Self-assembled palladium(ii) “click” cages: synthesis, structural modification and stabilityElectronic supplementary information (ESI) available: Experimental procedures, 1H NMR, DOSY and ESMS spectra, 1H NMR stacked plots, MMFF and DFT calculations and crystallographic data. CCDC reference numbers 819051and 819052. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c1dt10551e

Readily synthesised and functionalised di-1,2,3-triazole “click” ligands are shown to self-assemble into coordinatively saturated, quadruply stranded helical [Pd2L4](BF4)4cages with Pd(ii) ions. The cages have been fully characterised by elemental analysis, HR-ESMS, IR, 1H, 13C and DOSY NMR, DFT calculations, and in one case by X-ray crystallography. By exploiting the CuAAC “click” reaction we were able to rapidly generate a small family of di-1,2,3-triazole ligands with different core spacer units and peripheral substituents and examine how these structural modifications affected the formation of the [Pd2L4](BF4)4cages. The use of both flexible (1,3-propyl) and rigid (1,3-phenyl) core spacer units led to the formation of discrete [Pd2L4](BF4)4cage complexes. However, when the spacer unit of the di-1,2,3-triazole ligand was a 1,4-substituted-phenyl group steric interactions led to the formation of an oligomeric/polymeric species. By keeping the 1,3-phenyl core spacer constant the effect of altering the “click” ligands’ peripheral substituents was also examined. It was shown that ligands with alkyl, phenyl, electron-rich and electron-poor benzyl substituents all quantitatively formed [Pd2L4](BF4)4cage complexes. The results suggest that a wide range of functionalised palladium(ii) “click” cages could be rapidly generated. These novel molecules may potentially find uses in catalysis, molecular recognition and drug delivery. [ABSTRACT FROM AUTHOR]