Combining electron transfer, spin crossover, and redox properties in metal-organic frameworks.

Getzner, Livia; Paliwoda, Damian; Vendier, Laure; Lawson-Daku, Latévi Max; Rotaru, Aurelian; Molnár, Gábor; Cobo, Saioa; Bousseksou, Azzedine · Nat Commun · 2024

basic_science · Level V

Where this comes from

Abstract

Hofmann coordination polymers (CPs) that couple the well-studied spin transition of the Fe<sup>II</sup> central ion with electron-responsive ligands provide an innovative strategy toward multifunctional metal-organic frameworks (MOFs). Here, we developed a 2D planar network consisting of metal-cyanide-metal sheets in an unusual coordination mode, brought about by infinitely π-stacked redox-active bipyridinium derivatives as axial ligands. The obtained family of materials show vivid thermochromism attributed to electron transfer and/or electronic spin state change processes that can occur either independently or concomitantly. Importantly, the redox activity of the ligands within the structure leads to the quasi-reversible electrochemical reduction reaction on a spin-crossover complex at solid state. These observations have been confirmed via temperature-dependent single-crystal X-ray diffraction, magnetic measurements, Mössbauer, EPR, optical and vibrational spectroscopies as well as quantum chemical calculations.