1
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Giovanelli L, Ksari Y, Mrezguia H, Salomon E, Minissale M, Alemayehu AB, Ghosh A. Inverse Photoemission Spectroscopy of Coinage Metal Corroles: Comparison with Solution-Phase Electrochemistry. ACS ORGANIC & INORGANIC AU 2024; 4:485-491. [PMID: 39371327 PMCID: PMC11450770 DOI: 10.1021/acsorginorgau.4c00027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2024] [Revised: 06/10/2024] [Accepted: 06/12/2024] [Indexed: 10/08/2024]
Abstract
A combined direct and inverse photoemission study of coinage metal corroles suggests that the latter technique, in favorable cases, can provide some additional information relative to electrochemical measurements. Thus, whereas inverse photoemission spectroscopy (IPES) provides relative electron affinities for electron addition to different unoccupied orbitals, electrochemical reduction potentials shed light on the energetics of successive electron additions. While all three coinage metal triphenylcorrole (TPC) complexes exhibit similar ionization potentials, they exhibit dramatically different inverse photoemission spectra. For Cu[TPC], the lowest-energy IPES feature (0.74 eV) is found to be exceedingly close to the Fermi level; it is significantly higher for Ag[TPC] (1.65 eV) and much higher for Au[TPC] (2.40 eV). These differences qualitatively mirror those observed for electrochemical reduction potentials and are related to a partially metal-centered LUMO in the case of Cu- and Ag[TPC] and a fully corrole-based LUMO in the case of Au[TPC]; the latter orbital corresponds to the LUMO+1 in the case of Ag[TPC].
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Affiliation(s)
- Luca Giovanelli
- Aix-Marseille
Université, CNRS, IM2NP, Marseille 13397, France
| | - Younal Ksari
- Aix-Marseille
Université, CNRS, IM2NP, Marseille 13397, France
| | - Hela Mrezguia
- Aix-Marseille
Université, CNRS, IM2NP, Marseille 13397, France
| | - Eric Salomon
- Aix-Marseille
Université, CNRS, PIIM, Marseille 13397, France
| | - Marco Minissale
- Aix-Marseille
Université, CNRS, PIIM, Marseille 13397, France
| | - Abraham B. Alemayehu
- 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
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2
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Larsen S, Adewuyi JA, Thomas KE, Conradie J, Rousselin Y, Ung G, Ghosh A. Electronic Structure of Metallophlorins: Lessons from Iridium and Gold Phlorin Derivatives. Inorg Chem 2024; 63:9842-9853. [PMID: 38743029 PMCID: PMC11134504 DOI: 10.1021/acs.inorgchem.4c00483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Revised: 04/12/2024] [Accepted: 04/26/2024] [Indexed: 05/16/2024]
Abstract
Phlorins have long remained underexplored relative to their fully conjugated counterparts, such as porphyrins, hydroporphyrins, and corroles. Herein, we have attempted to bridge that knowledge gap with a scalar-relativistic density functional theory (DFT) study of unsubstituted iridium and gold phlorin derivatives and a multitechnique experimental study of iridium-bispyridine and gold complexes of 5,5-dimethyl-10,15,20-tris(pentafluorophenyl)phlorin. Theory and experiments concur that the phlorin derivatives exhibit substantially smaller HOMO-LUMO gaps, as reflected in a variety of observable properties. Thus, the experimentally studied Ir and Au complexes absorb strongly in the near-infrared (NIR), with absorption maxima at 806 and 770 nm, respectively. The two complexes are also weakly phosphorescent with emission maxima at 950 and 967 nm, respectively. They were also found to photosensitize singlet oxygen formation, with quantum yields of 40 and 28%, respectively. The near-infrared (NIR) absorption and emission are consonants with smaller electrochemical HOMO-LUMO gaps of ∼1.6 V, compared to values of ∼2.1 V, for electronically innocent porphyrins and corroles. Interestingly, both the first oxidation and reduction potentials of the Ir complex are some 600 mV shifted to more negative potentials relative to those of the Au complex, indicating an exceptionally electron-rich macrocycle in the case of the Ir complex.
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Affiliation(s)
- Simon Larsen
- Department
of Chemistry, University of Tromsø, N-9037 Tromsø, Norway
| | - Joseph A. Adewuyi
- Department
of Chemistry, University of Connecticut, 55 N. Eagleville Rd, Storrs, Connecticut 06269, United States
| | - Kolle E. Thomas
- Department
of Chemistry, University of Tromsø, N-9037 Tromsø, Norway
| | - Jeanet Conradie
- Department
of Chemistry, University of Tromsø, N-9037 Tromsø, Norway
- Department
of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, Republic of South Africa
| | - Yoann Rousselin
- ICMUB,
UMR CNRS 6302, Université Bourgogne Franche-Comte, BP 47870, Dijon Cedex 21078, France
| | - Gaël Ung
- Department
of Chemistry, University of Connecticut, 55 N. Eagleville Rd, Storrs, Connecticut 06269, United States
| | - Abhik Ghosh
- Department
of Chemistry, University of Tromsø, N-9037 Tromsø, Norway
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3
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Johannessen K, Johansen MAL, Einrem RF, M cCormick M cPherson LJ, Alemayehu AB, Borisov SM, Ghosh A. Influence of Fluorinated Substituents on the Near-Infrared Phosphorescence of 5d Metallocorroles. ACS ORGANIC & INORGANIC AU 2023; 3:241-245. [PMID: 37810408 PMCID: PMC10557119 DOI: 10.1021/acsorginorgau.3c00016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 07/03/2023] [Accepted: 07/05/2023] [Indexed: 10/10/2023]
Abstract
The influence of fluorinated substituents on the luminescent properties of rhenium-oxo, osmium-nitrido, and gold triarylcorroles was studied via a comparison of four ligands: triphenylcorrole (TPC), tris(p-trifluoromethylphenyl)corrole (TpCF3PC), tris{3,5-bis(trifluoromethyl)phenyl}corrole (T3,5-CF3PC), and tris(pentafluorophenyl)corrole (TPFPC). For each metal series examined, fluorinated substituents were found to enhance the luminescent properties, with the phosphorescence quantum yields and triplet decay times increasing in the order TPC < TpCF3PC < T3,5-CF3PC < TPFPC. Among the 11 complexes examined, the highest phosphorescence quantum yield, 2.2%, was recorded for Re[TPFPC](O).
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Affiliation(s)
| | | | - Rune F. Einrem
- Department
of Chemistry, UiT−The Arctic University
of Norway, 9037 Tromsø, Norway
| | - Laura J. McCormick McPherson
- EPSRC
National Crystallography Service, School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, U.K.
| | - Abraham B. Alemayehu
- Department
of Chemistry, UiT−The Arctic University
of Norway, 9037 Tromsø, Norway
| | - Sergey M. Borisov
- Institute
of Analytical Chemistry and Food Chemistry, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria
| | - Abhik Ghosh
- Department
of Chemistry, UiT−The Arctic University
of Norway, 9037 Tromsø, Norway
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4
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Alemayehu AB, Ghosh A. Phenol- and resorcinol-appended metallocorroles and their derivatization with fluorous tags. Sci Rep 2022; 12:19256. [PMID: 36357501 PMCID: PMC9649713 DOI: 10.1038/s41598-022-23889-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 11/07/2022] [Indexed: 11/12/2022] Open
Abstract
Boron tribromide-mediated demethylation of rhenium-oxo and gold meso-tris(4-methoxyphenyl)corrole and meso-tris(3,5-dimethoxyphenylcorrole), M[TpOMePC] and M[T(3,5-OMe)PC] (M = ReO, Au), have yielded the corresponding phenol- and resorcinol-appended metallocorroles, M[TpOHPC] and M[T(3,5-OH)PC], in good yields. The latter compounds proved insoluble in dichloromethane and chloroform but soluble in THF. The M[T(3,5-OH)PC] derivatives also proved moderately soluble in 0.05 M aqueous KOH. Unlike oxidation-prone aminophenyl-substituted corroles, the phenol- and resorcinol-appended metallocorroles could be readily handled in air without special precautions. The phenolic metallocorroles could be readily alkylated with 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecyl iodide ("FtI") to afford the fluorous-tagged metallocorroles M[TpOFtPC] and M[T(3,5-OFt)PC] in > 90% yields. The simplicity of the synthetic protocols promise a wide range of phenolic and fluorous-tagged porphyrin analogues with potential applications to diverse fields such as sensors, catalysis, and photodynamic therapy, among others.
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Affiliation(s)
- Abraham B. Alemayehu
- grid.10919.300000000122595234Department of Chemistry, University of Tromsø, N-9037 Tromsø, Norway
| | - Abhik Ghosh
- grid.10919.300000000122595234Department of Chemistry, University of Tromsø, N-9037 Tromsø, Norway
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5
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Sahu K, Angeloni S, Conradie J, Villa M, Nayak M, Ghosh A, Ceroni P, Kar S. NIR-emissive, singlet-oxygen-sensitizing gold tetra(thiocyano)corroles. Dalton Trans 2022; 51:13236-13245. [PMID: 35968801 DOI: 10.1039/d2dt01959k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Presented herein are two fully characterized gold tetrathiocyanocorroles representing a potentially significant new class of NIR-emissive 5d-metallocorroles. The four SCN groups on the bipyrrole unit of the corrole exert a powerful electron-withdrawing effect, upshifting both the oxidation and reduction potentials by roughly half a volt relative to their unsubstituted counterparts. That said, the upshift of the LUMO is somewhat higher than that of the HOMO so these complexes also exhibit a smaller HOMO-LUMO gap, as evinced in both electrochemical measurements and Q band energies (∼595 nm relative to ∼571 nm for their SCN-free counterparts). The new compounds exhibit NIR phosphorescence under ambient conditions with emission maxima around 900 nm (compared with 790 nm for simple Au triarylcorroles), phosphorescence quantum yields around 0.3%, phosphorescence lifetimes around 10 μs, and singlet oxygen sensitization with a quantum yield of around 50 ± 5% in solution, together signifying wide-ranging potential applications as triplet photosensitizers in oxygen sensing and photodynamic therapy.
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Affiliation(s)
- Kasturi Sahu
- School of Chemical Sciences, National Institute of Science Education and Research (NISER), Bhubaneswar - 752050, India.,Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai, 400 094, India.
| | - Sara Angeloni
- Department of Chemistry "G. Ciamician", University of Bologna, via Selmi 2, 40126 Bologna, Italy.
| | - Jeanet Conradie
- Department of Chemistry, UiT - The Arctic University of Norway, N-9037 Tromsø, Norway. .,Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, Republic of South Africa
| | - Marco Villa
- Department of Chemistry "G. Ciamician", University of Bologna, via Selmi 2, 40126 Bologna, Italy.
| | - Manisha Nayak
- School of Chemical Sciences, National Institute of Science Education and Research (NISER), Bhubaneswar - 752050, India.,Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai, 400 094, India.
| | - Abhik Ghosh
- Department of Chemistry, UiT - The Arctic University of Norway, N-9037 Tromsø, Norway.
| | - Paola Ceroni
- Department of Chemistry "G. Ciamician", University of Bologna, via Selmi 2, 40126 Bologna, Italy.
| | - Sanjib Kar
- School of Chemical Sciences, National Institute of Science Education and Research (NISER), Bhubaneswar - 752050, India.,Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai, 400 094, India.
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6
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Terner J, Thomas KE, Vazquez-Lima H, Ghosh A. Structure-sensitive marker bands of metallocorroles: A resonance Raman study of manganese and Gold Corrole derivatives. J Inorg Biochem 2022; 231:111783. [DOI: 10.1016/j.jinorgbio.2022.111783] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 02/23/2022] [Accepted: 02/26/2022] [Indexed: 11/30/2022]
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7
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Alemayehu AB, Thomas KE, Einrem RF, Ghosh A. The Story of 5d Metallocorroles: From Metal-Ligand Misfits to New Building Blocks for Cancer Phototherapeutics. Acc Chem Res 2021; 54:3095-3107. [PMID: 34297542 PMCID: PMC8382219 DOI: 10.1021/acs.accounts.1c00290] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
![]()
Porphyrin chemistry is Shakespearean: over a
century of study has
not withered the field’s apparently infinite variety. Heme
proteins continually astonish us with novel molecular mechanisms,
while new porphyrin analogues bowl us over with unprecedented optical,
electronic, and metal-binding properties. Within the latter domain,
corroles occupy a special place, exhibiting a unique and rich coordination
chemistry. The 5d metallocorroles are arguably the icing on that cake. New Zealand chemist Penny Brothers has used the word “misfit”
to describe the interactions of boron, a small atom with a predilection
for tetrahedral coordination, and porphyrins, classic square-planar
ligands. Steve Jobs lionized misfits as those who see things differently
and push humanity forward. Both perspectives have inspired us. The
5d metallocorroles are misfits in that they encapsulate a large 5d
transition metal ion within the tight cavity of a contracted porphyrin
ligand. Given the steric mismatch inherent in their structures,
the syntheses
of some 5d metallocorroles are understandably capricious,
proceeding under highly specific conditions and affording poor yields.
Three broad approaches may be distinguished. (a) In the metal–alkyl approach, a free-base
corrole is exposed to an alkyllithium and the resulting lithio-corrole
is treated with an early transition metal chloride; a variant of the
method eschews alkyllithium and deploys a transition metal–alkyl
instead, resulting in elimination of the alkyl group as an alkane
and insertion of the metal into the corrole. This approach is useful
for inserting transition metals from groups 4, 5, and, to some extent,
6, as well as lanthanides and actinides. (b) In our laboratory,
we have often deployed a low-valent
organometallic approach for the middle transition elements
(groups 6, 7, 8, and 9). The reagents are low-valent metal–carbonyl
or −olefin complexes, which lose one or more carbon ligands
at high temperature, affording coordinatively unsaturated, sticky
metal fragments that are trapped by the corrole nitrogens. (c)
Finally, a metal acetate approach provides
the method of choice for gold and platinum insertion (groups 10 and
11). This Account provides a first-hand perspective
of the three approaches, focusing on the last two, which were largely
developed in our laboratory. In general, the products were characterized
with X-ray crystallography, electrochemistry, and a variety of spectroscopic
methods. The physicochemical data, supplemented by relativistic DFT
calculations, have provided fascinating insights into periodic trends
and relativistic effects. An unexpected feature of many 5d metallocorroles,
given their misfit
character, is their remarkable stability under thermal, chemical,
and photochemical stimulation. Many of them also exhibit long triplet
lifetimes on the order of 100 μs and effectively sensitize singlet
oxygen formation. Many exhibit phosphorescence in the near-infrared
under ambient conditions. Furthermore, water-soluble ReO and Au corroles
exhibit impressive photocytotoxicity against multiple cancer cell
lines, promising potential applications as cancer phototherapeutics.
We thus envision a bright future for the compounds as rugged building
blocks for new generations of therapeutic and diagnostic (theranostic)
agents.
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Affiliation(s)
- Abraham B. Alemayehu
- Department of Chemistry, UiT—The Arctic University of Norway, N-9037 Tromso, Norway
| | - Kolle E. Thomas
- Department of Chemistry, UiT—The Arctic University of Norway, N-9037 Tromso, Norway
| | - Rune F. Einrem
- Department of Chemistry, UiT—The Arctic University of Norway, N-9037 Tromso, Norway
| | - Abhik Ghosh
- Department of Chemistry, UiT—The Arctic University of Norway, N-9037 Tromso, Norway
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8
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Alemayehu AB, Einrem RF, McCormick-McPherson LJ, Settineri NS, Ghosh A. Synthesis and molecular structure of perhalogenated rhenium-oxo corroles. Sci Rep 2020; 10:19727. [PMID: 33184456 PMCID: PMC7665048 DOI: 10.1038/s41598-020-76308-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 10/27/2020] [Indexed: 11/09/2022] Open
Abstract
As part of our efforts to develop rhenium-oxo corroles as photosensitizers for oxygen sensing and photodynamic therapy, we investigated the potential β-perhalogenation of five ReO meso-tris(para-X-phenyl)corroles, Re[TpXPC](O) (X = CF3, H, F, CH3, and OCH3), with elemental chlorine and bromine. With Cl2, β-octachlorinated products Re[Cl8TpXPC](O) were rapidly obtained for X = CF3, H, and CH3, but X = OCH3 resulted in overchlorination on the meso-aryl groups. Full β-octabromination proved slower relative to Cu and Ir corroles, but the desired Re[Br8TpXPC](O) products were finally obtained for X = H and F after a week at room temperature. For X = CH3 and OCH3, these conditions led to undecabrominated products Re[Br11TpXPC](O). Compared to the β-unsubstituted starting materials, the β-octahalogenated products were found to exhibit sharp 1H NMR signals at room temperature, indicating that the aryl groups are locked in place by the β-halogens, and substantially redshifted Soret and Q bands. Single-crystal X-ray structures of Re[Cl8TpCF3PC](O), Re[Cl8TpCH3PC](O), and Re[Br8TpFPC](O) revealed mild saddling for one Cl8 structure and the Br8 structure. These structural variations, however, appear too insignificant to explain the slowness of the β-octabromination protocols, which seems best attributed to the deactivating influence of the high-valent Re center.
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Affiliation(s)
- Abraham B Alemayehu
- Department of Chemistry, UiT - The Arctic University of Norway, 9037, Tromsø, Norway
| | - Rune F Einrem
- Department of Chemistry, UiT - The Arctic University of Norway, 9037, Tromsø, Norway
| | | | - Nicholas S Settineri
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720-8229, USA
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Abhik Ghosh
- Department of Chemistry, UiT - The Arctic University of Norway, 9037, Tromsø, Norway.
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9
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Thomas K, Settineri NS, Teat SJ, Steene E, Ghosh A. Molecular Structure of Copper and μ-Oxodiiron Octafluorocorrole Derivatives: Insights into Ligand Noninnocence. ACS OMEGA 2020; 5:10176-10182. [PMID: 32391505 PMCID: PMC7203988 DOI: 10.1021/acsomega.0c01035] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2020] [Accepted: 04/10/2020] [Indexed: 05/20/2023]
Abstract
Single-crystal X-ray structures were obtained for the copper and μ-oxodiiron complexes of 2,3,7,8,12,13,17,18-octafluoro-5,10,15-triphenylcorrole, hereafter denoted as Cu[F8TPC] and {Fe[F8TPC]}2O. A comparison with the crystal structures of other undecasubstituted Cu corroles, including those with H, Ar, Br, I, and CF3 as β-substituents, showed that the degree of saddling increases in the order: H ≲ F < Ar ≲ Br ≲ I < CF3. In other words, Cu[F8TPC] is marginally more saddled than β-unsubstituted Cu triarylcorroles, but substantially less saddled than Cu undecaarylcorroles, β-octabromo-meso-triarylcorroles, and β-octaiodo-meso-triarylcorroles, and far less saddled than Cu β-octakis(trifluoromethyl)-meso-triarylcorroles. As for {Fe[F8TPC]}2O, the moderate quality of the structure did not allow us to draw firm conclusions in regard to bond length alternations in the corrole skeleton and hence also the question of ligand noninnocence. The Fe-O bond distances, 1.712(8) and 1.724(8), however, are essentially identical to those observed for {Fe[TPFPC]}2O, where TPFPC3- is the trianion of 5,10,15-tris(pentafluorophenyl)corrole, suggesting that a partially noninnocent electronic structural description may be applicable for both compounds.
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Affiliation(s)
- Kolle
E. Thomas
- Department of Chemistry, UiT—The Arctic University of Norway, N-9037 Tromsø, Norway
| | - Nicholas S. Settineri
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720-8229, United States
- Department
of Chemistry, University of California Berkeley, Berkeley, California 94720, United States
| | - Simon J. Teat
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720-8229, United States
| | - Erik Steene
- 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
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10
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Reinholdt A, Alemayehu AB, Gagnon KJ, Bendix J, Ghosh A. Electrophilic Activation of Osmium-Nitrido Corroles: The OsN Triple Bond as a π-Acceptor Metallaligand in a Heterobimetallic Os VIN-Pt II Complex. Inorg Chem 2020; 59:5276-5280. [PMID: 32227864 PMCID: PMC7311052 DOI: 10.1021/acs.inorgchem.0c00654] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Presented herein is a first investigation of the chemical reactivity of osmium-nitrido corroles, which are known for their unusual thermal, chemical, and photochemical stability. Elemental chlorine perchlorinates the β-positions of the triarylcorrole but leaves the OsN unit untouched. The OsN unit is also unaffected by a variety of other electrophilic and nucleophilic reagents. Upon photolysis, however, the anion of Zeise's salt associates with the nitrido ligand to generate an OsVI≡N-PtII complex. The very short OsN-Pt linkage [1.895(9)-1.917(8) Å] and the downfield 195Pt NMR resonance (-2702 ppm) suggest that the OsN corrole acts as a π-accepting ligand toward the Pt(II) center. This finding represents a rare example of the successful photochemical activation of a metal-ligand multiple bond that is too kinetically inert to exhibit any appreciable reactivity under thermal conditions.
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Affiliation(s)
- Anders Reinholdt
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Abraham B Alemayehu
- Department of Chemistry, UiT - The Arctic University of Norway, N-9037 Tromsø, Norway
| | - Kevin J Gagnon
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720-8229, United States
| | - Jesper Bendix
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Abhik Ghosh
- Department of Chemistry, UiT - The Arctic University of Norway, N-9037 Tromsø, Norway
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11
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Thomas KE, Desbois N, Conradie J, Teat SJ, Gros CP, Ghosh A. Gold dipyrrin-bisphenolates: a combined experimental and DFT study of metal–ligand interactions. RSC Adv 2020; 10:533-540. [PMID: 35492572 PMCID: PMC9047278 DOI: 10.1039/c9ra09228e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 12/18/2019] [Indexed: 11/21/2022] Open
Abstract
Given that noninnocent and metalloradical-type electronic structures are ubiquitous among dipyrrin-bisphenolate (DPP) complexes, we synthesized the gold(iii) derivatives as potentially innocent paradigms against which the properties of other metallo-DPP derivatives can be evaluated. Electronic absorption spectra, electrochemical studies, a single-crystal X-ray structure, and DFT calculations all suggest that the ground states of the new complexes indeed correspond to an innocent AuIII–DPP3−, paralleling a similar description noted for Au corroles. Interestingly, while DFT calculations indicate purely ligand-centered oxidations, reduction of AuDPP is predicted to occur across both the metal and the ligand. The first gold dipyrrin-bisphenolates have been synthesized. Like their corrole analogues, they exhibit AuIII–L3− ground states, providing rare innocent paradigms for a class of complexes that commonly occur as metalloradicals.![]()
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Affiliation(s)
- Kolle E. Thomas
- Department of Chemistry
- UiT – The Arctic University of Norway
- Tromsø N-9037
- Norway
| | - Nicolas Desbois
- Institut de Chimie Moléculaire de l’Université de Bourgogne (ICMUB)
- UMR CNRS 6302
- Université Bourgogne-Franche Comté
- 21078 Dijon Cedex
- France
| | - Jeanet Conradie
- Department of Chemistry
- UiT – The Arctic University of Norway
- Tromsø N-9037
- Norway
- Department of Chemistry
| | - Simon J. Teat
- Advanced Light Source
- Lawrence Berkeley National Laboratory
- Berkeley
- USA
| | - Claude P. Gros
- Institut de Chimie Moléculaire de l’Université de Bourgogne (ICMUB)
- UMR CNRS 6302
- Université Bourgogne-Franche Comté
- 21078 Dijon Cedex
- France
| | - Abhik Ghosh
- Department of Chemistry
- UiT – The Arctic University of Norway
- Tromsø N-9037
- Norway
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12
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Abstract
Noninnocent ligands do not allow an unambiguous definition of the oxidation state of a coordinated atom. When coordinated, the ligands also cannot be adequately represented by a classic Lewis structure. A noninnocent system thus harbors oxidizing (holes) or reducing equivalents (electrons) that are delocalized over both the ligand and the coordinated atom. To a certain degree, that is true of all complexes, but the phenomenon is arguably most conspicuous in complexes involving ligands with extended π-systems. The electronic structures of such systems have often been mischaracterized, thereby muddying the chemical literature to the detriment of students and newcomers to the field. In recent years, we have investigated the electronic structures of several metallocorrole families, several of which have turned out to be noninnocent. Our goal here, however, is not to present a systematic account of the different classes of metallocorroles, but rather to focus on seven major tools (in a nod to A. G. Cairns-Smith's Seven Clues to the Origin of Life) that led us to recognize noninnocent behavior and subsequently to characterize the phenomenon in depth. (1) The optical probe: For a series of noninnocent meso-triarylcorrole derivatives with different para substituents X, the Soret maxima are typically exquisitely sensitive to the nature of X, red-shifting with increasing electron-donating character of the group. No such substituent sensitivity is observed for the Soret maxima of innocent triarylcorrole derivatives. (2) Quantum chemistry: Spin-unrestricted density functional theory calculations permit a simple and quick visualization of ligand noninnocence in terms of the spin density profile. Even for an S = 0 complex, the broken-symmetry method often affords a spin density profile that, its fictitious character notwithstanding, helps visualize the intramolecular spin couplings. (3) NMR and EPR spectroscopy: In principle, these two techniques afford experimental probes of the electronic spin density. (4) Structure/X-ray crystallography. Ligand noninnocence in metallocorroles is often reflected in small but distinct skeletal bond length alternations in and around the bipyrrole part of the macrocycle. In addition, for Cu and some Ag corroles, ligand noninnocence manifests itself via a strong saddling of the macrocycle. (5) Vibrational spectroscopy. Unsurprisingly, the aforementioned bond length alternations translate to structure-sensitive vibrational marker bands. (6) Electrochemistry. Noninnocent metallocorroles exhibit characteristically high reduction potentials, but caution should be exercised in turning the logic around. A high reduction potential does not necessarily signify a noninnocent metallocorrole; certain high-valent metal centers also undergo metal-centered reduction at quite high potentials. (7) X-ray absorption spectroscopy (XAS). By focusing on a given element, typically the central atom in a coordination complex, X-ray absorption near-edge spectroscopy (XANES) can provide uniquely detailed local information on oxidation and spin states, ligand field strength, and degree of centrosymmetry. For metallocorroles, some of the most clear-cut distinctions between innocent and noninnocent systems have come from the K-edge XANES of Mn and Fe corroles. For researchers faced with a new, potentially noninnocent system, the take-home message is to employ a good majority (i.e., at least four) of the above methods to arrive at a reliable conclusion vis-à-vis noninnocence.
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Affiliation(s)
- Sumit Ganguly
- Department of Chemistry and Arctic Center for Sustainable Energy, UiT−The Arctic University of Norway, N-9037 Tromsø, Norway
| | - Abhik Ghosh
- Department of Chemistry and Arctic Center for Sustainable Energy, UiT−The Arctic University of Norway, N-9037 Tromsø, Norway
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