Syntheses and solid-state structures of two cofacial (bis)dipyrrin dichromium complexes in different charge states

Carsch, Kurtis M.; Elder, Shelby E.; Dogutan, Dilek K.; Nocera, Daniel G.; Yang, Junyu; Zheng, Shao Liang; Daniel, Timothy D.; Betley, Theodore A.

doi:10.1107/s2053229621001388

Cited by 4 publications

(7 citation statements)

References 30 publications

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“…More significant alterations are observed in the dipyrrindione ligand scaffold, particularly elongations of the terminal C–O and alternate contractions/elongations of C–N bonds on the pyrrolic rings (Table S4). Similar changes to the ligand framework were also observed in palladium(II) tripyrrindione complexes upon one-electron reduction, as well as in a bis(dipyrrinato)-Pacman dichromium complex after treatment with potassium graphite reductant . Overall, these changes in the dipyrrindione bond lengths support the assignment of two subsequent one-electron reductions to the ligand frameworks in [CoCp 2 ] 2 [Pd(μ-OH)(pdp) • ] 2 .…”

Section: Resultssupporting

confidence: 70%

“…Similar changes to the ligand framework were also observed in palladium(II) tripyrrindione complexes upon one-electron reduction, 14 as well as in a bis(dipyrrinato)-Pacman dichromium complex after treatment with potassium graphite reductant. 45 Overall, these changes in the dipyrrindione bond lengths support the assignment of two subsequent one-electron reductions to the ligand frameworks in…”

Section: ■ Results and Discussionmentioning

confidence: 57%

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Ligand-Centered Triplet Diradical Supported by a Binuclear Palladium(II) Dipyrrindione

et al. 2021

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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.

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Section: Resultssupporting

confidence: 70%

Section: ■ Results and Discussionmentioning

confidence: 57%

Ligand-Centered Triplet Diradical Supported by a Binuclear Palladium(II) Dipyrrindione

et al. 2021

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“…Similar changes to the ligand framework were also observed in palladium(II) tripyrrindione complexes upon one-electron reduction, 32 as well as in a bis(dipyrrinato)-Pacman dichromium complex after treatment with potassium graphite reductant. 96 Overall, these changes in the dipyrrindione bond lengths support the assignment of two subsequent one-electron reductions to the ligand frameworks in Geometry optimization of the dianion dimer was performed using OLYP-D3/TZ2P with two Cs + cations (Figure S14). The bond lengths of the dipyrrindione scaffold were found to be in good agreement with the crystallographic data (Figure 8a and Table S6), whereas the calculated structure presents slightly contracted Pd-Pd distance (2.790 Å) and fold angle between dipyrrindione ligand planes (Table S8), likely associated to the size difference between the cobaltocenium and cesium cations.…”

Section: Characterization Of Ligand-based Reduction Productsmentioning

confidence: 60%

Stabilization of a Triplet Diradical on a Binuclear palladium(II) Dipyrrindione

Curtis¹,

Astashkin²,

Conradie³

et al. 2021

Preprint

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Porphyrins and other macrocyclic oligopyrroles form a versatile class of redox-active ligands and electron reservoirs. The stabilization of unpaired electrons within oligopyrrolic π systems adds to the available reactivity pathways and spin states of metal complexes for applications in catalysis and functional materials. In this context, 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 dinuclear complex. Electrochemical, spectroelectrochemical, and computational analyses indicate the accessibility of two reduction processes on the dipyrrindione frameworks of the dinuclear complex. The product of a two-electron reduction by cobaltocene was isolated and characterized. In the solid state, this cobaltoceni- um salt features a folded dianionic complex maintaining 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 triplet diradical supported by the dipyrrindione ligands. These dipyrroles, which are also known as propentdyopents and were initially isolated as urinary pigments and heme metabolites, extend the rich chemistry of bidentate dipyrrin ligands to include the stabilization of ligand-centered radicals.

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“…14 The case-based learning modules presented in this work are adapted from practical X-ray crystallography course designed for graduate or upper-level undergraduate chemistry students; 33 however, such learning modules have been implemented in the crystallography teaching for varied undergraduate experimental chemistry courses, 7 and also conducted in various teaching modalities, such as virtual setting during the COVID-19 pandemic. 34,35 ■ ACTIVITIES…”

Section: The Instructors Are Facilitators Of Open-ended Discus-mentioning

confidence: 99%

“…They will be able to address the space-group-choice comments from peerreviews during their publication process independently. 35,50 Because of their achievement, some of these students have been awarded crystallography scholarships. 61 Many students will keep employing small-molecule crystallography after they go on to their own independent research careers, and make important contributions to the field.…”

Section: ■ Impactmentioning

confidence: 99%

Resolving Space-Group-Choice Dilemma in Small-Molecule Crystallography for Chemistry Students Using Case-Based Learning Modules

Dong

Zheng

2021

J. Chem. Educ.

Self Cite

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Despite advances in software development, symmetry-related topics are among the most important yet confusing concepts in crystallography training for chemistry students who routinely use small-molecule crystallography in their scientific study. The case-based learning approach is very effective in stimulating students’ interests in self-exploring the course material and critically processing information to arrive at the most reasonable result. Learning modules such as applying concepts of the 17 two-dimensional space groups in Escher drawings and critically judging crystallography misconceptions can engage chemistry students and invoke their confidence in handling the crystal structures encountered in their research.

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Syntheses and solid-state structures of two cofacial (bis)dipyrrin dichromium complexes in different charge states

Cited by 4 publications

References 30 publications

Ligand-Centered Triplet Diradical Supported by a Binuclear Palladium(II) Dipyrrindione

Ligand-Centered Triplet Diradical Supported by a Binuclear Palladium(II) Dipyrrindione

Stabilization of a Triplet Diradical on a Binuclear palladium(II) Dipyrrindione

Resolving Space-Group-Choice Dilemma in Small-Molecule Crystallography for Chemistry Students Using Case-Based Learning Modules

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