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Urban A, De Feyter S. Making and Breaking Helical Open-Chain Oligopyrroles. Chempluschem 2024; 89:e202300708. [PMID: 38224308 DOI: 10.1002/cplu.202300708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 01/15/2024] [Accepted: 01/15/2024] [Indexed: 01/16/2024]
Abstract
Closed-chain oligopyrroles such as porphyrins or corroles have been well-established in literature and experience a steadily strong interest by several fields of science. However, their open-chain derivatives are comparatively underrepresented, despite their intriguing properties and promising applications. Here, we aim to review typical synthetic routes, as well as point towards several emergent properties, marking them as interesting candidates for various fields of study. The review focuses on two traditional methods (each starting from highly symmetric metalloporphyrins) and then expands its scope towards more recent variations before moving on to more exotic and recent highlights that have yet to be included into the canon. Key chemical reactivities (ring closure, substitution and fragmentation) are then followed by notable physicochemical properties, placing special emphasis on potential uses in molecular electronics and sensors.
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Affiliation(s)
- Adrian Urban
- Division of Molecular Imaging and Photonics, Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200 F, 3001, Leuven, Belgium
| | - Steven De Feyter
- Division of Molecular Imaging and Photonics, Department of Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200 F, 3001, Leuven, Belgium
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2
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Singh K, Kundu A, Adhikari D. Ligand-Based Redox: Catalytic Applications and Mechanistic Aspects. ACS Catal 2022. [DOI: 10.1021/acscatal.2c02655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kirti Singh
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, SAS Nagar, Manauli 140306, India
| | - Abhishek Kundu
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, SAS Nagar, Manauli 140306, India
| | - Debashis Adhikari
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, SAS Nagar, Manauli 140306, India
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Wu T, Wang S, Lv Y, Fu T, Jiang J, Lu X, Yu ZP, zhang J, Wang L, Zhou HP. A New Bis(thioether)-Dipyrrin N2S2 Ligand and Its Coordination Behaviors to Nickel, Copper and Zinc. Dalton Trans 2022; 51:9699-9707. [DOI: 10.1039/d2dt01282k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Tetradentate N2S2 coordination platforms are widespread in biological system and have endowed the metalloenzymes and metalloproteins with abundant reactivities and functions. However, there have only three types of N2S2 scaffolds...
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Tomat E, Curtis CJ. Biopyrrin Pigments: From Heme Metabolites to Redox-Active Ligands and Luminescent Radicals. Acc Chem Res 2021; 54:4584-4594. [PMID: 34870973 DOI: 10.1021/acs.accounts.1c00613] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Redox-active ligands in coordination chemistry not only modulate the reactivity of the bound metal center but also serve as electron reservoirs to store redox equivalents. Among many applications in contemporary chemistry, the scope of redox-active ligands in biology is exemplified by the porphyrin radicals in the catalytic cycles of multiple heme enzymes (e.g., cytochrome P450, catalase) and the chlorophyll radicals in photosynthetic systems. This Account reviews the discovery of two redox-active ligands inspired by oligopyrrolic fragments found in biological settings as products of heme metabolism.Linear oligopyrroles, in which pyrrole heterocycles are linked by methylene or methine bridges, are ubiquitous in nature as part of the complex, multistep biosynthesis and degradation of hemes and chlorophylls. Bile pigments, such as biliverdin and bilirubin, are common and well-studied tetrapyrroles with characteristic pyrrolin-2-one rings at both terminal positions. The coordination chemistry of these open-chain pigments is less developed than that of porphyrins and other macrocyclic oligopyrroles; nevertheless, complexes of biliverdin and its synthetic analogs have been reported, along with fluorescent zinc complexes of phytobilins employed as bioanalytical tools. Notably, linear conjugated tetrapyrroles inherit from porphyrins the ability to stabilize unpaired electrons within their π system. The isolated complexes, however, present helical structures and generally limited stability.Smaller biopyrrins, which feature three or two pyrrole rings and the characteristic oxidized termini, have been known for several decades following their initial isolation as urinary pigments and heme metabolites. Although their coordination chemistry has remained largely unexplored, these compounds are structurally similar to the well-established tripyrrin and dipyrrin ligands employed in a broad variety of metal complexes. In this context, our study of the coordination chemistry of tripyrrin-1,14-dione and dipyrrin-1,9-dione was motivated by the potential to retain on these compact, versatile platforms the reversible ligand-based redox chemistry of larger tetrapyrrolic systems.The tripyrrindione ligand coordinates several divalent transition metals (i.e., Pd(II), Ni(II) Cu(II), Zn(II)) to form neutral complexes in which an unpaired electron is delocalized over the conjugated π system. These compounds, which are stable at room temperature and exposed to air, undergo reversible one-electron processes to access different redox states of the ligand system without affecting the oxidation state and coordination geometry of the metal center. We also characterized ligand-based radicals on the dipyrrindione platform in both homoleptic and heteroleptic complexes. In addition, this study documented noncovalent interactions (e.g., interligand hydrogen bonds with the pyrrolinone carbonyls, π-stacking of ligand-centered radicals) as important aspects of this coordination chemistry. Furthermore, the fluorescence of the zinc-bound tripyrrindione radical and the redox-switchable emission of a dipyrrindione BODIPY-type fluorophore showcased the potential interplay of redox chemistry and luminescence in these compounds. Supported by computational analyses, the portfolio of properties revealed by this investigation takes the tripyrrindione and dipyrrindione motifs of heme metabolites to the field of redox-active ligands, where they are positioned to offer new opportunities for catalysis, sensing, supramolecular systems, and functional materials.
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Affiliation(s)
- Elisa Tomat
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721-0041, United States
| | - Clayton J. Curtis
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721-0041, United States
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Curtis CJ, Astashkin AV, Conradie J, Ghosh A, Tomat E. Ligand-Centered Triplet Diradical Supported by a Binuclear Palladium(II) Dipyrrindione. Inorg Chem 2021; 60:12457-12466. [PMID: 34347474 PMCID: PMC8389801 DOI: 10.1021/acs.inorgchem.1c01691] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Oligopyrroles
form
a versatile class of redox-active ligands and
electron reservoirs. Although the stabilization of radicals within
oligopyrrolic π systems is more common for macrocyclic ligands,
bidentate dipyrrindiones are emerging as compact platforms for one-electron
redox chemistry in transition-metal complexes. We report the synthesis
of a bis(aqua) palladium(II) dipyrrindione complex and its deprotonation-driven
dimerization to form a hydroxo-bridged binuclear complex in the presence
of water or triethylamine. Electrochemical, spectroelectrochemical,
and computational analyses of the binuclear complex indicate the accessibility
of two quasi-reversible ligand-centered reduction processes. The product
of a two-electron chemical reduction by cobaltocene was isolated and
characterized. In the solid state, this cobaltocenium salt features
a folded dianionic complex that maintains the hydroxo bridges between
the divalent palladium centers. X-band and Q-band EPR spectroscopic
experiments and DFT computational analysis allow assignment of the
dianionic species as a diradical with spin density almost entirely
located on the two dipyrrindione ligands. As established from the
EPR temperature dependence, the associated exchange coupling is weak
and antiferromagnetic (J ≈ −2.5 K),
which results in a predominantly triplet state at the temperatures
at which the measurements have been performed. The coordination and redox chemistry of the dipyrrindione
scaffold, which is found in several heme metabolites, is investigated
in heteroleptic palladium(II) complexes. The bis(aqua) complex undergoes
a deprotonation-driven dimerization to form a hydroxo-bridged binuclear
species. Crystallographic, electrochemical, and spectroscopic data,
as well as computational analysis, demonstrate that a two-electron
reduction of the binuclear complex leads to a diradical dianion with
spin density delocalized over the two dipyrrindione ligands.
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Affiliation(s)
- Clayton J Curtis
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 East University Blvd., Tucson, Arizona 85721, United States
| | - Andrei V Astashkin
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 East University Blvd., Tucson, Arizona 85721, United States
| | - Jeanet Conradie
- Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, Republic of South Africa.,Department of Chemistry, UiT - The Arctic University of Norway, N-9037 Tromsø, Norway
| | - Abhik Ghosh
- Department of Chemistry, UiT - The Arctic University of Norway, N-9037 Tromsø, Norway
| | - Elisa Tomat
- Department of Chemistry and Biochemistry, The University of Arizona, 1306 East University Blvd., Tucson, Arizona 85721, United States
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Curtis CJ, Tomat E. Heteroleptic palladium(II) complexes of dipyrrin-1,9-dione supported by intramolecular hydrogen bonding. J PORPHYR PHTHALOCYA 2020. [DOI: 10.1142/s1088424619501062] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The dipyrrin-1,9-dione framework, which is characteristic of the propentdyopent pigments deriving from heme metabolism, coordinates metal ions as monoanionic bidentate donors. The resulting analogs of dipyrrinato complexes undergo reversible ligand-based reductions, thus showcasing the ability of the dipyrrindione scaffold to act as an electron reservoir. Herein we report the synthesis and characterization of three heteroleptic palladium complexes of the redox-active dipyrrindione ligand. Primary amines were chosen as additional ligands so as to assemble complexes of planar geometries with complementary interligand hydrogen-bonding. Full chemical characterization confirms the hydrogen bonding interactions between the primary amine ligands and the acceptor carbonyl groups on the dipyrrolic ligand. The resulting heteroleptic compounds display reversible one-electron reduction events that are centered on the dipyrrindione ligand as revealed by voltammetry and spectroelectrochemistry data. Within these planar Pd(II) complexes, the propentdyopent motif therefore combines reversible ligand-based redox chemistry with interligand hydrogen bonding in the primary coordination sphere of the metal center.
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Affiliation(s)
- Clayton J. Curtis
- The University of Arizona, Department of Chemistry and Biochemistry, 1306 E. University Blvd., Tucson AZ 85721, USA
| | - Elisa Tomat
- The University of Arizona, Department of Chemistry and Biochemistry, 1306 E. University Blvd., Tucson AZ 85721, USA
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Abstract
Propentdyopents are naturally occurring dipyrroles deriving from the metabolism of heme and characterized by a dipyrrin-1,9-dione motif. The unusual name propentdyopent is due to the first colorimetric method (the Stokvis reaction) for the detection of these compounds, which were initially isolated from urine samples. Upon reduction in alkaline solutions, they produced red species that were termed pentdyopents to describe with Greek numerals their absorption maximum (525 nm) in the visible range. The precursors to the red pentdyopents were thus indicated as propentdyopents.Over the course of several decades, these dipyrrolic compounds have appeared in several studies of human physiology, typically associated to conditions of abnormal heme metabolism and/or oxidative stress. Concurrently, synthetic investigations have confirmed their chemical structure, reactivity, and ability to coordinate metals as bidentate monoanionic ligands. Notably, the planar dipyrrindione platform can undergo reversible one-electron redox processes and thereby act as an electron reservoir in metal complexes. In combination with the documented ability of the carbonyl groups to act as hydrogen-bonding acceptors, the coordination chemistry of propentdyopents could lead to new applications for this old class of pigments. Furthermore, the observation of these pigments in several clinical contexts could potentially delineate a role of propentdyopents as diagnostic biomarkers. This mini-review summarizes both the chemistry and biology of propentdyopents while highlighting the ample space for new discoveries.
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Affiliation(s)
- Elisa Tomat
- The University of Arizona, Department of Chemistry and Biochemistry, 1306 E. University Blvd., Tucson AZ 85721, USA
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van der Vlugt JI. Radical-Type Reactivity and Catalysis by Single-Electron Transfer to or from Redox-Active Ligands. Chemistry 2019; 25:2651-2662. [PMID: 30084211 PMCID: PMC6471147 DOI: 10.1002/chem.201802606] [Citation(s) in RCA: 127] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Indexed: 12/12/2022]
Abstract
Controlled ligand-based redox-activity and chemical non-innocence are rapidly gaining importance for selective (catalytic) processes. This Concept aims to provide an overview of the progress regarding ligand-to-substrate single-electron transfer as a relatively new mode of operation to exploit ligand-centered reactivity and catalysis based thereon.
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Affiliation(s)
- Jarl Ivar van der Vlugt
- Bio-Inspired Homogeneous and Supramolecular Catalysis Groupvan ‘t Hoff Institute for Molecular SciencesUniversity of AmsterdamScience Park 9041098 XHAmsterdamNetherlands
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9
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Saund SS, Goldschmid SL, Ng K, Stewart V, Siegler MA, Thoi VS. Exploring ligand non-innocence of coordinatively-versatile diamidodipyrrinato cobalt complexes. Chem Commun (Camb) 2019; 55:1825-1828. [PMID: 30672518 DOI: 10.1039/c8cc08674e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The non-innocence of diamidodipyrrin is explored in a series of cobaltous complexes with novel binding motifs. By varying the coordination modes, a reversible one-electron reduction is remarkably shifted by nearly 200 mV in a single metal-ligand platform. Our study illustrates a new strategy for modifying the redox activity of porphyrin-like scaffolds.
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Affiliation(s)
- Simran S Saund
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
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Gautam R, Petritis SJ, Tomat E. Redox-Switchable Cyan Fluorescence of a BODIPY Analog Inspired by Propentdyopent Pigments. Eur J Inorg Chem 2018. [DOI: 10.1002/ejic.201800941] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Ritika Gautam
- Department of Chemistry and Biochemistry; The University of Arizona; 1306 E. University Blvd. 85721 Tucson AZ USA
| | - Steven J. Petritis
- Department of Chemistry and Biochemistry; The University of Arizona; 1306 E. University Blvd. 85721 Tucson AZ USA
| | - Elisa Tomat
- Department of Chemistry and Biochemistry; The University of Arizona; 1306 E. University Blvd. 85721 Tucson AZ USA
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11
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Gautam R, Petritis SJ, Astashkin AV, Tomat E. Paramagnetism and Fluorescence of Zinc(II) Tripyrrindione: A Luminescent Radical Based on a Redox-Active Biopyrrin. Inorg Chem 2018; 57:15240-15246. [PMID: 30418755 DOI: 10.1021/acs.inorgchem.8b02532] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The ability of bilins and other biopyrrins to form fluorescent zinc complexes has been known for more than a century; however, the exact identity of the emissive species remains uncertain in many cases. Herein, we characterize the hitherto elusive zinc complex of tripyrrin-1,14-dione, an analogue of several orange urinary pigments. As previously observed for its Pd(II), Cu(II), and Ni(II) complexes, tripyrrindione binds Zn(II) as a dianionic radical and forms a paramagnetic complex carrying an unpaired electron on the ligand π-system. This species is stable at room temperature and undergoes quasi-reversible ligand-based redox chemistry. Although the complex is isolated as a coordination dimer in the solid state, optical absorption and electron paramagnetic resonance spectroscopic studies indicate that the monomer is prevalent in a tetrahydrofuran solution. The paramagnetic Zn(II) tripyrrindione complex is brightly fluorescent (λabs = 599 nm, λem = 644 nm, ΦF = 0.23 in THF), and its study provides a molecular basis for the observation, made over several decades since the 1930s, of fluorescent behavior of tripyrrindione pigments in the presence of zinc salts. The zinc-bound tripyrrindione radical is thus a new addition to the limited number of stable radicals that are fluorescent at room temperature.
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Affiliation(s)
- Ritika Gautam
- Department of Chemistry and Biochemistry , The University of Arizona , Tucson , Arizona 85721 , United States
| | - Steven J Petritis
- Department of Chemistry and Biochemistry , The University of Arizona , Tucson , Arizona 85721 , United States
| | - Andrei V Astashkin
- Department of Chemistry and Biochemistry , The University of Arizona , Tucson , Arizona 85721 , United States
| | - Elisa Tomat
- Department of Chemistry and Biochemistry , The University of Arizona , Tucson , Arizona 85721 , United States
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Gautam R, Astashkin AV, Chang TM, Shearer J, Tomat E. Interactions of Metal-Based and Ligand-Based Electronic Spins in Neutral Tripyrrindione π Dimers. Inorg Chem 2017; 56:6755-6762. [PMID: 28497967 DOI: 10.1021/acs.inorgchem.7b01030] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ability of tetrapyrrolic macrocycles to stabilize unpaired electrons and engage in π-π interactions is essential for many electron-transfer processes in biology and materials engineering. Herein, we demonstrate that the formation of π dimers is recapitulated in complexes of a linear tripyrrolic analogue of naturally occurring pigments derived from heme decomposition. Hexaethyltripyrrindione (H3TD1) coordinates divalent transition metals (i.e., Pd, Cu, Ni) as a stable dianionic radical and was recently described as a robust redox-active ligand. The resulting planar complexes, which feature a delocalized ligand-based electronic spin, are stable at room temperature in air and support ligand-based one-electron processes. We detail the dimerization of neutral tripyrrindione complexes in solution through electron paramagnetic resonance (EPR) and visible absorption spectroscopic methods. Variable-temperature measurements using both EPR and absorption techniques allowed determination of the thermodynamic parameters of π dimerization, which resemble those previously reported for porphyrin radical cations. The inferred electronic structure, featuring coupling of ligand-based electronic spins in the π dimers, is supported by density functional theory (DFT) calculations.
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Affiliation(s)
- Ritika Gautam
- Department of Chemistry and Biochemistry, The University of Arizona , Tucson, Arizona 85721, United States
| | - Andrei V Astashkin
- Department of Chemistry and Biochemistry, The University of Arizona , Tucson, Arizona 85721, United States
| | - Tsuhen M Chang
- Department of Chemistry and Biochemistry, The University of Arizona , Tucson, Arizona 85721, United States
| | - Jason Shearer
- Department of Chemistry, University of Nevada , Reno, Nevada 89577, United States
| | - Elisa Tomat
- Department of Chemistry and Biochemistry, The University of Arizona , Tucson, Arizona 85721, United States
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Three bilindione isomers: synthesis, characterization and reactivity of biliverdin analogs. J Biol Inorg Chem 2017; 22:727-737. [DOI: 10.1007/s00775-017-1444-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 01/17/2017] [Indexed: 01/16/2023]
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Bahnmüller S, Plotzitzka J, Baabe D, Cordes B, Menzel D, Schartz K, Schweyen P, Wicht R, Bröring M. Hexaethyltripyrrindione (H3Et6tpd): A Non-Innocent Ligand Forming Stable Radical Complexes with Divalent Transition-Metal Ions. Eur J Inorg Chem 2016. [DOI: 10.1002/ejic.201600934] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Stefanie Bahnmüller
- Institute of Inorganic and Analytical Chemistry; TU Braunschweig; Hagenring 30 38106 Braunschweig Germany
| | - Jacqueline Plotzitzka
- Institute of Inorganic and Analytical Chemistry; TU Braunschweig; Hagenring 30 38106 Braunschweig Germany
| | - Dirk Baabe
- Institute of Inorganic and Analytical Chemistry; TU Braunschweig; Hagenring 30 38106 Braunschweig Germany
| | - Birte Cordes
- Institute of Inorganic and Analytical Chemistry; TU Braunschweig; Hagenring 30 38106 Braunschweig Germany
| | - Dirk Menzel
- Institute of Condensed Matter Physics; TU Braunschweig; Mendelssohnstraße 2-3 38106 Braunschweig Germany
| | - Katharina Schartz
- Institute of Inorganic and Analytical Chemistry; TU Braunschweig; Hagenring 30 38106 Braunschweig Germany
| | - Peter Schweyen
- Institute of Inorganic and Analytical Chemistry; TU Braunschweig; Hagenring 30 38106 Braunschweig Germany
| | - Richard Wicht
- Institute of Inorganic and Analytical Chemistry; TU Braunschweig; Hagenring 30 38106 Braunschweig Germany
| | - Martin Bröring
- Institute of Inorganic and Analytical Chemistry; TU Braunschweig; Hagenring 30 38106 Braunschweig Germany
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Camp C, Arnold J. On the non-innocence of “Nacnacs”: ligand-based reactivity in β-diketiminate supported coordination compounds. Dalton Trans 2016; 45:14462-98. [DOI: 10.1039/c6dt02013e] [Citation(s) in RCA: 133] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
While β-diketiminate (BDI or ‘nacnac’) ligands have been widely adopted to stabilize a wide range of metal ions in multiple oxidation states and coordination numbers, in several occurrences these ligands do not behave as spectators and participate in reactivity.
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Affiliation(s)
- Clément Camp
- Univ Lyon
- CNRS, ESCPE Lyon
- Université Claude Bernard Lyon 1
- C2P2 UMR 5265
- F-69616 Villeurbanne
| | - John Arnold
- Department of Chemistry
- University of California
- Berkeley
- USA
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