Inclusion Compound of Poly(vinyl alcohol) with Multivalent Molybdenum Coordination Compound

An inclusion compound of Mo(VI,V,IV) complexes and poly(vinyl alcohol) (PVA) that contains some carbonyl groups was prepared by a photoelectron transfer reaction between PVA and 12-molybdophosphoric acid (PMo12). A dark-blue film was obtained when the aqueous solution of PMo12 and PVA was irradiated with UV light. The film exhibited the characteristic electron spin resonance (ESR) signal of Mo(V). The existence of Mo(VI,V,IV) complexes was supported by XPS analysis of the film. Furthermore, the infrared (IR) and ultraviolet–visible (UV–Vis) spectra of the film showed weak absorption bands at 1710 cm−1 and 300–314 nm that are consistent with carbonyl groups, which presumably are a result of partial oxidation of secondary hydroxyl groups on PVA. Differential scanning calorimetry (DSC) of the dark-blue film exhibited a peak at 220.3°C that is different from PMo12 and PVA. Except for the IR absorption at 1710 cm−1, the wavelengths and shapes of the other IR bands were similar to those of PVA. The UV–Vis spectrum of the film showed a new absorption band at 742–770 nm. In addition, the XRD spectrum of the film, the diffraction angles, and the crystalline sites were different from that in PMo12 or PVA. However, the peak shape was similar to that of PVA. In summary, the DSC, IR, UV–Vis, and XRD data support a Mo(VI,V,IV) complex that is included into the spiral tube structure of PVA, which contains some carbonyl groups.