Electrochemical Titrations of Nickel β-Oxoporphyrins with Imidazole

Connick, Patricia A.

doi:10.1149/2.f05932if

Cited by 3 publications

(2 citation statements)

References 4 publications

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“…The nickel and copper complexes of the isomeric trioxopyrrocorphins 3-O 2,7,12 or 3-O 2,7,18 were prepared, and their structure, axial binding properties, and electrochemical properties were studied. 48,49,61,62 We recently described the preparation of the hitherto unknown regioisomers of the triketones and revealed their unique electronic properties. 29,47 They are, against expectations for regular pyrrocorphins, aromatic, with the regioisomers varying significantly in their degree of aromaticity.…”

Section: Introductionmentioning

confidence: 99%

“…Among the β-oxoporphyrinoids, the triketones stand out as the least studied compound class. The nickel and copper complexes of the isomeric trioxopyrrocorphins 3-O 2,7,12 or 3-O 2,7,18 were prepared, and their structure, axial binding properties, and electrochemical properties were studied. ,,, We recently described the preparation of the hitherto unknown regioisomers of the triketones and revealed their unique electronic properties. , They are, against expectations for regular pyrrocorphins, aromatic, with the regioisomers varying significantly in their degree of aromaticity. As a reduction of one or two oxo-groups led to a degradation of the aromaticity, the aromatic nature of the trioxopyrrocorphins could be unambiguously linked to the presence of the β-oxo-substituents …”

Section: Introductionmentioning

confidence: 99%

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Photophysical Exploration of Two Isomers of Octaethyltrioxopyrrocorphin

Bhattacharya,

Nevonen,

Auty

et al. 2023

J. Phys. Chem. A

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The introduction of three β-oxosubstituents to octaethylporphyrin by means of an oxidation/rearrangement reaction generates the trioxopyrrocorphin chromophore. Pyrrocorphins (hexahydroporphyrins) are generally nonaromatic, but we recently demonstrated trioxopyrrocorphins to possess considerable aromatic character. This contribution explores the photophysical characteristics of these unusual chromophores. In agreement with density functional theory modeling, the UV–vis and magnetic circular dichroism spectra of the twoout of the four possibletriketone regioisomers investigated conform to the Gouterman model of porphyrinoid optical spectra, in alignment with their aromaticity. Their excited-state dynamics shed further light on the degree to which β-oxo substitutions tune the photophysical properties of porphyrinoids. Introduction of β-oxo functionalities increases the rate and yield of intersystem crossing and shortens the triplet state lifetime. Unexpectedly, the singlet oxygen generation yield of both pyrrocorphins remains relatively high, with modes of distortion from planarity likely enhancing triplet energy transfer. This work thus expands our understanding of a rare class of porphyrinoids and further characterizes them as sustaining aromatic porphyrinic π-systems. Our findings suggest triple β-oxo substitution as a viable route toward the development of novel, high-singlet oxygen yield porphyrinic photosensitizers.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photophysical Exploration of Two Isomers of Octaethyltrioxopyrrocorphin

Bhattacharya,

Nevonen,

Auty

et al. 2023

J. Phys. Chem. A

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Stepwise Reduction of β-Trioxopyrrocorphins: Collapse of the Oxo-Induced Macrocycle Aromaticity

et al. 2022

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The diatropic ring current that characterizes the unexpectedly aromatic octaethyltrioxopyrrocorphins gets drastically reduced upon chemical reduction of one and particularly two ketone moieties. With increasing reduction, the chromophores containing one pyrrole, one/two pyrrolinone, and one/two pyrrolines become more similar to regular, nonmacrocycle–aromatic pyrrocorphins (hexahydroporphyrins). Single-crystal diffraction analysis shows the reduction products to be idealized planar. With increasing reduction, their UV–vis spectroscopic signatures are those of conjugated but nonaromatic oligopyrroles. Their diatropic ring currents, as assessed by 1H NMR spectroscopy, showed them to possess largely nonaromatic π-systems. Dihydroxylation of select β,β′-dioxobacteriochlorin and β,β′-dioxoisobacteriochlorins also resulted in the formation of equivalent mixed pyrrole/two pyrrolinone/pyrroline chromophores. Computations were able to reproduce the experimental trends of the diatropic ring currents and filled in the data for the regioisomers that could not be experimentally accessed. The work further highlights the electronic influence of the β-oxo-substituents and, more specifically, the origin of the aromaticity of the trioxopyrrocorphins. It also presents a series of chemically robust pyrrocorphins, a chromophore class for which many chemically very sensitive members have been reported.

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