Electron Localization of Polyoxomolybdates with ε-Keggin Structure Studied by Solid-State 95Mo NMR and DFT Calculation

Abstract

We report electron localization of polyoxomolybdates with ε-Keggin structure investigated by solid-state (95)Mo NMR and DFT calculation. The polyoxomolybdates studied are the basic ε-Keggin crystals of [Me3NH]6[H2Mo12O28(OH)12{MoO3}4] · 2H2O (1), the crystals suggested to have a disordered {ε-Mo12} core of [PMo12O36(OH)4{La(H2O)2.75Cl1.25}4]·27H2O (2), and the paramagnetic Keggin crystals of [H2Mo12O30(OH)10{Ni(H2O)3}4] · 14H2O (3). The spectra of (95)Mo static NMR of these samples were measured under moderate (9.4 and 11.7 T) and ultrahigh magnetic fields (21.8 T). From spectral simulation and quantum chemical calculation, the NMR parameters of the chemical shift and quadrupole interactions for (95)Mo were estimated. By the analysis based on the result for 1, it was found for 2 that although the {ε-Mo12} core is disordered, the eight d(1) electrons in it are not completely localized on four Mo-Mo bonds. Furthermore, it was shown for 3 that the d(1) electrons are localized to make the Mo-Mo bonds, while the unpaired electrons are also almost localized on the paramagnetic Ni(II) ions.