A fascinating multifaceted redox-active chelating ligand: introducing the N,N′-dimethyl-3,3′-biquinoxalinium “methylbiquinoxen” platform

Leblanc, Nicolas; Sproules, Stephen; Fink, Karin; Sanguinet, Lionel; Alévêque, Olivier; Levillain, Eric; Powell, Annie K.

doi:10.1039/c5sc04904k

Cited by 8 publications

(12 citation statements)

References 58 publications

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“…In all cases these optical and vibrational signatures are in line with the one obtained by studying crystals of MBqn 0 -H + [BF4] for which the protonation has been perfectly proved. 5 However, we notice an increase of the IR vibration peak from 1638 to 1695 cm -1 as the bulkiness, and probably the twist angle around the central C-C bond, of the R substituent increases from methyl to benzyl (ESI).…”

Section: Resultsmentioning

confidence: 84%

“…where the dihedral angle is defined as φ = C2-C3-C3′-C2′. Remarkably, compared with Mbqn 0 -H + (φ = 2.5), 5 the larger dihedral angles for Pbqn 0 -H + confirm that the increase of the length of the R substituent leads to a twist of the molecule around the central C-C bond. Furthermore, monoprotonation induces an asymmetry within the organic moieties as well as between the organic moieties and the tetrathionate ion.…”

Section: Resultsmentioning

confidence: 94%

“…1) of the corresponding biquinoxen dications Rbqn 2+ , as already known for Mbqn 0 -H + . 5 Furthermore, the presence of sulfur in each elemental analysis (ESI) shows that the charge of the organic moieties is at least always partially balanced by some sulfur oxygen containing anions.…”

Section: Resultsmentioning

confidence: 99%

“…However the structure analysis revealed the features characteristic of a direduced monoprotonated species ( Figure 2), as it has been unambiguously described for Mbqn 0 -H + . 5 In particular, the two crystallographically independent Pbqn 0 -H + units adopt the typical cis-configuration (φ = 7.2° and 8.3°)…”

Section: Resultsmentioning

confidence: 99%

“…Indeed the Mbqn 2+ platform proved not only to combine a rich redox and Lewis acid/base chemistry combined with the chelating functionality, but also shows tuneable luminescence as well as providing the possibility of covalent functionalisation similar to the "click" chemistry approach. 5,6 Furthermore, besides being simple to synthesise in a pure form, in good yield and gram quantities in as little as two steps, the multiple properties are anchored on the same 1,4-diazine core structure of the Mbqn 2+ which offers exciting prospects for the design of organic or hybrid organic-inorganic based molecular compounds with interconnected and synchronous properties.…”

Section: Introductionmentioning

confidence: 99%

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An alternative method to access diverse N,N′-diquaternised-3,3′-biquinoxalinium “biquinoxen” dications

2017

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Section: Resultsmentioning

confidence: 84%

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

An alternative method to access diverse N,N′-diquaternised-3,3′-biquinoxalinium “biquinoxen” dications

2017

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Octahedral Iron Complexes of Pyrazine(diimine) Pincers: Ligand Electronic Effects and Protonation

2020

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Redox noninnocent ligands are known to be involved in altering the overall electronic nature of organometallic complexes by serving as an electron reservoir. Pyrazine(diimine) backbones in these complexes introduce enhanced π acidity over their more well-studied pyridine(diimine) analogues and open up the opportunity for functionalization of the nitrogen at the 4position of the ring. Herein we report the characterization of bischelated pyrazine(diimine) [(P z DI) 2 Fe] n+ (n = 0, 1, and 2) complexes for electronic and structural comparison to pyridine(diimine) complexes (PDI) with similar architectures. Cyclic voltammetry studies show three reductions, two of which are ligand-based and reversible. Reduction of [(P z DI) 2 Fe] 2+ (1) to [(P z DI) 2 Fe] + ( 2) and (P z DI) 2 Fe (3) gives rise to characteristic structural changes, such as imine CN bond lengthening, indicating the formation of a ligand radical, a conclusion which is further supported by electron paramagnetic resonance (EPR) and electronic structure calculations. Comparisons between the P z DI and PDI systems are highlighted. Complex 1 can be protonated at the uncoordinated pyrazine nitrogen, resulting in changes to its spectroscopic and redox properties; efforts to further functionalize the ligand are discussed.

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Modulations of a Metal–Ligand Interaction and Photophysical Behaviors by Hückel–Möbius Aromatic Switching

Kim

Park

et al. 2021

J. Am. Chem. Soc.

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In organometallic complexes containing π-conjugated macrocyclic chelate ligands, conformational change significantly affects metal−ligand electronic interactions, hence tuning properties of the complexes. In this regard, we investigated the metal−ligand interactions in hexaphyrin mono-Pd(II) complexes Pd[28]M and Pd[26]H, which exhibit a redox-induced switching of Huckel− Mobius aromaticity and subsequent molecular conformation, and their effect on the electronic structure and photophysical behaviors. In Mobius aromatic Pd[28]M, the weak metal−ligand interaction leads to the π electronic structure of the hexaphyrin ligand remaining almost intact, which undergoes efficient intersystem crossing (ISC) assisted by the heavy-atom effect of the Pd metal. In Huckel aromatic Pd[26]H, the significant metal−ligand interaction results in ligand-tometal charge-transfer (LMCT) in the excited-state dynamics. These contrasting metal−ligand electronic interactions have been revealed by time-resolved electronic and vibrational spectroscopies and time-dependent DFT calculations. This work indicates that the conspicuous modulation of metal−ligand interaction by Huckel−Mobius aromaticity switching is an appealing approach to manipulate molecular properties of metal complexes, further enabling the fine-tuning of metal−ligand interactions and the novel design of functional organometallic materials.

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A fascinating multifaceted redox-active chelating ligand: introducing the N,N′-dimethyl-3,3′-biquinoxalinium “methylbiquinoxen” platform

Abstract: N,N′-Dimethyl-3,3′-biquinoxalinium, “Methylbiquinoxen”: a stable redox-active chelating ligand with easily accessible functional states.

Cited by 8 publications

References 58 publications

An alternative method to access diverse N,N′-diquaternised-3,3′-biquinoxalinium “biquinoxen” dications

An alternative method to access diverse N,N′-diquaternised-3,3′-biquinoxalinium “biquinoxen” dications

Octahedral Iron Complexes of Pyrazine(diimine) Pincers: Ligand Electronic Effects and Protonation

Modulations of a Metal–Ligand Interaction and Photophysical Behaviors by Hückel–Möbius Aromatic Switching

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