Stereoselective Assembly of Gigantic Chiral Molybdenum Blue Wheels Using Lanthanide ions and Amino Acids.

The synthesis of chiral polyoxometalates (POMs) is a challenge because of the difficulty to induce the formation of intrin-sically chiral metal-oxo frameworks. Herein we report the stereoselective synthesis of a series of gigantic chiral Mo Blue (MB) POM clusters 1-5 that form by exploiting the synergy between coordinating lanthanides ions as symmetry breakers to produce MBs with chiral frameworks decorated with amino acids ligands; these promote the selective formation of en-antiopure MBs. All the compounds share the same framework archetype, based on {Mo124Ce4}, which forms an intrinsical-ly chiral or  configurations controlled by the configurations of functionalized chiral amino acids. The chirality and stability of 1-5 in solution are confirmed by CD, 1H NMR and Electrospray Ion Mobility-Mass Spectrometry (ESI-IMS-MS) study. In addition, the framework of the {Mo124Ce4} MB not only behaves as host, able to trap a chiral {Mo8} cluster that is not accessible by traditional synthesis, but also exhibits an enzyme-like selective oxidation of tryptophan to kynurenine in-situ. This work demonstrates the potential and applicability of our synthetic strategy produce gigantic chiral POM clusters capable of host-guest chemistry and selective synthetic transformations.