Pair of (Hg2II)3L2 Chiral Cages and Successive Transformation into (HgII)3L2 Chiral Cages: Chiral DOPA Recognition via Chiral Cages

Self-assembly of Hg(ClO4)2 with a pair of C3-symmetric chiral ligands, (1S,1'S,1″S,2R,2'R,2″R)-(benzenetricarbonyltris(azanediyl))tris(2,3-dihydro-1H-indene-2,1-diyl)trinicotinate (s,r-L) and (1R,1'R,1″R,2S,2'S,2″S)-(benzenetricarbonyltris(azanediyl))tris(2,3-dihydro-1H-indene-2,1-diyl)trinicotinate (r,s-L), produces a pair of chiral cages C4H8O2@[(Hg2II)3(ClO4)6(s,r-L)2(H2O)7](C4H8O2)7 and C4H8O2@[(Hg2II)3(ClO4)6(r,s-L)2(H2O)7](C4H8O2)7, respectively, via straightforward formation of the reduced Hg2II species with an inner cavity in which a single dioxane molecule is nestled. The pair of chiral cages are transformed into their downsized pair of cages, [Hg3II(ClO4)6(s,r-L)2] and [Hg3II(ClO4)6(r,s-L)2], respectively, in the presence of hydrochloric acid. The original chiral cages are more effective than the corresponding downsized cages for enantiorecognition of chiral 3,4-dihydroxyphenylalanine (DOPA) via the shifts of electrochemical oxidation potentials observed by linear sweep voltammetry (LSV) technique. Furthermore, the photoluminescence (PL) spectral shifts show that the downsized chiral cages significantly recognize chiral DOPA.