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Lee B, Phillips AD, Hanif M, Söhnel T, Hartinger CG. Triazolyl- vs Pyridyl-Functionalized N-Heterocyclic Carbene Complexes: Impact of the Pendant N-Donor Ligand on Intramolecular C-C Bond Formation. ACS ORGANIC & INORGANIC AU 2022; 2:511-524. [PMID: 36510612 PMCID: PMC9732886 DOI: 10.1021/acsorginorgau.2c00035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/29/2022] [Accepted: 08/29/2022] [Indexed: 12/16/2022]
Abstract
Organometallic Rh(Cp*) (Cp* = η5-pentamethylcyclopentadienyl) complexes with monodentate N-heterocyclic carbene (NHC) ligands bearing a pendant anthracenyl substituent have been shown to undergo intramolecular C-C coupling reactions. Herein, two bidentate NHC ligands substituted with pyridyl or triazolyl donor groups were prepared along with the corresponding MII/III (M = RuII, OsII, RhIII, IrIII) complexes. While the Rh(Cp*) complex featuring an NHC-triazole bidentate ligand underwent the equivalent reaction as the monodentate Rh(NHC) complex, i.e., it formed a polydentate ligand, the pyridyl-pendant derivative was unequivocally shown to be unreactive. This contrasting behavior was further investigated by density functional theory (DFT) calculations that highlighted significant differences between the two types of Rh(III) complexes with pendant pyridyl or triazolyl N-coordinating groups. Modeling of the reaction pathways suggests that the initial formation of a dicationic Rh(III) species is unfavorable and that the internal ligand transformation proceeds first by dissociation of the coordinated N atom of the pendant group from the Rh center. After the formation of a neutral η4-fulvene ligand via combined proton/single electron transfer, a cycloaddition occurs between the exo-ene bond of fulvene and the 9' and 10' positions on the pendant anthracenyl group. The resulting experimental UV-visible spectrum recorded in methanol of the polydentate triazolyl-based Rh species revealed the loss of the vibronic coupling typically associated with an anthracenyl functional group. Moreover, TD-DFT modeling indicates the presence of an equilibrium process whereby the N-coordination of the pendant triazolyl group to the RhIII center appears to be highly labile. Charge decomposition analysis (CDA) of the DFT-modeled species with the dissociated triazolyl group revealed a pseudo-η3-allylic interaction between the π-type MOs of the transformed anthracenyl group and the RhIII center; thus, the singly attached chelating ligand is classified as having rare nonadenticity.
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Affiliation(s)
- Betty
Y.T. Lee
- School
of Chemical Sciences, The University of
Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Andrew D. Phillips
- School
of Chemistry, University College Dublin, Belfield, Dublin 4 D04 V1W8, Ireland,
| | - Muhammad Hanif
- School
of Chemical Sciences, The University of
Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Tilo Söhnel
- School
of Chemical Sciences, The University of
Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Christian G. Hartinger
- School
of Chemical Sciences, The University of
Auckland, Private Bag 92019, Auckland 1142, New Zealand,
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2
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Brink A, Jacobs FJF, Helliwell JR. Trends in coordination of rhenium organometallic complexes in the Protein Data Bank. IUCRJ 2022; 9:180-193. [PMID: 35371500 PMCID: PMC8895017 DOI: 10.1107/s2052252522000665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 01/18/2022] [Indexed: 06/14/2023]
Abstract
Radiopharmaceutical development has similar overall characteristics to any biomedical drug development requiring a compound's stability, aqueous solubility and selectivity to a specific disease site. However, organometallic complexes containing 188/186Re or 99mTc involve a d-block transition-metal radioactive isotope and therefore bring additional factors such as metal oxidation states, isotope purity and half life into play. This topical review is focused on the development of radiopharmaceuticals containing the radioisotopes of rhenium and technetium and, therefore, on the occurrence of these organometallic complexes in protein structures in the Worldwide Protein Data Bank (wwPDB). The purpose of incorporating the group 7 transition metals of rhenium/technetium in the protein and the reasons for study by protein crystallography are described, as certain PDB studies were not aimed at drug development. Technetium is used as a medical diagnostic agent and involves the 99mTc isotope which decays to release gamma radiation, thereby employed for its use in gamma imaging. Due to the periodic relationship among group 7 transition metals, the coordination chemistry of rhenium is similar (but not identical) to that of technetium. The types of reactions the potential model radiopharmaceutical would prefer to partake in, and by extension knowing which proteins and biomolecules the compound would react with in vivo, are needed. Crystallography studies, both small molecule and macromolecular, are a key aspect in understanding chemical coordination. Analyses of bonding modes, coordination to particular residues and crystallization conditions are presented. In our Forward look as a concluding summary of this topical review, the question we ask is: what is the best way for this field to progress?
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Affiliation(s)
- Alice Brink
- Chemistry Department, University of the Free State, Nelson Mandela Drive, Bloemfontein, South Africa
- Department of Chemistry, The University of Manchester, Oxford Road, Manchester, United Kingdom
| | - Francois J. F. Jacobs
- Chemistry Department, University of the Free State, Nelson Mandela Drive, Bloemfontein, South Africa
| | - John R. Helliwell
- Department of Chemistry, The University of Manchester, Oxford Road, Manchester, United Kingdom
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3
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Microwave assisted synthesis of rhodium(+Ⅰ) N-heterocyclic carbene complexes and their cytotoxicity against tumor cell lines. J Organomet Chem 2022. [DOI: 10.1016/j.jorganchem.2022.122300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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4
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Tolbatov I, Marrone A. Reactivity of N-Heterocyclic Carbene Half-Sandwich Ru-, Os-, Rh-, and Ir-Based Complexes with Cysteine and Selenocysteine: A Computational Study. Inorg Chem 2021; 61:746-754. [PMID: 34894670 DOI: 10.1021/acs.inorgchem.1c03608] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The structure and the reactivity of four half-sandwich metal complexes of RuII, OsII, RhIII, and IrIII were investigated by means of density functional theory approaches. These piano-stool complexes, grouped in cym-bound complexes, RuII(cym)(dmb)Cl2, 1, and OsII(cym)(dmb)Cl2, 2, and Cp*-bound complexes, RhIII(Cp*)(dmb)Cl2, 3, and IrIII(Cp*)(dmb)Cl2, 4, with cym = η6-p-cymene, Cp* = η5-pentamethylcyclopentadienyl, and dmb = 1,3-dimethylbenzimidazol-2-ylidene, were recently proposed as anticancer metallodrugs that preferably target Cys- or Sec-containing proteins. Thus, density functional theory calculations were performed here to characterize in detail the thermodynamics and the kinetics underlining the targeting of these metallodrugs at either neutral or anionic Cys and Sec side chains. Calculations evidenced that all these complexes preferably target at Cys or Sec via chloro exchange, although cym-bound and Cp*-bound complexes resulted to be more prone to bind at neutral or anionic forms, respectively, of these soft protein sites. Further decomposition analyses of the activation free energies for the reaction between 1-4 complexes and either Cys or Sec, paralleled with the comparison among the optimized transition-state structures, allowed us to spotlight the significant role played by solvation in determining the overall reactivity and selectivity expected for these prototypical metallodrugs.
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Affiliation(s)
- Iogann Tolbatov
- Institut de Chimie Moleculaire de l'Université de Bourgogne (ICMUB), Université de Bourgogne Franche-Comté (UBFC), Avenue Alain Savary 9, 25000 Dijon, France
| | - Alessandro Marrone
- Dipartimento di Farmacia, Università degli Studi "G. D'Annunzio" Chieti-Pescara, Via dei Vestini, 66100 Chieti, Italy
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Cziferszky M, Truong D, Hartinger CG, Gust R. Determination of Relative Stabilities of Metal-Peptide Bonds in the Gas Phase. Chemistry 2021; 27:16401-16406. [PMID: 34554615 PMCID: PMC9298285 DOI: 10.1002/chem.202102385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Indexed: 11/09/2022]
Abstract
Understanding binding site preferences in biological systems as well as affinities to binding partners is a crucial aspect in metallodrug development. We here present a mass spectrometry‐based method to compare relative stabilities of metal‐peptide adducts in the gas phase. Angiotensin 1 and substance P were used as model peptides. Incubation with isostructural N‐heterocyclic carbene (NHC) complexes of RuII, OsII, RhIII, and IrIII led to the formation of various adducts, which were subsequently studied by energy‐resolved fragmentation experiments. The gas‐phase stability of the metal‐peptide bonds depended on the metal and the binding partner. Of the four complexes used, the OsII derivative bound strongest to Met, while RuII formed the most stable coordination bond with His. RhIII was identified as the weakest peptide binder and IrIII formed peptide adducts with intermediate stability. Probing these intrinsic gas‐phase properties can help in the interpretation of biological activities and the design of site‐specific protein binding metal complexes.
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Affiliation(s)
- Monika Cziferszky
- Department of Chemistry and Pharmacy, Institute of Pharmacy, University of Innsbruck, Innrain 80-82, A-6020, Innsbruck, Austria
| | - Dianna Truong
- School of Chemical Sciences, University of Auckland Private Bag, 92019, Auckland 1142, New Zealand
| | - Christian G Hartinger
- School of Chemical Sciences, University of Auckland Private Bag, 92019, Auckland 1142, New Zealand
| | - Ronald Gust
- Department of Chemistry and Pharmacy, Institute of Pharmacy, University of Innsbruck, Innrain 80-82, A-6020, Innsbruck, Austria
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Ségaud N, Johnson C, Farre A, Albrecht M. Exploring the stability of the NHC-metal bond using thiones as probes. Chem Commun (Camb) 2021; 57:10600-10603. [PMID: 34569555 PMCID: PMC8506647 DOI: 10.1039/d1cc02740a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The metal-carbon bond in N-heterocyclic carbene (NHC) metal complexes, which are ubiquitous in modern homogeneous catalysis, is often conjectured to be robust. Here, carbene dissociation was evaluated from a series of complexes with metals of relevance in catalysis containing either an Arduengo-type 2-imidazolylidene or a mesoionic 1,2,3-triazolylidene ligand through thione formation, revealing remarkable kinetic lability of the NHC-metal bond for, e.g. IrIII, RhIII, and NiII complexes.
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Affiliation(s)
- Nathalie Ségaud
- Department of Chemistry & Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Chloë Johnson
- Department of Chemistry & Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Albert Farre
- Department of Chemistry & Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Martin Albrecht
- Department of Chemistry & Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
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Lee BYT, Sullivan MP, Yano E, Tong KKH, Hanif M, Kawakubo-Yasukochi T, Jamieson SMF, Soehnel T, Goldstone DC, Hartinger CG. Anthracenyl Functionalization of Half-Sandwich Carbene Complexes: In Vitro Anticancer Activity and Reactions with Biomolecules. Inorg Chem 2021; 60:14636-14644. [PMID: 34528438 DOI: 10.1021/acs.inorgchem.1c01675] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
N-Heterocyclic carbene (NHC) ligands are widely investigated in medicinal inorganic chemistry. Here, we report the preparation and characterization of a series of half-sandwich [M(L)(NHC)Cl2] (M = Ru, Os, Rh, Ir; L = cym/Cp*) complexes with a N-flanking anthracenyl moiety attached to imidazole- and benzimidazole-derived NHC ligands. The anticancer activity of the complexes was investigated in cell culture studies where, in comparison to a Rh derivative with an all-carbon-donor-atom-based ligand (5a), they were found to be cytotoxic with IC50 values in the low micromolar range. The Ru derivative 1a was chosen as a representative for stability studies as well as for biomolecule interaction experiments. It underwent partial chlorido/aqua ligand exchange in DMSO-d6/D2O to rapidly form an equilibrium in aqueous media. The reactions of 1a with biomolecules proceeded quickly and resulted in the formation of adducts with amino acids, DNA, and protein. Hen egg white lysozyme crystals were soaked with 1a, and the crystallographic analysis revealed an interaction with an l-aspartic acid residue (Asp119), resulting in the cleavage of the p-cymene ligand but the retention of the NHC moiety. Cell morphology studies for the Rh analog 3a suggested that the cytotoxicity is exerted via mechanisms different from that of cisplatin.
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Affiliation(s)
| | | | - Ena Yano
- OBT (Oral Health-Brain Health-Total Health) Research Center, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | | | | | - Tomoyo Kawakubo-Yasukochi
- OBT (Oral Health-Brain Health-Total Health) Research Center, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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8
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Lenzen K, Planchestainer M, Feller I, Padrosa DR, Paradisi F, Albrecht M. Minimalistic peptidic scaffolds harbouring an artificial carbene-containing amino acid modulate reductase activity. Chem Commun (Camb) 2021; 57:9068-9071. [PMID: 34498652 PMCID: PMC8427656 DOI: 10.1039/d1cc03158a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Inspired by the boom of new artificial metalloenzymes, we developed an Fmoc-protected histidinium salt (Hum) as N-heterocyclic carbene precursor. Hum was placed via solid-phase peptide synthesis into short 7-mer peptides. Upon iridation, the metallo-peptidic construct displayed activity in catalytic hydrogenation that outperforms small molecule analogues and which is dependent on the peptide sequence, a typical feature of metalloenzymes.
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Affiliation(s)
- Karst Lenzen
- Department of Chemistry, Biochemistry & Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Matteo Planchestainer
- Department of Chemistry, Biochemistry & Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Isabelle Feller
- Department of Chemistry, Biochemistry & Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - David Roura Padrosa
- Department of Chemistry, Biochemistry & Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Francesca Paradisi
- Department of Chemistry, Biochemistry & Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Martin Albrecht
- Department of Chemistry, Biochemistry & Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
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9
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Loreto D, Merlino A. The interaction of rhodium compounds with proteins: A structural overview. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.213999] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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10
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Mansour AM, Radacki K, Shehab OR. Sulfonate improves water solubility and cell selective toxicity and alters the lysozyme binding activity of half sandwich Rh(iii) complexes. Dalton Trans 2021; 50:10701-10706. [PMID: 34337627 DOI: 10.1039/d1dt00979f] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Introduction of the propyl-sulfonic acid group at N1 of the coordinated 2-(2-pyridyl)benzimidazole ligand (L) in [RhCl(η5-C5Me5)L](CF3SO3) gives rise to a water-soluble complex, which can bind to the model protein lysozyme via non-covalent interactions. The complex shows selective moderate toxicity against Cryptococcus neoformans (MIC = 21.6-43.3 μM) and exhibits no cytotoxicity to healthy HEK293 cells.
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Affiliation(s)
- Ahmed M Mansour
- Department of Chemistry, Faculty of Science, Cairo University, Gamma Street, Giza, Cairo 12613, Egypt.
| | - Krzysztof Radacki
- Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Ola R Shehab
- Department of Chemistry, Faculty of Science, Cairo University, Gamma Street, Giza, Cairo 12613, Egypt.
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Burmeister H, Dietze P, Preu L, Bandow JE, Ott I. Evaluation of Ruthenium(II) N-Heterocyclic Carbene Complexes as Antibacterial Agents and Inhibitors of Bacterial Thioredoxin Reductase. Molecules 2021; 26:4282. [PMID: 34299558 PMCID: PMC8303947 DOI: 10.3390/molecules26144282] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 07/03/2021] [Accepted: 07/12/2021] [Indexed: 11/26/2022] Open
Abstract
A series of ruthenium(II) complexes with N-heterocyclic carbene (NHC) ligands of the general type (arene)(NHC)Ru(II)X2 (where X = halide) was prepared, characterized, and evaluated as antibacterial agents in comparison to the respective metal free benzimidazolium cations. The ruthenium(II) NHC complexes generally triggered stronger bacterial growth inhibition than the metal free benzimidazolium cations. The effects were much stronger against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) than against Gram-negative bacteria (Escherichia coli, Acinetobacter baumannii, Pseudomonas aeruginosa), and all complexes were inactive against the fungus Candida albicans. Moderate inhibition of bacterial thioredoxin reductase was confirmed for selected complexes, indicating that inhibition of this enzyme might be a contributing factor to the antibacterial effects.
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Affiliation(s)
- Hilke Burmeister
- Institute of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Beethovenstr. 55, 38106 Braunschweig, Germany; (H.B.); (L.P.)
| | - Pascal Dietze
- Applied Microbiology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Universitätsstr. 150, 44801 Bochum, Germany; (P.D.); (J.E.B.)
| | - Lutz Preu
- Institute of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Beethovenstr. 55, 38106 Braunschweig, Germany; (H.B.); (L.P.)
| | - Julia E. Bandow
- Applied Microbiology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Universitätsstr. 150, 44801 Bochum, Germany; (P.D.); (J.E.B.)
| | - Ingo Ott
- Institute of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Beethovenstr. 55, 38106 Braunschweig, Germany; (H.B.); (L.P.)
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Mansour AM, Radacki K, Shehab OR. Half-sandwich triazolato Rh(III) compound of pyridylbenzimidazole ligand with cell selective toxicity towards Cryptococcus neoformans. J Organomet Chem 2021. [DOI: 10.1016/j.jorganchem.2021.121928] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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13
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Abstract
Recent advances in structural studies unveiling the basis of the metal compounds/protein recognition process are discussed.
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Affiliation(s)
- Antonello Merlino
- Department of Chemical Sciences
- University of Naples Federico II
- Complesso Universitario di Monte Sant’Angelo
- Napoli
- Italy
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