M(II) effect on encapsulation of guests into a series of M 3 L 2 chiral cages: enantio-recognition.

Self-assembly of M(ClO 4 ) 2 (M 2+ = Ni 2+ , Cu 2+ , and Zn 2+ ) with (1 S ,1' S ,1'' S ,2 R ,2' R ,2'' R )-(benzenetricarbonyltris(azanediyl))tris(2,3-dihydro-1 H -indene-2,1-diyl) trinicotinate ( s , r -L) and the corresponding enantiomer ( r , s -L) as a pair of chiral tridentate donors gives rise to the chiral cage pairs [M 3 ( s , r - and r , s -L) 2 ](ClO 4 ) 6 . For the two pairs of [(Me 2 CO)(H 2 O)@M 3 ( r ,- s and s , r -L) 2 ](ClO 4 ) 6 (M 2+ = Ni 2+ and Zn 2+ ), the inner cavity is occupied by both an acetone and a single water molecule, whereas for the copper(II) pair of [Me 2 CO@Cu 3 ( r , s - and s , r -L) 2 ](ClO 4 ) 6 under the same conditions, the cavity is filled by only one acetone molecule. Thus, the encapsulation of guest molecules into the cages during self-assembly shows significant metal(II) ion effects. These chiral cages are effective for the enantio-recognition of chiral ( S )-2-butanol and ( R )-2-butanol via the shifts of the electrochemical oxidation potentials obtained by the linear sweep voltammetry (LSV) technique, density functional theory (DFT) calculations, and the chiral 2-butanol adsorption in the single-crystal-to-single-crystal (SCSC) mode.