide materials using molecular cages that serve as both structure-directing agents and counter-cations. Reaction of the [2.2.2] cryptand (DHS) linker with Pb^II in acidic media gave rise to the first porous and water-stable 2D metal halide semiconductor (DHS)₂Pb₅Br₁₄. The corresponding material is stable in water for a year, while gas and vapor-sorption studies revealed that it can selectively and reversibly adsorb H₂O and D₂O at room temperature (RT). Solid-state NMR measurements and DFT calculations verified the incorporation of H₂O and D₂O in the organic linker cavities and shed light on their molecular configuration. In addition to porosity, the material exhibits broad light emission centered at 617 nm with a full width at half-maximum (FWHM) of 284 nm (0.96 eV). The recorded water stability is unparalleled for hybrid metal halide and perovskite materials, while the generation of porosity opens new pathways towards unexplored applications (e.g. solid-state batteries) for this class of hybrid semiconductors.     

Facile low-temperature solid-state synthesis of efficient blue-emitting Cs3Cu2I5 powder phosphors for solid-state lighting

The discovery of new environmentally friendly luminescent materials with high photoluminescence quantum yield and long-term stability is critical for future solid-state lighting and displays applications. Although lead halide perovskite materials with excellent optical properties have been extensively investigated in recent years because they hold tremendous promise in optoelectronic devices, the toxicity of lead and poor air-stability still hinder their commercial applications. Moreover, while substantial work has been done on three-dimensional (3D) perovskite halides, the zero-dimensional (0D) halide emitters with bright luminescence remain elusive. Herein we report a facile solid-state reaction method to prepare an efficient lead-free all-inorganic halide material with 0D structure, Cs₃Cu₂I₅, with photoluminescence quantum yield up to 80%. Under ultraviolet excitation at 313 nm, the Cs₃Cu₂I₅ powder phosphors show a strong blue photoluminescence emission with peak at 445 nm and CIE color coordinates of (0.1486, 0.0873). Notably, Cs₃Cu₂I₅ exhibits good color stability at high temperatures and outstanding stability towards air exposure exceeding one month (30 days). These findings not only open up a door for the development of promising highly emissive low-dimensional halide materials for lighting and displays, but also offer a new scalable approach for the potential mass production of halide emitters.     

A novel atom-transfer cyclisation catalysed by indium metal in halogenated solvents

Treatment of tethered alkyne-allyl halides 1a-d with indium metal in halogenated solvents affords carbocyclic vinyl halides (3a-d) via a novel atom-transfer reaction. The reactions are operationally facile and proceed smoothly at room temperature even with sub-stoichiometric quantities of the metal. Use of a halogenated solvent containing a different halide than that contained in the substrate affords a mixture of products arising from intramolecular halide transfer and abstraction of a halide atom from solvent.