DFT Prediction and Experimental Investigation of Valence Tautomerism in Cobalt-Dioxolene Complexes

Gemma K. Gransbury; Marie Emmanuelle Boulon; Simon Petrie; Robert W. Gable; Roger J. Mulder; Lorenzo Sorace; Robert Stranger; Colette Boskovic

doi:10.1021/acs.inorgchem.8b03291

DFT Prediction and Experimental Investigation of Valence Tautomerism in Cobalt-Dioxolene Complexes

Gemma K. Gransbury, Marie Emmanuelle Boulon, Simon Petrie, Robert W. Gable, Roger J. Mulder, Lorenzo Sorace, Robert Stranger, Colette Boskovic^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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Abstract

The family of complexes of general formula [Co(Me _n tpa)(Xdiox)] ⁺ (tpa = tris(2-pyridylmethyl)amine, n = 0-3 corresponds to successive methylation of the 6-position of the pyridine rings; X = Br ₄ , Cl ₄ , H ₄ , 3,5-Me ₂ , 3,5-tBu ₂ ; diox = dioxolene) was investigated by density functional theory (DFT) calculations to predict the likelihood of valence tautomerism (VT). The OPBE functional with relativistic and solvent corrections allowed accurate reproduction of trends in spin-state energetics, affording the prediction of VT in complex [Co(Me ₃ tpa)(Br ₄ diox)] ⁺ (1 ⁺ ). One-electron oxidation of neutral precursor [Co ^II (Me ₃ tpa)(Br ₄ cat)] (1) enabled isolation of target compounds 1(PF ₆ ) and 1(BPh ₄ ). Solution variable-temperature UV-vis absorption and Evans method magnetic susceptibility data confirm DFT predictions that 1 ⁺ exists in a temperature-dependent valence tautomeric equilibrium between low-spin Co(III)-catecholate and high-spin Co(II)-semiquinonate forms. The solution VT transition temperature of 1 ⁺ is solvent-tunable with critical temperatures in the range of 291-359 K for the solvents measured. Solid-state magnetic susceptibility measurements of 1(PF ₆ ) and 1(BPh ₄ ) reveal the onset of VT transitions above room temperature.

Original language	English
Pages (from-to)	4230-4243
Number of pages	14
Journal	Inorganic Chemistry
Volume	58
Issue number	7
DOIs	https://doi.org/10.1021/acs.inorgchem.8b03291
Publication status	Published - 1 Apr 2019

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@article{3341eea37a3b4990918695114d9b4899,

title = "DFT Prediction and Experimental Investigation of Valence Tautomerism in Cobalt-Dioxolene Complexes",

abstract = " The family of complexes of general formula [Co(Me n tpa)(Xdiox)] + (tpa = tris(2-pyridylmethyl)amine, n = 0-3 corresponds to successive methylation of the 6-position of the pyridine rings; X = Br 4 , Cl 4 , H 4 , 3,5-Me 2 , 3,5-tBu 2 ; diox = dioxolene) was investigated by density functional theory (DFT) calculations to predict the likelihood of valence tautomerism (VT). The OPBE functional with relativistic and solvent corrections allowed accurate reproduction of trends in spin-state energetics, affording the prediction of VT in complex [Co(Me 3 tpa)(Br 4 diox)] + (1 + ). One-electron oxidation of neutral precursor [Co II (Me 3 tpa)(Br 4 cat)] (1) enabled isolation of target compounds 1(PF 6 ) and 1(BPh 4 ). Solution variable-temperature UV-vis absorption and Evans method magnetic susceptibility data confirm DFT predictions that 1 + exists in a temperature-dependent valence tautomeric equilibrium between low-spin Co(III)-catecholate and high-spin Co(II)-semiquinonate forms. The solution VT transition temperature of 1 + is solvent-tunable with critical temperatures in the range of 291-359 K for the solvents measured. Solid-state magnetic susceptibility measurements of 1(PF 6 ) and 1(BPh 4 ) reveal the onset of VT transitions above room temperature.",

author = "Gransbury, {Gemma K.} and Boulon, {Marie Emmanuelle} and Simon Petrie and Gable, {Robert W.} and Mulder, {Roger J.} and Lorenzo Sorace and Robert Stranger and Colette Boskovic",

note = "Publisher Copyright: Copyright {\textcopyright} 2019 American Chemical Society.",

year = "2019",

month = apr,

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doi = "10.1021/acs.inorgchem.8b03291",

language = "English",

volume = "58",

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T1 - DFT Prediction and Experimental Investigation of Valence Tautomerism in Cobalt-Dioxolene Complexes

AU - Gransbury, Gemma K.

AU - Boulon, Marie Emmanuelle

AU - Petrie, Simon

AU - Gable, Robert W.

AU - Mulder, Roger J.

AU - Sorace, Lorenzo

AU - Stranger, Robert

AU - Boskovic, Colette

PY - 2019/4/1

Y1 - 2019/4/1

N2 - The family of complexes of general formula [Co(Me n tpa)(Xdiox)] + (tpa = tris(2-pyridylmethyl)amine, n = 0-3 corresponds to successive methylation of the 6-position of the pyridine rings; X = Br 4 , Cl 4 , H 4 , 3,5-Me 2 , 3,5-tBu 2 ; diox = dioxolene) was investigated by density functional theory (DFT) calculations to predict the likelihood of valence tautomerism (VT). The OPBE functional with relativistic and solvent corrections allowed accurate reproduction of trends in spin-state energetics, affording the prediction of VT in complex [Co(Me 3 tpa)(Br 4 diox)] + (1 + ). One-electron oxidation of neutral precursor [Co II (Me 3 tpa)(Br 4 cat)] (1) enabled isolation of target compounds 1(PF 6 ) and 1(BPh 4 ). Solution variable-temperature UV-vis absorption and Evans method magnetic susceptibility data confirm DFT predictions that 1 + exists in a temperature-dependent valence tautomeric equilibrium between low-spin Co(III)-catecholate and high-spin Co(II)-semiquinonate forms. The solution VT transition temperature of 1 + is solvent-tunable with critical temperatures in the range of 291-359 K for the solvents measured. Solid-state magnetic susceptibility measurements of 1(PF 6 ) and 1(BPh 4 ) reveal the onset of VT transitions above room temperature.

AB - The family of complexes of general formula [Co(Me n tpa)(Xdiox)] + (tpa = tris(2-pyridylmethyl)amine, n = 0-3 corresponds to successive methylation of the 6-position of the pyridine rings; X = Br 4 , Cl 4 , H 4 , 3,5-Me 2 , 3,5-tBu 2 ; diox = dioxolene) was investigated by density functional theory (DFT) calculations to predict the likelihood of valence tautomerism (VT). The OPBE functional with relativistic and solvent corrections allowed accurate reproduction of trends in spin-state energetics, affording the prediction of VT in complex [Co(Me 3 tpa)(Br 4 diox)] + (1 + ). One-electron oxidation of neutral precursor [Co II (Me 3 tpa)(Br 4 cat)] (1) enabled isolation of target compounds 1(PF 6 ) and 1(BPh 4 ). Solution variable-temperature UV-vis absorption and Evans method magnetic susceptibility data confirm DFT predictions that 1 + exists in a temperature-dependent valence tautomeric equilibrium between low-spin Co(III)-catecholate and high-spin Co(II)-semiquinonate forms. The solution VT transition temperature of 1 + is solvent-tunable with critical temperatures in the range of 291-359 K for the solvents measured. Solid-state magnetic susceptibility measurements of 1(PF 6 ) and 1(BPh 4 ) reveal the onset of VT transitions above room temperature.

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U2 - 10.1021/acs.inorgchem.8b03291

DO - 10.1021/acs.inorgchem.8b03291

M3 - Article

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VL - 58

SP - 4230

EP - 4243

JO - Inorganic Chemistry

JF - Inorganic Chemistry

IS - 7

ER -

DFT Prediction and Experimental Investigation of Valence Tautomerism in Cobalt-Dioxolene Complexes

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