Tuning spin transitions of iron(II)-dpp systems
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Tuning spin transitions of iron(II)-dpp systems D. Natke1 · D. Unruh1 · B. Dreyer1,2 · S. Klimke1 · M. Jahns1 · A. Preiss1 · R. Sindelar2 · G. Klingelh¨ofer3 · F. Renz1
© Springer International Publishing AG, part of Springer Nature 2018
Abstract Chemical modifications of the yet reported iron(II) compound [Fe(dpp)2 (NCS)2 ]·Py (dpp = dipyrido[3,2a:2’3’c]phenazine, Py = pyridine) which shows abrupt spin crossover below room temperature with large hysteresis have been made. The purpose was to stabilize different spin states at room temperature as well as to adjust the spin crossover in temperature and hysteresis width. We modified the bidentate ligand dpp by substituting hydrogens at the phenazine by different functional groups. In addition, we substituted the thiocyanate monodentate ligands by NCSe− . The spin states of these compounds have been investigated by M¨ossbauer spectroscopy at two temperatures and temperature depending IR spectroscopy. These methods indicating that the chemical modifications are influencing the observed spin configuration of the complexes alongside the spin crossover behavior which changed to gradual and incomplete transitions. These promising results offer interesting possibilities for chemical adjustments of the shown spin crossover systems. Keywords Spin crossover · Hysteresis · Iron complexes · M¨ossbauer spectroscopy · dpp
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10751-017-1486-7) contains supplementary material, which is available to authorized users. This article is part of the Topical Collection on Proceedings of the International Conference on the Applications of the M¨ossbauer Effect (ICAME 2017), Saint-Petersburg, Russia, 3-8 September 2017 Edited by Valentin Semenov F. Renz
[email protected] 1
Institute of Inorganic Chemistry, Leibniz Universit¨at Hannover, Callinstraße 9, 30167 Hanover, Germany
2
Faculty II, University of Applied Science and Arts, Ricklinger Stadtweg 120, 30459 Hanover, Germany
3
Institut f¨ur Anorganische Chemie und Analytische Chemie, Johannes-Gutenberg-Universit¨at Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
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Hyperfine Interact (2018) 239:12
1 Introduction Coordination compounds showing a change of spin state triggered by external stimuli are named spin crossover compounds and are considered to enhance future electronic devices. The transition is depending on physical (e.g. temperature, pressure, electromagnetic radiation, etc.) and chemical (e.g. solvent, ligand exchange, pH, etc.) influences. With the change of spin state arise a change of physical properties (e.g. magnetic moment, bond length, color, etc.), which can be detected by various methods. M¨ossbauer spectroscopy is one of them and popularly used for iron compounds to gain information about spin and oxidation states [1–5]. For many possible applications, an abrupt spin transition near room temperature including a wide hysteresis is desired. The spin crossover compound [Fe(dpp)2 (NCS)2 ]·py (dpp
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