There are relatively few reports on the combination of viologen and polyoxometalates (POMs). Herein, we successfully synthesized three viologen−POM-based compounds by in situ transformation of ligands under hydrothermal conditions, namely, {M II (1,4-cby) 2 [H 2 (γ-Mo 8 O 26 )]}•nH 2 O (1: M = Ni, n = 4; 2: M = Co, n = 6), and [Ni II (1,3Isostructural compounds 1 and 2 exhibit two-dimensional (2D) layer structures with POMs as linking nodes, while compound 3 shows a one-dimensional (1D) metal−organic chain with dissociative POM anions. When the temperature increases, compounds 1−3 show good reversible thermochromism properties and also have a fluorescence quenching effect. Moreover, compounds 1−3 can also be used as detectors for organic amines, especially in the atmosphere of ammonia, ethylenediamine, and diethylamine with an obvious discoloration effect. In addition, compound 1 was used as a material for the preparation of memristors with superior properties (distinct temperature-adjusted resistive switching properties). It shows bipolar resistive switching (RS) behavior at different temperatures of 20, 50, and 100 °C. The results show that the 1-based memristor has good thermal stability, which is important for high-temperature environment applications. It also shows that crystalline viologen−POM-based compounds are ideal candidates for making memristors.

In this work, by using two kinds of viologen ligands three POM-based compounds were obtained under hydrothermal and solvothermal conditions, namely {Cu2(Cbybpy)6(Cl)2[H4(β-Mo8O26)3]}·12H2O (1), (HCbybpy)2·(β-Mo8O26) (2) (Cbybpy·Br = 1-(2'-Cyano-biphenyl-4-ylmethyl)-[4,4']bipyridinyl-1-ium bromide) and...

Four POM-based complexes were synthesized under hydrothermal conditions by using two kinds of triazole derivatives, namely [Cu2(Cmt)2(OH)Cl(β-Mo8O26)0.5] (1), [Cu(H2O)3(H3/2Tpm)2](HTpm)(PMo12O40)2·4H2O (2), [Cu3Cl2(H2Tpm)2(HTpm)4(PMo12O40)4]·26H2O (3), [Co3(HTpm)6(H2O)2(Mo13O42)2]·21H2O (4) (Cmt = 1-cyclopropylmethyl-1-H-[1,2,4]triazole, Tpm = 4-(3-[1,2,4]triazole-4-propyl)morpholine)....

In this work, four POM-based compounds containing viologen ligands were synthesized, namely {Cu II (tybipy) In compounds 1 and 3, Cu 2 + and mixed organic ligands modify POM anions. On the other hand, 2 and 4 are supramolecular structures only containing ligands and anions. Under Xe lamp with filter (300-400 nm) irradiation, these four compounds showed good photoresponse and photochromic ability, which can be used in mixed matrix films for visible UV detectors. Compounds 1-4 also have photoluminescence property and show good fluorescence quenching effect. A suspension of four compounds can be evenly spread on filter paper as inkless and erasable printing materials. Compounds 1 and 2 were also used as Hg 2 + fluorescence detectors. The fluorescence intensity of 1 decreased by ca. 90 % when the concentration of Hg 2 + increased to 40 mM. Moreover, we also prepared composites 1/2@Hg 2 + ,1@Cu 2 + , 1@Co 2 + by introducing 1/2 and Hg 2 + , Cu 2 + and Co 2 + to detection paper respectively, which can act as photochromic materials with features of fast color recovery.