Open Chemistry Journal


ISSN: 1874-8422 ― Volume 8, 2021

Iron(II) Spin Crossover Polymers of Planar N2O2 Schiff Base Templates and 4,4’-bis(pyridyl)urea Bridges

Lisa Zappe1, Charles Lochenie2, Thomas Martin3, Birgit Weber1, *
1 Department of Chemistry, Inorganic Chemistry IV, University of Bayreuth, Bayreuth, Germany
2 Institut de Science et d’Ingénierie Supramoléculaires, Strasbourg, France
3 Department of Chemistry, Inorganic Chemistry I, University of Bayreuth, Bayreuth, Germany



The synthesis of four new iron(II) coordination polymers [Fe(L1a)(bpua)] (1), [Fe(L1b)(bpua)](0.5bpua) (2), [Fe(L2a)(bpua)] (3), [Fe(L1b)(bpua)](yEtOH) (5) and one trinuclear complex [{Fe(L1a)(bpua)(MeOH)}2-µ{Fe(L1a)}](xMeOH) (4) with Schiff base-like N2O2 coordinating equatorial ligands (L1a, L1b and L2a) and 4,4’-bis(pyridyl)urea (bpua) as bridging axial ligand is described.

Materials and Methods:

Single crystal X-ray structure elucidation of the trinuclear module 4 and of the coordination polymer 5 reveals the presence of HS-LS-HS chains and all-HS infinite 1-D strands, respectively. As anticipated the presence of the bridging urea supports the supramolecular concatenation within an extended hydrogen-bonding network. Magnetic measurements reveal spin crossover behavior for four of the five complexes (14) that is strongly solvent dependent.

Results and Conclusion:

Interestingly, in two cases, complete removal of the solvent from the crystal packing leads to wider thermal hysteresis loops.

Keywords: Iron, Schiff base ligand, Spin crossover, Hydrogen bonding, Polymers, Thermal hysteresis.

Article Information

Identifiers and Pagination:

Year: 2019
Volume: 6
Issue: Suppl-1, M2
First Page: 10
Last Page: 18
Publisher Id: CHEM-6-10
DOI: 10.2174/1874842201906010010

Article History:

Received Date: 06/03/2018
Revision Received Date: 17/05/2018
Acceptance Date: 21/02/2019
Electronic publication date: 22/03/2019
Collection year: 2019

© 2019 Zappe et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: ( This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Chemistry, Inorganic Chemistry II, University of Bayreuth, Bayreuth, Germany;Tel: +49 921 552555; Fax: +49 921 552157; E-mail:

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