Synergistic spin transition between spin crossover and spin-peierls-like singlet formation in the halogen-bonded molecular hybrid system: [Fe(Iqsal) ₂][Ni(dmit)₂]×CH₃CN×H₂O

To introduce halogen-bond interactions between a cation and an anion, a novel Fe^III complex from iodine-substituted ligands involving a paramagnetic nickel dithiolene anion was prepared and characterized. The compound exhibited the synergy between a spin-crossover transition and a spin-Peierls-like singlet formation. The halogen-bond interactions between the iodine and the sulfur atoms stabilized the paramagnetic state of π-spins and played a crucial role in the synergistic magnetic transition between d- and π-spins. In addition, the compound showed the light-induced excited spin state trapping effect. Something to get crossover: An Fe^III complex with iodine-substituted ligands involving a paramagnetic nickel dithiolene anion shows a synergy between a spin-crossover transition and a spin-Peierls-like singlet formation. The halogen-bond interactions between the iodine and the sulfur atoms stabilized the paramagnetic state of π-spins and played a significant role in the synergistic magnetic transition between d- and π-spins.