Diastereoselective self-assembly of low-symmetry PdnL2n nanocages through coordination-sphere engineering

Metal-organic cages (MOCs) are popular host architectures assembled from ligands and metal ions/nodes. Assembling structurally complex, low-symmetry MOCs with anisotropic cavities can be limited by the formation of statistical isomeric libraries. We set out to investigate the use of primary coordination-sphere engineering (CSE) to bias diastereoselectivity within homo- and heteroleptic PdnL2n cages. Unexpected differences in stereoselectivity between alternative donor groups led us to recognise the significant impact of the second coordination sphere on isomer stabilities. From this, molecular-level insight into the origins of the diastereoselectivity was gained, highlighting the importance of both host-guest and host-solvent interactions, in addition to ligand design. This detailed understanding allows precision engineering of low-symmetry MOC assemblies without wholesale redesign of the ligand framework, and fundamentally provides a theoretical scaffold for the development of stimuli-responsive, shape-shifting MOCs.