Synthesis, crystal structure, photochromism and photo-regulated luminescence of a viologen-functionalized material

Viologen-functionalized materials have broad and desirable application prospects. Nowadays, synthesis of such materials and exploration of their new properties still remain a great challenge. In this work, one viologen-functionalized crystalline material, {[Cd(bcbpy)(tdc)(H 2 O)](0.5DMF)} n (bcbpy =1-(4-carboxybenzyl)-4,4′-bipyridinium, H 2 tdc = 2,5-thiophenedicarboxylic acid) has been constructed by solvothermal methods. The material features an interesting two-dimensional layered structure constructed from tdc 2– ligands, which is decorated with bcbpy ligands. Due to the presence of electron-deficient viologen moieties, the crystalline sample displays a reversible photochromic behavior driven by photo-induced electron transfer under irradiation of UV light within a short time. Curiously, the ground sample after mechanical grinding exhibits a different photochromic behavior. Moreover, photo-regulated luminescence properties of the material before and after mechanical grinding have also been studied.