Pressure Tuning of Coupled Structural and Spin State Transitions in the Molecular Complex [Fe(H 2 B(pz) 2 ) 2 (phen)] - Archive ouverte HAL Access content directly
Journal Articles Inorganic Chemistry Year : 2022

Pressure Tuning of Coupled Structural and Spin State Transitions in the Molecular Complex [Fe(H 2 B(pz) 2 ) 2 (phen)]

Abstract

The large volume change, which accompanies the molecular spin crossover (SCO) phenomenon in some transition metal complexes, prompts frequently the coupling of the SCO with other instabilities. Understanding the driving mechanism(s) of such coupled phase transitions is not only important for fundamental reasons but also provides scope for the development of multifunctional materials. The general theoretical expectation is that the coupling has elastic origin, and the sequence of transitions can be tuned by an externally applied pressure, but dedicated experiments remain scarce. Here, we used high-pressure and low-temperature single-crystal X-ray diffraction to investigate the high-spin (HS) to low-spin (LS) transitions in the molecular complexes [FeII(H2B(pz)2)2(bipy)] and [FeII(H2B(pz)2)2(phen)]. In the bipyridine complex, the SCO is continuous and isostructural over the whole T, P-range (100–300 K, 0–2 GPa). In the phenanthroline derivative, however, the SCO is concomitant with a symmetry-breaking transition (C2/c to P1̅). Structural analysis reveals that the coupling between the two phenomena can be tuned by external pressure from a virtually simultaneous HSC2/c–LSP1̅ transition to the sequence of HSC2/c–LSC2/c–LSP1̅ transitions. The correlation of spontaneous strain and order parameter behaviors highlights that the “separated” transitions remain still connected via strain coupling, whereas the “simultaneous” transitions are partially split.
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Dates and versions

hal-03790163 , version 1 (28-09-2022)

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Damian Paliwoda, Laure Vendier, William Nicolazzi, Gábor Molnár, Azzedine Bousseksou. Pressure Tuning of Coupled Structural and Spin State Transitions in the Molecular Complex [Fe(H 2 B(pz) 2 ) 2 (phen)]. Inorganic Chemistry, 2022, 61 (40), pp.15991-16002. ⟨10.1021/acs.inorgchem.2c02286⟩. ⟨hal-03790163⟩
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