Universität zu Köln

Arefyeva, Natalia, Sandleben, Aaron ORCID: 0000-0002-4141-7406, Krest, Alexander, Baumann, Ulrich, Schaefer, Mathias, Kempf, Maxim and Klein, Axel (2018). [2 x 2] Molecular Grids of Ni(II) and Zn(II) with Redox-Active 1,4-Pyrazine-Bis(thiosemicarbazone) Ligands. Inorganics, 6 (2). BASEL: MDPI. ISSN 2304-6740

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Abstract

Tetranuclear complexes [M-4(L-R)(4)] with M = Ni(II) or Zn(II), with a [2 x 2] grid-type structure, were assembled in good yields and purity from the easily accessible but unprecedented pyrazine-bridged bis(thiosemicarbazone) protoligands (ligand precursors) H2LR (1,4-pyrazine-2,5-bis(R-carbaldehyde-thiosemicarbazone); R = Me, Et, Pr-i, or Ph). The complexes were characterised in solution by NMR, MS, IR, and UV-Vis absorption spectroscopy and (spectro)electrochemical methods. HR-MS spectra unequivocally reveal that the tetranuclear species are very stable in solution and any measurements represent these species. Only at higher temperatures (fragmentation in solution: MS and in the solid: TG-DTA) or upon the addition of protons (acidic UV-Vis titrations) can the tetrameric entities be decomposed. Single crystal XRD measurement remained preliminary. Rapid loss of co-crystallised solvent molecules within the [2 x 2] grid-type structures resulted in crystals of very poor quality, but the results were qualitatively in line with spectroscopy, electrochemistry, and quantum chemical (DFT) calculations. IR and NMR spectroscopy point clearly to a thiolate coordination of dianionic (deprotonated) ligands. The electrochemistry reveals four electronically coupled and reversible one-electron reductions centred largely at the pyrazine bridges. EPR and UV-Vis spectroelectrochemical measurements in combination with DFT calculation support the assignment.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Arefyeva, Natalia UNSPECIFIED UNSPECIFIED UNSPECIFIED Sandleben, Aaron UNSPECIFIED orcid.org/0000-0002-4141-7406 UNSPECIFIED Krest, Alexander UNSPECIFIED UNSPECIFIED UNSPECIFIED Baumann, Ulrich UNSPECIFIED UNSPECIFIED UNSPECIFIED Schaefer, Mathias UNSPECIFIED UNSPECIFIED UNSPECIFIED Kempf, Maxim UNSPECIFIED UNSPECIFIED UNSPECIFIED Klein, Axel UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-184262
DOI:	10.3390/inorganics6020051
Journal or Publication Title:	Inorganics
Volume:	6
Number:	2
Date:	2018
Publisher:	MDPI
Place of Publication:	BASEL
ISSN:	2304-6740
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Inorganic Chemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language CENTERED MIXED-VALENCY; THIOSEMICARBAZONE METAL-COMPLEXES; GAUSSIAN-BASIS SETS; NICKEL(II) COMPLEXES; STRUCTURAL-CHARACTERIZATION; RUTHENIUM COMPLEXES; PLATINUM COMPLEXES; CRYSTAL-STRUCTURES; BUILDING-BLOCKS; SPIN-CROSSOVER Multiple languages Chemistry, Inorganic & Nuclear Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/18426