Spin Transitions in Fe(II) Metallogrids Modulated by Substituents, Counteranions, and Solvents

Two bis­(tridentate) Schiff base ligands H2Lx were used to construct three 2×2 grid-type tetranuclear Fe­(II) complexes 1–3 to obtain polynuclear spin-crossover materials. Magnetic susceptibility measurements show that the spin states of the complexes are related to the substituents of H2Lx, and that spin transition occurs only in complexes 1 and 2, which are derived from a bulky ligand, whereas complex 3 is diamagnetic. The transition temperatures of complexes 1 and 2 are close to room temperature and are dependent on counteranions. The spin transition of complex 1 can be reversibly tuned by the dehydration and hydration process.