Photoinduced Valence Tautomerism in Co Complexes

Sato, Osamu; Cui, Ai‐Li; Matsuda, Ryotaro; Tao, Jun; Hayami, Shinya

doi:10.1002/chin.200731206

Cited by 161 publications

(2 citation statements)

References 43 publications

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“…Optical Reflectivity. Some complexes based on the Co ion, 3,5-dbcat 2− , and 3,5-dbsq • − ligands are known to exhibit photoinduced properties 41,42,70,71 that correspond to a photoinduced valence tautomerism. These photoinduced can be followed by optical and/or magnetic measurements, because the two valence isomers present distinct optical and magnetic properties.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Impact of Positional Isomers on the Selective Isolation of cis-trans Isomers in Cobalt-Dioxolene Chemistry and Solvation Effects on the Valence Tautomerism in the Solid State

Jana¹,

Brandão

et al. 2021

Crystal Growth & Design

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Three new mononuclear cobalt compounds, (3,5-dbsq) CN (1), (3,5-dbsq)(3-NH 2 py) 2 ]•DMF (2) and trans- [Co(3,5dbcat)(3,5-dbsq)(4-NH 2 py) 2 ]•2DMF (3) (3,5-dbcat 2and 3,5-dbsq •− stand for 3,5-di-tertbutyl-catacholate and 3,5-di-tert-butyl-semiquinonate, respectively), derived from a redoxactive o-dioxolene ligand in presence of 4-ethylpyridine (4-Etpy), 3-aminopyridine (3-NH 2 py), and 4-aminopyridine (4-NH 2 py), respectively, have been synthesized and investigated with a view to examine possible influence of pyridine derivatives and solvation on the valence tautomeric (VT) process. Single crystal X-ray diffraction data for all compounds at room temperature suggest Co(III)(3,5-dbcat)(3,5-dbsq) charge distribution in these complexes. Further insight into the crystal structures discloses the diverse noncovalent interactions offered by the isomers of aminopyridine in 2 and 3, leading to the first example 2 of selective isolation of cis and trans isomers in cobalt-dioxolene chemistry induced by the positional isomers of the ancillary ligands. Variable temperature magnetic susceptibility data for all compounds between 2 and 300 K are consistent with the structural studies. At elevated temperatures, complex 1 exhibits a VT interconversion from low spin Co(III)-(3,5-dbcat)(3,5dbsq) to high spin Co(II)-(3,5-dbsq)(3,5-dbsq), triggered by the loss of lattice solvent molecules, while a partial interconversion is observed for complex 3 even heating up to 430 K. The present report overall highlights the impact of positional isomers on the selective isolation of cis-trans isomers in cobalt-dioxolene chemistry and solvation effects on the valence tautomerism in the solid state. Accession CodesCCDC 2073857-2073859 for 1-3 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or

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Section: ■ Results and Discussionmentioning

confidence: 99%

Impact of Positional Isomers on the Selective Isolation of cis-trans Isomers in Cobalt-Dioxolene Chemistry and Solvation Effects on the Valence Tautomerism in the Solid State

Jana¹,

Brandão

et al. 2021

Crystal Growth & Design

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“…Valence tautomers [1] are bi-stable functional molecular materials in which it is observed charge transference between redox active ligands and a metallic center followed by the change of spin of the metal [2], induced by external stimuli such as illumination [3] and/or changes in temperature and pressure [ 4 ].…”

mentioning

confidence: 99%

Towards controlling the valance tautomer interconversion character by solvation

Pinheiro¹,

Ribeiro²,

Stasiw³

et al. 2013

Acta Cryst Sect A

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Valence tautomers[1] are bi-stable functional molecular materials in which it is observed charge transference between redox active ligands and a metallic center followed by the change of spin of the metal[2], induced by external stimuli such as illumination[3] and/or changes in temperature and pressure[ 4 ]. Valence tautomerism (VT) interconversion is essentially entropically driven, associated with remarkable variations in optical and/or magnetic properties, and can be modulated with slight chemical changes. Typical examples of VT compounds are coordination compunds of Co and o-dioxolenes ligands[5]. Crystalsof complex [Co III (SQ)(Cat) (4-NO 2 -py) 2 ] (I), where py= pyridine, Cat = 3,5-di-tbutylcatecholate and SQ=3,5-ditbutylsemiquinonate, were first studied with respect to low spin (LS) to high spin (HS) thermo and photoinduced conversion. It was reported that I become HS

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Coordination Chemistry ofo‐Semiquinones

Pierpont

Kelly

2013

Patai's Chemistry of Functional Groups

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o ‐Semiquinone (SQ) radicals are ideally suited to chelate with transition metal ions. Ligand paramagnetism results in spin‐coupling interactions with paramagnetic metal ions, and complexes containing multiple SQ ligands have magnetic properties resulting from inter‐ligand coupling. The unpaired SQ electron resides in a ligand‐localized π orbital close in energy with the valence d orbitals of many transition metal ions. Electron transfer between ligand and metal may be observed under equilibrium conditions by monitoring the temperature‐dependence of spectral and magnetic properties in a process known as valence tautomerism. The redox potentials of common SQ ligands overlap with the redox potentials of metal ions contributing to redox series that may involve reversible electron transfer steps at both the metal and SQ ligands. Multielectron redox reactions involving SQ ligands are useful in small molecule transformations that involve substrate oxidation or reduction over a narrow range in electrochemical potential. These properties are unique to complexes containing ligands capable of changing their charged state by either intramolecular electron transfer within the complex molecule or by an exchange of charge with an external redox component. Reactions and processes of this type will be the focus of this review on the coordination chemistry of o ‐semiquinonate ligands.

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Photoinduced Valence Tautomerism in Co Complexes

Abstract: Coordination chemistry Z 0150 Photoinduced Valence Tautomerism in Co Complexes -[48 refs.]. -(SATO*, O.; CUI, A.; MATSUDA, R.; TAO, J.; HAYAMI, S.; Acc. Chem. Res. 40 (2007) 5, 361-369; Inst. Mater. Chem. Eng., Kyushu Univ., Higashi, Fukuoka 812-81, Japan; Eng.) -Lindner 31-206

Cited by 161 publications

References 43 publications

Impact of Positional Isomers on the Selective Isolation of cis-trans Isomers in Cobalt-Dioxolene Chemistry and Solvation Effects on the Valence Tautomerism in the Solid State

Impact of Positional Isomers on the Selective Isolation of cis-trans Isomers in Cobalt-Dioxolene Chemistry and Solvation Effects on the Valence Tautomerism in the Solid State

Towards controlling the valance tautomer interconversion character by solvation

Coordination Chemistry ofo‐Semiquinones

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