Synthesis, structures, simulated IR spectra and two-dimensional infrared correlation spectroscopy of two nitrogen-heterocyclic β-octamolybdate supported compounds

Two metal–organic β-octamolybdate supported compounds containing nitrogen-heterocyclic ligands, [Co(dpq)2 H2O]2[β-Mo8O26] 0.5H2O 1, (H3biim)4[β-Mo8O26] 2 (dpq = 1,10-phenanthroline-5,6-dione; H2bimm = 2,2′-biimidazole), have been hydrothermally synthesized and characterized by X-ray crystal structural analysis, elemental analysis, IR spectrum, UV–VIS DRIS, 2D-IR COS (two-dimensional infrared correlation spectroscopy), PXRD, TG analysis, simulated IR spectrum and theoretical calculations from HOMO–LUMO. X-ray crystal structural analyses reveal that compound 1 has the 1-D supramolecular structure, which is formed via hydrogen bonds between water molecules coordinated to Co2+. In compound 2, the 2-D supramolecular structure is built by aromatic–aromatic stacking interactions and H-bonds between ligands. Simulated IR spectra gained by quantum calculation are used for structure discussion, which is the first time that simulated IR results are used to reveal the relationship between bond vibrations of β-octamolybdate compounds and their related IR peak responses. Additionally, by using 2D-IR COS, structural properties like thermal and magnetic sensitivities have also been analyzed.