Valence Tautomerism in Dioxolene Complexes of Cobalt

Shultz, David A.

doi:10.1002/3527600590.ch8

Cited by 58 publications

(22 citation statements)

References 85 publications

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“…In contrast, the electronic degeneracy of [Co III‐LS (dbcat)(dbsq)(N‐N)] (dbcat=3,5‐dbcat or 3,6‐dbcat) with mixed‐valence dioxolene ligands is only 4 43. Thus, Δ S el = S el (II‐HS)− S el (III‐LS)>0 (II‐HS=[Co II‐HS (dbsq) 2 (N‐N)] and III‐LS=[Co III‐LS (dbcat)(dbsq)(N‐N)]) 43. Furthermore, the high‐temperature phase has a relatively longer ligand‐to‐metal bond length than that of the low‐temperature phase, because two electrons in the d orbital of the high‐temperature phase occupy an e g orbital, which has antibonding character.…”

Section: Valence Tautomerismmentioning

confidence: 97%

“…This weakens the chemical bond and hence results in a longer bond length. The weaker metal‐to‐ligand bonding leads to a shallower potential well and closer spacing of the vibrational levels 43. Hence, the density of the vibration between Co and its ligands in the high‐temperature phase [Co II‐HS (dbsq) 2 (N‐N)] is larger than that in the [Co III‐LS (dbcat)(dbsq)(N‐N)] structure.…”

Section: Valence Tautomerismmentioning

confidence: 99%

“…The variation in entropy Δ S arises from both electronic (Δ S el ) and vibrational (Δ S vib ) contributions. The interaction of spins in the Co compound [Co II‐HS (dbsq) 2 (N‐N)] (dbsq=3,5‐dbsq or 3,6‐dbsq; N‐N=nitrogen‐donor ancillary ligands) gives rise to 16 states, and its electronic degeneracy is 16 43. In contrast, the electronic degeneracy of [Co III‐LS (dbcat)(dbsq)(N‐N)] (dbcat=3,5‐dbcat or 3,6‐dbcat) with mixed‐valence dioxolene ligands is only 4 43.…”

Section: Valence Tautomerismmentioning

confidence: 99%

“…The interaction of spins in the Co compound [Co II‐HS (dbsq) 2 (N‐N)] (dbsq=3,5‐dbsq or 3,6‐dbsq; N‐N=nitrogen‐donor ancillary ligands) gives rise to 16 states, and its electronic degeneracy is 16 43. In contrast, the electronic degeneracy of [Co III‐LS (dbcat)(dbsq)(N‐N)] (dbcat=3,5‐dbcat or 3,6‐dbcat) with mixed‐valence dioxolene ligands is only 4 43. Thus, Δ S el = S el (II‐HS)− S el (III‐LS)>0 (II‐HS=[Co II‐HS (dbsq) 2 (N‐N)] and III‐LS=[Co III‐LS (dbcat)(dbsq)(N‐N)]) 43.…”

Section: Valence Tautomerismmentioning

confidence: 99%

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Control of Magnetic Properties through External Stimuli

Sato¹,

Tao²,

Zhang³

2007

Angew Chem Int Ed

1,071

615

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The magnetic properties of many magnetic materials can be controlled by external stimuli. The principal focus here is on the thermal, photochemical, electrochemical, and chemical control of phase transitions that involve changes in magnetization. The molecular compounds described herein range from metal complexes, through pure organic compounds to composite materials. Most of the Review is devoted to the properties of valence-tautomeric compounds, molecular magnets, and spin-crossover complexes, which could find future application in memory devices or optical switches.

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Section: Valence Tautomerismmentioning

confidence: 97%

Section: Valence Tautomerismmentioning

confidence: 99%

Section: Valence Tautomerismmentioning

confidence: 99%

Section: Valence Tautomerismmentioning

confidence: 99%

See 2 more Smart Citations

Control of Magnetic Properties through External Stimuli

Sato¹,

Tao²,

Zhang³

2007

Angew Chem Int Ed

1,071

615

View full text Add to dashboard Cite

show abstract

“…Calcd [Fe(bpb) 2 (NCBH 3 ) 2 ]·2CH 2 Cl 2 ·2C 2 H 5 OH (9). Yellow crystals of complex 9 were obtained accordingly to the synthetic method of complex 5 by using Fe(NCBH 3 Crystallographic Data Collection and Structure Determination. X-ray diffraction data were collected on Agilent SuperNova diffractometer using a Cu Kα radiation source (λ = 1.541 78 Å) and Rigaku IP diffractometer using graphite monochromated radiation Mo Kα (λ = 0.710 73 Å).…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Coligand and Solvent Effects on the Architectures and Spin-Crossover Properties of (4,4)-Connected Iron(II) Coordination Polymers

Shi

Wei

et al. 2015

Inorg. Chem.

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The self-assemblies of 1,4-bis(pyrid-4-yl)benzene (bpb) and Fe(NCX)2 (X = S, Se, BH3) afforded six coordination polymers with the general formula of [Fe(bpb)2(NCX)2]·Y (X = S and Y = 3C2H5OH·2.5H2O for complex 4, X = S and Y = 2C2H5OH for 5, X = Se and Y = 2C2H5OH·H2O for 6, X = Se and Y = 0.67CH2Cl2·1.33C2H5OH·0.67H2O for 7, X = BH3 and Y = 3C2H5OH·2H2O for 8, X = BH3 and Y = 2CH2Cl2·2C2H5OH for 9). The frameworks of complexes 4 and 5 with the NCS(-) anion as coligand are supramolecular isomers, of which complex 4 features a threefold self-interpenetrated three-dimensional (3D) CdSO4-type topological structure with a Schläfli symbol of 6(5)·8, and complex 5 is a two-dimensional (2D) 4(4) rhombic grid network. These two complexes are purely high-spin systems. Complexes 6 and 7 with the NCSe(-) anion as coligand, both having the 3D 6(5)·8 CdSO4-type framework, show gradual and incomplete spin-crossover behaviors with transition temperature T1/2 being equal to 86 and 96 K, respectively. The usage of NCBH3(-) anion as coligand leads to the formation of 2D 4(4) rhombic grid networks for both complexes 8 and 9, which undergo relatively abrupt, complete spin crossover with T1/2 being equal to 247 and 189 K, respectively. The structural divergences are attributed to the coligands NCX(-) (X = S, Se, BH3) and solvent molecules. Meanwhile, a significant coligand effect is observed on the spin-crossover behaviors of these complexes, and the completeness and transition temperature of spin-state conversion depends on the nature of the coligand, that is, T1/2(NCS(-)) < T1/2(NCSe(-)) < T1/2(NCBH3(-)). These results further facilitate the design and synthesis of spin-crossover complexes with spin-state conversion.

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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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Valence Tautomerism in Dioxolene Complexes of Cobalt

Cited by 58 publications

References 85 publications

Control of Magnetic Properties through External Stimuli

Control of Magnetic Properties through External Stimuli

Coligand and Solvent Effects on the Architectures and Spin-Crossover Properties of (4,4)-Connected Iron(II) Coordination Polymers

Coordination Chemistry ofo‐Semiquinones

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