Structure and two-dimensional correlation infrared spectroscopy study of two isomeric forms of the octamolybdate cluster

Two isomeric forms of the octamolybdate cluster, (NH4)2(Hbpy)2[Mo8O26](bpy)31 (bpy=bipydine), and [Cu2(imi)4]2[Mo8O26] 2 (imi=imidazole), were synthesized by hydrothermal method and characterized by X-ray single analysis, one-dimensional (1D) infrared spectroscopy and two-dimensional (2D) correlation infrared spectroscopy under thermal perturbation. In compound 1, the [Mo8O26] units are β-structure, and octamolybdate anion is ζ-structure in compound 2. The 2D IR correlation spectroscopy study indicates that the intensity changes of MoO band are more sensitive to the temperature variation than that of the Mo–O bond. The μ-Mo–O bond and framework vibrations in compound 1 are more sensitive to the temperature variation than that for compound 2. As the vibrations of μ-Mo–O bond accompanied by the transfer of an oxygen atom, the catalysis ability of compound 1 may be higher than that of compound 2.

Graphical abstractSynchronous and asynchronous correlation spectra of compounds 1 and 2 over a temperature range from 50 to 120 °C in the range of 400–1000 cm−1.Figure optionsDownload full-size imageDownload as PowerPoint slide