Effect of intermolecular anionic interactions on spin crossover of two triple-stranded dinuclear Fe(ii) complexes showing above room temperature spin transition

Abstract

Two new Fe(II)-based dinuclear triple helicates having the formula {[Fe₂(L)₃]·(CF₃SO₃)₄·6.5H₂O·CH₃OH} (complex 1) and {[Fe₂(L)₃]·(ClO₄)₄·7H₂O·1.35CH₃OH} (complex 2), displaying near room temperature spin transition have been synthesized and the effect of intermolecular interactions and co-operativity between metal centers on the spin crossover (SCO) has been studied. Picolinimidamide-based ligand system is chosen to provide maximum intermolecular interactions. Variable-temperature single crystal X-ray diffraction (SCXRD), magnetic study, and Hirshfeld analysis reveal that complex 1 shows a multistep spin transition, whereas, complex 2 shows an abrupt spin transition from [LS–LS] ↔ [HS–HS]. In complex 2 the presence of perchlorate anion induces high intermolecular O–H interaction that enhances the cooperativity resulting in high T_1/2 of 330 K. This study accentuates the interplay between anion effect, crystal packing, and supramolecular interactions in tuning the magnetic properties of SCO compounds.