Universität zu Köln

Butsch, Katharina, Haseloer, Alexander ORCID: 0000-0003-0480-7568, Schmitz, Simon, Ott, Ingo ORCID: 0000-0002-8087-4618, Schur, Julia and Klein, Axel ORCID: 0000-0003-0093-9619 (2021). Fe-III, Cu-II and Zn-II Complexes of the Rigid 9-Oxido-phenalenone Ligand-Spectroscopy, Electrochemistry, and Cytotoxic Properties. Int. J. Mol. Sci., 22 (8). BASEL: MDPI. ISSN 1422-0067

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Abstract

The three complexes [Fe(opo)(3)], [Cu(opo)(2)], and [Zn(opo)(2)] containing the non-innocent anionic ligand opo(-) (opo(-) = 9-oxido-phenalenone, Hopo = 9-hydroxyphenalonone) were synthesised from the corresponding acetylacetonates. [Zn(opo)(2)] was characterised using H-1 nuclear magnetic resonance (NMR) spectroscopy, the paramagnetic [Fe(opo)(3)] and [Cu(opo)(2)] by electron paramagnetic resonance (EPR) spectroscopy. While the EPR spectra of [Cu(opo)(2)] and [Cu(acac)(2)] in dimethylformamide (DMF) solution are very similar, a rather narrow spectrum was observed for [Fe(opo)(3)] in tetrahydrofuran (THF) solution in contrast to the very broad spectrum of [Fe(acac)(3)] in THF (Hacac = acetylacetone, 2,4-pentanedione; acac(-) = acetylacetonate). The narrow, completely isotropic signal of [Fe(opo)(3)] disagrees with a metal-centred S = 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(-) to Fe-III 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-II and Fe-III the very first one-electron reductions are metal-centred. Electronic absorption in the UV to vis range are due to pi-pi* transitions in the opo core, giving Hopo and [Zn(opo)(2)] a yellow to orange colour. The structured bands ranging from 400 to 500 for all compounds are assigned to the lowest energy pi-pi* transitions. They show markedly higher intensities and slight shifts for the Cu-II (brown) and Fe-III (red) complexes and we assume admixing metal contributions (MLCT for Cu-II, LMCT for Fe-III). 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)(2)], [Zn(opo)(2)], and [Fe(opo)(3)] show antiproliferative activities against HT-29 (colon cancer) and MCF-7 (breast cancer) cell lines in the range of a few mu M, comparable to cisplatin under the same conditions.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Butsch, Katharina UNSPECIFIED UNSPECIFIED UNSPECIFIED Haseloer, Alexander UNSPECIFIED orcid.org/0000-0003-0480-7568 UNSPECIFIED Schmitz, Simon UNSPECIFIED UNSPECIFIED UNSPECIFIED Ott, Ingo UNSPECIFIED orcid.org/0000-0002-8087-4618 UNSPECIFIED Schur, Julia UNSPECIFIED UNSPECIFIED UNSPECIFIED Klein, Axel UNSPECIFIED orcid.org/0000-0003-0093-9619 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-570763
DOI:	10.3390/ijms22083976
Journal or Publication Title:	Int. J. Mol. Sci.
Volume:	22
Number:	8
Date:	2021
Publisher:	MDPI
Place of Publication:	BASEL
ISSN:	1422-0067
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language Biochemistry & Molecular Biology; Chemistry, Multidisciplinary Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/57076