Dalton Transactions

doi: 10.1039/d5dt90148kpmid: N/A

doi: 10.1039/d5dt90149apmid: N/A

doi: 10.1039/d5dt90150bpmid: N/A

Kousar, Naseem; Patil, Gouthami; Kumbara, Ashwini Chikkabasur; Nisty, Basavesh; G. H., Rajesh; Sannegowda, Lokesh Koodlur

doi: 10.1039/d5dt01438gpmid: 40779700

Advancements in water splitting technologies are crucial for achieving sustainable hydrogen production. Development of highly efficient and economically viable catalysts is essential for commercialization of water electrolysers. While precious metals like platinum and iridium are renowned for their catalytic capabilities in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), their high cost and scarcity present significant challenges. Hence, various metal oxides, carbides, sulfides, phosphides, alloys, metal complexes, and composites have been examined as potential catalysts for water splitting reactions. This review offers a comprehensive analysis of Earth-abundant metal complexes as promising alternatives for water splitting catalysis. The fundamental principles underlying water splitting, including electrochemical dynamics, thermodynamics, and reaction kinetics, and their impact on catalytic performance have been evaluated. Emphasis is placed on the pivotal role of Earth-abundant metals such as manganese, iron, cobalt, nickel, and molybdenum and their recent innovations in catalyst design focussing on composites for enhancing the HER, OER, and integrated dual-function catalysis are discussed. Comparative evaluation related to advantages and limitations of these alternatives with respect to precious catalysts in terms of cost, availability, and environmental impact is presented. To integrate the same catalyst for HER and OER activities, insights into strategies for optimization of the performance are provided. Additionally, the review highlights the contributions of computational chemistry, including density functional theory studies in engineering catalyst design and understanding reaction mechanisms. Finally, an assessment of current challenges and future directions is presented to provide a holistic perspective on the transformative potential of Earth-abundant metal complexes in advancing sustainable water splitting technologies.

Roy, Saraswati; Roy, Sounak

doi: 10.1039/d5dt01174dpmid: 40771156

The production and storage of green hydrogen can be effectively achieved through water splitting driven by renewable electricity. Of the two half-reactions involved in electrochemical water splitting, the oxygen evolution reaction is kinetically sluggish and typically serves as the rate-limiting step, thereby constraining the overall efficiency of the process. Consequently, the development of highly efficient electrocatalysts capable of promoting the oxygen evolution reaction at low overpotentials and high current densities remains a formidable scientific pursuit. Emerging studies on the reaction pathways and transient intermediates of the oxygen evolution reaction highlight that, beyond the overarching thermodynamic considerations, subtle aspects of the catalyst's structural, surface, and electronic characteristics play a decisive role in dictating catalytic performance. Factors such as the presence of accessible vacant sites adjacent to the catalytically active metal centers—introduced via intrinsic or extrinsic defect formation—along with the ease of oxidation of the active metal, the d-orbital electron configuration in octahedrally coordinated environments, and metal–ligand covalency, have all been identified as key descriptors governing oxygen evolution reaction activity. Our research group has been actively investigating pristine and doped transition metal spinel and perovskite oxides as potential oxygen evolution reaction electrocatalysts. This article outlines a systematic approach for rationally designing next-generation oxygen evolution catalysts based on critical electronic descriptors.

Phan, Hoa; Thai, Kieu Thuy Thi; Funakoshi, Nobuto; Tran, Huyen Thu Thi; Yamashita, Masahiro; Shatruk, Michael

doi: 10.1039/d5dt01007apmid: 40576807

In this study, we report the synthesis and detailed characterization of a novel chain compound, composed of hydrogen-bonded dinuclear complexes, in which two Fe(ii) ions are bridged by a 2,2′-biimidazolate (bim2−) dianion. The crystal structure of [(tpma)Fe(μ-bim)Fe(Hbim)2] (1), where tpma = tris(2-pyridylmethyl)amine, exhibits a 1D zigzag chain architecture, formed through double hydrogen bonds between terminal 1H-2,2′-biimidazolate monoanions (Hbim−), with an N⋯H distance of 1.72 Å. Magnetic susceptibility measurements reveal weak antiferromagnetic coupling between the Fe(ii) centers with the exchange constant J = −1.4 cm−1, mediated by the bridging ligand. The directional hydrogen bonding network, combined with π–π and H–π intermolecular interactions, suggests potential for proton dynamics that could lead to ferroelectric behavior. This complex represents the first example of a bim2− ligand bridging two iron ions and the first dimeric complex containing both bim2− and Hbim− ligands, which form strong one-dimensional hydrogen bonds. Investigation of ferroelectric behavior and potential interplay between functional properties are ongoing.

Malenov, Dušan P.; Živković, Jelena M.; Zarić, Snežana D.

doi: 10.1039/d5dt00918apmid: 40726389

Hydrogen bonds in the second coordination sphere of metal complexes play a crucial role in the fine-tuning of their chemical and physical properties, including catalytic activity and selectivity. Our gas-phase computational study on hydrogen bonds of 180 aqua and ammine complexes of transition metals indicates that hydrogen bond energy depends on the charge of the complex, as well as on the ratio between the metal oxidation state (OS) and metal coordination number (CN), and is independent of the geometry of the complex, metal type and nature of other ligands. We have determined a linear increase in interaction energy with the increase in charge, as well as a linear increase of interaction energy with the increase in the OS/CN value. Based on the data presented in this work, we can predict and tune energies of hydrogen bonds in the second coordination sphere of metal complexes. That is, ligands of the same type in complexes with the same charge and the same OS/CN ratio will form hydrogen bonds with very similar energies, independent of all other factors.

He, Chuangchuang; Duan, Jincheng; Zhou, Yang; Cui, Junling; Ma, Xuebing

doi: 10.1039/d5dt01440apmid: 40791190

The direct covalent immobilization of the Hoveyda–Grubbs catalyst into hollow mesoporous polystyrene nanospheres is developed via Friedel–Crafts alkylation without molecular modification for economical and efficient olefin metathesis.

Kapelis, Matthew J.; Wilcoxen, Jarett

doi: 10.1039/d5dt01559fpmid: 40813279

Molybdenum containing enzymes play a pivotal role in the global carbon and nitrogen cycles using a common molybdopterin cofactor. Mechanistic studies have revealed a great deal about molybdenum enzymes but have yet to detail the impact the secondary binding interactions have on catalysis. Herein, we describe a double variant of formate dehydrogenase from Cupriavidus necator (CnFds) that changes the electrostatic and hydrogen bonding to the ligands to molybdenum resulting in a complete loss of formate oxidation activity, which occurs by outer sphere hydride transfer, and gain of nitrate reduction activity, which is proposed to follow an inner sphere oxygen atom transfer mechanism. We have assigned these observed changes to the stability of the terminal ligand which in turn directs the catalytic outcome. The results here illustrate the importance of the secondary sphere interactions in directing oxygen atom transfer vs. hydride transfer mechanisms in molybdenum containing enzymes.

Behling, Vreni; Heinrich, Jakob; Díaz, Dolores; Brohmer, Elias H. P.; Heinrich, Julian; Schlörer, Nils; Kupfer, Stephan; Kulak, Nora; Köhler, Phil

doi: 10.1039/d5dt01476jpmid: 40787785

We report herein a series of new silver compounds with dithiocarbamate ligands derived from amino acid esters (AAE-DTCs). Compounds [Ag{SSC-N(R′)(CH2R′′COOR)}]n (Ag(L1)–Ag(L5); N-dithioato-diethyliminodiacetate (L1), -ethyl-sarcosinate (L2), -tert-butyl-sarcosinate (L3), -methyl-l-prolinate (L4), -ethyl-N-benzylglycinate (L5)) were synthesised from in situ generated AAE-DTCs by salt metathesis with silver nitrate. The isolated products were characterised by different analytical techniques. Ag(L1), Ag(L4), and Ag(L5) were accessible to single-crystal X-ray structure determination, comprising hexameric subunits linked by dimeric units into a 1D-polymeric structure (Ag(L1)) and more homogeneous ribbon-like polymeric structures (Ag(L4) and Ag(L5)). DOSY NMR measurements and supporting DFT calculations were carried out to elucidate the structure of these compounds in solution, showing evidence for smaller agglomerates like dimers and tetramers. Additionally, as first evaluation of the biological activity of these complexes, ethidium bromide displacement assays and DNA melting curve experiments were carried out, the results showing moderate DNA binding abilities.