Light-driven coordination anions-directed regulation of chromism in three metal complexes assembled by cyano-equipped dithienylethene ligand

Abstract

Three coordination compounds were self-assembled successfully with Ag(I) ions and photo-responsive ligands featuring a cyano-equipped dithienylethene unit. Anions with different coordinating abilities were selected to construct distinct topologies, which are evidenced by X-ray crystallographic analysis. CF3 COO− and CF3 SO3− are involved into coordination in 1 and 3, respectively, whereas in 2 BF4− present merel y as ionic guests counterbalancing the framework charge. Anions also show their subtle effects on coordinated atoms, interactions, and ligand configurations. The quite different structures of 1–3 indicate an interesting anion-directed structural self-assembly.Followed examinations on photochromism illustrated that the reversible photo-isomerizations of three complexes are all retained after complexzation with Ag(I) center. Various degrees of bathochromic shifts in absorptions were observed as compared with that of the metal-free ligand. Therefore, the photo-switching of these compounds could be modulated conveniently and finely by varying simply the coordination anions and then triggering by light irradiation. The discussions of structure-properties relationship concluded that anions exert their effects on coordination structure through adjusting the configurations of ligands in complexes. Strong coordinating anions facilitate a pronounced conformational change of ligand whereas un-coordinating anion leads to smaller variation. The distinct structural changes of ligand result finally the different perturbation of photochromic behavior.