trans to cis photo-isomerization in merocyanine dysprosium and yttrium complexes

Abstract

We report the synthesis of two lanthanide complexes including a chelating merocyanine (MC) ligand obtained from the reaction of a bis(pyridinemethyl)amine substituted spiropyran with yttrium(III) or dysprosium(III) triflate salts, whose structures were confirmed both in the solid state and in solution by single crystal X-ray diffraction studies and NMR investigations. The obtained merocyanine metal complexes can reversibly undergo a photo-triggered transformation consisting of a partial isomerization of the trans-merocyanine ligand to its cis isomer (cis-MC) providing complexes in which the metal–phenolate bond is retained. SQUID magnetometry experiments in combination with ab initio calculations were used to evidence and rationalize the single-molecule magnet behavior of the dysprosium complex and to probe the changes in the dysprosium ion local environment upon photo-isomerization.