Mono-, homo- and hetero-dinuclear lanthanide(III) complexes with new acyclic compartmental Schiff bases

A series of homo-dinuclear lanthanide(III) complexes of the type: Ln2(LA)(X)2xn(H2O) and Ln2(LB)(X)2xn(H2O) (H4LA and H4LB are the Schiff bases obtained by condensation of 3-formylsalicylic acid and 4-N-dodecycldiethylenetriamine 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(H4LC)(NO3)3xnS, Ln(H4LD)(NO3)3xnS or La(H4LE)(NO3)3x4H2O, Ln2(LC)(NO3)2xnS, Ln2(LD)(NO3)2xnS or La2(LE)(NO3)2x4H2O, Ln1-Ln2(LC)(NO3)2xns or Ln1-Ln2(LD)(NO3)2xnS (n=1-3; S=H2O, CH3OH), respectively have been prepared by using the ligands H4LC, H4LD and H4LE, 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 fluorscence microprobe. The physicochemical properties of the prepared complexes have been compared with those of similar macrocyclic complexes. The magnetic behaviour of the complex Gd2(LA)(NO3)2x4H2O has revealed a decrease in the effective magnetic moment from 10.97 μB at room temperature to 7.96 μB 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. (orig.)