A mononuclear iron(III) complex with unusual changes of color and magneto-structural properties with temperature: synthesis, structure, magnetization, multi-frequency ESR and DFT study

Garg, Nitish Kumar; Goriya, Yogesh; Manojveer, Seetharaman; Muratović, Senada; Pajić, Damir; Cetina, Mario; Petreska, Irina; Krupskaya, Yulia; Kataev, Vladislav; Johnson, Magnus T.; Wendt, Ola F.; Žilić, Dijana (2022) A mononuclear iron(III) complex with unusual changes of color and magneto-structural properties with temperature: synthesis, structure, magnetization, multi-frequency ESR and DFT study. Dalton Transactions, 51 . pp. 2338-2345. ISSN 1477-9226 (print); 1477-9234 (web)

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Official URL: https://pubs.rsc.org/en/content/articlelanding/202...

Abstract

From the reaction of 2-hydroxy-6-methylpyridine (L) with iron(II) tetrafluoroborate, a new mononuclear iron(III) octahedral complex [FeL6](BF4)3 has been isolated. The color of the complex reversibly changed from red at room temperature to yellow-orange at the liquid nitrogen temperature. Magnetization measurements indicate that iron(III) in [FeL6](BF4)3 is in a high-spin state S = 5/2, from room temperature to 1.8 K. The high-spin ground state of iron(III) is also confirmed by DFT calculations. Although the spin-crossover of the complex is not observed, X-band and multifrequency high-field/high-frequency electron spin resonance (ESR) spectroscopy shows rather uncommon iron(III) spectra at room temperature and an unusual change with cooling. Spectral simulations reveal that the S = 5/2 ground state multiplet of the complex can be characterized by the temperature independent axial zero-field splitting parameter of |D| = +2 GHz (0.067 cm−1) while the value of the rhombic parameter E of the order of some tenths MHz increases on lowering the temperature. Single crystal X-ray diffraction (SCXRD) shows that the iron(III) coordination geometry does not change with temperature while supramolecular interactions are temperature dependent, influencing the iron(III) rhombicity. Additionally, the DFT calculations show temperature variation of the HOMO–LUMO gap, in agreement with the changes of color and ESR-spectra of the iron(III) complex with temperature.

Item Type:

Article

Uncontrolled Keywords:

ESR spectroscopy ; iron(III) complex ; thermochromism

Subjects:

NATURAL SCIENCES > Interdisciplinary Natural Sciences

Divisions:

Division of Physical Chemistry

Projects:

Project title	Project leader	Project code	Project type
Studija važnosti spinskih međudjelovanja kao osnova za nove pristupe u istraživanju materijala-SPES	Marina Ilakovac-Kveder	IP-2018-01-3168	HRZZ
Magneto-strukturne korelacije u molekulskim magnetskim kompleksima istraživane spektroskopijom elektronske spinske rezonancije-	Dijana Žilić	910-08/18-01/00324	MZO

Depositing User:

Senada Muratović

Date Deposited:

18 Feb 2022 10:11

URI:

http://fulir.irb.hr/id/eprint/6973

DOI:

10.1039/D1DT03751J