Cd-Viologen photochromic coordination compound for inkless and erasable printing and amine-selective sensing

A new crystalline inorganic-organic hybrid compound, namely, [Cd-2(bcbpy)(m-BDC)(2)(H2O)(4)]center dot 5H(2)O (1) has been solvothermally synthesized from the isophthalic acid (m-H2BDC) ligand and the viologen analog 1,1'-bis(3-carboxylatobenzyl)-(4,4'-bipyridinium) dichloride (H(2)bcbpyCl(2)). As a consequence of its photochromic response, compound 1 offers potential application as an inkless and erasable print medium by depositing the powdered sample on paper, and the printed image was retained in the dark for up to 48 h. Furthermore, based on the redox ability and Lewis acidic site of the viologen molecular, compound 1 exhibits quite different color changes when in contact with different amines vapor (NH3, EA = ethylamine, PA = n-propylamine, BA = n-butylamine, DEA = diethylamine and TEA = triethylamine), and it may be used as an emergency amine detection system in the future.