Above room temperature spin crossover in thioamide-functionalised 2, 6-bis(pyrazol-1-yl)pyridine iron(ii) complexes. Issue 1 (20th November 2018)

• Record Type: Journal Article
• Authors: Attwood, Max; Akutsu, Hiroki; Martin, Lee; Cruickshank, Dyanne; Turner, Scott S.
• Is Part Of: Dalton transactions. Volume 48:Issue 1(2018)
• Page Start: 90
• Page End: 98
• Publication Date: 2018-11-20
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c8dt03240h
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Two new Fe(ii ) complexes with thioamide functionalised ligands show spin-crossover above 300 K. 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 ofbppCSNHMe 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.