Sunlight-Induced In Situ Isomerization of Both Ligands in a Mixed-Ligand Coordination Polymer: From Photosalient to Photoinert Crystals.

Reaction of Zn(NO )  ⋅ 6H O, maleic acid (H mal) and trans-4-(1-naphthylvinyl)pyridine (trans-nvp) in the dark results in the formation of a one-dimensional coordination polymer (1D CP) [Zn(mal)(trans-nvp)] (1), which is photosalient in nature. The crystals of 1 pop violently under UV light and moderately in sunlight, and generate cyclobutane ligands. However, the same reaction mixture kept in visible light exhibits the rare example of in situ isomerization of both ligands: cis-trans transformation of maleate and trans-cis isomerization of the nvp ligands, and subsequent formation of another 1D CP [Zn(fum)(cis-nvp) (H O) ] (2, H fum=fumaric acid), which is found to be photoinert. Thus, altering the reaction condition from dark to visible light gives rise to photosalient to photoinert crystals.