Pressure-induced unexpected stabilization of the high-spin state of iron(II) in a metal-organic framework
17 04 2026
A paper, co-authored by Radosław Kamiński, was published in the Journal of The American Chemical Society journal (ACS). The investigations published in the article entitled “Pressure-induced unexpected stabilization of the high-spin state of iron(II) in a metal-organic framework” were conducted within a international collaboration with teams from France, and included the use of various experimental techniques ranging from high-pressure Raman spectroscopy, magnetic properties determination to synchrotron crystallography and X-ray emission spectroscopy. Many of these investigations were enabled by the expertise of high-pressure researchers at ESRF and Dr. Damian Paliwoda, a long-standing collaborator of Dr. R. Kamiński and Prof. K.N. Jarzembska.
The effect of hydrostatic pressure on the spin state of the metal-organic framework [Fe(Me-pbpy+)2[μ2-M(CN)4]2·2H2O] (pbpy = phenylbipyridinium, R = CH3, M = Pd) was investigated by Raman spectroscopy and single crystal X-ray diffraction. As expected, the application of a hydrostatic pressure of 1.2 GPa fully transforms the high-spin (S = 2) ferrous ions into the low-spin (S = 0) form. Surprisingly, further increase of the pressure to 2.0 GPa induces a pressure-driven return to the S = 2 state, which can be switched again to the S = 0 state at 2.5 GPa. This unusual sequence of pressure-driven spin-state transitions is completely reversible and is also observable in two analogous compounds with M = Pt and R = Br. High-pressure X-ray crystal structure analysis reveals concurrent pressure-driven structural changes, assigned to an electron transfer process between the redox-active ligands. These processes cause a simultaneous elongation of the metal-ligand bond lengths and a contraction of the lattice volume, stabilizing, thus, the high-spin state in the pressure range of ca. 1.5–2.3 GPa, opposite to classical thermodynamics of spin crossover.
Bibliographic data and link to the article:
L. Getzner, Y. Remili, D. Paliwoda, S. Gallego-Parra, J.E.F.S. Rodrigues, C.J. Sahle, R. Kaminski, Y. Li, L. Vendier, G. Molnár, S. Cobo, A. Bousseksou, Journal of the American Chemical Society 2025, 147 (50), 46497.
https://doi.org/10.1021/jacs.5c16808
