Issue 4, 2024

Spin-state versatility in Fe II4L6 supramolecular cages with a pyridyl-hydrazone ligand scaffold modulated by solvents and counter anions

Abstract

Discrete spin crossover (SCO) tetranuclear cages are a unique class of materials that have potential use in next-generation molecular recognition and sensing. In this work, two new edge-bridged SCO FeII4L6 (L = 2,7-bis(((E)-pyridin-2-ylmethylene)amino)benzo[lmn] [3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone) supramolecular cages with different counter anions: ClO4 (2) and CF3SO3 (3) were constructed via subcomponent self-assembly to investigate both solvent and anion influences on their magnetic properties and compare them to cage 1 with a BF4 anion. Pyridyl-hydrazone bidentate ligand scaffolds were employed to replace the ‘classical’ imidazole/thiazolyl-imine coordination units to induce SCO behaviour in these cages. 2 and 3 were structurally characterized by single-crystal X-ray diffraction analysis and electrospray ionization time-of-flight mass spectrometry. Magnetic susceptibilities of 1–3 and 1–3·desolvated indicate that the solvents’ presence is in favor of the low-spin (LS) state. While different counter anions in 1–3·desolvated affect the spin-state configurations of the four FeII metal centers. According to the 57Fe Mössbauer spectral analysis, the spin-state distributions in 1–3 at 80 K are [2 high-spin (HS)–2LS], [1HS–3LS] and [2HS–2LS], respectively and density functional theory calculations were employed to investigate the reasons. These findings provide insights to regulate the spin-state versatility of SCO FeII cage systems in the solid state.

Graphical abstract: Spin-state versatility in FeII4L6 supramolecular cages with a pyridyl-hydrazone ligand scaffold modulated by solvents and counter anions

Supplementary files

Article information

Article type
Paper
Submitted
01 août 2023
Accepted
18 oct. 2023
First published
01 nov. 2023

Dalton Trans., 2024,53, 1449-1459

Spin-state versatility in FeII4L6 supramolecular cages with a pyridyl-hydrazone ligand scaffold modulated by solvents and counter anions

W. Li, X. Li, K. Robeyns, M. Wolff, J. Kfoury, J. Oláh, R. Herchel, S. Demeshko, F. Meyer and Y. Garcia, Dalton Trans., 2024, 53, 1449 DOI: 10.1039/D3DT02474A

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