The reactions of chiral ligand (R)/(S)-1,1'-binaphthyl-2,2'-diyl phosphate (R-HL/S-HL) and ErCl3 center dot 6H(2)O afford two pairs of di- and tetranuclear enantiomers [Er-2(R/S-L)(4)(EtOH)(6)]Cl-2 center dot 6.5EtOH (R-1, S-1) and [Er-4(PO4)(R/S-L)(8)(EtOH)(3)(H2O)](2)Cl(OH)center dot 15EtOH center dot 11H(2)O (R-2, S-2). The nuclearity of these complexes is controllable and depends on the reaction temperature with a template effect. Their chirality was evidenced by circular dichroism (CD) spectra. R-1 exhibits two magnetic relaxation pathways under a zero field, with an apparent barrier of 40 K. Ab initio calculations revealed a ferromagnetic dipolar interaction between these two Er(III) ions, the equatorial nature of the ligand field, and the probable origin of the two relaxations.