Photochromic Performance of Two Cu(II)-One-Dimensional Solvatomorphs Controlled by Intermolecular Interactions

One of the benefits found in crystal engineering to build molecular materials is the possibility of understanding and thus finely controlling their photochromic performance in the solid state. We have discovered potential hints in this direction through the use of the photochromic ligand 1,2-bis(5-carboxy-2-methylthien-3-yl)cyclopentene, H2L, in reactions with either of two different Cu(II) salts for the formation of two new solvatomorphs of a coordination polymer, [Cu(L)(py)3]·2py (1a) and [Cu(L)(py)3]·2H2O·0.5Et2O (1b). H2L is a diarylethene ligand that exhibits reversible photocyclization, allowing to reversibly modify the molecular structure and properties of coordination compounds incorporating such moiety. While the backbone of both compounds is the same, their supramolecular organization significantly differs, leading to different photochromic properties, in particular regarding the reversibility of their photoswitching processes. These remarkable structure/property relations have been assessed by optical reflectivity and Raman measurements, in light of the respective crystallographic structures.