About

Nadia G. Léonard is an Assistant Professor in the Department of Chemistry & Biochemistry at the University of California, Santa Barbara, joining the faculty in 2023. Her research is centered on the design of inorganic molecular complexes and materials with unique physical and catalytic properties aimed at addressing global challenges related to energy storage and conversion, pollutant sensing, and sustainable catalysis. Her work applies principles from coordination chemistry, enzymatic active sites, and electrochemistry to rationally tune the behavior and reactivity of synthetic systems, with initial targets including the activation of pollutants such as CO2 into valuable multi-carbon organic products, the design of earth-abundant photoactive complexes for photochemical and catalytic applications, and the development of chemical sensing materials. Her approach combines synthesis with electrochemical and spectroscopic techniques, employing physical characterization, mechanistic analysis, and kinetic studies to improve complex design and optimize reactivity. Dr. Léonard's background includes a Sc.B. in Chemistry from Brown University and a Ph.D. in Chemistry from Princeton University, where she was an NSF Graduate Research Fellow working on earth-abundant transition metal catalysts for site-selective C–H functionalization. She further conducted postdoctoral research at the University of California, Irvine, focusing on understanding electrostatic interactions in enzymatic processes and their incorporation into synthetic systems. Her contributions to the field include advancing knowledge in catalysis, electrochemistry, and coordination chemistry, with numerous publications highlighting her research.

Research topics

• Chemistry
• Crystallography
• Materials science
• Inorganic chemistry
• Medicinal chemistry

Selected publications

• Mixed-Valent Dinuclear Nickel Complexes Enabled by an Expanded PNNP Pincer Ligand

  Inorganic Chemistry · 2025-10-30 · 1 citations

  articleCorresponding

  We report the synthesis and characterization of a family of mixed-valent dinickel complexes, formally Ni23+, featuring a naphthyridine-based PNNPiPr pincer ligand (PNNPiPr = 2,7-bis(di-iso-propylphosphino-methyl)-1,8-naphthyridine). The mixed valent Ni23+ complexes, [Ni2(μ-Br)2PNNPiPr]2[NiBr4] (1), [Ni2(κ2-OAc)3PNNPiPr] (2), and [Ni2(κ2-OPiv)3PNNPiPr] (3), were synthesized from the addition of two equivalents of a nickel(II) salt followed by an additional equivalent of Ni(COD)2 (COD = cyclooctadiene) to the PNNPiPr ligand. The delocalized Ni23+ mixed valence assignment was corroborated by single-crystal X-ray diffraction, electron paramagnetic resonance, and magnetic susceptibility measurements. In addition to these measurements, the presence of the Ni–Ni bond and symmetrical structure qualifies these complexes as Class III mixed valence in the Robin-Day classification scheme. Cyclic voltammetry experiments used to characterize the redox properties of these complexes exhibited a metal-centered, quasi-reversible couple associated with the Ni2(II,II)/Ni2(I,II) reduction event, with E1/2 values ranging from −0.83 V to −1.05 V vs (C5H5)2Fe+/0 in acetonitrile for the series. Further tracking by UV–vis spectroscopy showed that the mixed-valent and (PNNPiPr)Ni2(II,II) complexes can be interconverted through either chemical oxidation or reduction using ferrocenium tetrafluoroborate ([(C5H5)2Fe][BF4]) or cobaltocene ((C5H5)2Co), respectively.

  PublisherDOI

• Mixed-valency in multinuclear nickel complexes: From fundamentals to nickel enzymes

  Journal of Inorganic Biochemistry · 2025-11-11 · 1 citations

  articleOpen access

  Mixed-valent multi-metallic complexes provide crucial insight into how electron transfer operates in both biological proteins/enzymes and synthetic inorganic compounds. Nature offers striking examples, such as the oxygen-evolving complex (OEC) of photosystem II, where mixed valency plays an essential role in facilitating proton-coupled electron transfer (PCET). Elucidating the function of such systems serves as a foundation for the design of bioinspired catalysts. Nickel, with its rich redox flexibility, is well positioned to form mixed-valent binuclear complexes across several oxidation states, including Ni₂(I,0), Ni₂(I,II), and Ni₂(II,III) dinuclear complexes. Several such systems mirror the redox profiles of enzymes like acetyl-CoA synthase, which is central to C1 metabolism. This perspective highlights the emerging landscape of multinuclear nickel complexes, focusing on their structural classification and redox behavior. Special attention is given to a newly characterized family of Class III Ni₂(I,II) complexes, which exhibit fully delocalized valency. Collectively, this work underscores how mixed-valent states not only advance our understanding of electron transfer mechanisms but can also guide the development of new redox-active materials for catalysis. Professor Harry Gray has influenced the field of electron transfer in both inorganic and biological systems. Here, we explore the different variations of mixed valent enzymes in manganese, iron, and nickel and their roles in electron transfer; and specifically focus on multinuclear nickel mixed valent complexes. • The role mixed valent enzymes play in electron and proton-coupled electron transfer • Overview of multinuclear nickel mixed valent complexes • Robin-Day classification for nickel complexes and their redox behavior • A new family of binuclear mixed valent complexes featuring expanded naphthyridine ligand

  PublisherDOI

• Synthesis and anion binding properties of (thio)urea functionalized Ni( <scp>ii</scp> )-salen complexes

  Dalton Transactions · 2024-11-01 · 2 citations

  article

  Symmetric (thio)urea and an unsymmetric urea functionalized salen complexes of Ni(II) were synthesized and studied for anion binding using 1H and 19F NMR spectroscopy and DOSY NMR experiments.

  PublisherDOI

• Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes

  ChemRxiv · 2023-02-03

  preprintOpen accessSenior author

  The incorporation of charged groups proximal to a redox active transition metal center is an attractive strategy for altering redox behavior, installing electric fields, and enhancing catalysis. Vanadyl salen (salen = N,N-ethylenebis(salicylideneaminato)) complexes functionalized with a crown ether containing a non-redox active Lewis acidic metal cation (V-Na, V-K, V-Ba, V-La, V-Ce, and V-Nd) were synthesized. The electrochemical behavior of this series of complexes was investigated by cyclic voltammetry in solvents with varying polarity and dielectric constant (acetonitrile = 37.5; N,N-dimethylformamide = 36.7; and dichloromethane = 8.93). The vanadium(V/IV) reduction potential shifted anodically (&gt;900 mV in acetonitrile and &gt;700 mV in dichloromethane) with increasing cation charge as compared to complexes lacking the proximal cation. The reduction potential for all vanadyl salen-crown complexes measured in N,N-dimethylformamide was insensitive to cation charge magnitude, regardless of electrolyte or counter anion used. Titration studies of N,N-dimethylformamide into acetonitrile resulted in cathodic shifting of the vanadium(V/IV) reduction potential with increasing concentration of N,N-dimethylformamide. Binding constants of N,N-dimethylformamide (log(KDMF)) for the series of crown complexes show increased binding affinity in the order of V-La&gt;V-Ba&gt;V-K&gt;(salen)V(O), indicating an enhancement of Lewis acid/base interaction with increase of cation charge. The redox behavior of (salen)V(O) and (salen-OMe)V(O) (salen-OMe = N,N-ethylenebis(3-methoxysalicylideneamine) was also investigated and compared to the crown-containing complexes. For (salen-OMe)V(O), a weak association of triflate salt at the vanadium(IV) oxidation state was observed through cyclic voltammetry titration experiments and cation dissociation upon oxidation to vanadium(V) was identified. These studies demonstrates the non-innocent role of solvent coordination and cation/anion effects on redox behavior.

  PublisherOA PDFDOI

• Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen–Crown Complexes

  The Journal of Physical Chemistry A · 2023-06-14 · 19 citations

  articleOpen accessSenior authorCorresponding

  The incorporation of charged groups proximal to a redox active transition metal center can impact the local electric field, altering redox behavior and enhancing catalysis. Vanadyl salen (salen = N,N′-ethylenebis(salicylideneaminato)) complexes functionalized with a crown ether containing a nonredox active metal cation (V-Na, V-K, V-Ba, V-La, V-Ce, and V-Nd) were synthesized. The electrochemical behavior of this series of complexes was investigated by cyclic voltammetry in solvents with varying polarity and dielectric constant (ε) (acetonitrile, ε = 37.5; N,N-dimethylformamide, ε = 36.7; and dichloromethane, ε = 8.93). The vanadium(V/IV) reduction potential shifted anodically with increasing cation charge compared to a complex lacking a proximal cation (ΔE1/2 > 900 mV in acetonitrile and >700 mV in dichloromethane). In contrast, the reduction potential for all vanadyl salen–crown complexes measured in N,N-dimethylformamide was insensitive to the magnitude of the cationic charge, regardless of the electrolyte or counteranion used. Titration studies of N,N-dimethylformamide into acetonitrile resulted in cathodic shifting of the vanadium(V/IV) reduction potential with increasing concentration of N,N-dimethylformamide. Binding constants of N,N-dimethylformamide (log(KDMF)) for the series of crown complexes show increased binding affinity in the order of V-La > V-Ba > V-K > (salen)V(O), indicating an enhancement of Lewis acid/base interaction with increasing cationic charge. The redox behavior of (salen)V(O) and (salen-OMe)V(O) (salen-OMe = N,N′-ethylenebis(3-methoxysalicylideneamine) was also investigated and compared to the crown-containing complexes. For (salen-OMe)V(O), a weak association of triflate salt at the vanadium(IV) oxidation state was observed through cyclic voltammetry titration experiments, and cation dissociation upon oxidation to vanadium(V) was identified. These studies demonstrate the noninnocent role of solvent coordination and cation/anion effects on redox behavior and, by extension, the local electric field.

  PublisherOA PDFDOI

• CCDC 2108908: Experimental Crystal Structure Determination

  The Cambridge Structural Database · 2022-01-21

  datasetOpen access1st authorCorresponding
  PublisherDOI

• Cationic Effects on the Net Hydrogen Atom Bond Dissociation Free Energy of High-Valent Manganese Imido Complexes

  Journal of the American Chemical Society · 2022-01-18 · 48 citations

  articleOpen access1st author

  Local electric fields can alter energy landscapes to impart enhanced reactivity in enzymes and at surfaces. Similar fields can be generated in molecular systems using charged functionalities. Manganese(V) salen nitrido complexes (salen = N,N′-ethylenebis(salicylideneaminato)) appended with a crown ether unit containing Na+ (1-Na), K+, (1-K), Ba2+ (1-Ba), Sr2+ (1-Sr), La3+ (1-La), or Eu3+ (1-Eu) cation were investigated to determine the effect of charge on pKa, E1/2, and the net bond dissociation free energy (BDFE) of N–H bonds. The series, which includes the manganese(V) salen nitrido without an appended crown, spans 4 units of charge. Bounds for the pKa values of the transient imido complexes were used with the Mn(VI/V) reduction potentials to calculate the N–H BDFEs of the imidos in acetonitrile. Despite a span of >700 mV and >9 pKa units across the series, the hydrogen atom BDFE only spans ∼6 kcal/mol (between 73 and 79 kcal/mol). These results suggest that the incorporation of cationic functionalities is an effective strategy for accessing wide ranges of reduction potentials and pKa values while minimally affecting the BDFE, which is essential to modulating electron, proton, or hydrogen atom transfer pathways.

  PublisherOA PDFDOI

• CCDC 2108907: Experimental Crystal Structure Determination

  The Cambridge Structural Database · 2022-01-21

  datasetOpen access1st authorCorresponding
  PublisherDOI

• Correction to “Cobalt-Catalyzed C(sp²)–H Borylation with an Air-Stable, Readily Prepared Terpyridine Cobalt(II) Bis(acetate) Precatalyst”

  Organometallics · 2021-07-14 · 2 citations

  article1st authorCorresponding

  ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to "Cobalt-Catalyzed C(sp2)–H Borylation with an Air-Stable, Readily Prepared Terpyridine Cobalt(II) Bis(acetate) Precatalyst"Nadia G. LéonardNadia G. LéonardMore by Nadia G. Léonardhttps://orcid.org/0000-0002-0949-5471, Máté J. BezdekMáté J. BezdekMore by Máté J. Bezdekhttps://orcid.org/0000-0001-7860-2894, and Paul J. Chirik*Paul J. ChirikMore by Paul J. Chirikhttps://orcid.org/0000-0001-8473-2898Cite this: Organometallics 2021, 40, 15, 2761Publication Date (Web):July 14, 2021Publication History Published online14 July 2021Published inissue 9 August 2021https://pubs.acs.org/doi/10.1021/acs.organomet.1c00395https://doi.org/10.1021/acs.organomet.1c00395correctionACS PublicationsCopyright © 2021 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views1380Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (477 KB) Get e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

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• Cationic Effects on the Effective Hydrogen Atom Bond Dissociation Free Energy of High Valent Manganese Imido Complexes

  2021-09-13

  preprintOpen access1st authorCorresponding

  Local electric fields can alter energy landscapes to impart enhanced reactivity in enzymes and at surfaces. There has been renewed interest on their use in molecular systems, where they can be installed using charged functionalities. Manga-nese(V) salen nitrido complexes (salen = N,N’-ethylenebis(salicylideneaminato)) appended with a crown ether unit con-taining a Na+ (1-Na), K+, (1-K), Ba2+ (1-Ba), Sr2+ (1-Sr), La3+ (1-La), or Eu3+ (1-Eu) cation were investigated to experimen-tally demonstrate the effect of cation-induced electric fields on pKa, E1/2, and the effective bond dissociation free energy (BDFE) of N–H bonds. The series, which includes the manganese (V) salen nitrido without a crown appended, spans 4 units of charge. Bounds for the pKa values of the transient imido complexes were determined by UV-visible and 1H NMR spectroscopy. These values, together with the reduction potentials for the Mn(VI/V) couple measured by cyclic voltamme-try in acetonitrile, were used to calculated the N–H BDFEs of the imidos. Despite spanning &gt;700 mV and &gt;9 pKa units across the series, the hydrogen atom BDFE only spans ~ 5 kcal/mol (between 76 and 81 kcal/mol). These results suggest that incorporation of cationic functionalities is an effective strategy for accessing wide ranges of reduction potentials and pKa while minimally affecting BDFE, which is essential to modulating electron, proton, or hydrogen atom transfer path-ways.

  PublisherDOI

Frequent coauthors

• Paul J. Chirik

  18 shared

• Jenny Y. Yang

  University of California, Irvine

  10 shared

• Máté J. Bezdek

  10 shared

• Teera Chantarojsiri

  Mahidol University

  9 shared

• Scott P. Semproni

  Intel (United States)

  7 shared

• Hongyu Zhong

  ETH Zurich

  7 shared

• Stephan M. Rummelt

  Merck & Co., Inc., Rahway, NJ, USA (United States)

  7 shared

• Joseph W. Ziller

  University of California, Irvine

  6 shared

Labs

• Léonard LabPI

Awards & honors

• NSF Graduate Research Fellow