The reactions of dl-proline with chiral macrocyclic Ni II complex [Ni(SS-L)](ClO 4 ) 2 in acetonitrile/water gave a six-coordinate enantiomer formulated as [Ni(SS-L)(l-Pro)](ClO 4 ) 2 ·H 2 O (1). Another enantiomer of [Ni(RR-L)(d-Pro)](ClO 4 ) 2 ·H 2 O (2) was obtained when [Ni(RR-L)](ClO 4 ) 2 was used (L = 5,5,7,12,12,4,8,11tetraazacyclotetradecane, Pro = proline). Single-crystal X-ray diffraction analyses of complexes 1 and 2 revealed that the Ni II atom has a distorted octahedral coordination arrangement, being coordinated by Scheme 1. The sketch of [Ni(SS-L)] 2+ (left) and [Ni(RR-L)] 2+ (right).