MONO-DINUCLEAR, HOMO-DINUCLEAR AND HETERO-DINUCLEAR LANTHANIDE(III) COMPLEXES WITH NEW ACYCLIC COMPARTMENTAL SCHIFF-BASES

A series of homo-dinuclear lanthanide(III) complexes of the type: Ln2(L(A))(X)2.n(H2O) and Ln2(L(B))(X)2.n(H2O) (H4L(A) and H4L(B) are the Schiff bases obtained by condensation of 3-formylsalicylic acid and 4-N-dodecyldiethylenetriamine or 1,5-diamino-3-azapentane, respectively; X = NO3-, Cl-; n = 3-8;) has been prepared and characterized. The synthesis of mono- and hetero-dinuclear complexes failed. On the contrary, mono-, homo- and hetero-dinuclear lanthanide(III) complexes, Ln(H4L(C))(NO3)3.nS, Ln(H4L(D))(NO3)3.nS or La(H4L(E))(NO3)3.4H2O, Ln2(L(C))(NO3)2.nS, Ln2(L(D))(NO3)2.nS or La2(L(E))(NO3)2.4H2O, Ln1-Ln2(L(C))(NO3)2.nS or Ln1-Ln2(L(D))(NO3)2.nS (n = 1-3; S = H2O, CH3OH), respectively, have been prepared by using the ligands H4L(C), H4L(D) and H4L(E), which are the Schiff bases derived by condensation of 2,3-dihydroxybenzaldehyde with 1,5-diamino-3-azapentane, 1,5-diamino-3-thiapentane or 4-N-dodecyldiethylenetriamine, respectively. The metal/metal ratio and the homogeneity of the hetero-dinuclear complexes have been evaluated also by electron microscopy together with X-ray fluorescence microprobe. The physicochemical properties of the prepared complexes have been compared with those of similar macrocyclic complexes. The magnetic behaviour of the complex Gd2(L(A))(NO3)2.4H2O has revealed a decrease in the effective magnetic moment from 10.97-mu-B at room temperature to 7.96-mu-B at 4.2 K, and an antiferromagnetic coupling constant J = 0.211(4) cm-1. A superexchange mechanism through the bridging atoms has been proposed.