Spin crossover of a hydrogen-bonded dimeric FeIII complex with an unequivalent tetradentate Schiff base ligand and two imidazoles

A spin crossover Fe-III complex, [FeHim(2)L]BPh(4)center dot 2MeOH, was synthesized and studied, where Him = imidazole, H2L = N2O2 Schiff base ligand of the 1: 1: 1 condensation product of acetylacetone, ethylenediamine. and o-hydroxyacetophenone, and BPh4- = tetraphenylborate. The complex consists of a cyclic dimeric structure. {(...)[FeHim(2)L](...)(MeOH)(...)(MeOH)(...)}(2), constructed by the hydrogen bonds. Magnetic measurements revealed that a rather steep spin transition from the LS to HS Fe-III states occurs above 300 K. and the elimination of the methanol molecules changes the spin transition from steep to gradual due to destruction of the cyclic dimeric structure.