Verdazyls and Related Radicals Containing the Hydrazyl [R<sub>2</sub>N‐NR] Group

Hicks, Robin G.

doi:10.1002/9780470666975.ch7

Cited by 28 publications

(27 citation statements)

References 159 publications

(141 reference statements)

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“…The Zn-coordinated L 2-fragment can be considered an inorganic analogue of a verdazyl radical (Chart 1). [15] The long N-N bonds in the L 2-fragment result from the unpaired electron occupying a molecular orbital (SOMO) which has π * N-N antibonding character (vide infra). The observation of two distinct ligand redox states is likely related to electrostatic interactions with the cation, which localizes the additional negative charge.…”

mentioning

confidence: 99%

The Formazanate Ligand as an Electron Reservoir: Bis(Formazanate) Zinc Complexes Isolated in Three Redox States

et al. 2014

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Metal-mediated redox processes are of fundamental importance in a wide variety of bond formation and cleavage reactions. The utility of transition metal catalysts in this type of reactions stems from their ability to switch between two (or more) oxidation states. Recently, there has been increased interest in redox processes that do not occur at the metal centre, but instead take place within the ancillary ligand framework (so-called 'redox-active' or 'non-innocent' ligands). [1] The use of organic ligands as redox equivalents is of key importance in biological (enzymatic) transformations, [2] and has been shown to open new reactivity pathways in catalysis. [1c] The most studied ligands of this class are dithiolenes and dioxolenes, while recent work has focussed on α-diimines [3] and bis(imino)pyridines. [4] A class of ligands that has found widespread utility in the synthesis of metal complexes across the periodic table are the monoanionic β-diketiminates. [5] These are generally considered as stable ligand scaffolds without involvement in redox-chemistry. Recently, examples of β-diketiminate metal complexes were reported in which the ligand was either reduced to a metal-bound di-or trianion, [6] or oxidized to a neutral radical species. [7] However, the limited stability of β-diketiminate complexes upon changing oxidation state prevents widespread application. [8] Formazanates (1,2,4,5-tetraazapentadienyls), [9] which are close analogues of β-diketiminates, have received comparatively little attention as ligands in coordination chemistry. [10] The stability of organic 6-membered heterocyclic radicals (verdazyls) that are derived from formazans prompted us to explore the use of formazanates as potential redox-active ligands (Chart 1). Here we show that zinc complexes with formazanate ligands engage in remarkably facile and reversible redox-chemistry which allows the full characterization of bis(formazanate) L 2 Zn complexes in charge neutral, anionic or dianionic redox states.

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confidence: 99%

The Formazanate Ligand as an Electron Reservoir: Bis(Formazanate) Zinc Complexes Isolated in Three Redox States

et al. 2014

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“…10). Magnetic data for [CuBr 2 (2-Br-py) 2 ] show an absence of any interactions, with perfect Curie-type behavior [46].…”

Section: Halopyridine Complexes Of Metal Halidesmentioning

confidence: 94%

“…Its Fig. 6 Detail of the two crystallographically independent conducting slabs in (tTTF-I) 2 ClO 4 Organizing Radical Species in the Solid State with Halogen Bonding 97 electrocrystallization with halide anions afforded a 2:1 mixed valence salt, whose conductivity is limited by the steric constraints imposed by the bulky dimethylpropylene moiety (Fig. 8).…”

Section: Chiral Iodottf Saltsmentioning

confidence: 99%

“…A similar 1:1 salt was also reported with tTTF-I, formulated as (tTTF-I)(ClO 4 ), with one IÁ Á ÁO distance at 2.997 Å, i.e., 86% of the sum of the van des Waals radii. A particularly interesting 2:1 salt was also isolated with tTTF-I, formulated as (tTTF-I) 2 ClO 4 , where two oxygen atoms of the ClO 4 À anion are engaged in IÁ Á ÁO interactions, each of them however with a crystallographically independent tTTF-I molecule ( Fig. 6) [34].…”

Section: Iodottfs With Non-centrosymmetric Clo 4 à Anionmentioning

confidence: 99%

“…Radical species are investigated particularly in the solid state for their magnetic (and eventually conductive) properties, which closely depend on the interaction pathways established between them [1,2]. In this respect, intermolecular interactions are expected to play two strikingly different roles.…”

Section: Introductionmentioning

confidence: 99%

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Organizing Radical Species in the Solid State with Halogen Bonding

Fourmigué

Lieffrig

2014

Topics in Current Chemistry

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The electronic properties (conductivity, magnetism) of radical systems in the solid state essentially depend on (1) the extent of delocalization of the spin density in the molecule and (2) the intermolecular interactions between radicals. The halogen bond has proven very efficient in engineering such magnetic or conducting structures and recent advances along these lines are reviewed here. Three situations are considered: (1) halogenated radical species acting as halogen bond donors, as found in iodotetrathiafulvalene-based chiral conductors or bilayer systems, and in spin crossover (SCO) complexes with halogenated ligands, (2) radical species acting as halogen bond acceptors, such as neutral nitronyl species or anionic, mixed-valence dithiolene complexes, interacting with closed-shell halogen bond donors (iodoperfluoro alkanes and arenes, iodo- or bromo-pyridinium cations), and, finally, (3) charge transfer salts where both halogen bond donor and acceptor are radical species.

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DPPH (2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl) radical scavenging mixed-mode colorimetric assay(s)

Nenadis

Tsimidou

2017

Measurement of Antioxidant Activity &Amp; Capacity

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Verdazyls and Related Radicals Containing the Hydrazyl [R₂N‐NR] Group

Cited by 28 publications

References 159 publications

The Formazanate Ligand as an Electron Reservoir: Bis(Formazanate) Zinc Complexes Isolated in Three Redox States

The Formazanate Ligand as an Electron Reservoir: Bis(Formazanate) Zinc Complexes Isolated in Three Redox States

Organizing Radical Species in the Solid State with Halogen Bonding

DPPH (2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl) radical scavenging mixed-mode colorimetric assay(s)

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Verdazyls and Related Radicals Containing the Hydrazyl [R2N‐NR] Group

Cited by 28 publications

References 159 publications

The Formazanate Ligand as an Electron Reservoir: Bis(Formazanate) Zinc Complexes Isolated in Three Redox States

The Formazanate Ligand as an Electron Reservoir: Bis(Formazanate) Zinc Complexes Isolated in Three Redox States

Organizing Radical Species in the Solid State with Halogen Bonding

DPPH (2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl) radical scavenging mixed-mode colorimetric assay(s)

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Product

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Verdazyls and Related Radicals Containing the Hydrazyl [R₂N‐NR] Group