Structural Insights into Hysteretic Spin-Crossover in a Set of Iron(II)-2,6-bis(1H-Pyrazol-1-yl)Pyridine) Complexes |
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| Authors: | Dr Nithin Suryadevara Dr Asato Mizuno Lea Spieker Dr Soma Salamon Stephan Sleziona André Maas Dr Erik Pollmann Dr Benoît Heinrich Prof Dr Marika Schleberger Prof Dr Heiko Wende Dr Senthil Kumar Kuppusamy Prof Dr Mario Ruben |
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| Institution: | 1. Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany;2. University of Duisburg-Essen, Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), Lotharstraße 1, 47057 Duisburg, Germany;3. Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), CNRS-Université de Strasbourg, 23, rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France;4. Institute for Quantum Materials and Technologies (IQMT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany |
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| Abstract: | Bistable spin-crossover (SCO) complexes that undergo abrupt and hysteretic (ΔT1/2) spin-state switching are desirable for molecule-based switching and memory applications. In this study, we report on structural facets governing hysteretic SCO in a set of iron(II)-2,6-bis(1H-pyrazol-1-yl)pyridine) (bpp) complexes – Fe(bpp−COOEt)2](X)2 ⋅ CH3NO2 (X=ClO4, 1 ; X=BF4, 2 ). Stable spin-state switching – T1/2=288 K; ΔT1/2=62 K – is observed for 1 , whereas 2 undergoes above-room-temperature lattice-solvent content-dependent SCO – T1/2=331 K; ΔT1/2=43 K. Variable-temperature single-crystal X-ray diffraction studies of the complexes revealed pronounced molecular reorganizations – from the Jahn-Teller-distorted HS state to the less distorted LS state – and conformation switching of the ethyl group of the COOEt substituent upon SCO. Consequently, we propose that the large structural reorganizations rendered SCO hysteretic in 1 and 2 . Such insights shedding light on the molecular origin of thermal hysteresis might enable the design of technologically relevant molecule-based switching and memory elements. |
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| Keywords: | Spin-crossover X-ray diffraction Jahn-Teller distortion thermal hysteresis molecular devices |
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