aurorede

• Denjean, Aurore Evelyne Francine; Badia, David Balcells & Flores, Ainara Nova (2026). Impact of metal and active site configurations in hydrogenation reactions with N-doped graphene single atom catalysts. Journal of Materials Chemistry A. ISSN 2050-7488. 14(12), p. 6885–6893. doi: 10.1039/d5ta08094k. Full text in Research Archive Show summary

  Hydrogenation reactions are well-established transformations in both homogeneous and heterogeneous catalysis and are increasingly explored using single-atom catalysts (SACs). Despite this progress, a comprehensive understanding of the underlying reaction mechanisms remains limited, often restricted to specific systems. Moreover, the precise nature of the active sites is elusive, and their reactivity may be influenced by varying coordination numbers, hetero-atom doping, and other factors. To gain insight into hydrogenation reactions in nitrogen-doped graphene-based SACs, we conducted a thorough investigation into hydrogen transfer across Fe, Co, Mn, and Ru systems, considering different charges, spin states, pyrrolic and pyridinic sites. Our findings reveal substantial deviation from conventional homogeneous and heterogeneous systems, with SACs being strongly influenced by the nature of the active site. Analyses using Natural Bond Orbitals (NBO), natural charge, and natural decomposition analysis (NEDA) highlighted differences in nitrogen-metal interactions as a key factor driving the observed reactivity variations between Pyrr and Py systems, as well as between Ru and 1st-row metals.

• Borys, Andryj. M.; Denjean, Aurore Evelyne Francine; Vedani, Luca; Badia, David Balcells & Hevia, Eva (2025). Biphenylene Coordination and Ring‐Opening by Alkali‐Metal Nickelates. Angewandte Chemie International Edition. ISSN 1433-7851. 64(19). doi: 10.1002/anie.202501995. Full text in Research Archive Show summary

  Abstract The pre‐coordination of substrates to heterobimetallic complexes plays a key role in facilitating challenging bond activations and catalytic reactions. Herein, we report a family of low‐valent phenyl‐alkali‐metal nickelates containing a η 4 ‐coordinated biphenylene ligand and demonstrate how the coordination and solvation preferences of the alkali‐metal cation (Li, Na, or K) influence the rate of C─C bond oxidative addition at nickel through combined structural, spectroscopic and computational studies. The rate of C─C bond cleavage can be further manipulated by replacing the two phenyl‐carbanionic ligands with a cyclic 2,2′‐biphenyl scaffold, which affords thermally stable and symmetric spirocyclic nickelates upon ring‐opening.

• Denjean, Aurore Evelyne Francine; Flores, Ainara Nova & Badia, David Balcells (2024). Borrowing Hydrogen Mechanism in Amine Alkylation by Single Atom Nickel Catalysts. ACS Catalysis. 14(15), p. 11332–11342. doi: 10.1021/acscatal.4c02182. Full text in Research Archive Show summary

  The alkylation of amines with alcohols by borrowing hydrogen (BH) is a versatile synthetic route to various relevant compounds, including drugs and agrochemicals. The atom economy of this reaction, with water as the sole byproduct, entails a complex mechanism in which alcohol activation can follow multiple competing pathways. The interest in single atom catalysts (SACs) combining the advantages of homogeneous and heterogeneous systems motivated this computational study on BH catalyzed by nickel SACs. We found that the oxidation, charge, and spin states of the system, as well as the geometry of the support, all have a strong influence on the BH mechanism. The pyrrolic support was the most reactive in a dicationic state with nearly degenerate singlet and triplet configurations. The free energy of the catalyst hydrogenation by H2 was strongly correlated to its reactivity, thus being a useful descriptor. Further, the mechanism followed an unusual reaction pathway in which the support takes and delivers the H equivalents, with the metal playing a spectator role. This study provides useful insights for the further development of BH SACs.

• Denjean, Aurore Evelyne Francine; Rio, Jordan; Ciofini, Ilaria; Perrin, Marie-Eve L. & Payard, Pierre-Adrien (2024). Computed versus experimental energy barriers in solution: Influence of the type of the density functional approximation. Journal of Computational Chemistry. ISSN 0192-8651. doi: 10.1002/jcc.27436. Full text in Research Archive

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• Denjean, Aurore Evelyne Francine; Flores, Ainara Nova & Badia, David Balcells (2024). Amine Alkylation with Single Atom Nickel Catalysts: Computational Insights into the Hydrogen Borrowing Mechanism. Full text in Research Archive
• Denjean, Aurore Evelyne Francine; Flores, Ainara Nova & Badia, David Balcells (2024). Graphene-based Nickel(II) Single-Atom Catalyst for Borrowing Hydrogen: a DFT study. Full text in Research Archive
• Denjean, Aurore Evelyne Francine; Flores, Ainara Nova & Badia, David Balcells (2024). Computational Insights into Graphene-Based Single Atom Nickel Catalysts for Amine Alkylation via the Borrowing Hydrogen Mechanism. Full text in Research Archive
• Denjean, Aurore Evelyne Francine (2025). Structure, Reactivity, and Dynamics of Transition Metals for Catalysis Applications: A computational journey from molecular to single-atom systems. Universitetet i Oslo. Full text in Research Archive Show summary

  Computational studies hold a significant role in understanding and discovering increasingly complex and efficient chemical systems. In this thesis and its three articles, I will guide you through the fascinating aspects of transition metal systems, their application in catalysis, particularly in reactions for the synthesis of fine chemical precursors, and the different forms they can take. We will explore several computational techniques that will be used to study these systems, including nucleus-independent chemical shifts, non-covalent interaction plots, natural bond orbitals, natural energy decomposition analysis, ab initio molecular dynamics, and static density functional theory calculations. After discussing their strengths and weaknesses, we will see firsthand examples of how they can be employed to explain observed reactivity and to derive design principles for more efficient catalysts. We will begin this journey with molecular nickelate complexes incorporating alkali metal moieties (Li, Na, K); Article I, and finish it with N-doped graphene-based single-atom catalysts (SACs); Articles II & III. The first study will aim to shed light on the role of the alkali metal moiety, a novelty for systems used in the reaction studied. Our collaborator discovered that Li, Na, and K have significantly different effects on reactivity. But how and why? Computational insights will help to explain the differences in reactivity observed experimentally for C-C bond activation in biphenylene within these systems. Electron distribution and dynamic behavior will prove to be crucial for understanding their reactivity and structure. The second study will focus on systems that seek to preserve the strengths of molecular catalysts while integrating the qualities of heterogeneous systems. In SACs, the metal atoms are dispersed throughout a heterogeneous matrix, and these single sites are believed to exhibit behavior similar to that of homogeneous catalysts. Is this truly the case? The unique reactivity of SACs in hydrogenation reactions will be exposed through detailed structural and reactivity modeling. The different geometrical and electronic structures of the single sites will be seen to affect the reactivity of N-doped graphene SACs significantly. Additionally, the impact of the metal will be thoroughly investigated, as well as the active site configurations, for which natural charge, bond orbitals, and energy decomposition analysis will clarify the differences in reactivity. Overall, these two studies will show the power of computational tools both to explain experimental phenomena and to guide the design of more efficient systems.

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