The UV and IR Comparative Spectrophotometric Study of Some Saturated and Lacunary Polyoxometalates

Abstract

Objectives:The polyoxometalates are a class of inorganic compounds with controllable shapes and sizes, and with excellent properties that make them attractive for various applications. This study is aimed at the comparative UV and IR spectra of Keggin type polyoxometalates. Methods: Compounds under (UV and IR) investigations were divided into several groups to highlight similarities between compounds or classes of compounds for the same category. There are four types of saturated Keggin structures and six lacunar compounds included in this study. The study begins with the UV investigations on aqueous solutions with 10 -5 M concentration for these compounds. IR spectra were recorded as KBr pressed pellets. Results: The UV spectras presents large strong peaks between 185-195 nm corresponding to W = Od bonds, between 251-268 nm for W-O-W bridge bonds, depending on heteroatom types (As, Sb). The unsaturated cryptand ligand having Co 2+ coordinated presents the most intense peak, due to the involvement of oxygen atoms from terminal W = Od coordinative bonds with high electronic densities in coordination of W-O-Co bond. The IR spectra present many peaks that are associated as follows: for terminal bonds W = Od, 955-970 cm -1 ; for W-O-W bridging bonds, 790-910 cm -1 ; for W-O-As/Sb bonds to heteroatom, 690-760 cm -1 . Vibrations of the bonds between heteroatoms and oxygen (As/Sb-O) appear around 620-660 cm -1 . Conclusions: Similarities appear from the recorded spectra, between compounds of the same class, by category association. Very fi ne displacements of peaks that occur explain the infl uence of heteroatoms, addenda atoms or coordinated cations.

Oxidative Desulfurization of Gas Oil Catalyzed by (TBA)4PW11Fe@PbO as an Efficient and Recoverable Heterogeneous Phase-Transfer Nanocatalyst

“…As seen in Figure b, the peak at 257 nm is considered as a ligand–metal charge transfer transition of O 2– → W 6+ , where W atoms were positioned in W–O–W. In both (TBA) 4 PW 11 Fe and (TBA) 4 PW 11 Fe@PbO patterns, the absorption peaks around the wavelengths of 197–200 nm served as the evidence for π p –π d electronic transitions of terminal WO d …”

“…The observed peak shifts in the FTIR spectra of the synthesized nanocatalyst compared to the pure materials suggested the preparation of the (TBA) 4 PW 11 Fe@PbO composite. 32 The XRD patterns of the powder PbO, (TBA) 4 PW 11 Fe, and (TBA) 4 PW 11 Fe@PbO nanocatalyst are shown in Figure 3. On the basis of the obtained results, the main reflections of pure PbO are observed at 2θ values of 28.5°, 29°, 31.7°, 35.6°, 48.5°, 56°, and 59.6°, which associated with the (111), (002), ( 200), (210), (022), (222), and (311) crystal planes, respectively.…”

Photocatalytic Degradation of Methylene Blue under Visible Light Using TiO2 Thin Films Impregnated with Porphyrin and Anderson-Type Polyoxometalates (Cu and Zn)

“…The ZnPOM FTIR spectra and interpretation are similar to the one of CuPOM . The similitude is because both are very similar Anderson-type POMs, and according to the literature, they have characteristic peaks near each other [44]. Regarding the FT-IR spectra of TCPP/CuPOM/TiO 2 and TCPP/ZnPOMTiO 2 (Figure 2), these systems show similar spectra to each other because the materials only differ on the heteroatom of the POM.…”

Coordination of Palladium(II) and Platinum(II) Complexes to One Vacant Site in an α-Keggin-Type Polyoxotungstate

“…Several bands attributed to the Keggin-type polyoxotungstate structure were also observed at 954, 898, 855, 805, 753, and 720 cm −1 . 17 The spectral pattern of PdPt is different from those of Pt1 (1089, 1043, 951, 896, 859, 805, 758, and 727 cm −1 ) (Figure 2B), Pt2 (1099, 1047, 955, 915, 859, 801, 757, and 721 cm −1 ) (Figure 2C), 12 and K 7 [α-PW 11 O 39 ]•13H 2 O (1086, 1043, 953, 903, 862, 810, and 734 cm −1 ). 11,16 The FTIR spectrum of Pd2 showed bands at 1106, 1043, 969, 952, 892, 850, 796, 768, 738, and 710 cm −1 , as shown in Figure 2D.…”