Four Anderson– and isopolymolybdate–viologen photochromic materials for UV detection, inkless erasable printing, and ammonia detection

In this work, four POMs-based compounds are devised and synthesized by employing viologen organic ligand under hydrothermal and solvothermal conditions, namely [M2(H2O)6(Cpmbpy)2(TeMo6O24)] M = Ni (1); Co (2)), {[M(Cpmbpy)2(DMF)2(β-Mo8O26)][H4(β-Mo8O26)]}·4C2H7N (M = Cu (3); Co (4)), (Cpmbpy = 1–Cyclopropylmethyl–[4,4′]bipyridinyl–1–ium·chloride). Compound 1 or 2 exhibits one–dimensional (1D) POMs-Ni chain constructed from the [TeMo6O24]6− POMs and Ni metal ions. For compound 3 or 4, two 4,4′–bipyridine groups and two DMF molecules coordinate with a CuII ion to form a {Cu(Cpmbpy)2(DMF)2}4− subunit. And the two [β-Mo8O26]4− are directly connected the {Cu(Cpmbpy)2(DMF)2}4+ subunit to form a 1D chain structure. Compounds 1–4 exhibits photochromic properties under irradiation with a filtered Xe lamp (300–400 nm), showing rapid light response and varying degrees of color change. Four compounds can also be utilized as visible UV detectors and inkless erasable printing materials. In addition, compounds 1 and 2 exhibits a significant NH3 response.