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Amouri H. Luminescent Complexes of Platinum, Iridium, and Coinage Metals Containing N-Heterocyclic Carbene Ligands: Design, Structural Diversity, and Photophysical Properties. Chem Rev 2023; 123:230-270. [PMID: 36315851 DOI: 10.1021/acs.chemrev.2c00206] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The employment of N-heterocyclic carbenes (NHCs) to design luminescent metal compounds has been the focus of recent intense investigations because of the strong σ-donor properties, which bring stability to the whole system and tend to push the d-d dark states so high in energy that they are rendered thermally inaccessible, thereby generating highly emissive complexes for useful applications such as organic light-emitting diodes (OLEDs), or featuring chiroptical properties, a field that is still in its infancy. Among the NHC complexes, those containing organic chromophores such as naphthalimide, pyrene, and carbazole exhibit rich emission behavior and thus have attracted extensive interest in the past five years, especially carbene coinage metal complexes with carbazolate ligands. In this review, the design strategies of NHC-based luminescent platinum and iridium complexes with large spin-orbit-coupling (SOC) are described first. Subsequent paragraphs illustrate the recent advances of luminescent coinage metal complexes with nucleophilic- and electrophilic-based carbenes based on silver, gold, and copper metal complexes that have the ability to display rich excited state emissions in particular via thermally activated delayed fluorescence (TADF). The luminescence mechanism and excited state dynamics are also described. We then summarize the advance of NHC-metal complexes in the aforementioned fields in recent years. Finally, we propose the development trend of this fast-growing field of luminescent NHC-metal complexes.
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Affiliation(s)
- Hani Amouri
- CNRS, IPCM (UMR 8232), Sorbonne Université-Faculté des Sciences et Ingénerie Campus Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris, Cedex 05, France
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2
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Olumba ME, O’Donnell RM, Rohrabaugh TN, Teets TS. Panchromatic Excited-State Absorption in Bis-Cyclometalated Iridium Isocyanide Complexes. Inorg Chem 2022; 61:19344-19353. [DOI: 10.1021/acs.inorgchem.2c03136] [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]
Affiliation(s)
- Morris E. Olumba
- Department of Chemistry, University of Houston, 3585 Cullen Blvd., Room 112, Houston, Texas77204-5003, United States
| | - Ryan M. O’Donnell
- U.S. Army Combat Capabilities Development Command, Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland20783, United States
| | - Thomas N. Rohrabaugh
- U.S. Army Combat Capabilities Development Command, Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland20783, United States
| | - Thomas S. Teets
- Department of Chemistry, University of Houston, 3585 Cullen Blvd., Room 112, Houston, Texas77204-5003, United States
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Jiang C, Cañada LM, Nguyen NB, Teets TS. Luminescent “Chugaev-type” Cyclometalated Iridium(III) Complexes Synthesized by Nucleophilic Addition of Hydrazine. J Organomet Chem 2022. [DOI: 10.1016/j.jorganchem.2022.122561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Kochetygov I, Justin A, Asgari M, Yang S, Karve V, Schertenleib T, Stoian D, Oveisi E, Mensi M, Queen WL. 3D vs. turbostratic: controlling metal-organic framework dimensionality via N-heterocyclic carbene chemistry. Chem Sci 2022; 13:6418-6428. [PMID: 35733888 PMCID: PMC9159099 DOI: 10.1039/d2sc01041k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 05/09/2022] [Indexed: 11/29/2022] Open
Abstract
Using azolium-based ligands for the construction of metal-organic frameworks (MOFs) is a viable strategy to immobilize catalytically active N-heterocyclic carbenes (NHC) or NHC-derived species inside MOF pores. Thus, in the present work, a novel copper MOF referred to as Cu-Sp5-BF4, is constructed using an imidazolinium ligand, H2Sp5-BF4, 1,3-bis(4-carboxyphenyl)-4,5-dihydro-1H-imidazole-3-ium tetrafluoroborate. The resulting framework, which offers large pore apertures, enables the post-synthetic modification of the C2 carbon on the ligand backbone with methoxide units. A combination of X-ray diffraction (XRD), solid-state nuclear magnetic resonance (ssNMR) and electron microscopy (EM), are used to show that the post-synthetic methoxide modification alters the dimensionality of the material, forming a turbostratic phase, an event that further improves the accessibility of the NHC sites promoting a second modification step that is carried out via grafting iridium to the NHC. A combination of X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) methods are used to shed light on the iridium speciation, and the catalytic activity of the Ir-NHC containing MOF is demonstrated using a model reaction, stilbene hydrogenation.
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Affiliation(s)
- Ilia Kochetygov
- Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL) CH-1951 Sion Switzerland
| | - Anita Justin
- Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL) CH-1951 Sion Switzerland
| | - Mehrdad Asgari
- Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL) CH-1951 Sion Switzerland
- Department of Chemical Engineering & Biotechnology, University of Cambridge Philippa Fawcett Drive Cambridge CB3 0AS UK
| | - Shuliang Yang
- Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL) CH-1951 Sion Switzerland
- College of Energy, Xiamen University Xiamen Fujian 361102 China
| | - Vikram Karve
- Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL) CH-1951 Sion Switzerland
| | - Till Schertenleib
- Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL) CH-1951 Sion Switzerland
| | - Dragos Stoian
- Swiss-Norwegian Beamlines, ESRF BP 220 Grenoble 38043 France
| | - Emad Oveisi
- Interdisciplinary Centre for Electron Microscopy (CIME), École Polytechnique Fédérale de Lausanne (EPFL) CH-1015 Lausanne Switzerland
| | - Mounir Mensi
- Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL) CH-1951 Sion Switzerland
| | - Wendy L Queen
- Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL) CH-1951 Sion Switzerland
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Sutton GD, Olumba ME, Nguyen YH, Teets TS. The diverse functions of isocyanides in phosphorescent metal complexes. Dalton Trans 2021; 50:17851-17863. [PMID: 34787613 DOI: 10.1039/d1dt03312c] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In this Perspective, we highlight many examples of photoluminescent metal complexes supported by isocyanides, with an emphasis on recent developments including several from our own group. Work in this field has shown that the isocyanide can play important structural roles, both as a terminal ligand and as a bridging ligand for polynuclear structures, and can influence the excited-state character and excited-state dynamics. In addition, there are many examples of isocyanide-supported complexes where the isocyanide serves as a chromophoric ligand, meaning the low-energy excited states that are important in the photochemistry are partially or completely localized on the isocyanide. Finally, an emerging trend in the design of luminescent compounds is to use the isocyanide as an electrophilic precursor, converted to an acyclic carbene by nucleophilic addition which imparts certain photophysical advantages. This Perspective aims to show the diverse roles played by isocyanides in the design of luminescent compounds, showcasing the recent developments that have led to a substantial growth in fundamental knowledge, function, and applications related to photoluminescence.
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Affiliation(s)
- Gregory D Sutton
- University of Houston, Department of Chemistry, 3585 Cullen Blvd., Room 112, Houston, TX 77204-5003, USA.
| | - Morris E Olumba
- University of Houston, Department of Chemistry, 3585 Cullen Blvd., Room 112, Houston, TX 77204-5003, USA.
| | - Yennie H Nguyen
- University of Houston, Department of Chemistry, 3585 Cullen Blvd., Room 112, Houston, TX 77204-5003, USA.
| | - Thomas S Teets
- University of Houston, Department of Chemistry, 3585 Cullen Blvd., Room 112, Houston, TX 77204-5003, USA.
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Cañada LM, Kölling J, Wen Z, Wu JIC, Teets TS. Cyano-Isocyanide Iridium(III) Complexes with Pure Blue Phosphorescence. Inorg Chem 2021; 60:6391-6402. [PMID: 33844525 DOI: 10.1021/acs.inorgchem.1c00103] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
In this paper, we report a series of six neutral, blue-phosphorescent cyclometalated iridium complexes of the type Ir(C^Y)2(CNAr)(CN). The cyclometalating ligands in these compounds (C^Y) are either aryl-substituted 1,2,4-triazole or NHC ligands, known to produce complexes with blue phosphorescence. These cyclometalating ligands are paired with π-acidic, strongly σ-donating cyano and aryl isocyanide (CNAr) ancillary ligands, the hypothesis being that these ancillary ligands would destabilize the higher-lying ligand-field (d-d) excited states, allowing efficient blue photoluminescence. The compounds are prepared by substituting the cyanide ancillary ligand onto a chloride precursor and are characterized by NMR, mass spectrometry, infrared spectroscopy, and, for five of the compounds, by X-ray crystallography. Cyclic voltammetry establishes that these compounds have large HOMO-LUMO gaps. The mixed cyano-isocyanide compounds are weakly luminescent in solution, but they phosphoresce with moderate to good efficiency when doped into poly(methyl methacrylate) films, with Commission Internationale de L'Eclairage coordinates that indicate deep blue emission for five of the six compounds. The photophysical studies show that the photoluminescence quantum yields are greatly enhanced in the cyano complexes relative to the chloride precursors, affirming the benefit of strong-field ancillary ligands in the design of blue-phosphorescent complexes. Density functional theory calculations confirm that this enhancement arises from a significant destabilization of the higher-energy ligand-field states in the cyanide complexes relative to the chloride precursors.
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Affiliation(s)
- Louise M Cañada
- Department of Chemistry, University of Houston, 3585 Cullen Boulevard, Room 112, Houston, Texas 77204-5003, United States
| | - Johanna Kölling
- Department of Chemistry, University of Houston, 3585 Cullen Boulevard, Room 112, Houston, Texas 77204-5003, United States
| | - Zhili Wen
- Department of Chemistry, University of Houston, 3585 Cullen Boulevard, Room 112, Houston, Texas 77204-5003, United States
| | - Judy I-Chia Wu
- Department of Chemistry, University of Houston, 3585 Cullen Boulevard, Room 112, Houston, Texas 77204-5003, United States
| | - Thomas S Teets
- Department of Chemistry, University of Houston, 3585 Cullen Boulevard, Room 112, Houston, Texas 77204-5003, United States
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Olumba ME, Na H, Friedman AE, Teets TS. Coordination-Driven Self-Assembly of Cyclometalated Iridium Squares Using Linear Aromatic Diisocyanides. Inorg Chem 2021; 60:5898-5907. [PMID: 33784459 DOI: 10.1021/acs.inorgchem.1c00312] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Here, we demonstrate facile [4 + 4] coordination-driven self-assembly of cyclometalated iridium(III) using linear aryldiisocyanide bridging ligands (BLs). A family of nine new [Ir(C^N)2(μ-BL)]44+ coordination cages is described, where C^N is the cyclometalating ligand-2-phenylpyridine (ppy), 2-phenylbenzothiazole (bt), or 1-phenylisoquinoline (piq)-and BL is the diisocyanide BL, with varying spacer lengths between the isocyanide binding sites. These supramolecular coordination compounds are prepared via a one-pot synthesis, with isolated yields of 40-83%. 1H NMR spectroscopy confirms the selective isolation of a single product, which is affirmed to be the M4L4 square by high-resolution mass spectrometry. Detailed photophysical studies were carried out to reveal the nature of the luminescent triplet states in these complexes. In most cases, phosphorescence arises from the [Ir(C^N)2]+ nodes, with the emission color determined by the cyclometalating ligand. However, in two cases, the lowest-energy triplet state resides on the aromatic core of the BL, and weak phosphorescence from that state is observed. This work shows that aromatic diisocyanide ligands enable coordination-driven assembly of inert iridium(III) nodes under mild conditions, producing supramolecular coordination complexes with desirable photophysical properties.
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Affiliation(s)
- Morris E Olumba
- Department of Chemistry, University of Houston, 112 Fleming Building, Houston, Texas 77204-5003, United States
| | - Hanah Na
- Department of Chemistry, University of Houston, 112 Fleming Building, Houston, Texas 77204-5003, United States
| | - Alan E Friedman
- Department of Materials, Design, and Innovation, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Thomas S Teets
- Department of Chemistry, University of Houston, 112 Fleming Building, Houston, Texas 77204-5003, United States
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van Vuuren E, Malan FP, Landman M. Multidentate NHC complexes of group IX metals featuring carbon-based tethers: Synthesis and applications. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2020.213731] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Shon JH, Kim D, Gray TG, Teets TS. β-Diketiminate-supported iridium photosensitizers with increased excited-state reducing power. Inorg Chem Front 2021. [DOI: 10.1039/d1qi00382h] [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
Triazole and NHC-based bis-cyclometalated iridium β-diketiminate complexes emerge as some of the strongest reported visible-light photoreductants. Fast photoinduced electron transfer and photoredox catalysis on organohalide substrates are observed.
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Affiliation(s)
- Jong-Hwa Shon
- University of Houston
- Department of Chemistry
- Houston
- USA
| | - Dooyoung Kim
- University of Houston
- Department of Chemistry
- Houston
- USA
| | - Thomas G. Gray
- Case Western Reserve University
- Department of Chemistry
- Cleveland
- USA
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Excited-State Relaxation in Luminescent Molybdenum(0) Complexes with Isocyanide Chelate Ligands. INORGANICS 2020. [DOI: 10.3390/inorganics8020014] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Diisocyanide ligands with a m-terphenyl backbone provide access to Mo0 complexes exhibiting the same type of metal-to-ligand charge transfer (MLCT) luminescence as the well-known class of isoelectronic RuII polypyridines. The luminescence quantum yields and lifetimes of the homoleptic tris(diisocyanide) Mo0 complexes depend strongly on whether methyl- or tert-butyl substituents are placed in α-position to the isocyanide groups. The bulkier tert-butyl substituents lead to a molecular structure in which the three individual diisocyanides ligated to one Mo0 center are interlocked more strongly into one another than the ligands with the sterically less demanding methyl substituents. This rigidification limits the distortion of the complex in the emissive excited-state, causing a decrease of the nonradiative relaxation rate by one order of magnitude. Compared to RuII polypyridines, the molecular distortions in the luminescent 3MLCT state relative to the electronic ground state seem to be smaller in the Mo0 complexes, presumably due to delocalization of the MLCT-excited electron over greater portions of the ligands. Temperature-dependent studies indicate that thermally activated nonradiative relaxation via metal-centered excited states is more significant in these homoleptic Mo0 tris(diisocyanide) complexes than in [Ru(2,2′-bipyridine)3]2+.
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