Bicapped Keggin polyoxomolybdates: discrete species and experimental and theoretical investigations on the electronic delocalization in a chain compound

International audienceThree monomeric polyoxometalates [M(C10H8N2)3][α-PMo VI 9Mo V 3O40Zn2(C10H8N2)2]2H2O (M-PMo12Zn2, M = Fe, Co, Ru) with {Zn(bpy)2} 2+ units capped on reduced α-Keggin polyanions and [M(bpy)3] 2+ counter-ions were synthesized under hydrothermal conditions. The 1D polymer [N(C4H9)4][Ru(C10H8N2)3][α-PMo VI 8Mo V 6O43] (Ru-PMo14) was prepared by a similar strategy. In this chain capped reduced Keggin anions are linked via MoO -Mo bridges and are surrounded by both TBA + and [Ru(bpy)3] 2+ counter-ions. The compounds were characterized in the solid state by single crystal and powder X-ray diffraction and IR spectroscopy and in solution by 31 P NMR spectroscopy. 31 P diffusion ordered NMR spectroscopy (DOSY) indicates that the diffusion coefficient of the dissolved species of Ru-PMo14 could correspond to a dimeric structure. Magnetic susceptibility measurements performed on Ru-PMo14 show the existence of antiferromagnetic interactions between the d 1 electrons of the six Mo V centers at low temperature and a delocalization of these electrons at high temperature. DFT calculations allowed proposing a distribution of the electrons consistent with this magnetic behaviour