One-way photoisomerization of ligands for permanent switching of metal complexes

One-way photoisomerization of ligands within metal complexes is an almost unknown phenomenon. We disclosed that a diarylethene-based ligand L-o undergoes quantitative irreversible photoisomerization to a photo- and thermostable annulated isomer L-a both in a metal-free state and within a spin-crossover iron(II) complex. The modulation of the electronic structure of the ligand upon L-o to L-a photoisomerization provides a unique opportunity to change the physical properties, in this case magnetic properties, of the corresponding metal complexes permanently, which is highly attractive for constructing non-volatile permanent memories and components for emerging molecular electronics and spintronics. Importantly, destructive thermal back-switching, which is commonly observed in metal complexes with photochromic ligands, is completely suppressed with our strategy.