Fe<sup>III</sup>, Cu<sup>II</sup> and Zn<sup>II</sup> Complexes of the Rigid 9-Oxido-phenalenone Ligand—Spectroscopy, Electrochemistry, and Cytotoxic Properties
The three complexes [Fe(opo)<sub>3</sub>], [Cu(opo)<sub>2</sub>], and [Zn(opo)<sub>2</sub>] containing the non-innocent anionic ligand opo<sup>−</sup> (opo<sup>−</sup> = 9-oxido-phenalenone, Hopo = 9-hydroxyphenalonone) were synthesised fro...
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doaj-aae4c22e86bc4f32a93fd216bbb52fcc2021-04-12T23:04:09ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672021-04-01223976397610.3390/ijms22083976Fe<sup>III</sup>, Cu<sup>II</sup> and Zn<sup>II</sup> Complexes of the Rigid 9-Oxido-phenalenone Ligand—Spectroscopy, Electrochemistry, and Cytotoxic PropertiesKatharina Butsch0Alexander Haseloer1Simon Schmitz2Ingo Ott3Julia Schur4Axel Klein5Department für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, D-50939 Köln, GermanyDepartment für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, D-50939 Köln, GermanyDepartment für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, D-50939 Köln, GermanyInstitute of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Beethovenstrasse 55, D-38106 Braunschweig, GermanyInstitute of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Beethovenstrasse 55, D-38106 Braunschweig, GermanyDepartment für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, D-50939 Köln, GermanyThe three complexes [Fe(opo)<sub>3</sub>], [Cu(opo)<sub>2</sub>], and [Zn(opo)<sub>2</sub>] containing the non-innocent anionic ligand opo<sup>−</sup> (opo<sup>−</sup> = 9-oxido-phenalenone, Hopo = 9-hydroxyphenalonone) were synthesised from the corresponding acetylacetonates. [Zn(opo)<sub>2</sub>] was characterised using <sup>1</sup>H nuclear magnetic resonance (NMR) spectroscopy, the paramagnetic [Fe(opo)<sub>3</sub>] and [Cu(opo)<sub>2</sub>] by electron paramagnetic resonance (EPR) spectroscopy. While the EPR spectra of [Cu(opo)<sub>2</sub>] and [Cu(acac)<sub>2</sub>] in dimethylformamide (DMF) solution are very similar, a rather narrow spectrum was observed for [Fe(opo)<sub>3</sub>] in tetrahydrofuran (THF) solution in contrast to the very broad spectrum of [Fe(acac)<sub>3</sub>] in THF (Hacac = acetylacetone, 2,4-pentanedione; acac<sup>−</sup> = acetylacetonate). The narrow, completely isotropic signal of [Fe(opo)<sub>3</sub>] disagrees with a metal-centred <i>S</i> = 5/2 spin system that is observed in the solid state. We assume spin-delocalisation to the opo ligand in the sense of an opo<sup>−</sup> to Fe<sup>III</sup> electron transfer. All compounds show several electrochemical opo-centred reduction waves in the range of −1 to −3 V vs. the ferrocene/ferrocenium couple. However, for Cu<sup>II</sup> and Fe<sup>III</sup> the very first one-electron reductions are metal-centred. Electronic absorption in the UV to vis range are due to π–π* transitions in the opo core, giving Hopo and [Zn(opo)<sub>2</sub>] a yellow to orange colour. The structured bands ranging from 400 to 500 for all compounds are assigned to the lowest energy π−π* transitions. They show markedly higher intensities and slight shifts for the Cu<sup>II</sup> (brown) and Fe<sup>III</sup> (red) complexes and we assume admixing metal contributions (MLCT for Cu<sup>II</sup>, LMCT for Fe<sup>III</sup>). For both complexes long-wavelength absorptions assignable to d–d transitions were detected. Detailed spectroelectrochemical experiments confirm both the electrochemical and the optical assignments. Hopo and the complexes [Cu(opo)<sub>2</sub>], [Zn(opo)<sub>2</sub>], and [Fe(opo)<sub>3</sub>] show antiproliferative activities against HT-29 (colon cancer) and MCF-7 (breast cancer) cell lines in the range of a few µM, comparable to cisplatin under the same conditions.https://www.mdpi.com/1422-0067/22/8/3976Ironcopperzinc9-oxido-phenalenoneantiproliferativeredox |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Katharina Butsch Alexander Haseloer Simon Schmitz Ingo Ott Julia Schur Axel Klein |
spellingShingle |
Katharina Butsch Alexander Haseloer Simon Schmitz Ingo Ott Julia Schur Axel Klein Fe<sup>III</sup>, Cu<sup>II</sup> and Zn<sup>II</sup> Complexes of the Rigid 9-Oxido-phenalenone Ligand—Spectroscopy, Electrochemistry, and Cytotoxic Properties International Journal of Molecular Sciences Iron copper zinc 9-oxido-phenalenone antiproliferative redox |
author_facet |
Katharina Butsch Alexander Haseloer Simon Schmitz Ingo Ott Julia Schur Axel Klein |
author_sort |
Katharina Butsch |
title |
Fe<sup>III</sup>, Cu<sup>II</sup> and Zn<sup>II</sup> Complexes of the Rigid 9-Oxido-phenalenone Ligand—Spectroscopy, Electrochemistry, and Cytotoxic Properties |
title_short |
Fe<sup>III</sup>, Cu<sup>II</sup> and Zn<sup>II</sup> Complexes of the Rigid 9-Oxido-phenalenone Ligand—Spectroscopy, Electrochemistry, and Cytotoxic Properties |
title_full |
Fe<sup>III</sup>, Cu<sup>II</sup> and Zn<sup>II</sup> Complexes of the Rigid 9-Oxido-phenalenone Ligand—Spectroscopy, Electrochemistry, and Cytotoxic Properties |
title_fullStr |
Fe<sup>III</sup>, Cu<sup>II</sup> and Zn<sup>II</sup> Complexes of the Rigid 9-Oxido-phenalenone Ligand—Spectroscopy, Electrochemistry, and Cytotoxic Properties |
title_full_unstemmed |
Fe<sup>III</sup>, Cu<sup>II</sup> and Zn<sup>II</sup> Complexes of the Rigid 9-Oxido-phenalenone Ligand—Spectroscopy, Electrochemistry, and Cytotoxic Properties |
title_sort |
fe<sup>iii</sup>, cu<sup>ii</sup> and zn<sup>ii</sup> complexes of the rigid 9-oxido-phenalenone ligand—spectroscopy, electrochemistry, and cytotoxic properties |
publisher |
MDPI AG |
series |
International Journal of Molecular Sciences |
issn |
1661-6596 1422-0067 |
publishDate |
2021-04-01 |
description |
The three complexes [Fe(opo)<sub>3</sub>], [Cu(opo)<sub>2</sub>], and [Zn(opo)<sub>2</sub>] containing the non-innocent anionic ligand opo<sup>−</sup> (opo<sup>−</sup> = 9-oxido-phenalenone, Hopo = 9-hydroxyphenalonone) were synthesised from the corresponding acetylacetonates. [Zn(opo)<sub>2</sub>] was characterised using <sup>1</sup>H nuclear magnetic resonance (NMR) spectroscopy, the paramagnetic [Fe(opo)<sub>3</sub>] and [Cu(opo)<sub>2</sub>] by electron paramagnetic resonance (EPR) spectroscopy. While the EPR spectra of [Cu(opo)<sub>2</sub>] and [Cu(acac)<sub>2</sub>] in dimethylformamide (DMF) solution are very similar, a rather narrow spectrum was observed for [Fe(opo)<sub>3</sub>] in tetrahydrofuran (THF) solution in contrast to the very broad spectrum of [Fe(acac)<sub>3</sub>] in THF (Hacac = acetylacetone, 2,4-pentanedione; acac<sup>−</sup> = acetylacetonate). The narrow, completely isotropic signal of [Fe(opo)<sub>3</sub>] disagrees with a metal-centred <i>S</i> = 5/2 spin system that is observed in the solid state. We assume spin-delocalisation to the opo ligand in the sense of an opo<sup>−</sup> to Fe<sup>III</sup> electron transfer. All compounds show several electrochemical opo-centred reduction waves in the range of −1 to −3 V vs. the ferrocene/ferrocenium couple. However, for Cu<sup>II</sup> and Fe<sup>III</sup> the very first one-electron reductions are metal-centred. Electronic absorption in the UV to vis range are due to π–π* transitions in the opo core, giving Hopo and [Zn(opo)<sub>2</sub>] a yellow to orange colour. The structured bands ranging from 400 to 500 for all compounds are assigned to the lowest energy π−π* transitions. They show markedly higher intensities and slight shifts for the Cu<sup>II</sup> (brown) and Fe<sup>III</sup> (red) complexes and we assume admixing metal contributions (MLCT for Cu<sup>II</sup>, LMCT for Fe<sup>III</sup>). For both complexes long-wavelength absorptions assignable to d–d transitions were detected. Detailed spectroelectrochemical experiments confirm both the electrochemical and the optical assignments. Hopo and the complexes [Cu(opo)<sub>2</sub>], [Zn(opo)<sub>2</sub>], and [Fe(opo)<sub>3</sub>] show antiproliferative activities against HT-29 (colon cancer) and MCF-7 (breast cancer) cell lines in the range of a few µM, comparable to cisplatin under the same conditions. |
topic |
Iron copper zinc 9-oxido-phenalenone antiproliferative redox |
url |
https://www.mdpi.com/1422-0067/22/8/3976 |
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