Three binuclear Nd(III)-Nd(III), Dy(III)-Dy(III) and Ho(III)-Ho(III) complexes containing the dianion of chloranilic acid (CA) as bridging ligand have been synthesized, namely Ln~2(Phen)~4(CA)(NCS)~4 (Ln=Nd, Dy, Ho; Phen=1, 10-phenanthroline; CA=dianion of chloranilic acid). They have been characterized by elemental analyses, IR and electronic spectra, conductance and variable-temperature magnetic susceptibility. The observed susceptibility data were fit to those from theoretical magnetic equation by least-squares method, giving the parameters: Z'J'=-0.79(Nd), -0.67(Dy), -0.63cm^-^1(Ho); It indicates the existence of very weak antiferromagnetic spin exchange interaction between the rare earth ions in the complexes. Δ=-0.16(Nd), -0.76(Dy), -2.55cm^-^1(Ho); g=0.618(Nd), 1.739(Dy), 1.601(Ho); the agreement factor R≈10^-^4.

Key words: MAGNETISM, SYNTHESIS, DINUCLEAR COMPLEX, RARE EARTH, EXCHAHNGE INTERACTIONS, ANTIFERROMAGNETISM, INFRARED SPECTROPHOTOMETRY, ELEMENTAL ANALYSIS