Photoinduced Valence Tautomerism in Cobalt Complexes Containing Semiquinone Anion as Ligand: Dynamics of the High-Spin[CoII(3,5-dtbsq)2] to Low-Spin[CoIII(3,5-dtbsq)(3,5-dtbcat)] Interconversion

1995 ◽  
Vol 34 (1314) ◽  
pp. 1481-1483 ◽  
Author(s):  
David M. Adams ◽  
Bulang Li ◽  
John D. Simon ◽  
David N. Hendrickson
Keyword(s):  
High Spin ◽  
Cobalt Complexes ◽  
Valence Tautomerism

scholarly journals Cobalt complexes of the chelating dicarboxylate ligand “esp”: a paddlewheel-type dimer and a heptanuclear coordination cluster

2018 ◽  
Vol 47 (39) ◽  
pp. 13887-13893 ◽  
Author(s):  
Ryan J. Pakula ◽  
John F. Berry
Keyword(s):  
High Spin ◽  
Cobalt Complexes ◽  
Cluster Complex ◽  
Dicarboxylate Ligand

Reaction of CoCO3 with α,α,α′,α′-tetramethyl-1,3-benzenedipropionic acid (H2esp) in EtOH forms the paddlewheel-type dimer Co2(esp)2(EtOH)2, which hydrolyzes in MeCN to give a bowl-shaped heptacobalt coordination cluster complex; both compounds display antiferromagnetic interactions between high-spin Co(ii) ions.

scholarly journals Imido Cobalt Complexes with Imidyl Character

2021 ◽  
Author(s):  
alexander Reckziegel ◽  
Manjinder Kour ◽  
Beatrice Battistella ◽  
Stefan Mebs ◽  
Katrin Beuthert ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Spin Density ◽  
High Spin ◽  
Bond Activation ◽  
High Spin State ◽  
Cobalt Complexes ◽  
Spectroscopic Methods ◽  
Computational Studies ◽  
Ancillary Ligand ◽  
Unpaired Spin

We report on the synthesis of a variety of trigonal imido cobalt complexes [Co(NAryl)L<sub>2</sub>)<sup>–</sup>, (L = N(Dipp)SiMe<sub>3</sub>), Dipp = 2,6-diisopropylphenyl) bearing very long Co–NAryl bonds of around 1.75 Å. The electronic structure was interrogated using a variety of physical and spectroscopic methods indicating the first authenticated examples of cobalt bound imidyl species. Computational studies corroborate these findings and reveal that the high-spin state of these complexes gives rise to unpaired spin-density on the imide nitrogen and leads to its imidyl character. Obtained complexes are capable of intermolecular H atom abstraction from C–H bonds that yields the corresponding cobalt amides. Exchange of the Dipp-substituent on the imide by the smaller mesityl function (2,4,6-trimethylphenyl) effectuates the unexpected Me<sub>3</sub>Si shift from the ancillary ligand set to the imide nitrogen, followed by intramolecular C–H bond activation.<br>

scholarly journals Photoinduced Valence Tautomerism of a Cobalt-Dioxolene Complex Revealed with Femtosecond M-Edge XANES

2019 ◽  
Author(s):  
Ryan Ash ◽  
Kaili Zhang ◽  
Josh Vura-Weis
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
High Spin ◽  
Ground State ◽  
Extreme Ultraviolet ◽  
High Harmonic ◽  
Ligand Field ◽  
Intersystem Crossing ◽  
Valence Tautomerism ◽  
Reduced Forms

Cobalt complexes that undergo charge-transfer induced spin-transitions (CTIST) or valence tautomerism (VT) from low spin (LS) Co(III) to high spin (HS) Co(II) are potential candidates for magneto-optical switches. We use M-edge XANES spectroscopy with 40 fs time resolution to measure the excited-state dynamics of Co(III)(Cat-N-SQ)(Cat-N-BQ), where Cat-N-BQ and Cat-N-SQ are the singly and doubly reduced forms of the 2-(2-hydroxy-3,5-di-tert-butylphenyl-imino)-4,6-di-tert-butylcyclohexa-3,5-dienone ligand. The extreme ultraviolet probe pulses, produced using a tabletop high-harmonic generation light source, measure 3p3d transitions and are sensitive to the spin and oxidation state of the Co center. Photoexcitation at 525 nm produces a low-spin Co(II) ligand-to-metal charge transfer state which undergoes intersystem crossing to high-spin Co(II) in 67 fs. Vibrational cooling from this hot HS Co(II) state competes on the hundreds-of-fs timescale with back-intersystem crossing to the ground state, with 60% of the population trapped in a cold HS Co(II) state for 24 ps. Ligand field multiplet simulations accurately reproduce the ground-state spectra and support the excited-state assignments. This work demonstrates the ability of M-edge XANES to measure ultrafast photophysics of molecular Co complexes.<br><br><br>

Redox Pairs of Diiron and Iron–Cobalt Complexes with High-Spin Ground States

2016 ◽  
Vol 55 (19) ◽  
pp. 9725-9735 ◽  
Author(s):  
Deanna L. Miller ◽  
Randall B. Siedschlag ◽  
Laura J. Clouston ◽  
Victor G. Young ◽  
Yu-Sheng Chen ◽  
...  
Keyword(s):  
High Spin ◽  
Ground States ◽  
Cobalt Complexes ◽  
Iron Cobalt

High Spin Cobalt Complexes Supported by a Trigonal Tris(Phosphinimide) Ligand

2021 ◽  
Author(s):  
Heui Beom Lee ◽  
Nicholas Ciolkowski ◽  
Charles Winslow ◽  
Jonathan Rittle
Keyword(s):  
High Spin ◽  
Cobalt Complexes

scholarly journals Imido Cobalt Complexes with Imidyl Character

2021 ◽  
Author(s):  
alexander Reckziegel ◽  
Manjinder Kour ◽  
Beatrice Battistella ◽  
Stefan Mebs ◽  
Katrin Beuthert ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Spin Density ◽  
High Spin ◽  
Bond Activation ◽  
High Spin State ◽  
Cobalt Complexes ◽  
Spectroscopic Methods ◽  
Computational Studies ◽  
Ancillary Ligand ◽  
Unpaired Spin

We report on the synthesis of a variety of trigonal imido cobalt complexes [Co(NAryl)L<sub>2</sub>)<sup>–</sup>, (L = N(Dipp)SiMe<sub>3</sub>), Dipp = 2,6-diisopropylphenyl) bearing very long Co–NAryl bonds of around 1.75 Å. The electronic structure was interrogated using a variety of physical and spectroscopic methods indicating the first authenticated examples of cobalt bound imidyl species. Computational studies corroborate these findings and reveal that the high-spin state of these complexes gives rise to unpaired spin-density on the imide nitrogen and leads to its imidyl character. Obtained complexes are capable of intermolecular H atom abstraction from C–H bonds that yields the corresponding cobalt amides. Exchange of the Dipp-substituent on the imide by the smaller mesityl function (2,4,6-trimethylphenyl) effectuates the unexpected Me<sub>3</sub>Si shift from the ancillary ligand set to the imide nitrogen, followed by intramolecular C–H bond activation.<br>

Preparation, electrochemical behavior, and variable-temperature magnetic properties of Co(3,5-DBSQ)2 complexes of imidazole- or pyrazole-substituted ligands

2015 ◽  
Vol 93 (7) ◽  
pp. 769-774 ◽  
Author(s):  
Carolyn Dowling ◽  
Danielle R. Dinsdale ◽  
Martin T. Lemaire
Keyword(s):  
Magnetic Susceptibility ◽  
High Spin ◽  
Density Functional ◽  
Variable Temperature ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Magnetic Susceptibility Data ◽  
Valence Tautomerism ◽  
Susceptibility Data ◽  
Variable Temperature Magnetic Susceptibility

Herein we describe the preparation of four new Co(3,5-DBSQ)2 containing known 2-(2-pyridyl)benzimidazole 1, 2,2′-bisbenzimidazole 2, or 2,2-(1H-pyrazole-3,5-diyl)dipyridine 3. We investigate the electronic and variable-temperature magnetic susceptibility properties of these complexes. Complexes containing 2 and 3 are bimetallic and variable-temperature magnetic susceptibility data suggest observation of a stable intermediate (high-spin and low-spin) state for the bimetallic complex with 3, which does undergo valence tautomerism. Complexes 4–6 containing imidazole-based ligands 1 and 2 feature high-spin ground states and no valence tautomerism is observed in these materials. This experimental finding is corroborated with density functional theory calculations, which support the existence of a stable high-spin ground state in these complexes.

Controlling Valence Tautomerism of Cobalt Complexes Containing the Benzosemiquinone Anion as Ligand

1993 ◽  
Vol 32 (6) ◽  
pp. 880-882 ◽  
Author(s):  
David M. Adams ◽  
Andrea Dei ◽  
Arnold L. Rheingold ◽  
David N. Hendrickson
Keyword(s):  
Cobalt Complexes ◽  
Valence Tautomerism

Redox Activity and Two-Step Valence Tautomerism in a Family of Dinuclear Cobalt Complexes with a Spiroconjugated Bis(dioxolene) Ligand

2013 ◽  
Vol 135 (22) ◽  
pp. 8304-8323 ◽  
Author(s):  
Kerwyn G. Alley ◽  
Giordano Poneti ◽  
Peter S. D. Robinson ◽  
Ayman Nafady ◽  
Boujemaa Moubaraki ◽  
...  
Keyword(s):  
Cobalt Complexes ◽  
Redox Activity ◽  
Valence Tautomerism
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