> ## Content Index > Fetch the complete content index at: https://research-pop.com/llms.txt > Use this file to discover other available public pages before exploring further. # Westlake University researchers tune ruthenium complexes for electrocatalytic ammonia oxidation - URL: https://research-pop.com/westlake-university-researchers-tune-ruthenium-complexes-for-electrocatalytic-ammonia-oxidation/ - Published: 2026-09-18T13:13:55.000Z - Updated: 2026-09-18T13:13:55.000Z - Author: ResearchPOP - Tags: Chemistry, Energy ![](https://storage.ghost.io/c/7c/5e/7c5e0911-739b-4a35-94eb-3e810bf78ba7/content/images/2026/09/Screenshot-2026-09-18-at-14.50.48.png) **Source**: [https://doi.org/10.1021/jacs.6c14417](https://doi.org/10.1021/jacs.6c14417?ref=research-pop.com) ## At a glance A Westlake University team compared a series of ruthenium complexes bearing NMe₂, H and CF₃ substituents to examine how ligand electronics and a reversibly coordinating carboxylate shape ammonia oxidation. The complexes share the same broader coordination framework, allowing the researchers to follow how electron donation or withdrawal changes NH₃ binding, oxidation potential and catalytic current. The electron-donating NMe₂ derivative has a reported redox potential of 0.28 V versus ferrocene in acetonitrile, lower than the H and CF₃ versions. It also binds NH₃ more readily, yet produces the smallest catalytic plateau current in the series. The authors connect these trends to different stages of the catalytic sequence: electron donation supports ammonia coordination and the initial oxidation, while stronger electron withdrawal favours the subsequent cleavage of N–H bonds. Binding studies, voltammetry, kinetic analysis, control complexes and electrolysis build a molecular account of this balance. The results also show how the pendant carboxylate can move between coordinated and uncoordinated states, opening a site for NH₃ and then participating in proton-transfer chemistry during ammonia oxidation. ## Background Ammonia can serve as both a chemical feedstock and a carrier of hydrogen. Recovering its stored reducing equivalents electrochemically requires the ammonia oxidation reaction, in which NH₃ is ultimately converted into N₂ while electrons and protons are transferred through a sequence of bond-breaking and bond-forming steps. Molecular catalysts offer a way to examine these steps by changing one part of a ligand at a time while retaining a closely related metal environment. In a ruthenium complex, the electronic properties of the surrounding ligands influence how readily the metal centre is oxidized and how strongly it interacts with NH₃. Electron-donating groups can lower the potential needed for an initial metal-centred oxidation, while electron-withdrawing groups can make later proton- and electron-transfer steps more favourable. These effects do not necessarily move every part of the catalytic cycle in the same direction. The coordination geometry introduces another variable. A hemilabile ligand contains a donor group that can bind to the metal but can also move aside when another molecule needs access. In the complexes studied here, a pendant carboxylate occupies this role. Its reversible Ru–O coordination can help regulate access of NH₃ to ruthenium, while the carboxylate group remains positioned to assist proton transfer once catalysis begins. ## Research question How do ligand electronics and reversible carboxylate coordination work together to influence NH₃ binding, oxidation potential and catalytic current? The researchers also examine which stages benefit from electron donation, which favour electron withdrawal and how the pendant carboxylate contributes after ammonia coordinates to ruthenium. ## Inside the study ![](https://storage.ghost.io/c/7c/5e/7c5e0911-739b-4a35-94eb-3e810bf78ba7/content/images/2026/09/image-25.png) The authors prepared a related series of complexes described as [Ru(bpc-κ-N²O¹)(tpy-R)](PF₆), where bpc is derived from 2,2′-bipyridine-6-carboxylic acid and tpy-R is a substituted terpyridine. Changing R among NMe₂, H and CF₃ adjusts the electronic influence of the terpyridine ligand while preserving the central ruthenium–carboxylate framework. The structural comparison shows how this electronic change is coupled to the geometry of the Ru-bound carboxylate. The authors focus on the Ru–O¹–C¹–C² torsion angle, which affects how readily the Ru–O bond can open for incoming NH₃. Stronger electron donation and a larger torsion angle both favour ammonia coordination. The measured equilibrium constants consequently follow the order NMe₂ > H > CF₃. When NH₃ enters the coordination sphere, the carboxylate moves away from ruthenium and creates the corresponding Ru–NH₃ complex. This reversible change illustrates the hemilabile role of the ligand: the carboxylate helps define the resting coordination environment but does not permanently block the position required for substrate binding. Electrochemical measurements then separate the influence of the substituent on potential from its influence on catalytic current. The reported redox potentials are 0.28 V for the NMe₂ derivative, 0.57 V for the H derivative and 0.66 V for the CF₃ derivative, all measured versus the ferrocene couple in acetonitrile. The sequence shows that the electron-donating NMe₂ group makes the initial oxidation accessible at the lowest potential. The catalytic currents follow a different trend. Although the NMe₂ complex binds NH₃ most readily and is oxidized at the lowest potential, it gives the smallest catalytic plateau current in the series. The authors interpret this contrast by separating the beginning of the catalytic cycle from the steps that follow. Electron donation facilitates the initial oxidation but makes N–H bond cleavage less favourable. Moving toward the electron-withdrawing CF₃ substituent raises the oxidation potential while promoting the later deprotonation chemistry, leading to a larger catalytic response. Kinetic analysis supports an EC′ mechanism for the Ru–NH₃ complexes. An electrochemical oxidation step is followed by chemical transformations that regenerate the electroactive catalytic form. Within the proposed sequence, the coordinated ammonia is oxidized and deprotonated, and N–N bond formation proceeds through nucleophilic attack by another NH₃ molecule. This route connects the observed dependence on NH₃ coordination with the later formation of N₂. The pendant carboxylate remains involved after opening the coordination site. By comparing the catalyst with related control complexes, the researchers show that removing or constraining this group changes the catalytic response. The authors assign the difference to proton-transfer assistance by the nearby carboxylate, which can accept and relay protons as the coordinated nitrogen species undergo N–H bond cleavage. Time-dependent electrolysis and controlled-potential electrolysis were used to follow the products under sustained operation. For the NMe₂ complex under the specified electrolysis conditions, the reported Faradaic efficiencies for N₂ and H₂ were both above 90%. N₂ formation records the oxidation of ammonia, while H₂ formation at the counter electrode accounts for the accompanying proton reduction. Together with the spectroscopic, binding and electrochemical measurements, these product analyses support the proposed catalytic sequence. ## Takeaways and outlook The ruthenium series shows that NH₃ binding, oxidation potential and catalytic current describe different parts of ammonia oxidation. The NMe₂ substituent supports ammonia coordination and lowers the initial redox potential. The more electron-withdrawing members require a higher potential but better support the N–H cleavage chemistry that contributes to catalytic current. The hemilabile carboxylate connects these stages. It can release the ruthenium coordination site when NH₃ approaches and remain close enough to assist proton transfer after binding. In this way, the ligand does more than adjust the static electronic structure of the metal centre. Its movement and chemical participation help organize the reaction sequence. The authors' design picture combines two variables that can be tuned together: the electronic influence of the substituted terpyridine and the reversible coordination of the carboxylate. Balancing them offers a route toward molecular ammonia-oxidation catalysts that join accessible oxidation potentials with faster N–H cleavage and N–N bond formation. ## About the researchers Jun Li (Westlake University) is the first-listed author. Biaobiao Zhang (Westlake University) is the corresponding author. The other authors are Xiaohuo Shi (Westlake University) and Licheng Sun (Westlake University and Zhejiang Baima Lake Laboratory). ## Original research Jun Li, Xiaohuo Shi, Licheng Sun and Biaobiao Zhang. “Electronic Effects Modulated Hemilabile Carboxylate Coordination of Ruthenium Complexes for Electrocatalytic Ammonia Oxidation.” *Journal of the American Chemical Society*, published online 17 September 2026\. DOI: 10.1021/jacs.6c14417\. [Journal article](https://pubs.acs.org/doi/10.1021/jacs.6c14417?ref=research-pop.com) --- ## Research POP Notes This article reflects the independent interpretation of the Research POP team and does not represent the views of the authors, their institutions or the journal. If you identify any inaccuracies or have concerns regarding the content, figures or attribution, please contact us at [team.researchpop@gmail.com](mailto:team.researchpop@gmail.com). We will review the matter promptly and make corrections or remove the relevant material where appropriate.