Metallocorroles as inherently chiral chromophores: resolution and electronic circular dichroism spectroscopy of a tungsten biscorrole

Schies, Christine; Alemayehu, Abraham B.; Vázquez‐Lima, Hugo; Thomas, Kolle E.; Bruhn, Torsten; Bringmann, Gerhard; Ghosh, Abhik

doi:10.1039/c7cc02027a

Cited by 14 publications

(18 citation statements)

References 35 publications

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“…1 H and 13 C NMR spectra were recorded using a Bruker Avance III HD 400 FT spectrometer or a Bruker Avance III HD 600 FT spectrometer. Chemical shifts are given in ppm relative to the frequency of tetramethylsilane, and the solvent signal (for 1 H NMR, the respective residual proton signal) ( 1 H: CDCl 3 : δ 7.26 ppm, CD 2 Cl 2 : δ 5.32 ppm, CD 3 OD: δ 3.31 ppm; 13 C: δ CDCl 3 : δ 77.16 ppm, CD 2 Cl 2 : δ 53.84 ppm, CD 3 OD: δ 49.00 ppm) 92 was used as an internal standard.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Chiroptical Properties of Indolenine Squaraines with a Stereogenic Center at Close Proximity

et al. 2020

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A series of four indolenine squaraines bearing a chiral center at the 3-position of the indolenine moiety, with either an n-propyl or a phenyl group alongside a methyl group, were synthesized and obtained in a high purity of ≥98% for the desired stereoisomer. The indolenine precursors with a phenyl group attached at the chiral center were asymmetrically synthesized using a pericyclic-reaction cascade and obtained in a high ee of 98%, whereas the ones with an n-propyl group were prepared by kinetic resolution through asymmetric hydrogenation, resulting in an ee of up to 98%. X-ray crystallography revealed a slightly twisted geometry for the phenyl-substituted cisoid squaraine derivative, whereas the n-propyl-substituted derivative possessed the expected planar geometry. Variation of the substitution also influenced the optical properties, where the introduction of phenyl groups caused a progressive red-shift and reduction in squared transition moments, as well as reduced fluorescence quantum yields, Stokes shifts, and fluorescence lifetimes. All of the investigated compounds exhibited strong ECD signals, with Δε values of up to 24 M −1 cm −1 for the HOMO−LUMO transition. DFT calculations indicated that this was due to both large electric and magnetic transition moments, although the two vectors were mutually almost orthogonal.

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Section: ■ Experimental Sectionmentioning

confidence: 99%

Chiroptical Properties of Indolenine Squaraines with a Stereogenic Center at Close Proximity

et al. 2020

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“… 22 , 23 Fascinatingly, the complexes are chiral, thanks to their square antiprismatic coordination, and also conformationally stable and have been successfully resolved via chiral HPLC. 24 Their potential deployment as an inherently chiral structural element remains a fascinating prospect.…”

Section: Group 6 Metallocorroles (Mo and W)mentioning

confidence: 99%

The Story of 5d Metallocorroles: From Metal–Ligand Misfits to New Building Blocks for Cancer Phototherapeutics

et al. 2021

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Conspectus 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...

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“…The 'acetate method' has since become the method of choice for the synthesis of Au corroles. Understandably, we were intrigued by the possibility of inserting other heavier transition metals into corroles and, to our satisfaction, the rst 99 TcO, 8 ReO, 9 ReNAr, 10 RuN, 11 OsN, 12 and Pt 13,14 triarylcorroles (as well as Mo and W biscorroles [15][16][17] and quadruple-bonded Re corrole dimers 18 ) were synthesized in our Tromsø laboratory. Several of the 5d metallocorroles [19][20][21][22][23][24] were found to exhibit room-temperature NIR phosphorescence, leading to applications as oxygen sensors and as photosensitizers in photodynamic therapy and dye-sensitized solar cells.…”

Section: Introductionmentioning

confidence: 99%

Regioselective formylation of rhenium-oxo and gold corroles: substituent effects on optical spectra and redox potentials

et al. 2021

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Metallocorroles as inherently chiral chromophores: resolution and electronic circular dichroism spectroscopy of a tungsten biscorrole

Cited by 14 publications

References 35 publications

Chiroptical Properties of Indolenine Squaraines with a Stereogenic Center at Close Proximity

Chiroptical Properties of Indolenine Squaraines with a Stereogenic Center at Close Proximity

The Story of 5d Metallocorroles: From Metal–Ligand Misfits to New Building Blocks for Cancer Phototherapeutics

Regioselective formylation of rhenium-oxo and gold corroles: substituent effects on optical spectra and redox potentials

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