Dalton Transactions

doi: 10.1039/D2DT90050Epmid: N/A

doi: 10.1039/D2DT90051Cpmid: N/A

Kurup, Sudheer S.; Groysman, Stanislav

doi: 10.1039/d2dt00228kpmid: 35229862

Various valuable properties of azoarenes (azo dyes), including their vivid colors and their facile cistrans photoisomerization, lead to their wide use in the chemical industry. As a result, 700000 metric tons of azo dyes are produced each year. Most currently utilized synthetic methods towards azoarenes involve harsh reaction conditions and/or toxic reagents in stoichiometric amounts, which may affect selectivity and produce significant amounts of waste. An efficient alternative method towards this functional group includes transition metal catalyzed nitrene coupling. This method is generally more sustainable compared with most stoichiometric methods as it uses only catalytic amounts of co-reactants (metal catalysts), requires easily synthesizable organoazide precursors, and forms only dinitrogen as a by-product of catalysis. During the last decade, several catalytic systems were reported, and their reactivity was investigated. This perspective article will review these systems, focusing on various nitrene coupling mechanisms, and the substrate scope for each system. Particular attention will be devoted to the iron-alkoxide catalytic systems investigated in the PI's laboratory. The design and structural features of several generations of iron bis(alkoxide) complexes will be discussed, followed by the structureactivity studies of these catalysts in nitrene homo- and heterocoupling.

Yang, Xin; Guo, Ruike; Cai, Rui; Shi, Wei; Liu, Wenzhu; Guo, Jian; Xiao, Jiafu

doi: 10.1039/d2dt00037gpmid: 35231082

Electrochemical water splitting plays a crucial role in transferring electricity to hydrogen fuel and appropriate electrocatalysts are crucial to satisfy the strict industrial demand. However, the successfully developed non-noble metal catalysts have a small tested range and the current density is usually less than 100 mA cm2, which is still far away from the practical application standards. Aiming to provide guidance for the fabrication of more advanced electrocatalysts with a large current density, we herein systematically summarize the recent progress achieved in the field of cost-efficient and large-current-density electrocatalyst design. Beginning by illustrating the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) mechanisms, we elaborate on the concurrent issues of non-noble metal catalysts that are required to be addressed. In view of large-current-density operating conditions, some distinctive features with regard to good electrical conductivity, high intrinsic activity, rich active sites, and porous architecture are also summarized. Next, some representative large-current-density electrocatalysts are classified. Finally, we discuss the challenges associated with large-current-density water electrolysis and future pathways in the hope of guiding the future development of more efficient non-noble-metal catalysts to boost large-scale hydrogen production with less electricity consumption.

Li, Yue; Wang, Yutong; Fan, Weidong; Sun, Daofeng

doi: 10.1039/d1dt03842gpmid: 35225319

Flexible metalorganic frameworks (MOFs) have gradually attracted much attention due to their reversible structural changes and flexible structural responses. The basic research of flexible MOFs is to study their dynamic responses under different external stimuli and translate the responses into applications. Most research studies on flexible MOFs focus on gas storage and separation, but lack a systematic summary. Here, we review the development of flexible MOFs, the structural transformation under the external effects of temperature, pressure, and guest molecules, and their applications in gas storage and separation. Microporous MOFs with flexible structures provide unique opportunities for fine-tuning their performance because the pore shape and size can be controlled by external stimuli. The characteristics of breathing phenomena and large specific surface area make flexible MOFs suitable candidates for gas storage and separation. Finally, the application prospects of flexible MOFs are reported.

Han, Shan-Shan; Xu, Qian-Ting; Liu, Wenlong; Guo, Sheng-Ping

doi: 10.1039/d2dt00268jpmid: 35262145

Both borates and sulfides are important inorganic multifunctional materials. Encouraged by this background, thioborates attract considerable interest. However, their investigations are highly hindered by the scarcity of the available ones and the synthetic difficulty of the new ones. Here, we report a new thioborate KEu2In3B12S13 (1), which was obtained via a facile solid-state reaction in KI flux. It crystallizes in the trigonal R3m structure, and the three-dimensional structure features a six InS6 octahedron consolidated B12 icosahedron built {[In3B12S12]5} polyanionic framework and a unique In6S6 12-membered ring, representing a new type of compound. The B12S12 cluster is also different from the other known thioborates. The structural chemistry, optical and magnetic properties, as well as theoretical calculations of 1 were systematically studied. This study not only provides a new type of thioborate but also makes a breakthrough in the synthesis of thioborates.

Wu, Yu; Zhou, Huawei; Yin, Jie; Zhang, Xianxi

doi: 10.1039/d1dt04119cpmid: 35266936

The structural and electronic transport properties of tetragonal CH3NH3SnBr3 single crystals (T-MASnBr3 SCs) are rarely reported. In this study, we synthesized T-MASnBr3 single crystals by volatilizing DMF solvent at room temperature. The crystal system and space group of the T-MASnBr3 SC are tetragonal and P4/mmm, respectively. In addition, the nitrogen atom in the methylamine group exhibits position disorder. The band gap of the T-MASnBr3 SC was determined to be 2.07 eV using the Tauc plot. Six fluorescence peaks and a lifetime up to 10 microseconds were observed in the steady-state fluorescence spectra and time-resolved fluorescence spectra of the T-MASnBr3 SC, respectively. The carrier mobility (electron) of T-MASnBr3 was 321 cm2 V1 s1. The curve of ln(square resistance) against T1 was a straight line. The value of the activation energy (Ea) was 5421 J mol1. The stability of the T-MASnBr3 SC was good before 473 K. The results indicate that T-MASnBr3 SCs have promising applications in the field of temperature sensors.

Eilrich, Volker Jens; Grell, Toni; Lönnecke, Peter; Song, Chen; Matysik, Jörg; Hey-Hawkins, Evamarie

doi: 10.1039/d2dt00202gpmid: 35275151

The reaction of tetra-tert-butylcyclotetraphosphane cyclo-(PtBu)4 (L) with one to four equivalents of [AuCl(tht)] (tht = tetrahydrothiophene) leads to the formation of gold(I) complexes [(AuCl)nL] (n = 1–4, 1–4) in which the ligand coordinates up to four gold(I) chloride fragments. Complexes 1–4 show dynamic behaviour with redistribution of {AuCl} moieties which was investigated by 31P{1H} NMR spectroscopy, DFT calculations and single crystal as well as powder X-ray diffraction.

Redman, Holly J.; Huang, Ping; Haumann, Michael; Cheah, Mun Hon; Berggren, Gustav

doi: 10.1039/d1dt03896fpmid: 35212328

Sustainable sources of hydrogen are a vital component of the envisioned energy transition. Understanding and mimicking the [FeFe]-hydrogenase provides a route to achieving this goal. In this study we re-visit a molecular mimic of the hydrogenase, the propyl dithiolate bridged complex [Fe2(-pdt)(CO)4(CN)2]2, in which the cyanide ligands are tuned via Lewis acid interactions. This system provides a rare example of a cyanide containing [FeFe]-hydrogenase mimic capable of catalytic proton reduction, as demonstrated by cyclic voltammetry. EPR, FTIR, UV-vis and X-ray absorption spectroscopy are employed to characterize the species produced by protonation, and reduction or oxidation of the complex. The results reveal that biologically relevant iron-oxidation states can be generated, potentially including short-lived mixed valent Fe(i)Fe(ii) species. We propose that catalysis is initiated by protonation of the diiron complex and the resulting di-ferrous bridging hydride species can subsequently follow two different pathways to promote H2 gas formation depending on the applied reduction potential.

Wen, Ni; Chen, Siyuan; Lu, Qiuchen; Fan, Qinghua; Kuang, Quan; Dong, Youzhong; Zhao, Yanming

doi: 10.1039/d1dt04216epmid: 35212335

Metal vanadates have been popularly advocated as promising anode materials for lithium-ion batteries (LIBs) benefiting from their high theoretical specific capacity and abundant resources. Given that manganese and vanadium are reasonably economical elements and enjoy assorted redox reactions, they have extensive application prospects in energy storage systems. Here, we synthesized cubic MnV2O4 as an anode for LIBs by an efficient solgel process. As a result, the MnV2O4 electrode delivers distinguished electrochemical performance, including an appealing reversible specific capacity of nearly 1325 mA h g1 for 500 cycles at 200 mA g1, excellent cycling stability with a capacity of 399 mA h g1 up to 500 cycles at 2000 mA g1 and a favorable rate capability of 516/410 mA h g1 at 1000/2000 mA g1 (when the current density recuperates to 200 mA g1, the specific capacity still boosts as the number of cycles increases). What's more, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) under various scan rates and scanning electron microscopy (SEM) are executed to ascertain with a greater depth the electrochemical kinetic characteristics and morphology of the MnV2O4 electrode in different states. These results make known that MnV2O4 is a credible anode material for LIBs, and such a facile and economical synthetic route can be extended to the preparation of other metal vanadate materials.