Racemic Tartrate/Malate Anions Combine with Racemic Complex Cations to Form Optically Active Ionic Crystals

Spontaneous resolution has attracted continuing attention in various research fields since Pasteur's work on the crystallization behavior of racemic tartrate. Here, a unique example of this phenomenon is reported, involving ionic crystals generated from racemic RR/SS- tartrate or R/S-malate and racemic Delta Delta/??-[Ag3Rh2(2-aminoethanethiolato)(6)](3+) (Delta Delta/??-[1](3+)) in water. RR- and SS-tartrate selectively recognize the ?? and Delta Delta isomers of [1](3+) to produce ionic crystals of (??-[1])(2)(RR-tartrate)(3) and (Delta Delta-[1])(2)(SS-tartrate)(3), respectively, which can undergo spontaneous resolution. While spontaneous resolution also occurs when using R/S-malate, R- and S-malate select the opposite isomers of [1](3+) to give ionic crystals of (Delta Delta-[1])(2)(R-malate)(3) and (??-[1])(2)(S-malate)(3), respectively. In the presence of S-aspartate, (??-[1])(2)(R-tartrate)(3) and (Delta Delta-[1])(2)(S-tartrate)(3) are preferentially crystallized from Delta Delta/??-[1](3+) and RR/SS-tartrate at solution pH values of 6 and 10, respectively. This finding provides significant insight into the optical resolution of chemical species by spontaneous resolution and the origin of homochirality in nature.

Automated summary

Spontaneous resolution of chiral compounds interacting with specific metal complexes in water is reported in this study, leading to the formation of ionic crystals capable of undergoing spontaneous resolution. This finding offers significant insight into optical resolution of chemical species, spontaneous resolution, and the origin of homochirality in nature.