Ligand-Based Redox Isomers of [ZnII(C28H40NO2)2]:  Molecular and Electronic Structures of a Diamagnetic Green and a Paramagnetic Red Form

The [ONO] ligand {(ONOcat)3– = bis(3,5‐di‐tert‐butyl‐2‐phenoxy)amide} can be installed onto zirconium(IV) in two different protonation states. The reaction of (ONOcat)3– with ZrCl4 afforded the octahedral complex (ONOcat)ZrCl(THF)2 (1). This complex, characterized in the solid state by single‐crystal X‐ray diffraction and in solution by NMR,UV/Vis, and IR spectroscopy, is assigned as a zirconium(IV) complex coordinated to the fully reduced form of the [ONO] redox‐active ligand. When (ONOcat)H3 was doubly deprotonated and treated with ZrCl4, the complex (ONHO)ZrCl2(THF) (2) was isolated, in which one ligand proton remains on the [ONO] ligand. Exposure of 2 to dry O2 resulted in a four‐electron, two‐proton reaction to form the bis(hydroxo) complex [(ONOq)ZrCl2(μ‐OH)]2 (3), which shows that the [ONO] ligand platform can serve as both an electron and proton reservoir in small‐molecule reactions.

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“…[18] Deprotonation of (ON-O cat )H 3 with 3 equiv. nBuLi affords the trianionic form of the ligand, (ONO cat ) 3-.…”

Section: Resultsmentioning

confidence: 99%

A Redox‐Active Ligand as a Reservoir for Protons and Electrons: O₂ Reduction at Zirconium(IV)

Zarkesh

Heyduk

2011

Eur J Inorg Chem

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“…[21] The tridentate Schiff-base ligand 3,5-ditert-butyl-1,2-quinone-1-(2-hydroxy-3,5-di-tert-butylphenyl)-A C H T U N G T R E N N U N G imine [22] leads to stable coordination complexes with several metal ions, and exhibit different oxidation states ranging from 0 to À3 (see Scheme 1). Nevertheless, it usually coordinates in the mononegative Cat-N-BQ À or dinegative Cat-N-SQ 2À radical forms [23] generating mixed-valence species. Although complexes 2-4 have been previously synthesized, only preliminary studies on the IET LM of complex 2 have been reported.…”

Section: Ma C H T U N G T R E N N U N G (Cat-n-bq)a C H T U N G T R Ementioning

confidence: 99%

Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)₂] (M=Co, Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study

Evangelio

Bonnet

Cabañas³

et al. 2010

Chemistry A European J

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The different thermally induced intermolecular electron transfer (IET) processes that can take place in the series of complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)2], for which M=Co (2), Fe (3) and Ni(4), and Cat‐N‐BQ and Cat‐N‐SQ denote the mononegative (Cat‐N‐BQ−) or dinegative (Cat‐N‐SQ2−) radical forms of the tridentate Schiff‐base ligand 3,5‐di‐tert‐butyl‐1,2‐quinone‐1‐(2‐hydroxy‐3,5‐di‐tert‐butylphenyl)imine, have been studied by variable‐temperature UV/Vis and NMR spectroscopies. Depending on the metal ion, rather different behaviors are observed. Complex 2 has been found to be one of the few examples so far reported to exhibit the coexistence of two thermally induced electron transfer processes, ligand‐to‐metal (IETLM) and ligand‐to‐ligand (IETLL). IETLL was only found to take place in complex 3, and no IET was observed for complex 4. Such experimental studies have been combined with ab initio wavefunction‐based CASSCF/CASPT2 calculations. Such a strategy allows one to solicit selectively the speculated orbitals and to access the ground states and excited‐spin states, as well as charge‐transfer states giving additional information on the different IET processes.

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“…For instance, the tridentate ligand [(2-hydroxy-3,5-di-tert-butyl-1-phenyl)imino]-3,5-di-tert-butyl-1,2-benzoquinone ligand (Cat-N-BQ), may in principle exist in different oxidation states although it usually coordinates in the mononegative Cat-N-BQ or dinegative Cat-N-SQ radical forms (see Scheme 4). [63] Using such a ligand, in 1988 Pierpont et al reported the new complex [Co III (Cat-N-BQ)(Cat-N-SQ)] (12), although at that time no evidence for tautomeric interconversion was shown to take place. [64] A few years later, the temperature dependence of the spectral and magnetic properties of solutions of this compound in nonpolar solvents suggested the existence of the valence tautomeric equilibrium shown in Equation (4).…”

Section: Phenoxyl Ligandsmentioning

confidence: 99%

Valence Tautomerism: New Challenges for Electroactive Ligands

2005

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Valence tautomeric complexes combine redox-active ligands and transition metal ions with two or more accessible oxidation states, exhibiting two nearly degenerated electronic states with localized electronic structures. Charge distribution in such electronic isomers has an appreciable sensitivity to the environment so an external perturbation, like photons, temperature and/or pressure, may lead to an intramolecular electron transfer between both redox active units and therefore to a reversible interconversion between the two degenerated electronic states. Moreover, since each electronic isomer exhibits different optical, electronic and/or magnetic properties, these complexes are being proposed as candi-

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Ligand-Based Redox Isomers of [Zn^II(C₂₈H₄₀NO₂)₂]: Molecular and Electronic Structures of a Diamagnetic Green and a Paramagnetic Red Form

Cited by 77 publications

References 15 publications

A Redox‐Active Ligand as a Reservoir for Protons and Electrons: O₂ Reduction at Zirconium(IV)

A Redox‐Active Ligand as a Reservoir for Protons and Electrons: O₂ Reduction at Zirconium(IV)

Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)₂] (M=Co, Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study

Valence Tautomerism: New Challenges for Electroactive Ligands

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Ligand-Based Redox Isomers of [ZnII(C28H40NO2)2]: Molecular and Electronic Structures of a Diamagnetic Green and a Paramagnetic Red Form

Cited by 77 publications

References 15 publications

A Redox‐Active Ligand as a Reservoir for Protons and Electrons: O2 Reduction at Zirconium(IV)

A Redox‐Active Ligand as a Reservoir for Protons and Electrons: O2 Reduction at Zirconium(IV)

Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)2] (M=Co, Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study

Valence Tautomerism: New Challenges for Electroactive Ligands

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Ligand-Based Redox Isomers of [Zn^II(C₂₈H₄₀NO₂)₂]: Molecular and Electronic Structures of a Diamagnetic Green and a Paramagnetic Red Form

A Redox‐Active Ligand as a Reservoir for Protons and Electrons: O₂ Reduction at Zirconium(IV)

A Redox‐Active Ligand as a Reservoir for Protons and Electrons: O₂ Reduction at Zirconium(IV)

Coexistence of Two Thermally Induced Intramolecular Electron Transfer Processes in a Series of Metal Complexes [M(Cat‐N‐BQ)(Cat‐N‐SQ)]/[M(Cat‐N‐BQ)₂] (M=Co, Fe, and Ni) bearing Non‐Innocent Catechol‐Based Ligands: A Combined Experimental and Theoretical Study