Light-induced spin-state switching in Fe(ii) spin-crossover complexes with thiazole-based chelating ligands
Jo M. Amanyazova B. Yergeshbayeva S. Gakiya-Teruya M. Üngör I. Lopez Rivera P. Jen N. Lukyanenko E. Kurkin A.V. Erkasov R. Meisel M.W. Hauser A. Chakraborty P. Shatruk M.
29 May 2024Royal Society of Chemistry
Dalton Transactions
2024#53Issue 2510511 - 10520 pp.
Homoleptic complexes [Fe(4bt)3](ClO4)2 (1), [Fe(2bt)3](ClO4)2 (2), and [Fe(3tpH)3](ClO4)2 (3) were obtained by a reaction between the Fe(ii) precursor salt and the corresponding thiazole-based bidentate ligand (L = 4bt = 4,4′-bithiazole, 2bt = 2,2′-bithiazole, 3tpH = 3-(thiazol-2-yl)pyrazole). X-ray crystal structure determination revealed crystallization of solvent-free complex 1, a solvate 2·MeOH, and a co-crystal 3·2(3tpH). The crystal packing of all these complexes is dominated by one-dimensional interactions between the [Fe(L)3]2+ cations. These interactions are stronger in 2·MeOH and 3·2(3tpH), leading to cooperative and slightly hysteretic transitions between the high-spin and low-spin electronic configurations at ∼235 K and 159 K, respectively. In contrast, weaker intermolecular interactions in 1 result in a gradual spin crossover above 300 K, with the maximum fraction of the HS state ∼25% achieved at 400 K. Complexes 2 and 3·2(3tpH) exhibit light-induced excited spin state trapping (LIESST) under irradiation with white light or a 532 nm laser at 5 K. After the photoexcitation, the trapped metastable HS state relaxes to the ground LS state with the average relaxation temperature of 81 K and 68 K, respectively. Examination of the relaxation dynamics by optical absorption spectroscopy on a single crystal of 3·2(3tpH) revealed the sigmoidal shape of the relaxation curves at lower temperatures, attributed to cooperative effects, as well as a plateau at ∼10% of the HS fraction at intermediate temperatures, hinting at a more complex mechanism for the relaxation of the LIESST phase in this material.
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Department of Chemistry and Biochemistry, Florida State University, Tallahassee, 32306, FL, United States
Department of Chemistry, L.N. Gumilyov Eurasian National University, Astana, 010008, Kazakhstan
Department of Chemistry, University of Puerto Rico at Humacao, PR, Humacao, 00792, Puerto Rico
Department of Chemistry, Lomonosov Moscow State University, Moscow, 119234, Russian Federation
Department of Physics and National High Magnetic Field Laboratory, University of Florida, Gainesville, 32611, FL, United States
Department of Physical Chemistry, University of Geneva, Geneva, 4 CH-1211, Switzerland
Department of Chemistry, Indian Institute of Technology, Kharagpur, 721, India
Department of Chemistry and Biochemistry
Department of Chemistry
Department of Chemistry
Department of Chemistry
Department of Physics and National High Magnetic Field Laboratory
Department of Physical Chemistry
Department of Chemistry
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