Synthesis and characterizations of cyclic octanuclear mixed-valence vanadium(IV,V) clusters with polyoxometalate counterions.
Hydrothermal reaction of Na2WO4, VOSO4, 2,2'-bpy and H3PO4 has afforded in high yield the compound [V(IV)2V(V)6O14(bpy)8(PO4)2][PW11V(V)O40](bpy).12H2O (1). Compound 1 contains a novel octanuclear mixed valence V(IV,V) cluster, [V(IV)2V(V)6O14(bpy)8(PO4)2]4+, with [PW11V(V)O40]4- as counterion. In the vanadium cluster, four V(V) centers are localized and the remaining two V(IV) and two V(V) ions are disordered over four crystallographically equivalent positions. The isostructural compound [V(IV)2V(V)6O14(bpy)8(PO4)2][PMo11V(V)O40](bpy).3H2O (2) has also been synthesized. Thermodiffractometry experiments indicate that 2 is stable up to 360 degrees C. Redox activities for both the vanadium and molybdenum centers have been observed by solid-state electrochemical measurements performed on mechanically attached microparticles of 2. Magnetic measurements performed on have shown the occurrence of weak ferromagnetic interactions between the V(IV) centres (J = +0.34 cm(-1), H(ex) = -JS1 x S2), and combined with DFT calculations, have allowed to propose a localization of the two V(IV) centers on two of the four equivalent crystallographic sites. Finally high field electron paramagnetic resonance has evidenced the magnetic axial anisotropy of the paramagnetic centers (g(x) = g(y) = 1.975(3); g(z) = 1.939(4)).
Lisnard
Laurent
L
Institut Lavoisier, UMR 8180, Université de Versailles Saint-Quentin, 45 Avenue des Etats-Unis, 78035, Versailles Cedex, France.
Dolbecq
Anne
A
Mialane
Pierre
P
Marrot
Jérôme
J
Rivière
Eric
E
Borshch
Serguei A
SA
Petit
Sébastien
S
Robert
Vincent
V
Duboc
Carole
C
McCormac
Timothy
T
Sécheresse
Francis
F
D018360:Crystallography, X-Ray; D004563:Electrochemistry; D008280:Magnetics; D008956:Models, Chemical; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D013696:Temperature; D017973:Tungsten Compounds / Q000737:chemistry*; D014639:Vanadium / Q000737:chemistry*
D009942:Organometallic Compounds; D017973:Tungsten Compounds; D014639:Vanadium