A family of five dinuclear lanthanide complexes has been synthesized with general formula [LnIII2(valdien)2(NO3)2] where (H2valdien = N1,N3-bis(3-methoxysalicylidene)diethylenetriamine) and LnIII = EuIII1, GdIII2, TbIII3, DyIII4, and HoIII5. The magnetic investigations reveal that 4 exhibits single-molecule magnet (SMM) behavior with an anisotropic barrier Ueff = 76 K. The step-like features in the hysteresis loops observed for 4 reveal an antiferromagnetic exchange coupling between the two dysprosium ions. Ab initio calculations confirm the weak antiferromagnetic interaction with an exchange constant JDy−Dy = −0.21 cm−1. The observed steps in the hysteresis loops correspond to a weakly coupled system similar to exchange-biased SMMs. The Dy2 complex is an ideal candidate for the elucidation of slow relaxation of the magnetization mechanism seen in lanthanide systems. ; peer reviewed: yes ; NRC Pub: yes