Triazole-derivatized ligand-directed diverse structures and polyaniline-assisted capacitive performances of two new Anderson-type [AlMo6(OH)6O18]3−-based metal–organic complexes†

Abstract

Two new polyoxometalate-based metal–organic complexes (POMOCs), namely, H{Zn₂(Hpytty)₂[AlMo₆(OH)₆O₁₈](H₂O)₈}·6H₂O (1), H{Zn₂(Hpyttz)₂[AlMo₆(OH)₆O₁₈](H₂O)₈}·6H₂O (2) (H₂pytty = 3-(pyrazin-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, H₂pyttz = 3-(pyrid-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), were obtained under hydrothermal conditions using different N-rich triazole-derivatized ligands and they were characterized through powder X-ray diffraction (PXRD), single-crystal X-ray diffraction, and infrared spectroscopy. Both the title POMOCs show 2D supramolecular structures formed through hydrogen bonds, except that the [AlMo₆(OH)₆O₁₈]³⁻ anions in complex 2 are immobilized between the metal–organic units via coordination interaction. The capacitive performances of the carbon paper-based electrodes modified by complexes 1–2 were investigated, in which complex 2 achieved a larger specific capacitance of 1362 F g⁻¹ than that of 1 (1836 F g⁻¹) at a charge–discharge current density of 1 A g⁻¹. The enhancement in intramolecular bond strength is beneficial for improving the capacitance performance of complexes. In addition, after electrochemical conditioning with polyaniline, the electron–ion transfer rate, along with the pseudocapacitive activity of complexes 1–2 is also significantly improved.