Redox properties and electron transfer in a triarylamine-substituted HS-Co2+/LS-Co3+ redox couple

Linda Schnaubelt, Holm Petzold, J. Matthaeus Speck, Evgenia Dmitrieva, Marco Rosenkranz, Marcus Korb

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

A new tridentate phenanthroline-pyridyl-based ligand 1 containing a redox active Tara (triaryl amine) unit has been developed (1 = 4-((6-(1,10-phenanthrolin-2-yl) pyridin-2-yl) oxy)-N, N-di-p-tolylaniline). The complex [Co2+(1)(2)](ClO4/BF4)(2) was prepared and the order of the oxidation steps was analysed by cyclic voltammetry and EPR/UV-vis-NIR spectroelectrochemistry. Oxidation of [Co2+(1)(2)](2+) to [Co3+(1(+))(2)](5+) proceeds in two steps. The first step is the Co2+/3+ centred oxidation to [Co3+(1)(2)](3+) (E degrees'(M2+/3+) = 284 mV vs. Fc/Fc(+)) followed by oxidation of the Tara(0/+) centres (E degrees'(Tara) = 531 mV). Both kinds of oxidation processes were independently investigated in the analogous complexes [Zn(1)(2)](ClO4)(2) and [Co(2)(2)](BF4)(2) allowing an assignment of changes in the electronic spectra to the redox states (2 = 2-(6-phenoxypyridin- 2-yl)-1,10-phenanthroline). Although spectroelectrochemistry did not indicate substantial coupling between the redox centres the Tara unit is an efficient mediator for the self-exchange in the [Co2+/3+(1)(2)](2+/3+) couple. The electron transfer by self-exchange in [Co2+/3+(1)(2)](2+/3+) was further investigated by variable temperature (VT) H-1 NMR spectroscopy. In addition, the resonances found in the paramagnetic proton NMR spectra were assigned by using COSY, T-1 and EXSY measurements in combination with the Co-N distances obtained from X-ray analysis. [Co(1)(2)](2+) is found in the HS state. In contrast, the Fe2+ species [Fe(1)(2)](ClO4)(2) is a spincrossover system. The SCO was analysed in solution by VT H-1 NMR and VT/vis spectroscopy.

Original languageEnglish
Pages (from-to)2690-2698
Number of pages9
JournalDalton Transactions
Volume46
Issue number8
DOIs
Publication statusPublished - 28 Feb 2017
Externally publishedYes

Cite this

Schnaubelt, Linda ; Petzold, Holm ; Speck, J. Matthaeus ; Dmitrieva, Evgenia ; Rosenkranz, Marco ; Korb, Marcus. / Redox properties and electron transfer in a triarylamine-substituted HS-Co2+/LS-Co3+ redox couple. In: Dalton Transactions. 2017 ; Vol. 46, No. 8. pp. 2690-2698.
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abstract = "A new tridentate phenanthroline-pyridyl-based ligand 1 containing a redox active Tara (triaryl amine) unit has been developed (1 = 4-((6-(1,10-phenanthrolin-2-yl) pyridin-2-yl) oxy)-N, N-di-p-tolylaniline). The complex [Co2+(1)(2)](ClO4/BF4)(2) was prepared and the order of the oxidation steps was analysed by cyclic voltammetry and EPR/UV-vis-NIR spectroelectrochemistry. Oxidation of [Co2+(1)(2)](2+) to [Co3+(1(+))(2)](5+) proceeds in two steps. The first step is the Co2+/3+ centred oxidation to [Co3+(1)(2)](3+) (E degrees'(M2+/3+) = 284 mV vs. Fc/Fc(+)) followed by oxidation of the Tara(0/+) centres (E degrees'(Tara) = 531 mV). Both kinds of oxidation processes were independently investigated in the analogous complexes [Zn(1)(2)](ClO4)(2) and [Co(2)(2)](BF4)(2) allowing an assignment of changes in the electronic spectra to the redox states (2 = 2-(6-phenoxypyridin- 2-yl)-1,10-phenanthroline). Although spectroelectrochemistry did not indicate substantial coupling between the redox centres the Tara unit is an efficient mediator for the self-exchange in the [Co2+/3+(1)(2)](2+/3+) couple. The electron transfer by self-exchange in [Co2+/3+(1)(2)](2+/3+) was further investigated by variable temperature (VT) H-1 NMR spectroscopy. In addition, the resonances found in the paramagnetic proton NMR spectra were assigned by using COSY, T-1 and EXSY measurements in combination with the Co-N distances obtained from X-ray analysis. [Co(1)(2)](2+) is found in the HS state. In contrast, the Fe2+ species [Fe(1)(2)](ClO4)(2) is a spincrossover system. The SCO was analysed in solution by VT H-1 NMR and VT/vis spectroscopy.",
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Schnaubelt, L, Petzold, H, Speck, JM, Dmitrieva, E, Rosenkranz, M & Korb, M 2017, 'Redox properties and electron transfer in a triarylamine-substituted HS-Co2+/LS-Co3+ redox couple' Dalton Transactions, vol. 46, no. 8, pp. 2690-2698. https://doi.org/10.1039/c6dt04748c

Redox properties and electron transfer in a triarylamine-substituted HS-Co2+/LS-Co3+ redox couple. / Schnaubelt, Linda; Petzold, Holm; Speck, J. Matthaeus; Dmitrieva, Evgenia; Rosenkranz, Marco; Korb, Marcus.

In: Dalton Transactions, Vol. 46, No. 8, 28.02.2017, p. 2690-2698.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Redox properties and electron transfer in a triarylamine-substituted HS-Co2+/LS-Co3+ redox couple

AU - Schnaubelt, Linda

AU - Petzold, Holm

AU - Speck, J. Matthaeus

AU - Dmitrieva, Evgenia

AU - Rosenkranz, Marco

AU - Korb, Marcus

PY - 2017/2/28

Y1 - 2017/2/28

N2 - A new tridentate phenanthroline-pyridyl-based ligand 1 containing a redox active Tara (triaryl amine) unit has been developed (1 = 4-((6-(1,10-phenanthrolin-2-yl) pyridin-2-yl) oxy)-N, N-di-p-tolylaniline). The complex [Co2+(1)(2)](ClO4/BF4)(2) was prepared and the order of the oxidation steps was analysed by cyclic voltammetry and EPR/UV-vis-NIR spectroelectrochemistry. Oxidation of [Co2+(1)(2)](2+) to [Co3+(1(+))(2)](5+) proceeds in two steps. The first step is the Co2+/3+ centred oxidation to [Co3+(1)(2)](3+) (E degrees'(M2+/3+) = 284 mV vs. Fc/Fc(+)) followed by oxidation of the Tara(0/+) centres (E degrees'(Tara) = 531 mV). Both kinds of oxidation processes were independently investigated in the analogous complexes [Zn(1)(2)](ClO4)(2) and [Co(2)(2)](BF4)(2) allowing an assignment of changes in the electronic spectra to the redox states (2 = 2-(6-phenoxypyridin- 2-yl)-1,10-phenanthroline). Although spectroelectrochemistry did not indicate substantial coupling between the redox centres the Tara unit is an efficient mediator for the self-exchange in the [Co2+/3+(1)(2)](2+/3+) couple. The electron transfer by self-exchange in [Co2+/3+(1)(2)](2+/3+) was further investigated by variable temperature (VT) H-1 NMR spectroscopy. In addition, the resonances found in the paramagnetic proton NMR spectra were assigned by using COSY, T-1 and EXSY measurements in combination with the Co-N distances obtained from X-ray analysis. [Co(1)(2)](2+) is found in the HS state. In contrast, the Fe2+ species [Fe(1)(2)](ClO4)(2) is a spincrossover system. The SCO was analysed in solution by VT H-1 NMR and VT/vis spectroscopy.

AB - A new tridentate phenanthroline-pyridyl-based ligand 1 containing a redox active Tara (triaryl amine) unit has been developed (1 = 4-((6-(1,10-phenanthrolin-2-yl) pyridin-2-yl) oxy)-N, N-di-p-tolylaniline). The complex [Co2+(1)(2)](ClO4/BF4)(2) was prepared and the order of the oxidation steps was analysed by cyclic voltammetry and EPR/UV-vis-NIR spectroelectrochemistry. Oxidation of [Co2+(1)(2)](2+) to [Co3+(1(+))(2)](5+) proceeds in two steps. The first step is the Co2+/3+ centred oxidation to [Co3+(1)(2)](3+) (E degrees'(M2+/3+) = 284 mV vs. Fc/Fc(+)) followed by oxidation of the Tara(0/+) centres (E degrees'(Tara) = 531 mV). Both kinds of oxidation processes were independently investigated in the analogous complexes [Zn(1)(2)](ClO4)(2) and [Co(2)(2)](BF4)(2) allowing an assignment of changes in the electronic spectra to the redox states (2 = 2-(6-phenoxypyridin- 2-yl)-1,10-phenanthroline). Although spectroelectrochemistry did not indicate substantial coupling between the redox centres the Tara unit is an efficient mediator for the self-exchange in the [Co2+/3+(1)(2)](2+/3+) couple. The electron transfer by self-exchange in [Co2+/3+(1)(2)](2+/3+) was further investigated by variable temperature (VT) H-1 NMR spectroscopy. In addition, the resonances found in the paramagnetic proton NMR spectra were assigned by using COSY, T-1 and EXSY measurements in combination with the Co-N distances obtained from X-ray analysis. [Co(1)(2)](2+) is found in the HS state. In contrast, the Fe2+ species [Fe(1)(2)](ClO4)(2) is a spincrossover system. The SCO was analysed in solution by VT H-1 NMR and VT/vis spectroscopy.

KW - VALENCE TAUTOMERIC TRANSITION

KW - SPIN-CROSSOVER

KW - STRUCTURE VALIDATION

KW - MAGNETIC-PROPERTIES

KW - METAL-COMPLEXES

KW - LIGANDS

KW - SYSTEMS

KW - INTERCONVERSION

KW - SEMIQUINONE

KW - EXCHANGE

U2 - 10.1039/c6dt04748c

DO - 10.1039/c6dt04748c

M3 - Article

VL - 46

SP - 2690

EP - 2698

JO - Dalton Transactions: the international journal for inorganic, organometallic and bioinorganic chemistry

JF - Dalton Transactions: the international journal for inorganic, organometallic and bioinorganic chemistry

SN - 1477-9226

IS - 8

ER -