Macrocycles Bearing Ferrocenyl Pendants and their Electrochemical Properties upon Binding to Divalent Transition Metal Cations

Zhanghua Zeng, Matthew J. Belousoff, Leone Spiccia, Alan M. Bond, Angel A.J. Torriero

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Metal complexes of Cu2+, Co2+, Cd2+, Zn2+, and Ni2+ formed with the ligands [Fc(cyclen)](1) and [Fc(cyclen)2](2) (Fc=ferrocene, cyclen=1,4,7,10-tetraazacyclododecane) are synthesised and characterised. The X-ray structure of the Cu2+ complex of 2, Fc([Cu(cyclen)(CH3CN)]2(ClO4)4, is reported, and shows that the two positively charged Cu2+-cyclen units have a coordination number of five, adopting a distorted trigonal-bipyramidal configuration. The Cu2+-cyclen units are arranged in a trans-like configuration with respect to the Fc group, presumably to minimise electrostatic repulsion. The voltammetric oxidation of the free ligands 1 and 2 in a CH2Cl2/CH3CN (1:4) solvent mixture yields two closely spaced oxidation processes. Both electron-transfer steps are associated with the ferrocenyl moiety, implying strong communication between the cyclen nitrogen atoms and the ferrocenyl group. In contrast, cyclic voltammograms display only a simple reversible one-electron process if 1 and 2 are complexed with Cd2+, Cu2+, Zn2+, Ni2+, or Co2+. Binding of these metal ions produces a significant shift in the reversible midpoint potential (Em). Except for Ni2+, Em is linearly proportional to the charge density of the transition metal ion, demonstrating that 1 and 2 may undergo redox switching. The diffusion coefficients of Fc, DmFc, 1 and 2, and their metal ion complexes correlate well with their molecular weights.

Original languageEnglish
Pages (from-to)728-738
Number of pages11
JournalChemPlusChem
Volume83
Issue number7
DOIs
Publication statusPublished - 2018

Keywords

  • Cyclen
  • Cyclic voltammetry
  • Electrochemistry
  • Ferrocene
  • Macrocyclic ligands

Cite this

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title = "Macrocycles Bearing Ferrocenyl Pendants and their Electrochemical Properties upon Binding to Divalent Transition Metal Cations",
abstract = "Metal complexes of Cu2+, Co2+, Cd2+, Zn2+, and Ni2+ formed with the ligands [Fc(cyclen)](1) and [Fc(cyclen)2](2) (Fc=ferrocene, cyclen=1,4,7,10-tetraazacyclododecane) are synthesised and characterised. The X-ray structure of the Cu2+ complex of 2, Fc([Cu(cyclen)(CH3CN)]2(ClO4)4, is reported, and shows that the two positively charged Cu2+-cyclen units have a coordination number of five, adopting a distorted trigonal-bipyramidal configuration. The Cu2+-cyclen units are arranged in a trans-like configuration with respect to the Fc group, presumably to minimise electrostatic repulsion. The voltammetric oxidation of the free ligands 1 and 2 in a CH2Cl2/CH3CN (1:4) solvent mixture yields two closely spaced oxidation processes. Both electron-transfer steps are associated with the ferrocenyl moiety, implying strong communication between the cyclen nitrogen atoms and the ferrocenyl group. In contrast, cyclic voltammograms display only a simple reversible one-electron process if 1 and 2 are complexed with Cd2+, Cu2+, Zn2+, Ni2+, or Co2+. Binding of these metal ions produces a significant shift in the reversible midpoint potential (Em). Except for Ni2+, Em is linearly proportional to the charge density of the transition metal ion, demonstrating that 1 and 2 may undergo redox switching. The diffusion coefficients of Fc, DmFc, 1 and 2, and their metal ion complexes correlate well with their molecular weights.",
keywords = "Cyclen, Cyclic voltammetry, Electrochemistry, Ferrocene, Macrocyclic ligands",
author = "Zhanghua Zeng and Belousoff, {Matthew J.} and Leone Spiccia and Bond, {Alan M.} and Torriero, {Angel A.J.}",
year = "2018",
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Macrocycles Bearing Ferrocenyl Pendants and their Electrochemical Properties upon Binding to Divalent Transition Metal Cations. / Zeng, Zhanghua; Belousoff, Matthew J.; Spiccia, Leone; Bond, Alan M.; Torriero, Angel A.J.

In: ChemPlusChem, Vol. 83, No. 7, 2018, p. 728-738.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Macrocycles Bearing Ferrocenyl Pendants and their Electrochemical Properties upon Binding to Divalent Transition Metal Cations

AU - Zeng, Zhanghua

AU - Belousoff, Matthew J.

AU - Spiccia, Leone

AU - Bond, Alan M.

AU - Torriero, Angel A.J.

PY - 2018

Y1 - 2018

N2 - Metal complexes of Cu2+, Co2+, Cd2+, Zn2+, and Ni2+ formed with the ligands [Fc(cyclen)](1) and [Fc(cyclen)2](2) (Fc=ferrocene, cyclen=1,4,7,10-tetraazacyclododecane) are synthesised and characterised. The X-ray structure of the Cu2+ complex of 2, Fc([Cu(cyclen)(CH3CN)]2(ClO4)4, is reported, and shows that the two positively charged Cu2+-cyclen units have a coordination number of five, adopting a distorted trigonal-bipyramidal configuration. The Cu2+-cyclen units are arranged in a trans-like configuration with respect to the Fc group, presumably to minimise electrostatic repulsion. The voltammetric oxidation of the free ligands 1 and 2 in a CH2Cl2/CH3CN (1:4) solvent mixture yields two closely spaced oxidation processes. Both electron-transfer steps are associated with the ferrocenyl moiety, implying strong communication between the cyclen nitrogen atoms and the ferrocenyl group. In contrast, cyclic voltammograms display only a simple reversible one-electron process if 1 and 2 are complexed with Cd2+, Cu2+, Zn2+, Ni2+, or Co2+. Binding of these metal ions produces a significant shift in the reversible midpoint potential (Em). Except for Ni2+, Em is linearly proportional to the charge density of the transition metal ion, demonstrating that 1 and 2 may undergo redox switching. The diffusion coefficients of Fc, DmFc, 1 and 2, and their metal ion complexes correlate well with their molecular weights.

AB - Metal complexes of Cu2+, Co2+, Cd2+, Zn2+, and Ni2+ formed with the ligands [Fc(cyclen)](1) and [Fc(cyclen)2](2) (Fc=ferrocene, cyclen=1,4,7,10-tetraazacyclododecane) are synthesised and characterised. The X-ray structure of the Cu2+ complex of 2, Fc([Cu(cyclen)(CH3CN)]2(ClO4)4, is reported, and shows that the two positively charged Cu2+-cyclen units have a coordination number of five, adopting a distorted trigonal-bipyramidal configuration. The Cu2+-cyclen units are arranged in a trans-like configuration with respect to the Fc group, presumably to minimise electrostatic repulsion. The voltammetric oxidation of the free ligands 1 and 2 in a CH2Cl2/CH3CN (1:4) solvent mixture yields two closely spaced oxidation processes. Both electron-transfer steps are associated with the ferrocenyl moiety, implying strong communication between the cyclen nitrogen atoms and the ferrocenyl group. In contrast, cyclic voltammograms display only a simple reversible one-electron process if 1 and 2 are complexed with Cd2+, Cu2+, Zn2+, Ni2+, or Co2+. Binding of these metal ions produces a significant shift in the reversible midpoint potential (Em). Except for Ni2+, Em is linearly proportional to the charge density of the transition metal ion, demonstrating that 1 and 2 may undergo redox switching. The diffusion coefficients of Fc, DmFc, 1 and 2, and their metal ion complexes correlate well with their molecular weights.

KW - Cyclen

KW - Cyclic voltammetry

KW - Electrochemistry

KW - Ferrocene

KW - Macrocyclic ligands

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U2 - 10.1002/cplu.201700550

DO - 10.1002/cplu.201700550

M3 - Article

VL - 83

SP - 728

EP - 738

JO - ChemPlusChem

JF - ChemPlusChem

SN - 2192-6506

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