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.