University of Oulu

Dalton Trans., 2021,50, 15831-15840

A diamagnetic iron complex and its twisted sister : structural evidence on partial spin state change in a crystalline iron complex

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Author: Salojärvi, Esko1; Peuronen, Anssi1; Moilanen, Jani2;
Organizations: 1Inorganic Materials Chemistry research group, Department of Chemistry, University of Turku, FI-20014 Turku, Finland
2Department of Chemistry, P.O. Box 35, FI-40014 Jyväskylä, Finland
3Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
4Faculty of Science and Engineering/Physics, Åbo Akademi University FI-20500, Turku/Åbo, Finland
5NMR Research Unit, University of Oulu, P. O. Box 3000, 90014 Oulu, Finland
Format: article
Version: accepted version
Access: embargoed
Persistent link:
Language: English
Published: Royal Society of Chemistry, 2021
Publish Date: 2022-10-18


We report here the syntheses of a diamagnetic Fe complex [Fe(HL)₂] (1), prepared by reacting a redox non-innocent ligand precursor N,N′-bis(3,5-di-tert-butyl-2-hydroxy-phenyl)-1,2-phenylenediamine (H₄L) with FeCl₃, and its phenoxazine derivative [Fe(L′)₂] (2), which was obtained via intra-ligand cyclisation of the parent complex. Magnetic measurements, accompanied by spectroscopic, structural and computational analyses show that 1 can be viewed as a rather unusual Fe(III) complex with a diamagnetic ground state in the studied temperature range due to a strong antiferromagnetic coupling between the low-spin Fe(III) ion and a radical ligand. For a paramagnetic high-spin Fe(II) complex 2 it was found that, when crystalline, it undergoes a thermally induced process where 25% of the molecules in the material change to a diamagnetic low-spin ground state below 100 K. Single crystal X-ray studies conducted at 95 K afforded detailed structural evidence for this partial change of spin state of 2 showing the existence of crystallographically distinct molecules in a 3 : 1 ratio which exist in high- and low-spin states, respectively. Also, the magnetic behaviour of 2 was found to be related with the crystallinity of the material as demonstrated by near-IR radiation to unpaired electrons conversion ability of amorphous sample of 2.

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Series: Dalton transactions
ISSN: 1477-9226
ISSN-E: 1477-9234
ISSN-L: 1477-9226
Volume: 50
Issue: 43
Pages: 15831 - 15840
DOI: 10.1039/D1DT01607E
Type of Publication: A1 Journal article – refereed
Field of Science: 114 Physical sciences
116 Chemical sciences
Funding: E. S. wishes to thank the Magnus Ehrnrooth and Walter Ahlström foundations for financial support and Dr Jan-Erik Lönnqvist for elemental analysis. A. P., J. M. and A. M. gratefully acknowledge the financial support by Academy of Finland (projects 315829, 320015 and 332294). A. M. acknowledges financial support by University of Oulu (Kvantum Institute). Computational resources were provided by CSC-IT Center for Science in Finland and the Finnish Grid and Cloud Infrastructure (persistent identifier urn:nbn:fi:research-infras-2016072533).
Academy of Finland Grant Number: 332294
Detailed Information: 332294 (Academy of Finland Funding decision)
Copyright information: © The Royal Society of Chemistry 2021. The final authenticated version is available online at: