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

Kitchen, Jonathan A., White, Nicholas G., Jameson, Guy N.L., Tallon, Jeffery L. and Brooker, Sally (2011) Effect of counteranion X on the spin crossover properties of a family of Diiron(II) Triazole complexes [FeII2(PMAT)2](X)4. Inorganic Chemistry, 50 (10), 4586-4597. (doi:10.1021/ic200308k).

Abstract

Seven diiron(II) complexes, [FeII2(PMAT)2](X)4,varying only in the anion X, have been prepared, where PMAT is4-amino-3,5-bis{[(2-pyridylmethyl)-amino]methyl}-4H-1,2,4-triazoleand X = BF4- (1), Cl- (2), PF6-(3), SbF6- (4), CF3SO3-(5), B(PhF)4- (6), and C16H33SO3- (7). Most were isolated as solvates, and the microcrystalline ([3], [4] 3 2H2O, [5] 3H2O, and [6] 3 1/2MeCN) or powder ([2] 3 4H2O, and [7] 3 2H2O) samples obtained were studied by variable-temperature magnetic susceptibility and M€ossbauer methods. A structure determination on a crystal of [2] 3 2MeOH3H2O, 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 3/4IPA 3H2O and [7] 3 1.6MeOH 3 0.4H2O showed them to be [HS-HS] at 90 K, whereas magnetic andM€ossbauer studies on [5] 3H2O and [7] 3 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] 3 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] 3H2O 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 C16H33SO3- complexes, [6] 3 1/2MeCN and [7] 3 2H2O, are approximately [LS-HS] at all temperatures, with an onset of gradual SCO with T1/2 > 300 K.

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Contributors

Author: Jonathan A. Kitchen

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