Thermo- And photoinduced spin state switching in an iron(ii) 2D coordination network associated with large light-induced thermal hysteresis and tuning of dimensionality: Via ligand modulation

Ghosh, S and Kamilya, S and Pramanik, T and Mohanty, A and Rouzières, M and Herchel, R and Mehta, S and Mondal, A (2021) Thermo- And photoinduced spin state switching in an iron(ii) 2D coordination network associated with large light-induced thermal hysteresis and tuning of dimensionality: Via ligand modulation. In: Dalton Transactions, 50 (22). pp. 7725-7735.

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Abstract

Three iron(ii) complexes, Fe(L1)2(NCS)2(MeOH)2 (1), Fe(L1)2(NCSe)2(MeOH)2 (2), and Fe(L2)2(NCS)2n (3) (L1 = 2,5-dipyridyl-3,4-ethylenedioxythiophene and L2 = 2,5-diethynylpyridinyl-3,4-ethylenedioxythiophene), have been synthesized using redox-active luminescent ethylenedioxythiophene (EDOT)-based ligands, and characterized by variable temperature single-crystal X-ray diffraction, (photo)magnetic, optical reflectivity, and spectroscopy studies. Magneto-structural investigations revealed that 1 and 2 are mononuclear with a FeN4O2 octahedral coordination geometry and remain in a high-spin (HS) (S = 2) state in a temperature range of 2-280 K. Interestingly, a 2D coordination network structure with FeN6 surrounding each iron center was observed for 3, which exhibits reversible thermo-induced spin-state switching between the paramagnetic high-spin (HS) (S = 2) and diamagnetic low-spin (LS) (S = 0) states at around 105 K (T1/2). Furthermore, optical reflectivity and photomagnetic measurements at low temperature confirmed that 3 shows reversible ON/OFF switching between the photoinduced excited paramagnetic HS metastable state and diamagnetic LS state under light irradiation (ON mode using red light and OFF mode using green light). Finally, the photoinduced excited HS state can be reversibly relaxed back to the diamagnetic ground LS state by heating the system at ca. 88 K (TLIESST = 88 K) (light-induced excited spin state trapping (LIESST) effect). Furthermore, 3 also showed an exciting and unique 18 K wide light-induced thermal hysteresis (LITH) effect above liquid nitrogen temperature (100 K). DFT and CASSCF level theoretical calculations were utilized to better understand the magneto-structural correlations of these complexes. This journal is © The Royal Society of Chemistry.

Item Type:	Journal Article
Publication:	Dalton Transactions
Publisher:	Royal Society of Chemistry
Additional Information:	The copyright for this article belongs to Royal Society of Chemistry
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	31 Aug 2021 07:02
Last Modified:	31 Aug 2021 07:02
URI:	http://eprints.iisc.ac.in/id/eprint/69484

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