A novel salt formed by mixed-valence vanadium(IV, V) [(VO)(2)O(bpy)(2)(C2O4)(2)] anions and ferromagnetic [Cu-2(bpy)(4)(C2O4)] cations: Structure, spectroscopic characterization and magnetic properties

The new heterometallic, mixed-valence compound [Cu-2(bpy)(4)(C2O4)][(VO)(2) O(bpy)(2)(C2O4) (2)](2). 10H(2)O has been synthesized, its crystal structur e determined and its spectroscopic characterization accomplished by means o f solid-state vibrational (far and mid FTIR) spectroscopy, The title compou nd crystallises in the triclinic system, space group Pi (No. 2) [a = 13.488 (5) Angstrom, b = 14.160(6) Angstrom, c = 15.829(9) Angstrom, alpha = 87.22 (2)degrees, beta = 66.33(2)degrees, gamma = 64.49(2)degrees, V = 2471(2) An gstrom (3), Z = 1]. The compound consists of the cationic binuclear copper( TT) complex [Cu-2(bpy)(4)(C2O4)](2+), two anionic binuclear mixed valence v anadium(IV)-vanadium(V) complexes [(VO)(2)O(bpy)(2)(C2O4)(2)](-), and ten u ncoordinated water molecules, The copper atom exhibits a Jahn-Teller-distor ted octahedral coordination. The vanadium atoms adopt a strongly distorted octahedral coordination and form a characteristic O = V-O-V=O moiety with a significantly bent V-O-V link. The temperature dependence of the magnetic susceptibilities has been investigated in the temperature range 2-300 K and explained in terms of the ferromagnetic interaction between Cu-II ions giv ing J = 22.7 yJ (1.14 cm(-1)) and g = 2.014.