SINGLE-CRYSTAL AND MULTIFREQUENCY EPR STUDIES ON CHEMICAL ANALOGS OF AMAVADIN - V(IV)-DOPED CA[TI(HIDA)(2)]CENTER-DOT-6H(2)O, AND MO(V)-DOPED [PPH4][NB(HIDA)(2)] AND [NET4][TA(R,R-HIDPA)(2)] [H(3)HIDA = 2,2'-(HYDROXYIMINO)DIACETIC ACID, H(3)HIDPA = 2,2'-(HYDROXYIMINO)DIPROPIONICACID]

Q-band single-crystal and powder EPR spectra at multiple frequencies ( X, Q and 180 GHz) of V(IV)-doped Ca[Ti(hida)(2)]. 6H(2)O and Mo(V)-dop ed [PPh4][Nb(hida)(2)] and [NEt4][Ta(R,R-hidpa)(2)] (H(3)hida = 2,2'-( hydroxyimino)diacetic acid; H(3)hidpa 2,2'-(hydroxyimino)dipropionic a cid) are reported. The Ti{V} system has the spin-Hamiltonian parameter s g(11) = 1.910, g(22) = 1.987, g(33) = 1.990, A(11) = 176.4 G, A(22) = 53.5 G and A(33) = 46.3 G with non-coincidence between the principal axes of the g- and A-matrices. The Euler angles for the non-concidenc e are alpha = 11.5 degrees, chi = 4.63 degrees and gamma = 346.0 degre es. The triclinic EPR symmetry is consistent with the low (C-1) point symmetry of the [Ti{V}(hida)(2)](2-) anion in the solid state. The sma ll angles of non-coincidence between the principal axes of the g and A matrices are also evident from the Q-band powder spectrum, but not th e X-band spectrum. High-frequency (34-180 GHz) EPR measurements on pow ders of both the Nb(Mo) and Ta{Mo} systems reveal the presence of two magnetically distinct Mo centers in each case. The Nb(Mo) system has g -values of g(11(a)) = 1.9765, g(11(b)) = 1.9755, g(22(a)) = 1.9675, g( 22(b)) = 1.9665, g(33(a)) = 1.8870 and g(33(b)) = 1.8840, while the Ta {Mo} system has g(11(a)) = 1.976, g(11(b)) = 1.974, g(22(a)) = 1.970, g(22(b)) = 1.967, g(33(a)) = 1.894 and g(33(b)) = 1.892.