Chiral Recognition of Racemic Proline based on Chiral Macrocyclic Nickel(II) Complex: Synthesis and Crystal Structures

Abstract

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).

M(ii) effect on encapsulation of guests into a series of M3L2 chiral cages: enantio-recognition

“…8–16 Thus, recently, attractive construction of new chiral coordination cages for exploration of specific weak interactions between chiral cages and some chiral substrates has become a hot issue. Diverse research on recognition of chiral molecules via such chiral coordination species has focused specifically on the enantio-recognition of amino acids including chiral l - and d -proline, 17–20 as well as asymmetric catalysis reactions. 21–23 For efficient chiral recognition particularly, various electrochemical methods have been successfully employed.…”