Systematic control of the spin crossover profile in dinuclear iron(iii) complexes via the bridging ligand redox-state

Abstract

Switchable molecular materials that undergo multistep transitions are critical to advancing ternary data storage, complex logic systems, and highly sensitive colorimetric sensors. Dinuclear metal complexes capable of two-step spin crossover (SCO) interconversions of the form [LS–LS] ⇌ [LS–HS] ⇌ [HS–HS] (LS = low spin, HS = high spin) hold great promise for constructing such multistable systems. However, achieving reliable and predictable two-step SCO in discrete complexes remains a significant challenge. Here, we introduce a conceptual advance to overcome this limitation: the deliberate use of a mixed-valence bridging ligand to impose ligand field asymmetry, a strategy not previously propose..