Effect of counteranion X on the spin crossover properties of a family of diiron(II) triazole complexes [FeII2(PMAT) 2](X)4

Jonathan A. Kitchen, Nicholas G. White, Guy N.L. Jameson, Jeffery L. Tallon, Sally Brooker*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

62 Citations (Scopus)

Abstract

Seven diiron(II) complexes, [FeII2(PMAT) 2](X)4, varying only in the anion X, have been prepared, where PMAT is 4-amino-3,5-bis{[(2-pyridylmethyl)-amino]methyl}-4H-1,2,4-triazole and X = BF4- (1), Cl- (2), PF6 - (3), SbF6- (4), CF3SO 3- (5), B(PhF)4- (6), and C 16H33SO3- (7). Most were isolated as solvates, and the microcrystalline ([3], [4] ·2H2O, [5] ·H2O, and [6] ·1/2MeCN) or powder ([2] ·4H2O, and [7] ·2H2O) samples obtained were studied by variable-temperature magnetic susceptibility and Mössbauer methods. A structure determination on a crystal of [2] ·2MeOH· H2O, revealed it to be a [LS-HS] mixed low spin (LS)-high spin (HS) state dinuclear complex at 90 K, but fully high spin, [HS-HS], at 293 K. In contrast, structures of both [5] ·3/4IPA· H2O and [7] ·1.6MeOH·0.4H2O showed them to be [HS-HS] at 90 K, whereas magnetic and Mössbauer studies on [5] ·H2O and [7] ·2H2O revealed a different spin state, [LS-HS], at 90 K, presumably because of the difference in solvation. None of these complexes undergo thermal spin crossover (SCO) to the fully LS form, [LS-LS]. The PF6- and SbF6- complexes, 3 and [4] ·2H2O, appear to be a mixture of [HS-LS] and [HS-HS] at low temperature, and undergo gradual SCO to [HS-HS] on warming. The CF3SO3- complex [5] ·H2O undergoes gradual, partial SCO from [HS-LS] to a mixture of [HS-LS] and [HS-HS] at T1/2 ≈ 180 K. The B(PhF)4- and C 16H33SO3- complexes, [6] ·1/2MeCN and [7] ·2H2O, are approximately [LS-HS] at all temperatures, with an onset of gradual SCO with T1/2 > 300 K.

Original languageEnglish
Pages (from-to)4586-4597
Number of pages12
JournalInorganic Chemistry
Volume50
Issue number10
DOIs
Publication statusPublished - 16 May 2011
Externally publishedYes

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