Guest-Induced Multistep to Single-Step Spin-Crossover Switching in a 2-D Hofmann-Like Framework with an Amide-Appended Ligand

Manan Ahmed; Kasun S A Arachchige; Zixi Xie; Jason R Price; Jace Cruddas; Jack K Clegg; Benjamin J Powell; Cameron J Kepert; Suzanne M Neville

doi:10.1021/acs.inorgchem.2c01253

Guest-Induced Multistep to Single-Step Spin-Crossover Switching in a 2-D Hofmann-Like Framework with an Amide-Appended Ligand

Inorg Chem. 2022 Aug 1;61(30):11667-11674. doi: 10.1021/acs.inorgchem.2c01253. Epub 2022 Jul 21.

Authors

Manan Ahmed¹, Kasun S A Arachchige², Zixi Xie³, Jason R Price⁴, Jace Cruddas⁵, Jack K Clegg², Benjamin J Powell⁵, Cameron J Kepert³, Suzanne M Neville¹

Affiliations

¹ School of Chemistry, The University of New South Wales, Sydney 2052, Australia.
² School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Queensland 4072, Australia.
³ The School of Chemistry, The University of Sydney, Camperdown, New South Wales 2006, Australia.
⁴ Australian Synchrotron, ANSTO Clayton, Victoria 3800, Australia.
⁵ School of Mathematics and Physics, The University of Queensland, St. Lucia, Queensland 4072, Australia.

PMID: 35862437
DOI: 10.1021/acs.inorgchem.2c01253

Abstract

A detailed study of the two-dimensional (2-D) Hofmann-like framework [Fe(furpy)₂Pd(CN)₄]·nG (furpy: N-(pyridin-4-yl)furan-2-carboxamide, G = H₂O,EtOH (A·H₂O,Et), and H₂O (A·H₂O)) is presented, including the structural and spin-crossover (SCO) implications of subtle guest modification. This 2-D framework is characterized by undulating Hofmann layers and an array of interlayer spacing environments─this is a strategic approach that we achieve by the inclusion of a ligand with multiple host-host and host-guest interaction sites. Variable-temperature magnetic susceptibility studies reveal an asymmetric multistep SCO for A·H₂O,Et and an abrupt single-step SCO for A·H₂O with an upshift in transition temperature of ∼75 K. Single-crystal analyses show a primitive orthorhombic symmetry for A·H₂O,Et characterized by a unique Fe^II center─the multistep SCO character is attributed to local ligand orientation. Counterintuitively, A·H₂O shows a triclinic symmetry with two inequivalent Fe^II centers that undergo a cooperative single-step high-spin (HS)-to-low-spin (LS) transition. We conduct detailed structure-function analyses to understand how the guest ethanol influences the delicate balance between framework communication and, therefore, the local structure and spin-state transition mechanism.