Controlled Crystal Transformations of a Chiral Conglomerate with Heterotactic Helical Coordination Arrays

Abstract

Helix represents the most essential molecular chiral symmetry at a supramolecular level. Here, a unique quasiracemate conglomerate {[Cd­(L)­I­(H2O)3]­[Cd­(HL)­I2(H2O)2]­(H2O)4} n (1, HL = N-(3,5-di­(pyridin-3-yl)-4H-1,2,4-triazol-4-yl)­nicotinamide), which crystallizes in P21 space group and consists of two different sets of helical enantiomers, has been successfully constructed. Remarkably, crystal transformations from the chiral quasiracemate 1 to two different achiral racemates {[Cd­(L)­I­(H2O)3]·(H2O)3} n (2) and {[Cd­(HL)­I2(H2O)2]­(H2O)} n (3) can be achieved controllably by introducing acid and base additives, via solvent-mediated crystal transformations.