Conformationally dynamic copper coordination complexes

Charette, Bronte J.; Griffin, Paul J.; Zimmerman, Claire M; Olshansky, Lisa

doi:10.1039/d2dt00312k

Cited by 12 publications

(59 citation statements)

References 48 publications

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“…The Cu–N pyr bonds shorten slightly to 1.994(2) and 1.990(2) Å, while the Cu–N2 contact contracts significantly to 2.094(2) Å upon oxidation (Table ). This contraction of nearly 0.4 Å is consistent with similar phenomena observed in Cu I/II tripicolylamine systems, and overall, the bond lengths are similar to other reported cupric chloride dipicolylanisidines. , The complex has a τ 5 = 0.13 using the geometry index proposed by Addison and Reedijk for five-coordinate complexes, consistent with a slightly distorted square pyramidal geometry …”

Section: Resultssupporting

confidence: 88%

“…However, synthesis using CuCl provided an inner-sphere chloride ligand that enabled the isolation of stable CuCl(dpaa OMe ) and CuCl(dpaa H ) complexes (Chart b). Similar to the CuCl(dpa R ) complexes reported in ref , elemental analysis revealed that in the solid state, the CuCl(dpaa OMe ) complex can exist as a μ-Cl bridging dimer with the formula {[Cu(dpaa OMe )] 2 (μ-Cl)}{CuCl 2 }.…”

Section: Resultssupporting

confidence: 74%

“…The Cu–N pyr bond distances for this complex, Cu–N1 and Cu–N3, of 2.053(1) Å and 2.012(1) Å are unremarkable in the context of Cu I dipicolyamine complexes and consistent with strong bonding interactions (Table ). ,,− The Cu–N aniline distance, Cu–N2, of 2.478(1) Å is longer than in the corresponding dipicolylanisidine (2.286(3) Å) and dipicolylthioanisidine (2.181(2) Å) complexes reported by Karlin and co-workers. This lengthening likely results from the comparatively electron-deficient nature of the aniline donor containing acyl substitution in the para -position.…”

Section: Resultsmentioning

confidence: 71%

“…The solution-phase structures of the Cu I complexes were studied by 600 MHz 1 H NMR spectroscopy in d 2 -DCM. We have previously reported that the CuCl(dpa R ) complexes shown in Chart b are fluxional in solution and exhibit broadened and deshielded 1 H NMR spectra relative to the free ligands . Similarly, both CuCl(dpaa OMe ) and CuCl(dpaa H ) exhibit broadened and deshielded 1 H NMR spectra (Figures S2 and S3), suggesting that these complexes are also fluxional in solution.…”

Section: Resultsmentioning

confidence: 79%

“…This order of events is in contrast to typical small-molecule systems in which instantaneous ET is followed by slower solvent and internal reorganization of the nuclear coordinates . Thus, rather than creating structurally locked systems like those described above, we have designed ligands that are dynamic and capable of stabilizing both Cu I and Cu II . Further, these ligands contain twisted intramolecular charge transfer (TICT) fluorophores that undergo triggered conformational rearrangements upon photoexcitation to preferentially stabilize the Cu II state.…”

Section: Introductionmentioning

confidence: 99%

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Toward Improved Charge Separation through Conformational Control in Copper Coordination Complexes

et al. 2022

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The continued development of solar energy as a renewable resource necessitates new approaches to sustaining photodriven charge separation (CS). We present a bioinspired approach in which photoinduced conformational rearrangements at a ligand are translated into changes in coordination geometry and environment about a bound metal ion. Taking advantage of the differential coordination properties of CuI and CuII, these dynamics aim to facilitate intramolecular electron transfer (ET) from CuI to the ligand to create a CS state. The synthesis and photophysical characterization of CuCl(dpaaR) (dpaa = dipicolylaminoacetophenone, with R = H and OMe) are presented. These ligands incorporate a fluorophore that gives rise to a twisted intramolecular charge transfer (TICT) excited state. Excited-state ligand twisting provides a tetragonal coordination geometry capable of capturing CuII when an internal ortho-OMe binding site is present. NMR, IR, electron paramagnetic resonance (EPR), and optical spectroscopies, X-ray diffraction, and electrochemical methods establish the ground-state properties of these CuI and CuII complexes. The photophysical dynamics of the CuI complexes are explored by time-resolved photoluminescence and optical transient absorption spectroscopies. Relative to control complexes lacking a TICT-active ligand, the lifetimes of CS states are enhanced ∼1000-fold. Further, the presence of the ortho-OMe substituent greatly enhances the lifetime of the TICT* state and biases the coordination environment toward CuII. The presence of CuI decreases photoinduced degradation from 14 to <2% but does not result in significant quenching via ET. Factors affecting CS in these systems are discussed, laying the groundwork for our strategy toward solar energy conversion.

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Section: Resultssupporting

confidence: 88%

Section: Resultssupporting

confidence: 74%

Section: Resultsmentioning

confidence: 71%

Section: Resultsmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

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Toward Improved Charge Separation through Conformational Control in Copper Coordination Complexes

et al. 2022

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Ligand Modifications Produce Two‐Step Magnetic Switching in a Cobalt(dioxolene) Complex

KC,

Woods,

Olshansky

2023

Angewandte Chemie

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Mononuclear monodioxolene valence tautomeric (VT) cobalt complexes typically exist in their low spin (l.s.) CoIII(cat2‒) and high spin (h.s.) CoII(sq•‒) forms (cat2‒ = catecholato, and sq•‒ = seminquinonato forms of 3,5‐di‐tBu‐1,2‐dioxolene), which reversibly interconvert via temperature‐dependent intramolecular electron transfer. Typically, the remaining four coordination sites on cobalt are supported by a tetradentate ligand whose properties influence the temperature at which VT occurs. We report that replacing one chelating pyridyl arm of tris(2‐pyridylmethyl)amine (tpa) with a weaker field ortho‐anisole moiety facilitates access to a third magnetic state, and examine a series of related complexes. Variable temperature crystallographic, magnetic, calorimetric, and spectroscopic studies support that this third state is consistent with l.s. CoII(sq•‒). Thus, our ligand modifications not only provide access to the VT transition from l.s. CoIII(cat2‒) to l.s. CoII(sq•‒), but at higher temperatures, the complex undergoes spin crossover from l.s. CoII(sq•‒) to h.s. CoII(sq•‒), representing the first example of two‐step magnetic switching in a mononuclear monodioxolene cobalt complex. We hypothesize that ligand dynamicity may facilitate access to the rarely observed l.s. CoII(sq•‒) intermediate state, suggesting a new design criterion in the development of stimulus‐responsive multi‐state molecular switches.

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Ligand Modifications Produce Two‐Step Magnetic Switching in a Cobalt(dioxolene) Complex

KC,

Woods,

Olshansky

2023

Angew Chem Int Ed

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Conformationally dynamic copper coordination complexes

Abstract: The interplay between oxidation state and coordination geometry dictates both kinetic and thermodynamic properties underlying electron transfer events in copper complexes. An ability to stabilize both CuI and CuII oxidation...

Cited by 12 publications

References 48 publications

Toward Improved Charge Separation through Conformational Control in Copper Coordination Complexes

Toward Improved Charge Separation through Conformational Control in Copper Coordination Complexes

Ligand Modifications Produce Two‐Step Magnetic Switching in a Cobalt(dioxolene) Complex

Ligand Modifications Produce Two‐Step Magnetic Switching in a Cobalt(dioxolene) Complex

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