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Keszei S, Wang Y, Zhou H, Ollár T, Kováts É, Frey K, Tapasztó L, Shen S, Pap JS. Hydrogen evolution driven by heteroatoms of bidentate N-heterocyclic ligands in iron(II) complexes. Dalton Trans 2024; 53:14817-14829. [PMID: 39171517 DOI: 10.1039/d4dt02081b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2024]
Abstract
While Pt is considered the best catalyst for the electrocatalytic hydrogen evolution reaction (HER), it is evident that non-noble metal alternatives must be explored. In this regard, it is well known that the binding sites for non-noble metals play a pivotal role in facilitating efficient catalysis. Herein, we studied Fe(II) complexes with bidentate 2-(2'-pyridyl)benzoxazole (LO), 2-(2'-pyridyl)benzthiazole (LS), 2-(2'-pyridyl)benzimidazole (LNH), and 2-2'-bipyridyl (Lpy) ligands - by adding trifluoroacetic acid (TFA) to their acetonitrile solution - in order to examine how their reactivity towards protons under reductive conditions could be impacted by the non-coordinating heteroatoms (S, O, N, or none). By applying this ligand series, we found that the reduction potentials relevant for HER correlate with ligand basicity in the presence of TFA. Moreover, DFT calculations underlined the importance of charge distribution in the ligand-based LUMO and LUMO+1 orbitals of the complexes, dependent on the heterocycle. Kinetic studies and controlled potential electrolysis - using TFA as a proton source - revealed HER activities for the complexes with LNH, LO, and LS of kobs = 0.03, 1.1, and 10.8 s-1 at overpotentials of 0.81, 0.76, and 0.79 V, respectively, and pointed towards a correlation between the kinetics of the reaction and the non-coordinating heteroatoms of the ligands. In particular, the activity was associated with the [Fe(LS/O/NH)2(S)2]2+ form (S = solvent or substrate molecule), and the rate-determining step involved the formation of [Fe(H-H)]+, during the weakening of Fe-H and CF3CO2-H bonds, according to the experimental and DFT results.
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Affiliation(s)
- Soma Keszei
- Centre for Energy Research, Institute of Technical Physics and Materials Science, H-1121, Konkoly-Thege út 29-33, Budapest, Hungary.
- Centre for Energy Research, Surface Chemistry and Catalysis Department, H-1121, Konkoly-Thege út 29-33, Budapest, Hungary
| | - Yiqing Wang
- International Research Center for Renewable Energy (IRCRE), State Key Laboratory of Multiphase Flow in Power Engineering (MFPE), Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Haotian Zhou
- International Research Center for Renewable Energy (IRCRE), State Key Laboratory of Multiphase Flow in Power Engineering (MFPE), Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Tamás Ollár
- Centre for Energy Research, Surface Chemistry and Catalysis Department, H-1121, Konkoly-Thege út 29-33, Budapest, Hungary
| | - Éva Kováts
- Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, P.O. Box 49, H-1525 Budapest, Hungary
| | - Krisztina Frey
- Centre for Energy Research, Surface Chemistry and Catalysis Department, H-1121, Konkoly-Thege út 29-33, Budapest, Hungary
| | - Levente Tapasztó
- Centre for Energy Research, Institute of Technical Physics and Materials Science, H-1121, Konkoly-Thege út 29-33, Budapest, Hungary.
| | - Shaohua Shen
- International Research Center for Renewable Energy (IRCRE), State Key Laboratory of Multiphase Flow in Power Engineering (MFPE), Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - József Sándor Pap
- Centre for Energy Research, Surface Chemistry and Catalysis Department, H-1121, Konkoly-Thege út 29-33, Budapest, Hungary
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Török P, Lakk-Bogáth D, Kaizer J. Effect of Redox Potential on Diiron-Mediated Disproportionation of Hydrogen Peroxide. Molecules 2023; 28:molecules28072905. [PMID: 37049667 PMCID: PMC10096046 DOI: 10.3390/molecules28072905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 03/20/2023] [Accepted: 03/22/2023] [Indexed: 04/14/2023] Open
Abstract
Heme and nonheme dimanganese catalases are widely distributed in living organisms to participate in antioxidant defenses that protect biological systems from oxidative stress. The key step in these processes is the disproportionation of H2O2 to O2 and water, which can be interpreted via two different mechanisms, namely via the formation of high-valent oxoiron(IV) and peroxodimanganese(III) or diiron(III) intermediates. In order to better understand the mechanism of this important process, we have chosen such synthetic model compounds that can be used to map the nature of the catalytically active species and the factors influencing their activities. Our previously reported μ-1,2-peroxo-diiron(III)-containing biomimics are good candidates, as both proposed reactive intermediates (FeIVO and FeIII2(μ-O2)) can be derived from them. Based on this, we have investigated and compared five heterobidentate-ligand-containing model systems including the previously reported and fully characterized [FeII(L1-4)3]2+ (L1 = 2-(2'-pyridyl)-1H-benzimidazole, L2 = 2-(2'-pyridyl)-N-methyl-benzimidazole, L3 = 2-(4-thiazolyl)-1H-benzimidazole and L4 = 2-(4'-methyl-2'-pyridyl)-1H-benzimidazole) and the novel [FeII(L5)3]2+ (L5 = 2-(1H-1,2,4-triazol-3-yl)-pyridine) precursor complexes with their spectroscopically characterized μ-1,2-peroxo-diiron(III) intermediates. Based on the reaction kinetic measurements and previous computational studies, it can be said that the disproportionation reaction of H2O2 can be interpreted through the formation of an electrophilic oxoiron(IV) intermediate that can be derived from the homolysis of the O-O bond of the forming μ-1,2-peroxo-diiron(III) complexes. We also found that the disproportionation rate of the H2O2 shows a linear correlation with the FeIII/FeII redox potential (in the range of 804 mV-1039 mV vs. SCE) of the catalysts controlled by the modification of the ligand environment. Furthermore, it is important to note that the two most active catalysts with L3 and L5 ligands have a high-spin electronic configuration.
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Affiliation(s)
- Patrik Török
- Research Group of Bioorganic and Biocoordination Chemistry, University of Pannonia, H-8201 Veszprém, Hungary
| | - Dóra Lakk-Bogáth
- Research Group of Bioorganic and Biocoordination Chemistry, University of Pannonia, H-8201 Veszprém, Hungary
| | - József Kaizer
- Research Group of Bioorganic and Biocoordination Chemistry, University of Pannonia, H-8201 Veszprém, Hungary
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Bavi EP, Shakerinasab E, Hamidinezhad H, Nazifi E. A green and facile approach for fabrication of biocompatible anti-Parkinson chitosan-gelatin-green tea extract composite particles with neuroprotective and Neurotherapeutic effects: In vitro evaluation. Int J Biol Macromol 2022; 224:1183-1195. [DOI: 10.1016/j.ijbiomac.2022.10.204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 10/19/2022] [Accepted: 10/22/2022] [Indexed: 11/05/2022]
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Biomimetic Radical Chemistry and Applications. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27072042. [PMID: 35408441 PMCID: PMC9000372 DOI: 10.3390/molecules27072042] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 03/16/2022] [Indexed: 01/02/2023]
Abstract
Some of the most interesting aspects of free radical chemistry that emerged in the last two decades are radical enzyme mechanisms, cell signaling cascades, antioxidant activities, and free radical-induced damage of biomolecules. In addition, identification of modified biomolecules opened the way for the evaluation of in vivo damage through biomarkers. When studying free radical-based chemical mechanisms, it is very important to establish biomimetic models, which allow the experiments to be performed in a simplified environment, but suitably designed to be in strict connection with cellular conditions. The 28 papers (11 reviews and 17 articles) published in the two Special Issues of Molecules on "Biomimetic Radical Chemistry and Applications (2019 and 2021)" show a remarkable range of research in this area. The biomimetic approach is presented with new insights and reviews of the current knowledge in the field of radical-based processes relevant to health, such as biomolecular damages and repair, signaling and biomarkers, biotechnological applications, and novel synthetic approaches.
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