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Above room temperature spin crossover in thioamide-functionalised 2,6-bis(pyrazol-1-yl)pyridine iron(ii) complexes

Attwood, Max, Akutsu, Hiroki, Martin, Lee, Cruickshank, Dyanne and Turner, Scott S. (2019) Above room temperature spin crossover in thioamide-functionalised 2,6-bis(pyrazol-1-yl)pyridine iron(ii) complexes Dalton Transactions, 48 (1). pp. 90-98.

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Abstract

This work describes the synthesis of two novel functionalised 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligands, namely 2,6-bis(pyrazol-1-yl)pyridine-4-carbothioamide (bppCSNH2) and N-methyl-2,6-bis(pyrazol-1-yl)pyridine-4-carbothioamide (bppCSNHMe). The corresponding solvated or non-solvated Fe(II) salts, [Fe(bppCSNH2)2]X2 and [Fe(bppCSNHMe)2]X2 (X = BF4− or ClO4−) were synthesised and their properties measured by SQUID magnetometry, Evans NMR, differential scanning calorimetry and single crystal X-ray diffraction. In the solid state [Fe(bppCSNH2)2]2+ salts persist in the low spin state below 350 K. The structure of [Fe(bppCSNH2)2](BF4)2·2MeNO2 shows a network of intermolecular interactions responsible for the low spin state stabilisation, relative to the prototypical [Fe(bpp)2]2+ spin crossover (SCO) salts. By contrast the complexes of bppCSNHMe both display abrupt SCO above 300 K. [Fe(bppCSNHMe)2](BF4)2·MeNO2 requires solvent loss before SCO can be observed centred at 332 K. The non-solvated [Fe(bppCSNHMe)2](ClO4)2 shows SCO centred at 325 K. Analysis of solvated and non-solvated crystal structures suggests that cooperativity is facilitated by thioamide-group interactions with neighbouring pyrazolyl and pyridyl moieties.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Chemistry
Authors :
NameEmailORCID
Attwood, Maxm.attwood@surrey.ac.uk
Akutsu, Hiroki
Martin, Lee
Cruickshank, Dyanne
Turner, Scott S.S.S.Turner@surrey.ac.uk
Date : 14 November 2019
DOI : 10.1039/c8dt03240h
Copyright Disclaimer : © The Royal Society of Chemistry 2019
Depositing User : Clive Harris
Date Deposited : 08 Mar 2019 09:25
Last Modified : 06 Jul 2019 05:26
URI: http://epubs.surrey.ac.uk/id/eprint/850699

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