Construction of Five POM Compounds by Tuning Spacer Length and Piperazine/Morpholine Groups: Electrochemical Sensing Properties and Application on Capacitor Materials

Abstract

Through tuning piperazine and morpholine groups and spacer length in organic ligands, five [Mo 8 O 26 ] 4− -based compounds have been obtained, [(H 2 tep) 2morpholine, and tpm = 4-(2-(4H-1,2,4-triazol-4yl)propyl)morpholine). In compound 1, the N atom of tep directly connects the Mo atom of a [γ-Mo 8 O 26 ] 4− anion through a Mo−N bond without transition-metal ions. The [γ-Mo 8 O 26 ] 4− anions in 2 are linked by a Zn atom to construct an inorganic layer with tep ligand coordination with Zn and Mo atoms by Zn−N and Mo−N bonds.The N atom in the piperazine group does not link with the metal atoms in 1 and 2. However, the O atom in the morpholine group in 3−5 coordinates with Ag, Cu, and Co atoms, respectively. Compound 3 shows a 3D framework with 2D layers linked by binuclear Ag clusters. Compounds 4 and 5 are isostructural, containing two kinds of chains. The chains connect each other to form a 3D framework. Both N and O of tem and tpm participate to link metal atoms in 3−5, which are conducive to build high-dimensional structures. The spacer length, piperazine and morpholine groups, and different metal ions all exhibit effects on structures under hydrothermal conditions. Furthermore, electrocatalytic reduction of KNO 2 and KBrO 3 and electrocatalytic oxidation of ascorbic acid were studied. These compounds can be used as electrochemical sensors for detecting NO 2 − . They also show selective photocatalytic properties. Compounds 1−5 own properties of capacitor materials.